Title of Invention: PARTING BLADE AND TOOL HOLDER THEREFOR Abstract: A tool holder includes a tool shank and a tool head connected to the tool shank. The tool head has a rear surface. An insert seat or a blade pocket is partially formed on both the tool head and the tool shank, and extends rearwardly of the tool head's rear surface. Adjacent to at least a portion of a shank side surface there is a reinforcement portion connecting the shank side surface and the tool head. Detailed Description: RELATED AP PLICATIONS This is a Continuation of U.S. patent application Ser. No. 16/386,953 filed 17 Apr. 2019, now U.S. Patent No. ______ , which is a Bypass Continuation-in-Part of PCT/IL2018/051254, filed 20 Nov. 2018. Priority is claimed to U.S. Provisional Patent Application No. 62/589,132 filed Nov. 21, 2017 and to U.S. Provisional Patent Application No. 62/741,619 filed Oct. 5, 2018. The contents of the aforementioned applications are incorporated by reference in their entirety. FIELD OF THE INVENTION The subject matter of the present invention relates to a parting blade (also referred to as “blade” hereinafter) and tool holder (together with the blade called a “cutting tool assembly”) configured for relatively long overhang applications or large depth of cut applications. BACKGROUND OF THE INVENTION As the name suggests, parting blades can be considered to have a ‘blade’ shape. More specifically, parting blades have narrow elongated bodies, configured for metal-cutting operations, in particular parting and slitting operations. More precisely, the elongated blade shape is defined as follows. An elongated parting blade comprises opposing first and second side surfaces extending between first and second longitudinal edges and between first and second end edges which are shorter than the longitudinal edges. A blade thickness dimension defined between the first and second side surfaces is smaller than a blade width dimension defined between the longitudinal edges. The blade width dimension is smaller than a blade longitudinal dimension defined between the first and second end edges. Such parting blades also comprise an insert seat configured to hold a cutting insert (also referred to as “insert” hereinafter). Parting blades are elongated making them particularly suitable for relatively long overhang parting applications. It is known that longer overhang applications are more susceptible to bending and vibrations than relatively shorter overhang applications. Alternative to the terminology of a long overhang is reference to the workpiece being machined. Accordingly, the present application provides a solution for machining operations requiring a large depth of cut (e.g. a workpiece with a diameter greater than 50 mm, preferably greater than 60mm or 70 mm, even up to, for example 130 mm). The embodiments hereinafter are not actually limited to said 130 mm depth of cut, but such diameter size is rare. Tool holders configured for holding such parting blades do so along the periphery thereof, specifically along the longitudinal edges thereof, via the use of opposing jaws of the tool holder. The longitudinal edges and jaws are configured with tapered constructions to allow clamping and sliding motion of the parting blade relative to the tool holder to provide different overhang lengths. One such prior art cutting tool assembly 10 is described in EP 2822720B1, assigned to the present applicant, and is schematically exemplified in FIG. 1. This cutting tool assembly 10 shows a commonly used orientation of a parting blade 12, cutting insert 14 and tool holder 16, configured for parting a workpiece 18. This publication also discloses the use of high pressure coolant through, i.e. internal to, the tool holder and the parting blade to cool the insert. Another prior art cutting tool assembly 20 is disclosed in the Sandvik Group Magazine entitled “Meet Sandvik #2-2017” (page 7), hereinafter called “the magazine”. A parting blade 22 according to this disclosure has been schematically reproduced in FIG. 2 and shown held by a tool holder 24 identical to that shown in FIG. 1 (it is noted that in the magazine a different tool holder is disclosed). It should be understood that this reproduction is to assist basic understanding only, and the comments generally made hereinafter directed to “FIG. 2” are to be directed at the disclosure in the magazine, should there be any inaccuracy. Additionally, a workpiece 25 has been schematically added for understanding. The parting blade 22 in the magazine differs primarily from the parting blade 12 in FIG. 1, in that the insert seat 26 of the parting blade is rotated 90° to use the feed motion in the y-axis. Stated differently, the rake surface 50 of the parting blade 22 in FIG. 2 is basically perpendicular to an elongation of the parting blade 22, whereas the rake surface 48 of the parting blade 12 is basically parallel to an elongation of the parting blade 12. Said pocket orientation is alleged to provide better stability and less vibration since the cutting force is directed more towards the longitudinal extension of the parting blade and thereby allow significantly higher feed rates. The parting blade 22 also shows a parting blade configured for coolant therethrough, as shown by the coolant outlets (the basic positions of which being schematically designated 28 and 30) visible adjacent to a cutting insert 32 and a sealing device 34 mounted on the blade 22. It is an object of the present invention to provide a new and improved parting blade, and tool holder, and tool cutting assembly. SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention, there is provided an elongated parting blade having a basic elongation direction and comprising: opposing first and second side surfaces extending between first and second longitudinal edges and also extending between opposing first and second end edges which are shorter than and extend transverse to the first and second longitudinal edges; and an insert seat associated with the first longitudinal edge and the first end edge; the insert seat comprising first and second insert jaws which form an insert-receiving gap (also referred to as “gap” hereinafter) at a location they oppose each other, the insert-receiving gap opening out in a