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IndustryArena Forum > MetalWorking Machines > Shopmaster/Shoptask > Pneumatic Power Draw Bar for Shopmaster Mill Turn - DONE
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  1. #1
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    Pneumatic Power Draw Bar for Shopmaster Mill Turn - DONE

    I finally pulled the trigger and built a pneumatic cylinder/belleville washer type power draw bar for my Shopmaster Mill Turn. I had previously built and posted a draw bar using a butterfly impact wrench for which the long term results were lacking. The torque seemed to be unpredictable and temperamental based on air pressure. The impact wrench sometimes would stick and bypass air. I may not have had large enough supply. Also, over time, the socket and bolt head started to gall and stick. I was afraid I would get galling on the draw bar threads.

    I'm very happy with the new system and its performance. Here is a video review of it:

    https://www.youtube.com/watch?v=P188_Xuwogw

  2. #2
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    Re: Pneumatic Power Draw Bar for Shopmaster Mill Turn - DONE

    I like this. I have the same Shopmaster Mill Turn with an Acorn conversion. Can you provide me with the part numbers for the pneumatic cylinder and the belleville washers? Looks easy enough to build.

  3. #3
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    Re: Pneumatic Power Draw Bar for Shopmaster Mill Turn - DONE

    Quote Originally Posted by brittf View Post
    I like this. I have the same Shopmaster Mill Turn with an Acorn conversion. Can you provide me with the part numbers for the pneumatic cylinder and the belleville washers? Looks easy enough to build.
    the Cylinder is a Fabco PA48-CR1.000 Pancake 4" Bore 1" Stroke Multi Stage Pneumatic Cylinder (data sheet attached). I went with this one only because it was used and a good deal on ebay. It looks like there is another one available on ebay but at a higher asking price. I am running 40 PSI so a 2 stage should only require 80 PSI.

    The washers are Tormach Power drawbar spring #31319. They are $2.96 each and they use 8 stacked alrernatly.

    With the oversize hybrid servos, new controls, and the power draw bar, it has become a useful tool. It is really lacking in rigidity so will never be able to do aggressive work. I will likely mostly be working aluminum and am not in a hurry so.... I did tie mine to a wall. Have you done anything to help with this limitation?

    I have attached the 3D model in DWG format in case that will help with your layout.

  4. #4
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    Re: Pneumatic Power Draw Bar for Shopmaster Mill Turn - DONE

    Thank you for the reply. I built a more rigid base out of 2 inch square tubing with 3/16" wall thickness. It is diagonally braced on three sides. I also built what I call an exoskeleton out of the same tubing, diagonally braced and tied into the top frame for the z-axis drive. The idea was to take any side-to-side and front-to-back movement in the top of the machine and transmit it into the base. I'll post up some pictures in the next day or so.

  5. #5
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    Quote Originally Posted by brittf View Post
    Thank you for the reply. I built a more rigid base out of 2 inch square tubing with 3/16" wall thickness. It is diagonally braced on three sides. I also built what I call an exoskeleton out of the same tubing, diagonally braced and tied into the top frame for the z-axis drive. The idea was to take any side-to-side and front-to-back movement in the top of the machine and transmit it into the base. I'll post up some pictures in the next day or so.
    That would be great. Was the difference it made worth the effort?

  6. #6
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    Re: Pneumatic Power Draw Bar for Shopmaster Mill Turn - DONE

    The forum has been really sluggish today and I was not able to upload pictures. If you want to private message me with an email address I'll send the pictures to you.

    Did it make a difference and was it worth it? Yes and no. I think there was an improvement and although it is more rigid it is not as rigid as I would like it to be. I still have to take light cuts or I get a lot of chatter. Most of my work in in aluminum so it's not too bad. Since it is a hobby for me, and most of what I make is not critical, I can live with its capabilities. Converting the control to the Centroid Acorn did make a difference in reliability. I'm still losing steps in the Z-axis even though I upgraded the stepper motors. I'm thinking I will need to upgrade to a servo system with feedback.

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