# Steel Ring Under Asian Knee Mill Drawbar?



## Chips O'Toole (Dec 29, 2019)

I have a GMC 9x49 mill with variable speed. I had to lower the head in order to move the mill. After I did this, a steel ring fell out of the top spindle hole where the drawbar lives. It fits the drawbar precisely. It's not a flat washer. It's maybe 3/16" thick.

Before I spend all day poring over confusing parts diagrams, can someone tell me what this ring is and whether I need it?

I'm on my second drawbar. For all I know, this thing was somehow related to the original bar. I had to get a new drawbar because the shear pin in the old bar went. Since then, I have installed a new pin, but I'm still using what I think is a Jet drawbar.

The mill has made some hooting noises at high speed since the drawbars were swapped, and I am wondering if an unnecessary spacer ring could have something to do with that.

The best parts diagram I've found is from Hardinge, and it shows a "washer" on the Bridgeport's drawbar, but this is a fat ring.


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## matthewsx (Dec 29, 2019)

Probably because the drawbar is/was too long to fully engage collets.

John


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## Chips O'Toole (Dec 29, 2019)

I am now looking at zoomed-in drawbar pictures, and I see rings on bars for variable-speed machines. I wonder if I have an extra ring. Maybe the ring from the old bar stayed in there. I guess I should go look at both bars side by side and see what the story is.

Maybe I'm supposed to have an O-ring to keep this thing from sliding off the bar.


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## 4ssss (Dec 29, 2019)

Not does it add dimension to the draw bar, it also keeps the mill head from being scalded if you happen to over tighten the draw bar. On a Bridgeport, the draw bar rides on top of the spindle and there is a bearing there also. Maybe the washer is a bit big and it's somehow rubbing there. I'm looking at this in my head, so I may be off.


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## middle.road (Dec 29, 2019)

+1 on what John said.
Mine on my BP got lost when we rotated the head during it's move. Last seen rolling away like a tire downhill.
Had to fab a new one.


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## Canuck75 (Jan 18, 2020)

Chips O'Toole,-

Just to add an extra little element the discussion I installed a Torrington bearing to my King PDM30 (RF31) drawbar, This puts all the wrench torque to work pulling on the collet instead of losing any of it to friction.

You can check to see if your drawbar is the right length quite easily. Put a end mill (for example) into a selected collet and pull it in tight. Undo the drawbar gently (the collet should stay locked in place), gently unscrew the drawbar until it is free of the collet. Now measure how much space is between the drawbar washer and the top of the spindle, should be 1" or more to use up all the collet thread length. Using up the available thread length in the collets will give more life to your drawbar.

For what it is worth.


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## middle.road (Jan 19, 2020)

Canuck75 said:


> Chips O'Toole,-
> 
> Just to add an extra little element the discussion I installed a Torrington bearing to my King PDM30 (RF31) drawbar, This puts all the wrench torque to work pulling on the collet instead of losing any of it to friction.
> 
> ...


Now there's a idea.
Now why didn't I think of doing it with a thrust bearing when I was messing with mine?
Guess I'll go back and revisit this. Problem is I think I might need a new drawbar.


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