Approaches to turning a spool-shaped object (capstan drum)?

[Jimsehr]

I have made thousands of parts in production or one offs similar to what you are trying to do. My go to way is an ID collet. Can you use a 5c collet on your lathe ?
I would chuck part drill and bore 2.06 bore then go to an Id collet. The Id collets are turned in place so you can reload part as many times as needed and maintain concentricy. You can then move the id collet to a mill and drill and tap part there also bore the 1 inch dia bore.
Hardinge makes Id collets but they are real pricy
Rovi also makes good Id collets and they go up to 6 inch dia in 5c collets. I have been making my own Id collets for over 60 years . And I mostly make about 20 blanks at a time. but for one piece you might find a Rovi set up for cheap and you will have it for years. You just replace the heads for different sizes needed.
Rovi has a you tube demo of how to use them if you want to see them working.

 

[verbotenwhisky]

Hi All,

I'm thinking about a hobby project for which I want to turn a small capstan drum to fit on a shaft. I worked up a conceptual model (drawing attached) with function but not machinability in mind and have since been trying to think through how it could actually be turned. I think I see a couple challenges to actually making this design:

1. My first thought was this seems similar to a pulley, and the standard way I see for turning pulleys is to drill/bore out the center bore, then mount the part on a mandrel and turn the OD features. But seems a tapered or other mandrel wouldn't provide good support for a piece this long, especially considering the center bore is only about half of the part length.​

​

I think mounting this in a chuck without tail support would probably work, though it would require 2 setups (drill/bore the shaft bore and OD in one setup, then flip and bore out the cavity). Securing it for the second setup could be a little tricky, but maybe this is still the best way?​

2. Tool/tool holder clearance when turning the external recess between the "spool ends." I imagine I would use several partial depth cuts with a parting tool to make a starting "kerf" at one end to avoid plunging the turning tool, but seems the angle of the tool/holder required for turning to the far shoulder could interfere with the part at the start of the cut.​

Totally open to changing the design to make it easier to machine, e.g. making the end "flange" a separate part that gets welded/screwed to the main body or...

Would appreciate if anyone has any thoughts on this--thanks for reading!

Mike
View attachment 464369

I think I would use a piece of stock longer than the part and turn the outer-features between centers then bore it out, just me...

 

[MikeMT]

Thanks for the ideas Jimsehr and verbotenwhisky. Jimsehr I don’t have 5c collet capability but I’ll file that approach away if I ever do.

Thanks again everyone!

 

[Jimsehr]

What lathe do you have and what nose piece does it have.
And do you have soft jaws on your chuck.

 

[Larry$]

I don’t have 5c collet capability

5C collet systems have some drawbacks, But are my go to for small parts (Up to 1.25" diameter.) They can hold work with quite short amounts in the collet. The chucks have a longer very smooth nose that is finger friendly when polishing right up to the chuck. An internal depth stop can be used. I have 5C collet blocks and spin indexer. Both handy devices that use the same collets. Another rabbit hole for you to consider.

 

[MikeMT]

What lathe do you have and what nose piece does it have.
And do you have soft jaws on your chuck

Lathe is a PM 1130V with D1-4 spindle mount / MT5 internal taper. As for soft jaws…sigh, still on the todo list.

5C collet systems have some drawbacks, But are my go to for small parts

Some day I’d like to jump down that 5c collet rabbit hole, they seem very useful/convenient for a number of use cases.