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tribbil

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I’ve been building my CNC since about 07, the Easy board I built blew the pc, sooooo I thought it was time for an upgrade, bought some boards from Routout and ordered new X & Y 10 x 2mm Acme thread from Merchant Dice, made a tap from the end of the rod, drilled out the plastic nut from 6mm that was worn to 19/64” and cut a new thread for the X axis nut, no slop, no backlash and was smooth, was well chuffed. Y axis might prove to be a problem because it will need a link from ¼” stepper to 10mm acme so will need something with a bit of bendy in it, and possibly a new short thread tap and ram it on with a bit of sticky stuff.
But I have a problem; X axis is through a cam belt drive from an old scanner with plastic gears, (I assume there called gears) it only has 20 teeth with a 1mm pitch as far as I can tell, and is rather small to cope with my larger 10mm thread, I would like to increase its size a little to allow a/ a keyway in the shaft b/ less strain on the belt. It would be a simple matter to copy the original in ally but to increase its diameter and get the right number of teeth with the right spacing just blows my mind, Does anybody know if there’s a program or formula for working out such things? I have been looking for some time now but must be asking the wrong question

 
Its a bit late and I may not have read your post correctly, but I will attempt an answer at your question.

I believe you may be over thinking your problem. You will be limited on a set number of diameters based on the pitch that you will actually be able to cut a full set of teeth on, no half-tooths 3/4-tooths etc. and when you pick one closest to what you want, count the teeth and divide by the teeth on the other gear and you will have your gear ratio, which you should be able to correct for in your software
 
Griff they are called timing pulleys. they are readily available by several vendors. As far as the right numbrer of teeth this cam be programed in you software later. a bigger gear or tin this case pulley will have more teeth .
Tin
 
OK
Thanks guy's for the explanations, I think I got something going here, if I take 12.4mm x pi/39 (the number of teeth & groves) I get an answer of 0.9998mm or something near 1mm, which is what some sites predicted about belt size, now if I 360/19 I get 18.94Deg per tooth (I think). Then I suppose I have to figure out how to actually do it, depth, shape & never used a rotary table before, should be interesting, even thought about using a slitting saw, does any of this sound right?

And thanks again for your time
 

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