# Super Simple Power Draw Bar for PM-728V-T



## Tio Loco (Sep 25, 2020)

Seems like a lot of the butterfly impact wrench installations are way over thought or over engineered or whatever. Came up with a very simple design.

Leaving it engaged doesn't seem like a huge issue, ad the wrench spins freely, but if desired, just bringing the quill down about 25mm will disengage it.

I may upgrade it with some sort of handle actuator as it still can be a reach, but it sure beats the two wrench-three handed-still might drop your cutter or face mill or drill chuck onto the table method.


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## rwm (Sep 25, 2020)

That is slick. I find it doesn't take much force on the drawbar to clamp the collet. I wonder if a stepper motor would work?
Robert


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## Tio Loco (Sep 25, 2020)

rwm said:


> That is slick. I find it doesn't take much force on the drawbar to clamp the collet. I wonder if a stepper motor would work?
> Robert



Interesting idea... not sure if it would move fast enough, that instant burst of speed and impact when using an impact wrench, you don't even need the spindle wrench...


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## rwm (Sep 25, 2020)

And you post this right after I finish my drawbar hammer!
R


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## KVan (Dec 28, 2020)

rwm said:


> That is slick. I find it doesn't take much force on the drawbar to clamp the collet. I wonder if a stepper motor would work?
> Robert



I'm using a higher torque NEMA 34 for my powerlift, but I don't think it has enough to properly tighten the drawbar. The impact is doing 60-90 ft. lb. the stepper is about 80 in. lb.


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## KVan (Dec 28, 2020)

Tio Loco said:


> Seems like a lot of the butterfly impact wrench installations are way over thought or over engineered or whatever. Came up with a very simple design.
> 
> Leaving it engaged doesn't seem like a huge issue, ad the wrench spins freely, but if desired, just bringing the quill down about 25mm will disengage it.
> 
> ...


Agreed on the idea of over engineered, this answered my question. Thank you.


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## KVan (Jan 6, 2021)

Follow Up to my original question:

I did the fixed impact wrench and it worked very well with the following exceptions.
1. When using the mill in a drill press fashion, the drawbar would not engage the socket cleanly and make noise.
2. Noisy, not from the impact wrench spinning, but from the drawbar being non-concentric and wobbling in the socket. It made an obnoxious clicking sound.

I opted for a more tradition style albeit a bit more compact that the one's I have seen. There is very little torsional force on the actual impact so rather than go the route of attaching to the head I just mounted it to the motor and spindle cover. I have been using it for a couple of days and it is working great.


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## Tio Loco (Jan 6, 2021)

Very nice!


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## KVan (Jan 6, 2021)

Tio Loco said:


> Very nice!


Than you.


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## Jim F (Jan 6, 2021)

Those ratchets will be shot very quickly turning with the spindle.


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## Just for fun (Jan 6, 2021)

Jim F said:


> Those ratchets will be shot very quickly turning with the spindle.


That's exactly what I was thinking!


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## Tio Loco (Jan 7, 2021)

I'm curious why that would be the case. I put an in-line oiler on the ratchet so it gets lubrication with every use, and the mill certainly does not turn anywhere near the native rpm of the ratchet under air power.

And as I wrote, the socket can be disengaged by just dropping the quill about 12mm.


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## Jim F (Jan 7, 2021)

Undo wear in the motor cylinder and on the impact mechanism.
The motor cylinder is just flash chrome plated, they do not like running without oil.


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## chipinator (Feb 1, 2021)

If you don't like the impact wrench setup, what's the alternative to purchasing an expensive custom power draw bar?  Yes, I get making one, but what type?  Tool(s)? Designs?  I would like to be able to use R8 collet chucks to hold my tooling with the use of a power draw bar.  Any suggestions?


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## KVan (Feb 2, 2021)

chipinator said:


> If you don't like the impact wrench setup, what's the alternative to purchasing an expensive custom power draw bar?  Yes, I get making one, but what type?  Tool(s)? Designs?  I would like to be able to use R8 collet chucks to hold my tooling with the use of a power draw bar.  Any suggestions?


The idea was to have the impact engaged when the spindle is at the top most position. After making a bracket and using this design, I found that that when I frequently use the drilling function and raising the quill it wouldn't (at times) cleanly engage and make unexpected noise. Further more when engaged it would make a noise that was somewhat annoying, but that is easily overcome buy lowering the quill 1/2" as #Tio Loco pointed out. I also agree with #Tio Loco that most of the designs are way over thought and engineered. The unit I designed cost about $60 for the impact, materials and fittings. I've been using it for a few weeks now and it works like a charm.
You only need a couple of things to make this work, something to hold the impact wrench (and it doesn't take much since there isn't a lot rotational force) and some way to make it go up and down. Again, you don't need high compression springs to do this. I used 3/8"x 2 1/2" springs from Amazon and a 1" stiffer compression spring (Home Depot special) to add a little extra lift. My entire unit is held on with 4, M4 screws through 16Ga sheet metal. If you want to keep it really simple, just hand hold the impact (that's what I did during the build). 
Any way you choose can't be wrong no matter how complex or simple, think about it, you get to conceptualize and design a part, make it using cool tools and machines, test it, refine it, and make it work. In my opinion that's what this hobby is all about.