direction towards the first end edge. In accordance with a second aspect of the present invention, there is provided an elongated parting blade having a basic elongation direction and comprising: opposing first and second side surfaces extending between first and second longitudinal edges and also extending between opposing first and second end edges which are shorter than and extend transverse to the first and second longitudinal edges; and an insert seat associated with the first longitudinal edge and the first end edge; the insert seat being configured with a lower seat abutment surface formed by a first longitudinal edge extremity of the first longitudinal edge, and a rear seat abutment surface formed by a first end edge extremity of the first end edge; wherein the lower seat abutment surface and the rear seat abutment surface extend non-parallel to each other. It will be understood that both the first and second aspects both define a similar concept in alternative ways, namely an insert seat configuration, to provide the advantages over both of the prior art parting blades in FIGS. 1 and 2. To elaborate, the insert seat in FIG. 1 provides better chip evacuation than that shown in FIG. 2, because there is no insert jaw 36 (FIG. 2) located above the rake surface 48 of the cutting insert 14, allowing more space for the chips to flow unimpeded. However, the theoretical additional stability of the parting blade 22 in FIG. 2 is not provided. By contrast, the insert seat 26 in FIG. 2 has a coolant outlet 28 extremely close to the cutting insert (i.e. which proximity is due to the existence of the insert jaw 36 which comprises the coolant outlet 28) and the parting blade 22 thereof has the alleged additional stability but lacks the additional chip evacuation capability of the configuration in FIG. 1. Yet another independent advantage that has been found, is that for high feed applications (e.g. greater than 0.20 mm/rev), the use of an elastic jaw is more disadvantageous than in normal feed applications (e.g. lower than or equal to 0.20 mm/rev) since it quickly loses the elasticity thereof due to the increased forces. It will be understood that an insert seat for high feed devoid of an elastic jaw is an independent benefit in itself. Accordingly, a third aspect is a parting blade for high feed applications (e.g. equal to or higher than 0.20 mm/rev) or relatively long depth of cut (e.g. >50 mm), the parting blade comprising an insert seat configured with a lower seat abutment surface and a rear seat abutment surface; wherein the lower seat abutment surface and the rear seat abutment surface extend non-parallel to each other. Preferably, a lower seat abutment surface can extend basically perpendicular to the rear seat abutment surface. More preferably, the rear seat abutment surface can extend basically at a right angle to the lower seat abutment surface. To clarify, said parting blade is devoid of a jaw extending above the insert seat (i.e. extending opposite the lower seat abutment surface or even over only a gap formed between the lower seat abutment surface and the rear seat abutment surface). It will be understood that said parting blade with insert seat devoid of said jaw extending over the gap or lower seat abutment surface is an independently advantageous feature which can be applicable to any of the other aspects. However, it will also be understood that the other aspects are not limited to this specific type of insert seat. Even though the present invention as shown in FIG. 3 does not have the advantageous benefit of a coolant outlet as proximate to a cutting edge on the side of the rake surface as that shown in FIG. 2, it is believed the advantageous chip evacuation capability outweighs this detriment, especially for such parting blade that may be used for comparatively high feed rates and the associated chips. According to any of the above aspects, preferably, a lower seat abutment surface can extend basically perpendicular to the elongation direction and a rear seat abutment surface can extend basically parallel to the elongation direction. More preferably, the rear seat abutment surface can extend basically at a right angle to the lower seat abutment surface and can extend basically parallel to the elongation direction. According to any of the above aspects, there can be provided an additional insert seat associated with the second longitudinal edge and the first end edge. Preferably the additional insert seat has a corresponding insert seat construction. It will be noted that in the configuration in FIG. 2, the flexible connection 38 of the first and second insert jaws 36, 40 is located close to an opposing corner 42 associated with the second longitudinal edge 44 and the first end edge 46. It will be understood that such configuration only allows a single insert seat associated with the first end edge 46 (noting that the first edge is the shorter edge of the parting blade and hence is relatively closely located). By contrast, referring to FIG. 3, since the comparative flexible connection on the insert jaws is not located proximate to an adjacent corner of the first edge, a second insert can be provided which is associated with the first edge. It will be understood that by providing additional insert seats on a single parting blade, the tool life of the parting blade is significantly increased. This is an independent benefit to the present invention, in addition to the improved chip flow discussed above. According to any of the above aspects, there can be provided an additional insert seat(s) associated with the second end edge. As is understood from the prior art parting blade in FIG. 2, the non-indexable design would likely derive from the flexible connection 38 of the insert seat 26 located at the short edge of the parting blade. Noting that unlike FIG. 1, the cutting forces in FIG. 2 would more likely require a stopper positioned at the rear 47 of the blade, it was clearly preferred not to provide a damageable flexible connection for abutment against a stopper. However, for the above aspects which do not comprise a flexible connection at such location, there is a further advantage that at least one insert seat can be located at both of the first and second end edges. According