# Power Drawbar Ideals?



## Kroll (Sep 12, 2019)

Guys been watching more Youtubes on making a power drawbar for the mill.Over time I have collected some material and parts that I will be using for this fall time project.But I can't seem to find any info on the cylinder that can either lift or pull the impact to the draw bar.I read some post that nothing to it but I have no ideal what size that I need.Guys has anyone here made a power drawbar and if so could you share little infor and maybe some pics,what you like about yours and what you would change if you had a do over.Thanks guys


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## MontanaLon (Sep 12, 2019)

I have been thinking about this as well. I am interested to see what others have done.


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## Cadillac STS (Sep 12, 2019)

What kind of mill is it for?


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## Cadillac STS (Sep 12, 2019)

A project just for doing it is nice, nothing wrong with that. But for a Bridgeport a bolt on complete system is $135 on eBay.


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## Kroll (Sep 13, 2019)

It’s BP,w/vs so others have said these are easy to do but still don’t know about the air cylinder.I did see the lever type draw bars on bay which at that price is tempting.


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## davidcarmichael (Sep 13, 2019)

Kroll said:


> It’s BP,w/vs so others have said these are easy to do but still don’t know about the air cylinder.I did see the lever type draw bars on bay which at that price is tempting.



On a small bench mill with no quill I used two 10mm dia air cylinders (one each side). They just need enough combined cylinder area and air pressure to lift the butterfly wrench clear of the draw bar (if that's what you are using). The stroke was only 10mm as that was all I needed but 15 or 20mm would have been fine. These cylinders are dirt cheap on Ebay. I sandwiched them between a base block fixed to the top of the spindle/gear housing and a steel (not aluminum) block that had a hole in the middle and grub screws to hold the HF butterfly wrench securely, (I removed the rubber boot). The butterfly wrench was modified so that air/oil could be injected into either the right or left hand port. All the valving was done using cheap two and 5-port air valves from Ebay operating at 12V.

When I switched to a BP "clone" with a quill (and draw bar) that moved a full 5 inches, I wanted the impact wrench to be able to move far enough to tighten or slacken the draw-bar with the quill at any point in its travel. I used two 20mm dia air cylinders with 150mm stroke (from Ebay) to lift the wrench (the same HF one) and a pair of linear shafts and linear bearings to guide it. Adjustable air damper valves on the 5-port valve outlets allow you to dampen the movement so the power draw bar does not slam up and down at full speed. This was not an easy build (the PM mill was not designed to make this easy).

Both of these worked just great and the latter one was really important to me as the mill is very tall, and I am not. I use TTS tooling and a lot of the benefit is lost if you have to climb a ladder to slacken or tighten the draw bar.

If I had a BP then I would probably go with an over-the-counter purchase. I have no idea how the BP keeps the draw bar hex head at the same height despite using a quill. I assume there is some kind of sliding, keyed aspect to the draw bar.

If anyone is thinking of using Bellville washers and some Tormach-type cylinder, or a cylinder and lever construction, then I have six unused Tormach washers available. I gave up on this approach when I calculated the huge forces involved in compressing the Bellville washers enough to slacken the TTS collet. Of course the great advantage of the impact wrench approach is that you can easily use R8 tooling when it is called for. TTS at 3/4" dia does not provide enough grip for serious face milling and quite a few other high torque tasks.


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## Kroll (Sep 13, 2019)

That’s also my problem just not that tall tired getting milk create standing on it.When raise quill you can see DP but as you lower quill the drawbar goes down with it.So I guess do a search on bay for air cylinder see what pops up thanks guys for help


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## Cadillac STS (Sep 13, 2019)

With eBay drawbar setup you put the quill all the way up then the butterfly impact wrench is pulled down to engage the drawbar nut.  Lever one way loosen and the other way tighten.


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## Cadillac STS (Sep 14, 2019)

And if you want to make one of that same style:









						How to: DIY Bridgeport Power Draw Bar! - NYC CNC
					

Post Views: 4,249




					www.nyccnc.com


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## Cadillac STS (Sep 14, 2019)

Looking through the different styles people spend time on an air cylinder to pull it down to the draw bar.  Then hit a switch to set the whole thing in action.  My opinion is that is too complicated when simply reaching up and pulling it down works.


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## davidcarmichael (Sep 14, 2019)

Kroll said:


> That’s also my problem just not that tall tired getting milk create standing on it.When raise quill you can see DP but as you lower quill the drawbar goes down with it.So I guess do a search on bay for air cylinder see what pops up thanks guys for help



Here is a link to where I posted pictures of my setup.








						PM 835S Power Drawbar
					

So, has anyone installed a power drawbar on a PM 835S? Why would anyone want a power drawbar you ask? The first "big" project I'm doing is going to require an end mill and a drill bit for each step. It is a very odd shaped part and when I get it where I want it I don't want to move it until the...




					www.hobby-machinist.com


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## aliva (Sep 17, 2019)

Here's mine post #6
https://www.hobby-machinist.com/threads/power-draw-bar-for-the-bp.78729/#post-672221
amazon has air cylinders you don't need much more than 3" of stroke and enough pressure to hold the air ratchet on the draw bar.


			Amazon.ca : air cylinder


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## Kroll (Oct 17, 2019)

Guys quick question about the guide post,looking at some of the Youtubes and some of the pics it looks like the guide post are off center little from the impact.Is this true or am I seeing things if so are the guide post in middle between the actuator and the impact?I'm drilling holes for my impact in plate just wanting to kinda get an ideal for the guide post location.


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