When making a pulley, Steps?

I'm making a replacement motor pulley. At this point I've got the steps cut in, and a starter hole for the 5/8" bore I'm going for. But in the back of my head I've got this nagging doubt about whether the whole thing will end up concentric or not. Initially, I had a fairly large block of 4" aluminum, and I put it between centers and cut the smaller step in, and faced off both ends. Then I put the small end in my 4 jaw chuck and indicated it to less than .001" runout, and parted it. After that I drilled a 1/2" hole and will use a small boring bar to get to my 5/8" ID.

Seems logical in steps to me, but I'm still wondering if it might have been better to bore the hole for the shaft, then put the whole thing on the shaft between centers. It'll be my first pulley, and I want to make more eventually. Since I was unsure of myself, I felt I'd ask before making the final bore in the pulley.

Terry

I advise putting a concentric turned shaft between centers in the hole. You can put the shaft between the chuck and the tailstock center. Any error will be magnified by the larger diameters of the pulley. This will be revealed when you mount the pulley on the motor and turn it on. You will have to put in a set screw to keep it from rotating under pressure of a cut. There are tapered mandrels and expanding mandrels that are used for making true running pulleys also. Your set screw will have to be put in very deep to avoid being cut. You might machine the smallest did. step NEARLY to finished size. Then,drill and tap the bottom of the groove for the set screw. I'd file a good flat spot on the shaft to screw the set screw onto. Otherwise,if the set screw cuts a raised ring onto the shaft,it will be a job getting it out of the pulley,and will certainly gouge up the bore of the pulley.

Do not remove the shaft from the 4 jaw until the pulley is finished. File the flat spot while the shaft is in the lathe. You cannot loosen 2 jaws and put the shaft back in by tightening those 2 jaws. The shaft will not run true if you try this.

Made my first pulley this weekend.
5 step with a 1.125 bore.
.25 broach
Figuring out the grind for the forming tool was the biggest problem.
Used a 4 jaw. She stayed on the lathe for all processes until it came off for broaching.
Had to counter bore the back, as the broach bushing wasn't long enough.
Was easier than I thought.
However, I'm not sure I did it correctly.
This is doable for the HM.
Have fun with your project. I did.

Daryl
MN

when I make a pulley I measure the shaft on which it will mount. bore the pulley .0005 over this size put the set screw in and cut the keyway then I make a dummy shaft with keyway calculating depth of keyway with a slightly larger shaft with keyway cut in it I chuck it up and indicate it in. then I machine it to the mounting shaft size. I then put the pulley blank on the dummy shaft with key and tighten set screw the pulley will now run just how it will run on the mount shaft. I then skim cut all surfaces and cut the grooves, I cut the grooves with the compound set at the right angle each different range of pulleys has a different angle I have a set of browning sheave gauges that have all the angles listed on the different leaves. I machine the grooves with an carbide tipped parting tool yes it will cut in just the edge try it. have many pulleys for machine tools with great success also have recut worn out pulleys with the same method bill

I have made several pulleys and I usually try to cut them all in one go. That being said, I don't think pulleys for normal use need that kind of precision. I doubt that .010 concentricity error would be noticeable on pulleys used on ~1800 RPM motors, or even higher speed spindles. A lot of commercial pulleys are cast zinc and automotive pulleys (some of which turn 10,000 RPM) are certainly not precision made. If you are making pulleys for precision grinding machines that turn very high RPMs, maybe it's a big deal, but for what most of us on here do, I doubt very tight concentricity standards will make any difference.

I would have mounted it on a tapered mandrel so that I am cutting between centers. I would then be able to assure concentricity.
For most machines that level is not needed, but for a tablesaw, or mill I would want accurate precision pulleys to avoid hysteresis and vibration.

I agree with the arbor and centers , kind of hard to mess it up turned that way. Been done that way for many years. Concentric bore and diameters.

Turn the OD's, grooves and bore in one setup, concentricity is then assured without question within the machines abilities, is this a large part?

Meaning that it will have to be moved to a larger machine for finishing, otherwise I do not understand the question, please elaborate.

when you bore and cut of at the same time it will be concentric but as soon as you setscrew it to the motor shaft or whatever it will run out whatever the clearance between the pulley and shaft clearance is times 2 my method makes the pulley run truer because the pulley is made as if it were on the motor shaft. and yes it will not matter most of the time but aren't we trying to do things the best we can ? it is time consuming but its a hobby meant to kill time and make something better than alright why make it at all go to the hardware store and buy the cast junk they sell bill

Bill, while many people on this site will agree with you, there are others who see machining as a means to a different end, such as auto restoration or other hobbies, so spending extra time eliminating inaccuracies that likely will make no difference is not something everyone will be interested in. It's certainly not something I am interested in, as I have many projects piled up and a limited amount of time to accomplish gains to those projects. I purchase the things that I can and I make the things that are not available for purchase, including pulleys. Besides, what's the motor shaft runnout? How well is the motor balanced to begin with? I think taking reasonable efforts to maintain concentricity on a pulley is worthwhile, I'm not going to sweat the load if my pulley has 3 or even 10 thou of runnout, even on a milling machine, as the vibration from the tool will swamp any from the pulley. For those of you for which machining is the hobby, I say go for it if that's what makes you happy, but others may have other things that they enjoy killing time on.