failing that, any other ideas?
1605 ballscrew is the most produced ballscrew so are the cheapest. Miniatures are harder to make and made in far less volume so expect to pay a lot more.
100 points to the first person who finds 3 issues with the screenprints!
Some of the links are not working at the moment, but you can get to all the download we have on the site in this link.
including solid works files of most of the Gten nuts.
Your time format displays as for example 3:43 PM when I thought the whole world had agreed to use the 24 hour format.... it should read 15:43 !
do you honestly think i would give away 100 imaginary points that easily????
how long a ballscrew do you need?
The ballnuts from China are made from a fairly hard grade of steel. However I did check a RM1204 ballnut from Chai and I could file it, so you should be able to machine them.
There are some suppliers on AliExpress (http://www.aliexpress.com/store/group/ball-screw/609097_211302591.html) with small ballscrews - it might be worth asking if they have what you need although it's a bit of a long shot.
Could you not mount the ballscrew somewhere else, for instance to the front of the table perhaps using the convenient T-slot? It's clearly not as nice as having it under the table, since the force will be off centre and you'll need to protect it from swarf, but I don't think either of these are a big deal compared to what might happen if you mill that much out of the table. It wouldn't require modification to the machine in addition to being a lot cheaper.
could you mount the nut on the edge of the apron for the x axis, and the front or the back for the y. That may lower the axis of the screw enough to get a reasonable one in there.
rather than having the nut between the table and the apron, you could mount it at the edge of the apron so all that has to pass between the table and the apron is the screw.
I think i2i was saying put the ballnuts on the ends of the axes, instead of near the middle. That way, assuming you have room for the 16mm screw under each, you would just need to use a longer ballscrew to get the same travel. It's actually rather like how I mounted it on my lathe cross slide (http://www.mycncuk.com/forums/lathe-build-logs/4497-micro-lathe-zero-backlash*-conversion.html). There I extended the saddle with a milled block of steel, then mounted the ballnut to that to get it outside. I also had to mill a fair bit from the bed to fit the RM1204 ballscrew in.
Edit: Didn't see post #13 before submitting this.
any critical thoughts on this design?
I would mount the stepper motor to a block of aluminium since the posts are not particularly strong, wont conduct much heat from the motor and also look like a grandfather clock. Also you might have difficulty fitting the belt/pulley between two posts? It would certainly limit your choice of ratios.
Probably negligent, but instead of making the ballnut mount match the circular profile of the nut, I'd make the mount closer to a rectangle so it fixes to a greater area of the bed since that should be stronger.
still have to decide on a pulley ratio so i can incorporate it into my design, any thoughts?
now that i have me some screws i need to get them machined. i have arranged for a friend to do this for me as the boxford doesn't have much in the way of change-gears and im afraid id screw it up (pun intended).
1) pulleys, is there really any difference betweel xl and htd or other types of pulley?
2) bearings, i see alot of people using angular contact bearings, wouldn't ball thrust bearings be a cheaper alternative or is their something im missing?
3) i see that using belleville washers is also quite common for preloading the bearings, would an easily available split washer not do the job?
Why couldn't you get them machined by the seller? Assuming you bought them from China it should be very cheap. It's not easy to do it yourself due to the hardness of the surface.
1) Different tooth shapes which are more/less accurate (backlash etc). HTD is generally considered the best for this application.
2) Could be, but I think they'd be harder to mount and pre-load accurately? Also possibly lower efficiency, but I'm not sure.
3) No since it wouldn't apply an even force on the bearing ring. Belleville washers may not be nessecary - it depends how you mount the bearings. The BK/BF blocks don't use them, instead they rely on the bearings being ground such that when they are tightened together the correct pre-load is applied, or they use shims. If you do use Belleville washers then you can put the ballscrew in tension, which is good since it increases the stiffness of the system a little (or a lot depending).
firstly, im getting the screws machined free of charge, why pay if i dont need to?
so, do i turn 12mm ballscrews down to 5mm to use magnetos or 8mm and just use ball thrust bearings. or in other words is 5mm sufficient if i ever hope for this machine to cut steel?