Holding a timing pulley to open bore

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rronald

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I want to bore an aluminum 40 tooth T5 pulley for a much larger shaft.

I'm replacing the gear on the spindle that normally drives the change gears for my PM-1130v lathe. In place of the change gears, I now have an encoder for an Electronic Lead Screw (ELS). The encoder is driven by a T5 timing belt so the spindle gear needs to match T5 timing belts.. Currently, I have a 3d printed gear in place that probably would work long term. But, I'd already ordered an aluminum pulley and would like to make it fit.

The gear I've ordered is from Maedler. It's a 16224000. Looks like this:
1704128845740.png
I plan to pry/press/hammer the flanges off, so it should end up like the one to the right in the picture. The pulley OD is 62.82 mm. It comes with an 8mm bore...which is just a tad smaller than the 48 mm bore that I need. :) I think in the above picture, the bore is about the size of the visible hub. So almost everything except the toothed area is going to be removed.

To cut this on a lathe, I was thinking about 3d printing the pieces shown below. The teeth and the dimensions will match the pulley. I've got 5mm of plastic "behind" the pulley so that there's space to do the bore w/o cutting into the 4-jaw chuck jaws.

I have all the expertise of someone who is just starting at this. Does this seem like a reasonable approach for workholding? The lathe seems to be the appropriate tool for the job, but I do have a CNC mill (a printNC) and I probably could mill the bore area.



1704128645631.png
 
so rather than hammer the flanges off. Cut them off on the lathe. There is so much less that can go wrong with that. Just cut until they disappear.
You can make a mandrel to mount the gear on and turn them off.

Once they are off, you can use your quadrants to hold the gear, or simply take a piece of metal strapping (I have thin copper and brass) that I can wrap around the gear, and that will allow the gear to be placed in a 4 jaw or less desirable a 3 jaw. zero the 4 jaw on the existing hole, then bore it out.

That's my method.
 
If I interpret your post correctly you will ultimately be machining that shoulder off by boring? If that's the case, grab the pulley by that shoulder in a 3 jaw and machine those flanges off. You may need to use a parting tool for the one by the chuck. Then chuck the pulley up in a 4 jaw and bore the hole.
 
These tooth pulleys are often only welded about the core, liable to come apart too soon and be projectiles from the four jaw. I did enlarge the bore of and dismantle some years ago for use of encoders mounting to a car driving simulator. I had some extra belting laying around, cut it to lengths so to go 90% the circumference, 2-3 layers so the 4 jaws are clamping the rubber belts only. Pass the boring bar and the rings fall off. Front one hangs on the boring bar, the second ring gets caught up in the spindle bore of the lathe.

03001a0e.jpg
 
After de-flanging I would use a piece of pvc pipe to grip the pulley around the outer diameter which will protect the teeth. Cut slits in the pipe.
Maybe use pie sections of pipe if you can't get a snug fit with a single piece. Mount in your 4-jaw and indicate the hub
You might check that the hub is concentric with the teeth first- you never know- could be off and ruin your efforts

One thing I found with these pulleys is if you specify a certain bore diameter from the vendor it may be off center and off size.
Best is to buy smaller bore and bore it yourself to size like you are doing
 
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Why knock off the flanges!

Hold the gear by them!

Just leave them in place, keeps the belt from wondering.

Sent from my SM-G781V using Tapatalk
 
Usually the flanges have runout
Plus they are pretty flimsy and might collapse
 
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Alexander McGilton said:
These tooth pulleys are often only welded about the core, liable to come apart too soon and be projectiles from the four jaw. I did enlarge the bore of and dismantle some years ago for use of encoders mounting to a car driving simulator. I had some extra belting laying around, cut it to lengths so to go 90% the circumference, 2-3 layers so the 4 jaws are clamping the rubber belts only. Pass the boring bar and the rings fall off. Front one hangs on the boring bar, the second ring gets caught up in the spindle bore of the lathe.

View attachment 472879
Click to expand...
That's a good idea and I was pleased by the idea of using one of the two extra belts I ordered to find the right length for this project (my way of saying I bought one too small and one too large). Unfortunately, I realized that the extra belts I have are for the other drive used in my ELS (going from servo to output shaft) and are HTD 5M and not T5. However, I will see if they are close enough to use. They have the same tooth pitch and an identical pitch diameter....it's just a different tooth shape and it might be close enough for holding the pulley.
 
Clamping on the pulley teeth will not always square up the pulley. I would glue the pulley's to a piece of round stock (faced and turned) using super glue and than put the package in the 4 jaw chuck to get the hole on center. When done, boil the 2 parts in water for half an hour to separate the parts or put them in an ultrasonic bath and some acetone.
 
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