Crowning a pulley for a flat belt Question

[Jim Dobson]

Crowning a pulley for a flat belt, been trying on some ali before moving onto brass using the top slide set at 1° + and then set at 1° - and it ain't an easy exercise to achieve a simple crowned pulley!

Any hints on how to do this? I thought this was going to be really simple, its kicking my arse!

 

[darkzero]

What type of issues were you having? I recrowned the drums on a HF belt sander I used to have. Was the first & only time I ever tried crowning something. It came out fine, well it fixed my belt tracking issues. The drums were plastic & were 6" wide though so that probably made it a lot easier for success. I also did 1° on about 1/3 of the ends.

 

[Jim Dobson]

G'day Will, I can get the first crown done coming in from the tailstock to the chuck to the top of the crown. Its the next one going away from the crown again to the chuck that keeps stuffing me up. I'm close to resorting to using a file.

 

[darkzero]

Jim, as in the chuck getting stuffed with chips? Or are you having tool clearance issues? I'm assuming a pulley for a flat belt is pretty narrow, say like 1-3" wide or so? Can you mount the pulley on a long mandrel to turn between centers to give you more room to work with? Or flip the pulley after you've done one side so you can do the other side also coming in from the tailstock side?

 

[darkzero]

And if it is aluminum chips/stringers stuffing up your chuck, you shouldn't have that problem when you do the brass one. You won't get them stringers with brass like you would with aluminum.

 

[Jim Dobson]

G'day Will, sorry mate I should have been a lot more clearer.
I'm trying to make (in the end) a drive pulley out of brass approx 1" in diameter and 1" wide and bored for a 6mm shaft out of bar stock with just a gentle crown in the middle to take a small flat belt (its to drive a model steam accessory).
Chucked up the brass and thought it would be a super simple and quick job. Found out that it wasn't working out like that and stopped wasting brass and went to ali to try and work out how to do it.
Not sure if I'm just having a brain fart here, but its got me stuffed.

 

[Ulma Doctor]

maybe i'm misunderstanding, your misunderstanding...

if you turn your compound to cut a 1° taper, to the headstock and use the compound to crown the desired portion of the pulley,
you could then turn the compound 90°
turn the tool post 90° to the work
from that position, move the carriage to achieve the desired start point for turning the second 1° taper

if i have misunderstood your problem, i apologize in advance

 

[Flyinfool]

Some pics of the problem might help us.
What you described in the first post is how I do them.
When you say stuffing you up, what exactly do you mean? What problem are you having?

WHen crowning for a falt belt idealy you want the surface a radius, that is real hard to do on a manual, simple on a CNC. The ones I do have 1/3 of the belt width as a flat diameter and just the ends tapered at ±1°.

 

[Jim Dobson]

Thanks all, managed it finally, that camber is 1.5° -

 

[Ulma Doctor]

very nice!!!