Bridgeport Manual to CNC conversion...

[Davek0974]

Thinking out loud...

With the drive to the quill rack, probably from the left side as done in the FlashCut kits etc, without measuring i think the quill pinion does 2 full turns for full travel so about 75mm/turn, with a 4:1 or maybe 5:1 belt reduction from servo to pinion shaft, would that give enough resolution/torque - the motor would only ever do 8 or 10 full revs??

I could probably make a bracket pair which could take one or two layshafts which could offer much higher reduction ratios.

Maybe even look into worm-gear reduction.

Just working things through...

[Colin Barron]

Is there much backlash on the quill gear, i have seen a drive with a ballscrew on the front of the head.

[Davek0974]

No the quill pinion is pretty firm. Yes the screw on the front is a popular method because its the only place you can get a direct connection to the quill, trouble is its an awkward connection and i'm not happy with it yet.

[Davek0974]

Finally scraped up the cash for proper thrust bearings on the X & Y axes. Got Nachi P4 matched pairs from BearingBoys Ltd


I fitted them in DB or back-to-back style, seemed the best option here - the preload is taken up by the screw nut rather than the bearing retainer.

What a difference, smooth as silk now and no shims needed :)

Will measure backlash again to see what change it has made.

[m_c]

Dave, have you get any pictures of the existing setup/quill?

[Davek0974]

A few pics here...




The weak spot is the joint between the coupler and the quill - there is a flat recess milled on the quill about 15mm dia and i picked up on that face, it really needs more contact above and below the bolt but then you lose more z axis travel and thats bad enough already.

Its the little round boss on the right of this part...

[m_c]

How much Z travel would you lose, if you bridged between the current single bolt mounting, and the end of the quill (where you currently clamp on the second spindle bracket)?
.
If you were to bridge between the two, then you should get a stable piece to then mount the ball nut to.