Drawbar Belleville washers

DaOne · Jul 12, 2018

Hey guys, I got a older VF-2 I am going through. The drawbar has a ton of tool changes on it and I am sure its in need of some TLC. Before I pull it I would love to get the washers ordered up to rebuld it. Anyone happen to have a correct part number? Maybe Key Bellevilles or Mc Master etc?? The original drawbar is part number 93-30-3410D with a stack that should be 79 washers and 1000-1200 pounds.

npolanosky · Aug 1, 2018

Following/bumping this, might be interested in doing the same on my VF3

Milland · Aug 1, 2018

Check these threads:

https://www.practicalmachinist.com/vb/haas/haas-belleville-washers-167312/

https://www.practicalmachinist.com/vb/cnc-machining/ok-little-help-reuiblding-drawbar-162552/

DaOne · Aug 2, 2018

I have not had time to yank it apart yet but when I do I plan to document it. I built myself a drawbar force gauge to test it. its currently at 900 pounds. Needs some love as it should be between 1000 and 1300 pounds.

saltfever · Aug 3, 2018

Love the pic of the gauge and many thanks for posting it. As a new owner of a used, tired, TM-1 I'm very interested. I'm not asking for plans but I am not sure of where, or how, to react the pull force. I think i can see the 1.128" dia. cylinder but is there another critical dimension on the stroke length?

Milland · Aug 3, 2018

saltfever said:
Love the pic of the gauge and many thanks for posting it. As a new owner of a used, tired, TM-1 I'm very interested. I'm not asking for plans but I am not sure of where, or how, to react the pull force. I think i can see the 1.128" dia. cylinder but is there another critical dimension on the stroke length?

Ideally you'd have essentially zero stroke length when trying to read a stud tension gauge, so using a hydraulic cylinder with O-rings and a bourdon tube could introduce measurement errors. I plan on making one of these myself, but would be using a load cell and digital readout for minimal stroke/load loss.

saltfever · Aug 3, 2018

I hope this is not thread drift since this is about Belleville washers.
Excellent point Milland. I think you are saying force changes with stroke length. That would certainly introduce error in the measurement. I know that Belleville washers can have two characteristics. A spring constant or no constant depending on their stacking orientation. I don't know the Haas stacking pattern so thanks for pointing out a serious source of potential error. My question is how do you react the force to get the reading? Where on the holder-to-spindle interface do you insert the sensor?

Milland · Aug 3, 2018

saltfever said:
I hope this is not thread drift since this is about Belleville washers.
Excellent point Milland. I think you are saying force changes with stroke length. That would certainly introduce error in the measurement. I know that Belleville washers can have two characteristics. A spring constant or no constant depending on their stacking orientation. I don't know the Haas stacking pattern so thanks for pointing out a serious source of potential error. My question is how do you react the force to get the reading? Where on the holder-to-spindle interface do you insert the sensor?

I'd either use a tensile load element, or a compressive cell in a "saddle" arrangement so load is transferred to the stud. Just modify a unused tool holder by drilling out the threads and body to allow a minimum of a 13/16" column tapped for the stud to go through the body and then down to the load element.

saltfever · Aug 3, 2018

Perfect. Thanks for the descriptive "picture"! :-)

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