to any of the above aspects, regardless of the insert seat type, a longitudinal edge associated with an insert seat can extend in an oblique direction such that it extends underneath the insert seat. Stated differently, an elongation direction of a parting blade can be non-orthogonal to a rake surface of a cutting insert. It will be understood that in both the prior art blades in FIGS. 1 and 2, the longitudinal edge 44, 45, does not extend in an oblique elongation direction of the parting blade such that it extends underneath the insert seat. Similarly, the rake surfaces 48, 50 in both disclosures is either basically parallel or basically perpendicular with the elongation direction. By providing such feature (hereinafter the “oblique parting blade construction”), the present invention, in theory, provides a more stable parting blade than is known in the prior art, since the cutting force applied to a parting blade is more directed along the length of the blade. While appreciating that different variables such as workpiece diameter varies cutting force direction, the most preferred oblique angle θ, fulfills the condition: 60°>θ>0°, more preferably 50°>θ>10°, and most preferably 40°>θ>20°. Additionally, it is believed values are more beneficial as they tend to 30°. The oblique angleθ being measurable between a line perpendicular to the shank axis and the forwardmost obliquely extending longitudinal edge. Even though such oblique parting blade construction can be advantageous with regard to the cutting force direction, the removal of material directly underneath a cutting insert, e.g. at the longitudinal edge side of an insert seat weakens the construction strength of the insert seat. Accordingly, in addition to providing the oblique parting blade construction, said weakening can be countered by providing an orthogonal sub-edge adjacent the insert seat. To elaborate, an orthogonal sub-edge portion of a longitudinal edge associated with an insert seat can extend in a non-oblique direction (e.g. not extending obliquely under the insert seat or, stated differently, extending orthogonal to a rake surface), and a connected oblique sub-edge can extend from the orthogonal sub-edge towards an opposing end edge. Such orthogonal sub-edge portion can provide two independent benefits. A first benefit of strengthening of the insert jaw associated with the longitudinal edge (i.e. allowing it to be thicker and/or to extend directly underneath the cutting insert and provide more support, and a second benefit that the insert seat is moved closer to the middle of the first or second end edge, thereby directing the cutting force even more centrally along the elongation direction of the parting blade. Accordingly, in a fourth aspect of the present invention, there is provided an elongated parting blade having a basic elongation direction and comprising: opposing first and second side surfaces extending between first and second longitudinal edges and also extending between opposing first and second end edges which are shorter than and extend transverse to the first and second longitudinal edges; and an insert seat associated with the first longitudinal edge and the first end edge; the insert seat being recessed towards the second longitudinal edge. Stated differently, the term “recessed towards the second longitudinal edge” could alternately be defined as distanced from an imaginary extension line of the first longitudinal edge in a direction towards the second longitudinal edge. Regardless of the terminology used, it will be understood that such aspect provides the centralization of the cutting force as described above. It will also be understood that any of the features stated above with respect to the first, second and third aspects are also applicable to this aspect which defines a preferred location of an insert seat and not a specific insert seat construction. In accordance with a fifth aspect of the present invention, there is provided an elongated parting blade having a basic elongation direction and comprising: opposing first and second side surfaces extending between first and second longitudinal edges and also extending between opposing first and second end edges which are shorter than the first and second longitudinal edges; the first and second longitudinal edges extending along the basic elongation direction; the parting blade further comprising an insert seat opening out to or proximate to the first end edge; the insert seat comprising a lower seat abutment surface and at least one additional abutment surface; and wherein, the first longitudinal edge comprises a proximate portion which is proximate to, and extends underneath, the lower seat abutment surface. More precisely, the insert seat can open out to one of (a) the first end edge, (b) both the first end edge and first longitudinal edge, or (c) the first longitudinal edge at a portion thereof adjacent to the first end edge. Preferably, the proximate portion extends underneath the entire insert seat. Preferably, the proximate portion extends in both a rearward direction and a downward direction (DR, DD). Preferably an oblique blade angle θ1, measurable between the downward direction DD and the proximate portion fulfills the condition: 60°>θ1>0°, more preferably 50°>θ1>10°, and most preferably 40°>θ1>20°. Additionally, it is believed values of the oblique blade angle θ1 are more beneficial as they tend to 30°. The above mentioned at least one additional abutment surface can be either an abutment surface of an upper jaw (similar to the pocket type shown in FIG. 2, the upper jaw being designated as “36”, and accordingly the at least one additional abutment opposes the lower seat abutment surface) or can be a rear seat abutment surface (similar to the pocket type shown in FIG. 5B, designated as “134B”, and accordingly the at least one additional abutment is basically perpendicular to the lower seat abutment surface). The precise orientation of the additional abutment surface is not of importance, rather it will be understood that typically an insert needs to be secured by more than one abutment surface and the location of the lower seat abutment surface is being used to describe the relative orientation of the proximate portion. It will