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How should I attach the bevel gear for my power feed

F

fixerup

Super User
I am making some progress installing the power feed on my X axis for my milling machine. The support mount is completed, just need to clean up the edges to size. This week-end I will make two 3/4" -20 retaining nuts to secure the lead screw via some thrust bearing.
Then I need to secure the bevel gear to the lead screw. The bevel gear has a 5/8" bore with a 1/8" keyway. My milling machine lead screw is 5/8" but doesn't have a keyway feature and no threads to secure the bevel from sliding in the keyway. Would it be acceptable to drill a hole through the bevel gear shoulder and lead screw and then put a
1. 1/8" spring pin , or 1/8" aluminum pin which could shear in case of emergency Doh!
2. drill and tap the bevel gear shoulder for a set screw which locks to the lead screw
OR
3. remove the lead screw cut a keyway slot, reduce the diameter of the end of the lead screw, cut a thread for a locking nut to secure the bevel gear and make a new handle for manual use.

I like option 1 and 2 because I don't need to heavily modify the existing lead screw, I need just one through hole or a dimple for the set screw. To make sure I have the proper spacing meshing between the bevel gears I would put a .030" shim before drilling the hole and then adjust the shim for a 2 degree movement of the bevel gear meshing.

So far all the power feed I have seen don't have set screws or through pins. I thought it would be a good idea to ask for your thought before I do the irreversible.
Any advise is appreciated

The picture shows the end of the lead screw and the long bevel gear shoulder with the thread use for the locking nut for the .125" scale dial.
20240314_214932.jpg
 
I put 3 set screws 120 degrees apart & haven't filed flats in my leadscrew(yet) as it hasn't been an issue, but if it becomes one that's what I will do as well.

Only been using it for a month but have been using it quite a bit.
 
On my previous CNC converted mill I used belt to gear driven steppers. The gears were attached to the leadscrew with two grub screws with slight divots and no slippage over many years. I do like Jswain's idea of three screws, the 120 degree separation just seems like a good idea.
 
Thanks you all for the input. Three set screws will definitely secure the bevel gear properly. Will do.
Today I made the 3/4"-20 nuts which keeps the lead screw in place. To make an internal threads I usually test my threading fit progress with the mating screw. I can't remove the lead screw from the mill easily without moving the mill away from the wall or removing the mill table. So I made a test stub screw to specification using the 3 wires to measure .717" . Proceeded to make the nut to fit my test screw. Once the test screw fitted I then removed the freshly threaded nut from the lathe chuck and tried it on the lead screw. Bingo it fitted like a glove. Those three wire thread measuring tool don't get used often but definitely saved my bacon today.
The picture shows a 3/4" dia rod of freetanium steel ( electrical grounding rod I found on the side of the road) with the famous three wire. Note the mic shows .755. Which calculates to .755 - .0437= .711" I was off spec by .006" . My cutter could of used stone honing to achieve better small cuts.
Below the mic you can see the lead screw and thrust bearing.
20240315_102022.jpg
lite cuts.
 
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