Cheap DIY cast iron pulleys

[Graziano]

I've been making some pulleys for my latest project and was talking to my machining guru about making them. My friend pointed out that aluminium is easy enough to machine but tends to wear out fairly quickly, mild steel on the other hand tends to rust in this climate if not used all the time and after a while the rust pits chew up the belts. This left cast iron as a suitable material as it's slower to rust and lasts better than the aluminium. While I was racking my brains for a source of iron, my friend reaches into his cupboard and hands me an old body builder's dumb bell. Later on at the dump shop I spotted some more cast iron weights going cheap. I reckon some of you already have used cast iron weights for pulleys as they are the ideal shape and material for the job and would be fairly common, but I thought I'd tip you folks off for future reference :2tsup:.

Cheers,
Mark


http://www.woodworkforums.com/attachment.php?attachmentid=207274&stc=1&d=1336127094

[Ueee]

Thanks Mark,:2tsup:
The idea of using dumbbells has never crossed my mind. I'll keep my eye out!

Ewan

[jhovel]

That looks like a 2 groove M section pulley. I've not seen a dumbell weight that thick. Do you have a photo of the weight itself?
I have a few dumbell and barbell weights here, but nothing thicker than about 20mm - just bigger diameters.
Joe

[Graziano]

That looks like a 2 groove M section pulley. I've not seen a dumbell weight that thick. Do you have a photo of the weight itself?
I have a few dumbell and barbell weights here, but nothing thicker than about 20mm - just bigger diameters.
Joe

No, I didn't think to document the dumbbell before machining it, although it was a nice hammertone blue colour :D, I made a 96mm and an 80mm pulley from it to cut the 2880 rpm motor to 2400 rpm of the grinder wheel. The pulleys are 35mm thick overall, so the dumbbell ends were about 50mm thick to begin with as I had to machine a lot off the rough ends to clean it up.

Here's a similar but much better looking one I found on the internet, they are a one piece casting:
http://ak1.ostkcdn.com/images/products/P11045646.jpg

[Dave J]

I have seen them used for fly wheels and things like that, but never seen one used as a pulley, good thinking. I see it's a smaller M pulley, I was wondering how you got a double pulley out of a weight until I read the belt, LOL
Did you find any hard spots, or was it one of the better quality name brand ones?

If anyone is thinking of using a new one, just remember they are now Chinese and look at some of the stuff we get in precision machinery, so it would definitely be crap in weights.

Dave

[Graziano]

Dave, I have no idea of the quality, it had no markings on it. I had to use carbide to get through the outside skin as it blunted a piece of WKE45 tool steel in seconds. Once through the skin it machined fine. There was barely space to fit the two grooves in it as I was getting close to the undercut bit. The two 5mm grub screws are at the bottom of the grooves as there's no room elsewhere for them. The shaft hole is 5/8th of an inch if that helps with scale and it's 80mm across.

[Ueee]

You could easily bolt several of the long pole type removable weights together to make larger or stepped pulleys. (you can tell i have never gone to the gym) Depending on the bore required you may have to bush them, but thats about the only downside.

Ewan

[Graziano]

I forgot to mention is how the pulley is machined which was another neat bit of advice: the first part to be machined is the hollow in the side of the pulley. That lets you grip the casting from the inside of the hollow using the outside surface of the chuck jaws against the rim. After that you can machine the rest of the pulley without once removing it from the chuck: grooves, side, and bore are all done in one go and are wobble free. The rim however did however get a bit too thin as I reduced the outside to the right diameter and you are limited in how small you can make a pulley by your chuck jaw size.

Edit: Once the casting is gripped on the machined rim, I centre drill and bring up a live centre in the tailstock to help hold the pulley in position when machining and give it some stability.

[Graziano]

You could easily bolt several of the long pole type removable weights together to make larger or stepped pulleys. (you can tell i have never gone to the gym) Depending on the bore required you may have to bush them, but thats about the only downside.

Ewan

That's true, you could true up the sides and thread and tap one before bolting them together, come to think of it the holes would almost always have to be sleeved, still the sleeve could carry the grubscrews and could be shrunk in by heating the weights first.

[franco]

The type below are also good for making screw-on chuck back plates, adapter plates etc. Even new, where they are available separately from A Mart, they are a cheap source of cast iron discs. I have made a 160mm back plate, a 100 mm back plate and an adapter plate to fit a 3 jaw chuck to a rotary table from various sizes of these.

I was expecting to find hard spots in them, but the cast iron turned surprisingly well, with only one small hard spot in the 160 mm backplate.

After I spent some time doing slow interrupted cuts to get rid of the lettering on the first one some one suggested chiselling off the letters before starting machining, which saves a lot of time and the unpleasant interrupted cuts.

Frank.

[Graziano]

Franco, thanks for the heads up, never occurred to me to buy new, or to use them as faceplates, I needed some last year that size.

[aametalmaster]

I am always picking up older weights for future projects. The newer weights are thinner and have bigger center holes and way too much writing cast into the sides. The writing isn't sticking out its recessed so you can't turn it off without making the plate thinner...Bob

[Graziano]

I am always picking up older weights for future projects. The newer weights are thinner and have bigger center holes and way too much writing cast into the sides. The writing isn't sticking out its recessed so you can't turn it off without making the plate thinner...Bob

Bob, it sounds like they've made the weights look bigger for their actual weight, possibly to look more impressive. I've noticed a lot of the newer weights such as dumbbells are actually plastic with sand or something filing them, so usable cast iron may be getting harder to find.