also be understood that the lower seat abutment surface can, and often will, be other than a flat surface but that it basically lies in a seat plane PS (see FIG. 16B). The seat plane being basically perpendicular to the first and second side surfaces and parallel with the forward and rearward directions (DF, DR). The elongated parting blade can have a linear shape or a non-linear shape. For example, the elongated parting blade can be bent or curved. In embodiments where the parting blade comprises a bend, the bend can preferably be located at about the center of the length of the blade. Preferably, the bend can be exactly in the middle of the length of the blade, allowing the blade to be equally indexable about the middle thereof. Such blade can have, for example, in a mounted position, a vertically extending clamping portion and an obliquely extending cutting portion (which portions can switch functions when indexed, if indexable). Accordingly, for example, the blade can be mounted in a relatively compact tool holder 64 as shown in FIG. 3, yet still have the advantageous oblique orientation provided in the cutting assemblies shown, for example, in FIGS. 6 and 7A. Additionally, such blade can be mounted in a standard tool holder 16 or 24 (e.g. shown in FIGS. 1 and 2) designed for a non-oblique blade. It will be understood that such parting blade can even be mounted at different overhang lengths if desired. This being in addition to an advantageous force application. Initial tests were made with a linear blade having an oblique angle of 15° (FIG. 7A) and −15° (not shown) as well as 0° (FIG. 3) with the stability being excellent at all angles. In recent tests a linear blade with an oblique orientation angle of 30° (in a configuration similar to the blade shown in FIG. 7A) was found to have superior results (performing approximately twice the number of slits to the aforementioned embodiments). A non-linear blade of the type shown in FIGS. 16A-16E and having an oblique orientation angle of 30° is expected to have similar benefits to the linear blade tested. In accordance with a sixth aspect of the present invention, there is provided an elongated parting blade having a basic elongation direction and comprising: opposing first and second side surfaces extending between first and second longitudinal edges and also extending between opposing first and second end edges which are shorter than and extend transverse to the first and second longitudinal edges; and an insert seat associated with the first longitudinal edge and the first end edge; the first end edge further comprising a projecting portion which projects further in the basic elongation direction than the insert seat; the projecting portion comprising a blade outlet aperture directed towards the insert seat. Even though the provision of the projecting portion decreases the above discussed chip evacuation space available, the advantageous provision of coolant is believed to outweigh this detriment in at least some cases. In accordance with a seventh aspect of the present invention, there is provided a parting blade and sealing device for the parting blade, the parting blade comprising: opposing first and second side surfaces extending between and peripheral edges; and an insert seat; the parting blade further comprising an internal coolant arrangement comprising a blade inlet aperture out to both the first and second side surfaces, a blade outlet aperture opening out at or towards the insert seat, and a blade passageway extending from the blade inlet aperture to the blade outlet aperture; the sealing device comprising a sealing portion configured to seal the blade inlet aperture at the second side surface and an at least partially threaded shank portion which is longer than a blade thickness measured from the first to second side surface; the parting blade being devoid of a threaded hole configured for receipt of the threaded shank portion. It will be understood that the shank portion is configured to extend through the blade and threadingly connect to a threaded hole of a tool holder holding the parting blade. Since the parting blade can be manufactured without a threaded hole for attaching the sealing device too, the manufacture of the blade is simplified (e.g. by providing a simple threadless hole); the parting blade can potentially be made thinner than a comparative blade with a threaded hole (since typically at least three thread rotations are needed for secure connection defining a minimum blade thickness). Another advantage may be that it is theoretically possible to secure the blade inlet aperture with direct engagement to the tool holder thereby possibly allowing high pressure coolant transfer without the need for a sealing ring and associated construction between the parting blade and tool holder. Accordingly, it is believed theoretically possible to provide a parting blade having a blade thickness of 2.2 mm or less, preferably 2.0 mm or less and most preferably between 1.7 mm to 1.9 mm, inclusive. Said thickness refers to the thickness of the entire blade (it will be understood that parting blades exist which have a very small thickness near an insert seat and an enlarged spaced apart from the insert seat). The present aspect can be applied to elongated parting blades, particularly having a basic elongation direction, first and second longitudinal edges and opposing first and second end edges which are shorter than and extend transverse to the first and second longitudinal edges, an insert seat being associated with the first longitudinal edge and the first end edge. Additionally, unlike some of the other aspects of the present application, the advantage of a parting blade devoid of threaded holes between the opposing first and second side surfaces thereof is advantageous even to parting blades which are not elongated (for example parting blades of the type disclosed in WO2018/047162, there called “adaptors”, said patent application being assigned to the present applicant and the contents of which are incorporated by reference herein). It will be appreciated that the benefit of a parting blade devoid of a threaded hole, allowing a very small blade thickness is not related to the shape of the parting blade. In summary, the