I need to make a 6 sheave pulley

[Janderso]

The fact that I've never turned a single sheave pulley shouldn't deter me from this project.
I do have it's opposite for dimensions.
This is for my 1930's (Canedy-Otto, Royal 16- by Cincinnati lathe and tool) drill press.

My thoughts on how to begin.

1. Drill and bore 6" material to spec.
2. Cut to length.
3. Mount on the arbor I had previously turned for concentricity, face both sides to final length. ( I'm turning between centers.)
4. Cut the taper-shape the cone..
5. Using a parting/grooving tool, plunge to sheave depth.
6. set compound to desired angle and cut half of the first sheave. Change to the opposite angle to finish the taper.
7. Move over designated length, lock the apron each time, plunge to final depth. Rinse and repeat.

I am working from smallest to largest.

Please critique my thought process. Go ahead, giggle and point out my mistakes. I can take it.

Thank you,
Jeff

 

[davidpbest]

Jeff, I’m a huge admirer of Keith Fenner. He’s taught me a lot. But if I were doing this, I’d approach the sequence the other way around. My thought is always to tackle riskiest and most complex operations first if feasible - that way if you blow it and have have to scrap the part, you don’t have a ton of time in it for the mundane operations.

I kinda cringe at using a parting tool off-angle, particularly the kind Keith is using (long/narrow, press-fit insert with no top clamp). That’s just asking for the insert to fly out of the tool holder, potentially damaging the toolholder insert seat and perhaps gouging your part. Anyway, my point is that cutting the angled grooves looks the most risky to me if done with a parting tool.

I’d first cut the groove profiles with the material chucked up in a 4J, no tailstock involved. Pick the least flexible parting tool available, preferably with a top-clamp to secure the insert. From my tool crib I would be using one like this, or if it doesn’t cut deep enough, then this one ,which has an incredibly rigid blade and is the best at securing wedge-type inserts that I have tried. Or you could grind your own profile tool with the required angle and go into the part perpendicular to the spindle axis.

Then, once the grooves are machined, proceed with boring, parting off, and facing the back side if necessary.

I’ll be interested to read other suggestions.

 

[Janderso]

David,
I have the first type of parting tool you mentioned.
Just to be clear, you would cut the cone in the 4 jaw and the sheaves prior to drilling and boring?
If chucked in the 4 jaw, the work is going to be long. How would you cut the length to size once the sheaves are completed?

Thank you,
Jeff

 

[davidpbest]

Just to be clear, you would cut the cone in the 4 jaw and the sheaves prior to drilling and boring?

Yes

If chucked in the 4 jaw, the work is going to be long.

Long hours, or part stick-out? I’m not following. I’m assuming the raw stock would be a cylinder of material 1” or more longer than the finished part. A 4J can secure a 10” stickout with ¾” of chuck jaw engagement in my experience. If the tailstock makes it more safe for you, then employ it.

How would you cut the length to size once the sheaves are completed?
Thank you,
Jeff

I’d part it off (or cut it off on the bandsaw) the fillip it around and face off the back side to bring it to length.

 

[rabler]

My inclination is always to try to turn features that are suppose to be concentric in the same setup. So I'd definitely try to cut the belt grooves and bore the center in the same setup without breaking it down. Chuck it up, drill/bore for the shaft first, and you could use that hole with a large center to add rigidity while turning the belt grooves, without pulling it out of the chuck. Least chance of getting things out of round/true.

 

[jbobb1]

I agree with David's approach. The only thing I would add is, if you use a tailstock and live center, use it only when roughing. Finish the bore OD's and grooves in one set up with no center. Concentricity and proper balance are important

 

[machPete99]

Just curious here, but does this pulley need to have an internal keyway cut?
I would think that could get problematic as the width of the pulley increases, at least with typical broach tooling.

 

[Janderso]

Long hours, or part stick-out?

Long hours for sure
No, what I meant was the area in the jaws would have to be removed at some point. I am not sure how I would trim that to size.
I'm thinking of using 6" Durabar for the project.
On the other hand, the material would be plenty snug with .750" in the 10" Bison 4 jaw.
I could probably live with it. Heavy pulley.
I haven't thought this all the way through, I'm just kicking the tires with you guys how you would go about it.

 

[Janderso]

I agree with David's approach. The only thing I would add is, if you use a tailstock and live center, use it only when roughing. Finish the bore OD's and grooves in one set up with no center. Concentricity and proper balance are important

I'm listening.

 

[Janderso]

Just curious here, but does this pulley need to have an internal keyway cut?
I would think that could get problematic as the width of the pulley increases, at least with typical broach tooling.

Yes, I was planning on using a broach. The drilling, boring and keyway was my first operation on my first attempt in my head