Power drawbar for milling machine.

[Nortonscustom]

While back saw a post about a power drawbar made from a butterfly impact wrench. Can't find the thread now but figured I'd post a few pictures of the butterfly impact based drawbar I built.

Goal was to try to make it entirely out of parts and material I already had and to get some practice on the new mill. Still ended up having to buy a few fittings but that's just how projects go.


Started by making the base plate and support for the impact wrench. Used bronze flange bushings in the support.

Next made the control valve body and switch lever. The valve body also doubles as a manifold. The two straight ports get one way check valves and will feed the cylinder. The angled ports feed the air motor.

Added a couple steel buttons to the switch lever to contact with the steel pins of the control valve.

Here's a picture of the inner workings on the control valve. You need to add an exhaust port to the valve in order to make it remote.

Here's all the bits ready for assembly. Added a mini inline oiler to the control valve to keep things lubed. The little hex shaped manifold on the air cylinder was actually a high school shop class project. It's been sitting in the top shelf of my toolbox for 20 plus years. Knew I would use it some day! Out of the top of that manifold is an exhaust flow control valve. It releases the air trapped by the check valves and controls the retract speed of the cylinder.

Here's the gizmo assembled and ready to go. It works like a champ and was a fun project.

 

[DocsMachine]

Very nicely done! Excellent work.

Doc.

 

[NASTYZEN]

Woha! Nice tool you built yourself. I so need to make one of those for my mill.

 

[t-spec]

Thats top quality craftsmanship, really nice!

 

[A_Pmech]

Very nice work!

 

[Slowboat]

Wow - awesome job.

 

[zkling]

Very nice, that is a step above most with the air cylinder on the down feed.

 

[bobadame]

That is very nicely done. Are you interested in selling plans?

 

[TS3g]

Excellent job!

 

[Nortonscustom]

Woha! Nice tool you built yourself. I so need to make one of those for my mill.

Yes you do! It's a hoot.

Thank's for the compliments guy's!


Bobadame, no plans as of yet. Slowly trying to convert my graph paper sketches into CAD drawings but Soild Works is proving to be a worthy adversary for me.

 

[Kevin54]

Beautiful work indeed!!!

I do have to say that these homemade power drawbars are putting a hurt on Kurt. Hey that rhymes.

I like it, and need to get my but in gear and get mine made.

Norton.....if you have sketches, if you would like, I can do you some 2D drawings from the sketches for freebies. I don't have any 3D drawing packages, but I can make you up a hell of a set of 2D's

 

[ebonyswan]

Sadly, I have no idea what this actually does?

 

[Kevin54]

Sadly, I have no idea what this actually does?

If you've ever been around a milling machine, like a Bridgeport, or similar, you have a bar that runs down from the top of the quill through the quill, and it is threaded on the end. This is used to pull or DRAW your collets up into the quill, hence the name drawbar. Normally you have a 3/4" wrench to loosen and tighten the drawbar, then smack it on top to dislodge the collet that is still being held in by the compression of the collet. The collet has slots so that it give relief and clearance to hold in your cutters (end mills). A power drawbar does away with the need to use a wrench and hammer, and works off of pneumatics. All you have are two buttons to push. One to draw it up tight, and one to reverse it. the same thing as using an impact wrench to tighten and loosen your lugnuts. The power drawbar will move up or down though to engage the hex end of the drawbar so there is no accidental interference between the two. That is what the two post with the springs allow.

I hope that explains it. If not, I can probably find you an exploded pic of what is what on a mill if you are not familiar with the workings of one.

 

[zkling]

Here's a quick video that gives you the gist of why and how.

 

[raddksn]

I'm new to the machining world. This thing looks cool but how do you start the threads in the collet and lineup the r-8 key?

 

[fnieto]

Nice job! even looks **** assembled.

 

[Kevin54]

I'm new to the machining world. This thing looks cool but how do you start the threads in the collet and lineup the r-8 key?

The drawbar doesn't engage whether manually or with a power drawbar until the key is engaged into the collet anyhow.

Now on the other hand, I have always removed the keys in my mills, both at home and at work. Some collets fit the keys just fine, and other collets at times, you have to file out to fit the key. Or if the key gets loose, you can also have alignment problems. To remedy that a lot of people will "Y" the slot out at the top of the collet.

If you want to remove the keyway, and I have never had a problem with the collet slipping in any mill just so you know. You can get a large set of pliers, or a large spanner and remove the collar at the bottom of the quill. On the collar, you will see a setscrew. Loosen it. Now you can unscrew the collar. Once you remove the collar, you will see another setscrew. Remove the setscrew, and it may be a locking setscrew to lock the setscrew underneath of it, but the setscrew is the keyway. It is a standard setscrew with the end cut into a key.

After removing it, put the collar back on and tighten it. When you put the setscrew into the collar, you have to be careful as to how tight you tighten it. Even though it is something like a #8 setscrew, if you torque it down too tight, it will elongate the roundness of the quill and make it hard to retract it all of the way without binding. Just back it off enough so the quill retracts on it's own with the factory spring loaded assist.

Running production parts, and when you have to swap out collets quite a bit, the key in the quill is a pain in the ***. Like I said above, I have removed them in the mills I ran and have never had the first problem with a collet spinning inside of the quill, and I have ran BP's and similar for over 35 years.

 

[the gypsy]

That is interesting. I must say that is not what I was imagining. This is why pics are important. Videos are even better.

 

[classicJackets]

Beautiful work indeed!!!

I do have to say that these homemade power drawbars are putting a hurt on Kurt. Hey that rhymes.

I like it, and need to get my but in gear and get mine made.

Norton.....if you have sketches, if you would like, I can do you some 2D drawings from the sketches for freebies. I don't have any 3D drawing packages, but I can make you up a hell of a set of 2D's

I'm in school and have both SolidWorks and Autodesk Inventor, so if you want them in 3-D it would be good practice for me and have potential. If Kevin does 2-D (or not!), send me a PM if you want them in 3-D.
Doug