features of the seventh aspect can also be applied to a non-elongated blade, for example a non-elongated parting blade with one or more insert seats. It will be noted that the first, second, third and fourth aspects are directed to construction associated with the insert seat, the fifth aspect with the blade shape, and the sixth and seventh aspects are directed to coolant construction features. Accordingly, it will be understood that either the sixth and seventh can be combined with any of the non-related features of the first to fifth aspects to provide an even further advantageous parting blade. It will also be understood that a parting blade according to any of the first four aspects, can be devoid of a coolant construction, if desired. Additional to what is stated in the discussion of the threaded hole aspect (sixth aspect), a parting blade may be able to be made thinner than known comparative blades due to the extra stability provided by the orientation of the cutting insert directing the cutting force longitudinally into the blade. Accordingly, according to any of the above aspects, a parting blade can have a blade thickness of 2.2 mm or less. Said blade thickness can be in accordance with the values defined above. As will be discussed below with respect to the tool holder, a preferred tool holder for any of the aspects can hold a parting blade in a single position, i.e. without the possibility of changing the overhang length thereof as exemplified in the prior art parting blades in FIGS. 1 and 2. In embodiments where such feature is taken into account, according to any of the above aspects, a ratio of a maximum blade length LB and shank length LS, both of which being measured parallel to an elongation direction, can fulfill the condition LS/LB <0.45, preferably LS/LB <0.40 and most preferably LS/LB <0.35. The shank length LS being the shortest distance measurable from a second end edge to a blade inlet aperture configured for an insert seat located at the first end edge. It will be understood that if the maximum blade length LB is theoretically divided into a shank length LS (for mounting to a tool holder) and the remainder being an overhang length Lo, the combination of the insert seat constructions detailed above and the cutting tool assembly not being configured for different overhangs (as will be described below) allow a much shorter shank length LS than was previously used for parting blades. In theory, the shank length LS can even be as short as approximately the same length as a blade width WB. According to an eighth aspect of the present invention, there is provided a tool holder comprising: a tool shank having a shank axis defining forward and rearward directions; and a tool head connected to the tool shank; the tool shank comprising opposing uppermost and lowermost shank surfaces which define upward and downward directions perpendicular to the shank axis, and further comprising first and second shank side surfaces which define first and second side directions perpendicular to the shank axis and the upward and downward directions; the tool head extending in the forward and downward directions from a front shank portion of the tool shank and comprising a blade pocket; the blade pocket comprising a peripheral wall formed with a pocket opening which opens out in the upward direction. Without being bound to the details in the previous paragraph, the general concept of the present invention is to provide a tool holder having a traditional (“horizontal”) shank orientation similar to that shown in FIG. 1 and a non-traditional (“vertical” or “basically vertical”) parting blade orientation similar to that shown in FIG. 2, thereby allowing the tool holder to be mounted to turrets in traditional machines (typically lacking vertical movement capability) while providing the stability benefits of the design in FIG. 2. Current testing has shown that the present invention provides even better stability than the prior art designs. As the above-mentioned traditional machines lack vertical movement capability, according to preferred embodiments the tool holder is configured to hold a parting blade in a single position (i.e. without the possibility of changing the overhang length, such capability being available in the prior art tool holders in FIGS. 1 and 2. While such capability has always been one of the key features of a parting blade cutting tool assembly, it is believed that the trade off of providing superior stability outweighs such disadvantage. Stated differently, the tool holder and tool assembly aspects of the present invention are not restricted to the insert seat constructions or coolant constructions detailed in the previous aspects, although may clearly be advantageous if used in conjunction therewith. It has also been subsequently found that even with machines with vertical movement capability, the present invention is advantageous since typically the vertical movement capability is configured for lighter or weaker machining. The blade pocket is configured to hold a parting blade. The blade pocket can be located in the middle of the tool head (e.g. inside a groove, not shown). Preferably, however, the blade pocket is located at a side surface of the tool head. The peripheral wall can comprise two side wall portions extending from the pocket opening. The side wall portions can extend in the downward direction. According to a preferred embodiment, the sidewall portions can extend in the downward and rearward directions from the pocket opening. Without being bound to theory, it is believed that the downward and rearward orientation (e.g. FIG. 6) is advantageous over the only downward (90°) orientation (FIG. 3), in that vibration of the parting blade during machining is less likely to result in the unclamped part of the parting blade swinging away from the workpiece due to cutting forces and returning in a pendulum manner to impact it (it will be understood that such motion is extremely small). It is further believed that the oblique parting blade construction is superior, as explained above. Nonetheless, FIG. 3 certainly constitutes one possible embodiment of the present invention. It will be noted that any basic upward inclination of the parting blade would provide the basic