workholding question from a new hobby machinist.

I

illillill

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What is the best or easiest way (not always the same thing) to mount a a pair of 3 groove step pulleys to the lathe so I can true it up. I want to keep it concentric to the center bore as much as possible.

I have only been using a lathe for a few days time, so I might be missing something simple. I am trying to true up the pulleys on my 4x6 HF band saw. I thought it would be an easy learning project, but I'm unsure how to mount the work.

Each pulley is visibly out of round. It's chewing up the belt & it is a source of vibration, that I'm trying to minimize. The center bore is a good fit on the shaft with no wobble. The motor shaft has almost no run out, but the pulley outside, grooves, & front/back looks to be off quite a bit as it spins.

I have a 3 jaw & 4 jaw chuck, live & dead centers, a faceplate, but no lathe dogs yet. The lathe is a grizzly G0516 w/milling attachment, so it's big enough to do the job. I don't think I'll butcher the part unless it comes loose when turning.

I've tried to put it in the 4 jaw chuck first, but I haven't got the hang of centering it yet, & I get way to much run out measuring from the center bore. The pulley was cast so I can't be sure that it was drilled perpendicular to the pulley groves or the faces of the pulley, so that's probably half my problem. I not only have problems centering the workpiece in the chuck, but I have problems getting the center bore parallel to the center axis of the lathe.

The 3 jaw chuck is worse than the 4 jaw chuck in regards to runout, so that's out.

I thought about turning it between centers, but I'd have no way to turn it without lathe dogs.

My other thought was to turn a hunk of scrap aluminum (I don't have any steel that size yet) down to the size of the bore & with out removing it from the chuck put the pulley on it & tighten the set screw, but I'm not sure that will work, even with a flat for the set screw to sit on. The other pulley I want to do this to has a different diameter bore. So I'd have to machine 2 pieces to a specific diameter, but not able to do that every time, yet. Like I said I'm new to using lathes.

Is there a way to do this that I'm not seeing? Or will one of the methods I thought of work? Thanks for any help. I did search but I always see people making new pulley's from scratch & I don't have any material to do that today.
 
Make a tightly fitting shaft that fits in the bore of the pulley. Mount one end in the chuck and the other should be supported by the tailstock.

Ray
 
I'm with Ray C on this project. I would put a sacrificial shaft in the lathe.( keep it as short as possible) Turn down a section that just fits the ID of the pulley.( file the last little bit to get a snug fit if you have too).
Put your pulley on & tighten up the set screw in the pulley. At this point you should have the pulley running true to the lathe. Your now ready to true up the Vees in the pulley
Phil
 
Actually, you'd be better off mimicking the motor shaft as closely as possible. If it has 0.002 clearance, so should your mockup shaft. That way it will run exactly the same on the motor. Just take some careful measurements from the shaft and turn your arbor as close to it as you can, and lock the pulley onto it without removing it from the machine. If you just snug the set screw(s) enough to mark your arbor, then file a flat, or turn a relief groove in that location, when you back off the set screw(s), there will be no upset(s) to hang the pulley bore on.

Normally, I would agree with the guys before me as far as getting concentricity correct between OD and ID, but not in this specific case, allowing for the motor shaft to be undersized.
 
illillill said:
What is the best or easiest way (not always the same thing) to mount a a pair of 3 groove step pulleys to the lathe so I can true it up. I want to keep it concentric to the center bore as much as possible.

I have only been using a lathe for a few days time, so I might be missing something simple. I am trying to true up the pulleys on my 4x6 HF band saw. I thought it would be an easy learning project, but I'm unsure how to mount the work.

Each pulley is visibly out of round. It's chewing up the belt & it is a source of vibration, that I'm trying to minimize. The center bore is a good fit on the shaft with no wobble. The motor shaft has almost no run out, but the pulley outside, grooves, & front/back looks to be off quite a bit as it spins.

I have a 3 jaw & 4 jaw chuck, live & dead centers, a faceplate, but no lathe dogs yet. The lathe is a grizzly G0516 w/milling attachment, so it's big enough to do the job. I don't think I'll butcher the part unless it comes loose when turning.

