Power Feed

3

38super

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Apr 23, 2018
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Been wanting power feed in X and mostly Z. Bought a pair of 150in/lb units designed for a Bridgeport ($254 ea, free ship). Proto work is done and tested. Final assembly is waiting on lead screw ball bearing and a couple don't drill that just yet holes. So, below is a list of make, modify and buy parts.

Modify: Bridgeport power drive mount - this mount supports the power drive unit and replaces the right side Rockwell X axis lead screw bearing holder. The mount is modified to use the 3 existing 1/4-20 Rockwell. The Rockwell hole pattern interferes with the mid power drive mount holes but there are two other mount holes that can be xfer punched for 6mm drill n tap.
edit: Cut off threaded portion of provided worm gear. This leaves the threaded portion of the Rockwell lead screw exposed allowing the lead screw extension to attach.

Make:
Lead screw bearing holder (15x35x11), supports lead screw bearing and attaches to modified bridgeport power drive mount.
Power Drive sleeve - Mates power drive needle bearing and worm gear ID to Rockwell X axis lead screw OD. Requires 1/8" broach and customiaed woodruff key.
Rockwell X axis lead screw extension - Allows use of existing Rockwell dial & handle. Requires 1/8" keyway cut and woodruff key.
Bridgeport power drive worm gear chip shield - 3.125 x 0.22" aluminum disk, undercut to fit the power drive casting.

Buy:
15x35x11 seal bearing
3ea 1/4-20 CS
2ea 1/4-20 x 3/16 set screws

Will post pics of parts before/after. If there is interest, will work on dimension dwgs.

IMG_2189.JPG

IMG_2190.JPG
 
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Working the Z axis, the casting is spot faced. The power drive mounting holes are spaced wider than the Rockwell bearing flange. A bit of grinding is in my future. Will make a sacrificial sleeve to protect the shaft.
287880
Provided power drive mount - before & after.

IMG_2191.JPG
 
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Z power feed installed, gear reduction housing will impact the mill base. Webbing was machined away on backside of power feed mount to reduce the mounting flange diameter. This also reduces metal removal from the knee casting. Need to convert the Z crank handle from a drive pin to a plunger. Otherwise remove the Z axis handle during power feed use :black eye:.

287928
 
Last pic folks:
Stretched an O ring over the worm gear boss to retain the chip shield.
Z axis handle drive pin was drilled out, cross drilled/tapped (1/4-20) that hole for a retention device (weed wacker line).
Made a 0.240 plunger (shown retracted).
Added a thin washer to retain Z handle on drive shaft extension.
288110
Is it worth it? Kinda spendy, lot of fiddly stuff for mounting. X feed is very controllable, Z feed handle will smack your hand if the plunger is engaged. Do be careful.

TTFN
38super
 
For the X Axis feed, did you have to make the housings shown in attachment IMG_2191.JPG or is that only needed for Z axis?

Did you end up losing any X Axis travel?

thanks!
 
The modified BP pwr drive housing/mount are near same for X and Z, the Z pwr drive housing should be clearanced to clear the Rockwell knee casting (post #2, pic 1). Might save some grinding. I had previously marked the DRO X scale for max & C/L, still hits those marks.

HTH
 
FYI!! Same or similar BP power feed prices have dropped to half or less. This pandemic is having economic consequences, to our advantage.

Build somethin' *****in.

Beers,
38super
 
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