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## chipinator (Feb 2, 2021)

KVan - Where did you get the handle and base that's attached to the butterfly forward/reverse switch on the impact wrench?  Did you drill and tap the butterfly switch to attach it?  Thanks.


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## KVan (Feb 2, 2021)

It was a part of the build, a scrap piece of AL and a 3/8" rod tapped and threaded and a ball mill to cut a grove. I took the paddle off the impact, drilled and tapped the holes for M3 screws, there's not a lot of force on this. The knob is just a 3D printed ball that is tapped or you can order one from McMaster-Carr knobs | McMaster-Carr. I actually did that whole setup as an after thought, the springs aren't really stiff, just enough to lift the impact, so I was just pushing the impact down and operating the butterfly.


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## Tio Loco (May 20, 2021)

KVan said:


> The idea was to have the impact engaged when the spindle is at the top most position. After making a bracket and using this design, I found that that when I frequently use the drilling function and raising the quill it wouldn't (at times) cleanly engage and make unexpected noise. Further more when engaged it would make a noise that was somewhat annoying, but that is easily overcome buy lowering the quill 1/2" as #Tio Loco pointed out.


 KVan nailed it. My original design was a PITA to use.  Noisy if the ratchet was engaged, and always fiddly if trying to use the quill for drilling multiple holes where you don't want the quill returning far enough to engage.

So, here's my take on V2. For the carriage, I used leftover parts from a batch of Amazon parts designed for 3D printer construction/repair. The 8mm rods worked out nice. Don't ask me how I know this, but don't try to cut them with a band saw, go straight to a cutoff wheel.  

I replaced the linear ball bearings (crap) in the pillow blocks with self lubricating plastic ones called Drylin (



).

I initially bought springs from McMaster, but they proved too stiff. On a hunch, I dug into my RC truck bins and found springs that were a perfect fit. I considered a handle like KVan made, but for now I'm pretty happy with just  operating the butterfly manually. Time will tell.


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## Tipton1965 (May 20, 2021)

Looks much better.  Now you know why many of the impact wrench installations are way over thought or over engineered.  Because they work better!


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## chipinator (May 20, 2021)

Tio Loco...I would buy one if you made another.  I need one for my PM-728V-T.  I was going to make one but why reinvent the wheel.


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## Tio Loco (May 21, 2021)

chipinator said:


> Tio Loco...I would buy one if you made another.  I need one for my PM-728V-T.  I was going to make one but why reinvent the wheel.


Thanks, but unfortunately I have to pass. I have an ever growing list of projects on my plate, and with the exception of the Drylin bearings, this one was built with materials that I had on hand, which I now no longer have on hand. Also, I didn't draw up any plans for this one (bad idea) and just made it on the fly.

If you decide to build one, I'll gladly share some basic dimensions.

This is the ratchet I pickedm mostly because the nose is relatively uniform diameter (just a slight taper): https://www.amazon.com/gp/product/B000MQEKTY

The 3D printer motion rods are here:  https://www.amazon.com/Sunhokey-Hardened-Chrome-Metric-Tolerance/dp/B07XD4FBVM/

If I were doing it again I would just bore the the carriage block for the Drylin bearings and use external snap rings to secure them. That would eliminate the side wings, 20 holes drilled, and the alignment issues to get the pillow blocks properly aligned for smooth travel, but the pillow blocks are here: https://www.amazon.com/Furiga-Printer-Linear-Bearing-Bushing/dp/B08BZ48XZN

The Drylin bearings are here: https://www.amazon.com/gp/product/B076NWK2NK

For springs, you're on your own, like I said, they were RC truck shock springs, but they've been in the bin for years.


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## chipinator (May 21, 2021)

I had to ask .  I appreciate the response and the links.  I'll give it a go when, like you, I have an opportunity.


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## aliva (May 21, 2021)

Jim F said:


> Those ratchets will be shot very quickly turning with the spindle.


I've been using my CP butterfly ratchet for 5 years still going


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## Tio Loco (May 21, 2021)

aliva said:


> I've been using my CP butterfly ratchet for 5 years still going
> View attachment 366754



I believe Jim F. was referring to leaving the ratchet engaged and driving it with the mill....


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## aliva (May 22, 2021)

Tio Loco said:


> I believe Jim F. was referring to leaving the ratchet engaged and driving it with the mill....


Then I agree, it would be hard on the ratcheting mechanism


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