advantage of the present invention, even if the parting blade would be slanted rearwardly (not shown), instead of vertically in FIG. 3 and forwardly in FIG. 6. Nonetheless, a rearward slant would require the tool head to have a more bulky construction in the forward direction than a vertical slant, and a vertical slant more than a forward slant. As shown in FIG. 6 the forward slant allows the tool head to have a compact shape near a lowermost point thereof (i.e. the material shown in dashed lines is not needed whereas it is present in FIG. 3. The peripheral wall can comprise a stopper wall portion. The stopper wall portion is for providing the parting blade with a fixed height relative (i.e. single position). The stopper portion is preferably located opposite the pocket opening. The stopper wall portion is preferably straight. The stopper wall can be connected to one or both of the side wall portions. The tool holder can comprise a clamp configured to hold a parting blade to the blade pocket. The clamp can be located adjacent to one of the side wall portions. Such arrangement can provide the strong peripheral clamping arrangement of the prior art. According to one preferred embodiment, the clamp is located adjacent the side wall portion closest to the tool shank. This allows the other side wall portion (i.e. the forwardmost side wall portion) to be relatively smaller, allowing the benefits of the compact design of the tool head. It is noted that this is the opposite arrangement to known prior art cutting assemblies, which are known to have a cutting insert at the same side of a blade which is held with a moveable clamp This is the traditional design because the cutting forces are primarily directed to the side of the blade held with a static (and hence more stable) component. However for the present invention, where there is an interest to reduce the size of the tool holder at the front end thereof and the cutting forces are more longitudinally directed than in the traditional blade arrangements (e.g. as shown in FIG. 1), it is believed that this is preferred. According to a different embodiment, the peripheral wall can comprise a single side wall portion extending from the pocket opening, and a clamp can form a second side wall portion opposite the first side wall portion. In such case the clamp can be integral to the tool holder with one or more flexible connections (allowing compact construction) or a separate component (allowing ease of manufacture, similar to the clamp 54 shown in FIG. 1). In such embodiment, the preferred compact tool head design may be outweighed by a preference for clamping access at the front of the tool holder. The side wall portions can longer than the stopper wall portion. Stated differently, the blade pocket can have an elongated shape. It will be understood that the longer the blade pocket, the more stable the clamping. According to the rule of thumb of the prior art tool holders, an overhang of a parting blade is typically about 1/3 of the overall length of the parting blade, with the remainder being required to be clamped. However a longer blade pocket also necessitates a larger tool head. Accordingly, it is preferred to minimize the length of the blade pocket to provide sufficiently strong clamping while reducing the tool head size. Preferably a side wall portion length LSW (measured from the pocket opening to a stopper wall portion) and a stopper length LST (measurable between two side wall portions subtracting the space taken by a clamp, if present; stated differently, equivalent to the blade width WB) fulfill the condition LSW<3LST, preferably LSW<2LST, most preferably LSW<1.5LST. In theory it is preferred that LSW ≥LST. Accordingly, the number of screws used for a clamping mechanism could be less than the traditional three or four. The side wall portions are preferably tapered to provide a similar clamping construction to that seen in FIG. 1. Similarly, the longitudinal edges of a parting blade can be correspondingly tapered. It is noted that since the present tool holder does not provide overhang adjustment, it is not strictly necessary for the longitudinal edges to be parallel or parallel along their entire length. Nonetheless clamping the longitudinal edges, and more preferably tapered longitudinal edges, is still believed to provide the most advantageous clamping arrangement, even though other arrangements could be theoretically possible (e.g. screw holes formed in the blade and pocket face, or more preferably screw holes combined with tapered side edges. Even though a parting blade free of such screw holes is still the most preferred configuration. According to an embodiment, a pocket face comprises a threaded hole. The threaded hole can be adjacent a tool holder outlet aperture. In such case the tool holder could be configured for high pressure coolant (e.g. greater than 20 bar, or preferably greater than 60 bar). The pocket face could, theoretically, be devoid of a sealing element (e.g. an o-ring) between the blade pocket and parting blade. The tool holder can be preferably configured to hold the parting blade in a single position (i.e. only providing a single overhang length). Nonetheless, it is envisaged that a fine-tuning component could be used for fine-tuning of the position of the parting blade. For example, such component can be located adjacent the stopper wall portion. According to an embodiment, a sealing hole can be formed in the parting blade. The sealing hole can be configured to receive a shank of a sealing device therethrough. The sealing can be elongated in the elongation direction. A sealing hole can be significantly larger than a pocket face hole configured to receive a shank of a sealing device extending through the sealing hole. Such construction can facilitate said fine-tuning. Alternatively, such construction can ease production of the blade and/or tool holder by reducing tolerance requirements and/or allow for fine-tuning of the position of the blade. While the tool shank exemplified in the drawings is basically square in cross section, it will be understood that such shanks can be other shapes such as circular in cross section (i.e. cylindrical). For a cylindrical shank, for example, the uppermost and lowermost shank