I've tried to put it in the 4 jaw chuck first, but I haven't got the hang of centering it yet, & I get way to much run out measuring from the center bore. The pulley was cast so I can't be sure that it was drilled perpendicular to the pulley groves or the faces of the pulley, so that's probably half my problem. I not only have problems centering the workpiece in the chuck, but I have problems getting the center bore parallel to the center axis of the lathe.

The 3 jaw chuck is worse than the 4 jaw chuck in regards to runout, so that's out.

I thought about turning it between centers, but I'd have no way to turn it without lathe dogs.

My other thought was to turn a hunk of scrap aluminum (I don't have any steel that size yet) down to the size of the bore & with out removing it from the chuck put the pulley on it & tighten the set screw, but I'm not sure that will work, even with a flat for the set screw to sit on. The other pulley I want to do this to has a different diameter bore. So I'd have to machine 2 pieces to a specific diameter, but not able to do that every time, yet. Like I said I'm new to using lathes.

Is there a way to do this that I'm not seeing? Or will one of the methods I thought of work? Thanks for any help. I did search but I always see people making new pulley's from scratch & I don't have any material to do that today.
Click to expand...

If you have a Harbor Freight store near you call them for an exchange. They are were good about exchanging their machines. Should have to repair a new machine.

You are talking about an arbor with a bolt clamp. Make sure the shafts that the pulleys are mounted on to see if they were not bent. If it was mine I would follow the advise of the other posters. Mount the pulleys in a four chuck.
 
Thanks, that is what I was going to try unless someone had a better idea.

Will Aluminum work for this shaft? The only thing I have that is the right size is 6061-T6 aluminum rod. I'd have to machine it down to 14mm (.5905 inch). I know i can cut the aluminum to that size (eventually), but with the added rotational force of the pulley will the cutting forces bend the rod? Like I said I'm new, & being overly cautious. I will be taking light cuts, but there will probably some chatter as it will be interrupted cutting. I'm only going to clean up the pulley to make it spin true. The pulley's are approximately 3 inches in diameter, made of cast iron & weigh I'm guessing about a pound.
 
If you have the stuff, put a center hole in your mockup shaft for both turning the shaft, and machining the pulley and use a cente in your tailstock. Aluminum wouldn't be the absolute best choice, but will work. Take your time and of course, slow the speed down when skimming the flanks of the pulley. You shouldn't have to take so much off that it will take long to do the job, so taking light cuts will not cause the aluminum shaft to bend. Of course, make as short as you can get by with.
 
I agree with mounting the pulley on a fabricated shaft supported by a live center in the tail stock. But a word of caution. After you get everything mounted, DON'T turn the lathe on until you rotate the pulley manually. This will let you visually check to see how far things are out of alignment. You may find that the bore is not perpendicular to the pulley by enough that you won't be able to true it up.

If that's the case you'll either have to see if HF will supply a new pulley or bore it out and press in a new sleeve and then key it for the shaft.

Hope that helps.

Steve
 
If the pullys are true to each other. Why not locate on one of the pully diameters in the three jaw chuck and true the bore up and then sleeve it back to the motor shaft dia.
 
I found a bolt that I was able to turn down to the proper size, to make the mandrel to hold the pulleys on like someone suggested. I used the power feed for the 1st time as well, & it made the bolt fairly smooth. I'm sure with some practice I'll be able to get a nice finish like I see on other peoples parts.

I was able to get the pulleys trued up nicely. They actually were machined pretty good, but the factory put a really thick & uneven coat of paint on the pulleys. This awful paint job is what made the pulleys look like they weren't spinning true. I only took the slightest amount of metal off the pulleys, mostly just removed that thick paint job. I noticed some voids in the castings, probably why they put so much paint on the pulleys in the first place. I checked the run out with my dial indicator & it was much less than before. I'm happy, I learned a bit about machining parts, & got the chance to turn aluminum even though I didn't use it, steel of an unknown material (bolt), & the cast pulleys. The cast iron made a terrible screeching sound, but they turned well, smoother than the steel bolt.

Thanks for the help everyone. I got a few hours more practice using my lathe & I feel much more comfortable using it now. I only turned the wrong handle once or twice this time.:))

Now I need to find a new project to continue learning how to do this machining stuff.
 
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