making a pulley on a lathe

[Dan]

Want to ask advice on my first project. I did do a good long look around and did not find (not that it is not here some where, I am sure) this exact information.

I need to make a 6" sheave/pulley for a gear reduction that will drive a motorized bicycle. The belt is asymmetrical. My mill/lathe is a HF multipurpose machine model 5980.
http://images.harborfreight.com/manuals ... 9/5980.PDF

What I am planing is to use a mandrel,
http://www.use-enco.com/CGI/INSRIT?PART ... A=262-3310

If this is advisable, do I need an arbor press to properly set the mandrel?
http://littlemachineshop.com/products/p ... &category=
Or is there some other method you would suggest?

Any thoughts on this are greatly appreciated.


I am excited, a whole bunch of money and time has gone into this and is almost time to start making chips!
(Some will be to big and some to small, but hey.)

[TGriffin]

The 6" diameter is going to be pretty large to turn on a mandrel. You would need to take really light cuts to keep it from spinning. A better bet would be to mount the blank to a faceplate or hold it in the chuck to do the work. Make sure you turn the diameter and the bore in one set-up to maintain concentricity.

Tom

[Torch]

The link goes to a 1/8" mandrel. No way that's going to be heavy enough for what you want to do, so I'm hoping you meant to use something heavier. I would think something more like 5/8" for a 6" pulley.

How do you intend to affix the pulley to the eventual shaft? Key? If so, then perhaps you could make your own mandrel with a key, bore the hole and broach the keyway. Make it a slip-fit and secure it with a bolt.

As Tom said, turning a 6" pulley with a 1/2hp lathe is going to be a challenge, depending on the material. Light cuts will work IF the material chosen doesn't work harden, and you can gear down the spindle speed low enough. Aluminium should be doable, and rust-resistant. The lighter weight could be an advantage for a bicycle too. Or maybe a free-machining steel (12L14 or 1144) or grey cast iron. Those will rust so you might not want them for a bicycle. You might get away with 303 or (xxx) 416 stainless steel. Not the most rust-resistant, so I wouldn't use it in a marine application but might be OK for a bicycle. Considerably tougher than Aluminium, however.

[Harold_V]

You might get away with 303 or 316 stainless steel. Not the most rust-resistant, so I wouldn't use it in a marine application but might be OK for a bicycle. Considerably tougher than Aluminium, however.

The issue of rusting can be addressed by passivation. Even if stainless is not passivated, unless it's subjected to a severe environment (sea spray), it will rust only superficially. The passivation process removes free iron from the surface and creates a barrier, preventing oxidation. It is the free iron that oxidizes.

300 series stainless and chlorine do not play well together

If one were to make the decision to make a sheave from stainless, with such a small lathe, 303 (S or Se) would be pretty much mandatory. It would prove to be a nightmare with 304 or 316.

.

Harold

[Torch]

It would prove to be a nightmare with 304 or 316

Oooops! Sorry about the typo. I meant 416 might be suitable for that lathe, not 316! I have edited the original.

[Dan]

Thanks all! Wow, glad I asked and I do thank you for taking the time to es-school me.

I was planing on using aluminum. 1" thick so as to leave .125 for the "ears" (enough, to much?)

"How do you intend to affix the pulley to the eventual shaft? Key? If so, then perhaps you could make your own mandrel with a key, bore the hole and broach the keyway. Make it a slip-fit and secure it with a bolt."

Cool Torch, that will work and is inexpensive. Am going to invest in a face plate as you suggested Tom. I did not know they existed and my dinky 4" chuck just does not cut it for a lot of things.

Harold, "passivation" Had to look that up. Fascinating. http://en.wikipedia.org/wiki/Passivation_(chemistry)

$17K, 2 years and 8 months of school has gone into making this happen. (and I built a workshop in the backyard)((Insane you say? Not according to the voices in my head))

Thanks again Tom, Torch and Harold!

Dan

[warmstrong1955]

The keyed shaft is a good idea for an arbor. I made some impellers not long ago, and that's what I did, and it worked quite well.


I faced, bored, and broached the hubs, setup and welded them together, and then turned the OD.
To turn the OD, I bought some keyed 1018 shafting from Enco. Real easy....just cut off a piece in the saw and deburr the ends. Chuck it up true to the world, and ready to rock and roll. With your pulley, I'd drill & tap the end, and hold it all tight with a capscrew & washer. My assemies had a couple of setscrews in the hubs, which was plenty adequate to hold 'em on the arbor.

http://www.use-enco.com/CGI/INPDFF?PMPA ... PG=INLMK32

Bill

[Torch]

I was planing on using aluminum. 1" thick so as to leave .125 for the "ears" (enough, to much?)

I've made a couple of pulleys out of aluminium quite successfully, but one was for a cogged belt and the other for a multi-rib belt. Nothing for a V-belt, so I can't help you much there. V-belts grip by exerting pressure on the sides of the "V", not the root, so there will be more outward pressure than the cogged or multi-rib varieties. How many HP are you planning on? I'm sure there's a reference work on the web somewhere that will offer some guidance on the required dimensions based on the HP to be transmitted.

[Dan]

Cool Warmstrong. That link is temporally down but got me looking around and found this. For 20 bucks, seems ideal. http://www.fastenal.com/web/products/_/ ... ameter:950|~

I did not consider that, Torch. I think most manufactures use aluminum and I have had one on a motorbike for a few years (made by a friend who is a pro) The engine that will drive this is 2.5 HP. Got me wondering though. If that is the best choice.

http://www.bicycle-engines.com/49cc-Gas ... Shaft.html


Dan

[Torch]

Ummm, that collared keyway bushing is what you would use to guide a broach. The slot is way too deep, probably too wide, and I suspect it's hardened. Not something you can readily drill and tap.

2-1/2hp doesn't sound too bad spread out over a 6" pulley.

[warmstrong1955]

Torch is right about the keyway bushing at Fastenal. Wrong thing. That's for broaching.
If you can't get the Enco link to work, close your browser and then give it another shot after you restart.
If not:
http://www.fastenal.com/web/products/de ... rchMode%3D

http://www.mcmaster.com/#keyed-shafts/=oqcf6j Shorter lengths are available at McMaster, and are 1045.

I bought what I needed at Enco, price was better, and 1018 is fine for a weld fixture and lathe arbor.

Bill

[GlennW]

Why use a mandrel?

Start with stock just s bit wider than the pulley will be and grab it on the OD with the chuck jaws.

Face the exposed side, turn the OD, groove it, then bore it.

Flip it over and face the other side to get to the required pulley width.

Everything will be concentric if done properly.