surfaces, and first and second shank side surfaces can be thin line portions, parallel to the shank axis, at the defined extremity positions. Unique advantages of a tapered shank construction have been found, as detailed below. According to a ninth aspect of the present invention, there is provided a tool holder comprising: a tool shank having a shank axis defining forward and rearward directions; and a tool head connected to the tool shank and comprising an insert seat or a blade pocket; the tool shank comprising opposing uppermost and lowermost shank surfaces which define upward and downward directions perpendicular to the shank axis; first and second shank side surfaces which define first and second side directions perpendicular to the shank axis and the upward and downward directions; wherein adjacent to at least a portion of the first shank side surface there is a reinforcement portion connecting the first shank side surface and the tool head. The reinforcement portion can provide additional structural strength to support the tool head. It will be understood that there are extremely high cutting forces in the long overhang application subject the present subject matter, and the reinforcement portion assists to reduce bending forces on a tool head. After development of the tool holder for a parting blade, it was found that the reinforcement portion also improves performance of other cutting tool types. When the tool shank is mounted to a turret recess, the reinforcement portion is configured to extend outside of the recess and alongside the turret. Preferably, the reinforcement portion extends further in the downward direction than the lowermost shank surface. In such embodiments, it is preferred that the reinforcement portion can comprise a relief portion directly adjacent the lowermost surface. In configurations where it is desired that the reinforcement portion abut a turret side surface, the relief portion only extends a limited distance in the downward direction and further downward therefrom the reinforcement portion increases in thickness towards the second side direction (i.e. generally towards the tool shank). Stated differently, the relief portion can provide a neck shape to the reinforcement portion According to one embodiment, a shank width of the tool shank can be configured such that the second shank side surface does not contact the turret recess and the reinforcement portion abuts a turret side surface. Preferably, in such embodiment there is the aforementioned relief portion. However it will be understood that while such abutment may help somewhat with stability, the primary benefit of the reinforcement portion is not believed to be derived from such abutment. Rather the additional structural support between the tool head and tool shank. Accordingly, it will be understood that the second shank side surface can be configured to contact the turret recess and the reinforcement portion can be configured to be spaced from the turret. Preferably, the reinforcement portion has a blade shape. To elaborate, a reinforcement portion width HW measured parallel to the first and second side directions can be the smallest dimension of the reinforcement portion. Such configuration provides two benefits, firstly the moment or bending forces are most efficiently countered with such orientation of the blade shape, secondly there is a minimal projection of the reinforcement portion from the turret. While the reinforcement portion can be uniform in cross section and extend from the tool head to a shank end, it will be understood that the most critical area for support is adjacent to the tool head. Accordingly, preferably the reinforcement portion can extend from the tool head until only a central portion of the tool shank (i.e. not until a shank rear end, although that is certainly one option). While this is optional, it provides the benefit of reduction of material required for the tool head. Similarly, a reinforcement portion height dimension (measured parallel to the upward and downward directions) can be greatest adjacent the tool head and can have a reduced height dimension at a larger distance therefrom. The reinforcement portion can have a tapering height with increasing distance from the tool head. Preferably, the reinforcement portion can lie in the same plane as a blade pocket. Stated differently, for parting and grooving applications it is optimal for the reinforcement portion to be in the same plane as the cutting insert. Preferably, the reinforcement portion can be formed with a portion of an insert seat or blade pocket. Said portion can be a sidewall extending from a pocket surface. Preferably the height dimension proximate to the tool head is at least half the height of the tool shank. More preferably at least equal to the height of the tool shank. In terms of the reinforcement portion height HR, this means that proximate to the tool head the reinforcement portion height HR is equal to at least one and a half times the tool shank height HS (HR≥1.5HS) and preferably HR≥2HS. A concave surface of the tool holder can extend from the front of tool shank to the front uppermost point of the tool head. The front concave surface can define a tool overhang length from the pocket opening to a height of the uppermost surface of the shank portion, when measured perpendicular to a pocket elongation direction. It will be understood, similar to the previous aspect, that while the tool shank exemplified in the drawings is basically square in cross section, such shanks can be other shapes such as circular in cross section (i.e. cylindrical). It will be understood that any of the features mentioned in connection with the previous aspect can be incorporated into the present aspect. According to a tenth aspect of the present invention, there is provided a tool holder comprising: a tool shank having a shank axis defining forward and rearward directions; and a tool head connected to and extending forward of the tool shank; the tool shank comprising opposing uppermost and lowermost shank surfaces which define upward and downward directions perpendicular to the shank axis; first and second shank side surfaces which define first and second side directions perpendicular to the shank axis and the