South Bend 16" 5C draw tube build

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forhire

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I needed a 5C draw tube for a SB16 at the school. I watched ebay for a while but a few weeks ago finally decided to just build one. I ordered some DOM, a thrust bearing, and balance came from the scrap bin. I modeled it loosely after the Clausing draw tube. I figured a few of you may be interested in the steps/build. I cranked this out on a Saturday morning at work on the cnc. My students did get the chance to drill and tap the set screws. ;)

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Similar to the one I made:
https://www.hobby-machinist.com/threads/hand-wheel-collet-closer-build.62278/
except no CNC (except for rounding the hand wheel corners), made mostly from scrap and junk, cut to fit, designed while I worked (though you probably did, too.) They have much in common...

The only issue I have had with mine is that the hand wheel tends to loosen the collet after multiple starts of the spindle. Too much acceleration, too much inertia of the hand wheel assembly -- and too good of a thrust bearing. ;-)
 
Bob Korves said:
Similar to the one I made:
https://www.hobby-machinist.com/threads/hand-wheel-collet-closer-build.62278/
except no CNC (except for rounding the hand wheel corners), made mostly from scrap and junk, cut to fit, designed while I worked (though you probably did, too.) They have much in common...

The only issue I have had with mine is that the hand wheel tends to loosen the collet after multiple starts of the spindle. Too much acceleration, too much inertia of the hand wheel assembly -- and too good of a thrust bearing. ;-)
Click to expand...

Thanks for the link. I like your tommy bar holes. Unfortunately tommy bars and students can be a bad combo. Anything that can be over tightened will be. I haven't noticed any issues with it coming loose. My wheel is about 6" diameter.

I originally wanted one of my students to make it but we needed it Monday morning. Like you this fit to the parts and material. Conversational at the control allows you to job shop the cnc. I'm pretty sure I spent more time looking for material and suitable soft jaws than making parts.
 
forhire said:
My wheel is about 6" diameter.
Click to expand...
Mine is also 6" diameter, the size of the stock I started with. After some use, I think that is the correct diameter for my 13x40 lathe. Tommy bars can definitely be dangerous. My cure is to only allow the bar in the tool rack or in my hand, with no exceptions -- except for one photo... ;)
 
If you can't trust students with a tommy bar, you could mill some "grippers" on the outside edge.
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derf said:
If you can't trust students with a tommy bar, you could mill some "grippers" on the outside edge.
Click to expand...

I can't really say I've had the need for tommy bars even with the smooth cranks. One day I did have a student tighten some work so tight I had to use the strap wrench to break it loose. I like the idea of milling in some gripper. That would be simple.
 
Grippers are fine, and will help slippery oily hands get a good grip. Be careful as to their shape and surface finish. Make sure clothing will not tend to get caught up with whatever gripper surface you use. The one in the photo that derf put up in post 5 looks safe enough to me, things like knurling and rough blasted surfaces could be dangerous. Also consider the distance of the wheel from the headstock or gear cover. Mount the handle far enough away that your hand and forearm cannot get jammed into the gap.
 
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