Advice please

[D-man]

Nice one Greeny! Its helical rack and pinion pal, I can get the pinion teeth count but not what mod it is

Any ideas it's not wrote on or anything.


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[Greeny]

Sorry don't know much about helical r&p.( or any r&p if truth be known )
I suppose you could move axis by hand & measure how far you need to move it to rotate pinion 1 revolution.
This would give you a very rough but sensible number which you could then refine by trial & error.

Hopefully someone else will have a much better answer!

[JAZZCNC]

Mark it and rotate one ful revolution and measure distance moved.. . . Simplizzzzz

[JAZZCNC]

how many teeth on pinion and whats it's diameter

[D-man]

how many teeth on pinion and whats it's diameter

23 teeth and 32mm dia mate

[D-man]

OK so im getting round about 96.16mm for one revolution of the pinion.

96.16 divided by 8000 = 0.01202 steps per revolution ???

[m_c]

OK so im getting round about 96.16mm for one revolution of the pinion.

96.16 divided by 8000 = 0.01202 steps per revolution ???

Wrong way to think about it.
You need steps per mm.
So if it takes 8000steps to move one pinion rotation of 96.16mm, then you divide the 8000 by 96.12, which gives 83.19467554 steps per mm.

[D-man]

Wrong way to think about it.
You need steps per mm.
So if it takes 8000steps to move one pinion rotation of 96.16mm, then you divide the 8000 by 96.12, which gives 83.19467554 steps per mm.

I did try it that way but didn't want to mention in fear of looking daft, as I calculated it as it was written

Cheers for the help lads much appreciated.

Attached a few pics just in case I've missed or got something wrong









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[JAZZCNC]

OK so im getting round about 96.16mm for one revolution of the pinion.

96.16 divided by 8000 = 0.01202 steps per revolution ???

Nah wrong got it wrong.

You now have distance pinion travels for one rev which is 96.16 but you have 5:1 ratio so this drops to 19.232 for one rev of the motor which is the affective pitch. So now simply divide 1600 by pitch to get the steps per mm ie: 1600/19.232 = 83.194 steps per mm

Doh didn't see MC done it.!

[m_c]

23 teeth and 32mm dia mate

1.25MOD is 32.69mm OD.
24DP is 1.09" (27.68mm), and 20DP is 1.308" (33.22mm), and 22DP does not appear to be a common size.

So assuming 1.25MOD and me reading the correct number from the chart, gives a pitch of 3.926mm per tooth, or 90.289mm for one rotation of the gear.

Or to assume 20DP, it would be 91.7194mm per rotation.

Are you sure it's a 23 tooth gear?
As even working backwards from 96.16mm, it doesn't fall on any common tooth size.
That's assuming I'm not making a complete hash of the calculations.

Off course, easier option would be just to measure the distance over as many teeth as possible and calculate the tooth pitch that way.