upward and downward directions; wherein the tool holder further comprises an insert seat or a blade pocket which is partially formed on the tool head and extends rearward of the tool head. Stated differently, a tool holder having a shank portion to be held by a turret or machine and a tool head to provide support, proximate to a workpiece, to a parting blade or cutting insert machining the workpiece, in combination with the parting blade or cutting insert being sized so that it extends rearward of the tool head provides a compact tool assembly with hitherto unknown relatively large depth of cut. According to an eleventh aspect of the present invention, there is provided a tool holder comprising a blade pocket which in turn comprises a pocket surface and one or more sidewalls; wherein the tool holder further comprising a resilient biasing element located along the pocket surface and is configured to provide a biasing force towards one of the tool abutment surfaces or an area to which two tool abutment surfaces converge. According to a twelfth aspect of the present invention, there is provided a rotationally symmetric parting blade comprising opposite first and second side surfaces; a peripheral edge connecting the first and second side surfaces; and a plurality of circumferentially spaced insert seats formed along the peripheral edge; wherein each insert seat has only a single blade coolant passageway associated therewith; each coolant passageway extending from a blade inlet aperture proximate the center of the parting blade but offset therefrom to a blade outlet aperture opening out at or towards the insert seat. Preferably the blade outlet aperture is configured to be directed above a rake surface of a cutting insert held by the associated insert seat. According to a thirteenth aspect of the present invention, there is provided a cutting tool assembly comprising a tool holder, parting blade and a cutting insert; the tool holder comprising a pocket surface with at least one hole extending therein; the parting blade comprising at least one insert seat and at least one hole proximate to the insert seat and configured to eject or mount the insert to the insert seat; wherein, when the parting blade is mounted to the tool holder, a fastener extends through the at least one hole in the parting blade and enters the at least one hole in the pocket surface to assist in securing the parting blade to the tool holder. Preferably the holes formed in the pocket surface are threaded and the fastener is a screw with a corresponding threading. Preferably the at least one hole formed in the parting blade is devoid of threading. According to one preferred embodiment the parting blade comprises at least one additional hole which is not configured for ejection or mounting of an insert seat, and the parting blade is secured to the tool holder with a fastener extending through said at least one additional hole and at least one other fastener extending through said at least one hole configured to eject or mount the insert to the insert seat. According to a fourteenth aspect of the present invention, there is provided a tool assembly comprising: a tool holder and either a parting blade or a cutting insert; wherein the tool holder comprises a tool shank having a shank axis defining forward and rearward directions and a constant cross sectional shape perpendicular to the shank axis; and a tool head connected to and extending forward of the tool shank and comprising different cross section to the shank portion; wherein an insert seat or blade pocket is at least partially formed on the tool head; wherein when the parting blade or cutting insert is mounted to the insert seat or blade pocket at least a portion of the parting blade or cutting insert extends rearward of the tool head. According to a fifteenth aspect of the present invention, there is provided a tool assembly comprising: a tool holder and either a parting blade or a cutting insert; wherein the tool holder comprises a tool shank having a shank axis defining forward and rearward directions; a tool head connected to and extending forward of the tool shank and comprising a rearwardly facing tool head rear surface; and a pocket at least partially formed on the tool head and configured to hold the parting blade or cutting insert; wherein, when the parting blade or cutting insert is mounted to the pocket it extends rearward of the tool head rear surface. According to a sixteenth aspect of the present invention, there is provided a cutting tool assembly comprising a tool holder and parting blade according to any of the previous aspects. It will be understood that the following features are applicable to all of the aspects. The cutting tool assembly can further comprise a cutting insert. The cutting insert can comprise a cutting edge which is wider than the entire parting blade. The tool holder can be configured to hold a parting blade only along a periphery thereof together with abutment of a pocket surface. The parting blade's body can be a unitary one-piece construction (i.e. the term “body” excluding cutting inserts and sealing devices). Preferably the tool holder (i.e. shank portion and tool head) can be a unitary one-piece construction. Stated differently, the tool head is preferably integrally connected to the shank portion. It will be understood that it is feasible to secure two different such components together, e.g. with screws, however such construction is typically weaker or less compact and thus there is a large preference for said unitary one-piece construction. The parting blade can be symmetrical about a bisecting plane extending parallel with and equally spaced from the first and second side surfaces. The parting blade can have 180 degrees rotational symmetry about a blade axis that extends through the center of, and in a direction perpendicular to, the first and second side surfaces. The parting blade can have mirror symmetry about a lateral plane extending perpendicular to the first and second side surfaces and located midway between the opposing first and second end edges. Such construction can result in a double-ended parting blade which is not rotationally symmetric about a blade axis
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