2 X 48 Belt Grinder (again)

[TOOLMASTER]

go sloooooooooooowwwwwww

like 50

 

[rwm]

After the last post I decided to try the slowest speed possible. My lathe will only go down to 60 rpm. I used the same reamer to finish the deeper half of the bore at this speed. It didn't seem to make as much vibration but when I examined the bore I had the exact same chatter pattern. I have used reamers in the past and never had this issue. I realize I started too fast the first time but 60 rpm should be sufficiently slow. Could it be that once the bore has chatter marks it becomes impossible to overcome?
In any event, I took a light finishing pass with a boring bar and I have a reasonably snug fit on the shaft. I hope it will not loosen when the high spots wear down. I think this will be functional but this is not the kind of work I like to see leaving my shop. I may eventually re-make the whole darn pulley. But it was not a cheap slug of aluminum.
I invite further comment. Should I trash this reamer and buy a spiral cut?
Oh yeah, I cut a key way in this mess.

Now I have to drill a hole and hit the keyway! Or should I avoid the keyway. I have seen it done both ways.
R

 

[Chipper5783]

I feel your pain. How much material were you taking with the reamer? You really don't want to take too much, but you also don't want to take too little. I'm sure there are plenty of formula and tables. My guess is that aluminum would be pretty tolerant of light cuts with a reamer. On a critical hole, I'll drill quite a bit under size, then bore it to near size, then finish with the reamer.

With this being your driving wheel, make the axle between centers, then just secure the shaft with Loctite. You can then skim the wheel OD and it will be very concentric (should run nice and smooth, and the chatter in the bore will not be an issue - makes a nice surface for the Loctite to grab).

 

[FOMOGO]

I would agree with Chipper above, you need to be closer to your finish diameter before reaming. Work is looking good though. You can always bush it if it proves to be to big, but you'll probably be fine. Mike

 

[mzayd3]

I agree with both chipper and fomogo. I learned that 1/32" is about the most you want to remove with a reamer.


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[f350ca]

I'll agree with less of a cut and lots of WD40 for lube. I usually ream at about 1/2 the speed you drilled the hole and feed the reamer aggressively. And retract often to clear the cuttings or you'll ream over sized.

Greg

 

[rwm]

Thanks for the tips guys. In summary it sounds like too fast a speed and too deep a cut. I should have bored it closer to final ID. FYI, this wheel will be direct drive off the motor so no loctite. I thought about sleeving it but that would end up being more work than re-making it correctly.
R

 

[strantor]

I thought about sleeving it but that would end up being more work than re-making it correctly.
R

Why do you say that? I've never actually done a sleeve but it seems to me like it would be a simple affair.
You could take a few light cuts and then press fit an 11/16 brass rod in there and then drill out the rod

 

[rwm]

True...well I wanted a keyway so I would need to bore the hole out even larger, say like 1" and then press in a brass rod. I was concerned about getting the right fit between the sleeve and the pulley. I will go that route if the pulley loosens in use. Thanks!
OK...next issue I need help with. The set screw path is 2.5" deep. My 1/4 x 20 tap is not long enough to reach the bottom. How do I deal with that? Can I make some kind of tap extension?
There's this from McMaster but they are pricey:

R

 

[chips&more]

You cannot make this pulley in one operation on the lathe then set screw it and then mount it on the motors shaft and expect it to run true. The chances of it running true with this process are slim to none. If you want it to run true, you must finish the bore, leave the OD roughed out and put in the set-screw(s). Then return to the lathe with a turned shaft the diameter of the motors shaft in the chuck. Mount the unfinished pulley, probably using a ball bearing/dead center in the tail stock. And then finish the pulley. Hope this helps…Dave.