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koda2
06-11-2012, 11:55 PM
How are pulley sheaves typically machined on a lathe?
I am actually trying to make a set of 2" diameter bending dies for 5/8" OD SS tubing, so each "sheave" would actually only be turned to a depth of half radius.

Dave A.

x39
06-12-2012, 12:10 AM
I've made sheaves in aluminum with radiused bottoms by plunging a standard parting tool almost to depth, then following it with a tool ground to the desired radius. The ones I made had a 1/4" radius, and I made the initial cut with an 1/8" wide parting tool. Worked for me, YMMV.

lakeside53
06-12-2012, 12:21 AM
For most belts the bottom doesn't have to be "radiused"; the belt doesn't ride on the bottom.

Rough it out, then just figure the two angles and cut the sides with the compound. A small boring bar works well.


Edit... hmmm... I see you don't want to make a pulley! Rough it out, then make a "form tool" from HSS for the final cuts. Big radius and plunge cutting in steel usually mean chatter unless you keep it all very rigid.

oldtiffie
06-12-2012, 04:39 AM
I think the OP has one of these in mind:

https://www.machineryhouse.com.au/Bender-Accessories

For something like this?:

https://www.machineryhouse.com.au/Manual-Pipe-Benders

winchman
06-12-2012, 06:58 AM
Rough out the part on the lathe, then put it on the rotary table, and finish the shape with a 5/8" end mill. Looks sorta like this on the mill:

http://i431.photobucket.com/albums/qq32/sbwhart/Tool%20Post%20Grinder/100_2534.jpg

x39
06-12-2012, 08:39 AM
Rough out the part on the lathe, then put it on the rotary table, and finish the shape with a 5/8" end mill.
Interesting approach, I like it!

TGTool
06-12-2012, 10:13 AM
Marv Klotz's programs can be used to get a set of X-Y coordinates to rough it out with a cutoff tool. Or the same could be generated with a spreadsheet or CAD program.

Finishing could also be done with 5/8" drill rod, hardened on the face and used as a tangential tool. Setup permitting, that could mean putting the rod in the boring bar holder, rotating it to be transverse to the ways and then hoisting it up the holder to the "over the top" position.

metalmagpie
06-12-2012, 10:25 AM
I like the idea of using a H/V rotary table and a 5/8" endmill but I'd do the whole job with it.

If you want a quick/dirty way of making a bend or two, turn a piece of 5/8" plate to your desired bend ID. Now you have a hockey puck that should just touch the inside of your bend, right? Open the mill vise a tad over 5/8" and drop your tube into the mill vise. Drop the puck on top and tighten the vise. Now the whole bending situation is 5/8" wide no wider. Bend your tube.
The mill vise jaws will keep the tube from going oval or kinking sideways.

Never done this but read about it here, always wanted to try it.

metalmagpie

koda2
06-12-2012, 12:15 PM
Thanks for the replies. I was afraid there is no easy way.

I am limited in the tools that I have available and it looks like I may have to be creative. The mill portion of my 3 in 1 is not very robust.

I found one shop that had a tubing bender and they bent some material I had but it simply flattened and I suspect they tried to use a pipe bender instead. (They wouldn't let me look at their equipment.)

A pipe bender applies force in only three areas whereas a tubing bender uses a mandrel to apply force all the way around the bend.
http://www.grainger.com/Grainger/RIDGID-Lever-Tubing-Bender-4A521
It allows for the tubing to be curved or "bent" without distortion.

I can't find anyone who can do 5/8" tubing, so I may have to make something to do a "one-off" bend.

Dave A.