Converting 220v 50Hz to 110v 60Hz
It depends totally on your appliance motor.
If the motor is a universal motor (it has brushes), then the frequency is much less important. In this case a simple 220/120 transformer will work just fine providing it can support 2A at 120V. 

If the motor is a 60Hz AC synchronous variety you will lower both the speed of the appliance motor and increase the losses in the motor (so it gets hotter). 

Since you gave no idea of the appliance or motor type it's hard to judge what might be the effects of a lower operating frequency. 

Update:

Since you now have given more information, I would suggest that the frequency (50 or 60Hz) will have ABSOLUTELY NO impact on the tool.
The manual shows that this is a speed adjustable application. These types of motors are almost always a 'universal' brushed motor with a phase controlled speed adjustment.
Today we start to see BLDC motors used in some tools, but this does not appear to be one of those (they have an SMPS power supply).
As I said, IMO all you need is a 220/120 voltage convertor and your tool will work fine.    

I would recommend that you buy a voltage convertor that clearly supports your 175W load (though I didn't see this power rating in the manual). Don't buy a 'travel adapter' as many are based on an autotransformer and can be very hit an miss in terms of reliability.
Something like this is ideal. No bells and whistles and clearly just a transformer (though this one is an autotransformer it's ideal for double insulated tools).