Upgrading the CNC mill -3. Moving a threaded hole in steel plate.
by John
this is the new Y axis servo motor, sitting on its mounting plate, after the old servo has been removed
Unfortunately the existing M8 threaded holes in the mounting plate are just in the wrong position for the new motor’s 8mm mounting holes.
So, do I 1. make a new mounting plate and assembly? 2. machine or file the new motor’s holes to fit the old plate? Or 3. Fill the old mounting plate hole, then drill and tap new holes in the correct position ??
- seemed a lot of work 2. would have looked ugly and probably voided the motor’s warranty 3. Seemed tricky, but I decided to give it a go. If unsuccessful I could always revert to 1.
Filling the old holes. Could have used steel thread and silver soldered it into place. In retrospect, would probably have been the best option. Could have used steel thread and Loctited it into place…. decided against, in case subsequent machining softened the Loctite. Could have filled the old holes with bronze, and drilled and tapped new threaded holes…. well, for better or worse, that’s what I decided to do.
The new holes impinged about 25-33% on the old holes.
The old holes were bronzed. I improved my technique as I moved around the holes.
After cleaning up on the mill, the new holes were center drilled
Then drilled to size, and tapped. revealed that the bronze did not entirely fill the voids.
I wondered if the bronze would accept a suitable degree of tightening of the M8 cap screws, but all seemed fine. Note the jacking bolts, to prevent distortion of the weldment in the milling vice.
The bronze-steel sandwich did cause the tapping drill to wander slightly, but not enough to cause concern. Next time I will try silver soldering in a steel filler piece.
Meanwhile, I have been removing parts and wires from the electrical enclosure.
The servo controllers are removed. Bit of a rats’ nest hey! About 90% to go…
johnsmachines 
Hi John,
I want you to know that I read every word you write and study every photo to share about the fascinating projects you are involved in. While I have no experience operating – much less modifying – CNC mills and lathes, I do understand their control systems and how they operate and have dealt many times with rat nests of wiring.
You are intrepid to plunge into the bowels of these machines. It blew me away that you machined a new gear from scratch.
If I’ve been quiet these past couple of weeks, it’s because I’m in awe and unable to otherwise make comments of any use or particular value. But I sure do enjoy watching you progress with the rebuild.
Aloha,
Richard
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Thanks Richard. Your feedback is really appreciated. John
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BTW, why did you silver solder the holes in the plate instead of welding them?
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Hi Richard, the holes are actually filled with bronze. I didn’t fill them with weld because weld is too hard to drill and tap. As it turned out, the bronze was a bit soft, and when the drills hit the steel-bronze interface they tended to wander into the bronze, so were not absolutely straight and perpendicular to the surface. Next time I will make threaded mild steel inserts and Loctite them into place. I will post some pics. John
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Hi John
I thought I posted a comment last night cannot see it so will do it again.
Enjoy your videos very much please keep posting them. I did a cnc conversion on a bridgeport copy a few years ago and I know what is involved, you are going to have fun. Are you using Mach and what version 3 or 4. I use Mach3 and have put MSM screen set and love it, it has a great layout you should look at it.
Keep the videos coming.
Cheers
John
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Hi John, Mach 3. Dont know about MSM screen, so I will check it. Ignore my dummy spit. I will keep posting. John
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