After several months of using my first mill, I decided that tool changes are taking way to long, so I decided a power drawbar should speed things up a little. Here is my own version of the power drawbar. I got some ideas from others on this site and by looking at the ones you can purchase.

It is comprised of a plate with an impact wrench that slides on 5/8" linear shafts and an air cyclinder to push it down onto the drawbar. I dont have the airlines connected yet, Im still waiting for some fittings in the mail.

Let me know what you think.

Vince

Thats a nice one. Mine is alittle more simple I have to reach up and grab it pull it down . Its been on my mill for about 15 years .But it works great

After several months of using my first mill, I decided that tool changes are taking way to long, so I decided a power drawbar should speed things up a little. Here is my own version of the power drawbar. I got some ideas from others on this site and by looking at the ones you can purchase.

It is comprised of a plate with an impact wrench that slides on 5/8" linear shafts and an air cyclinder to push it down onto the drawbar. I dont have the airlines connected yet, Im still waiting for some fittings in the mail.

Let me know what you think.

Vince

nice work

I purchased the pillow block bearings and cylinder holder but machined everything else. It was actually the first time I have ever used a vise to hold parts, so I was just experimenting a little. It is actually very simple but looks complex. I cant wait for the air fittings to arrive so that I can try it out :)

Vince

Hi;
you may have a bit of a problem to let the taper unlock
unless you make a captive drawbar, also try to make a chanfer in the socket to allow it to fall readily into the drawbar hex, anyway it looks good
regards
rasta

Vince,

It's not often that I take the time to comment on some ones work but your's is exceptional. There have been a couple of suggestions offered so I'll add a couple of more; replace the shiney socket with an impact grade socket and valve the action so that it does not start until the socket is on the draw bar.

Way To Go BigVinney,

Servo

Vince - very nice and VERY beefy looking. How do your controls look?

The socket is on there temporarily, I need to get an impact socket still. As far as valving the cylinder will go first and then the motor will spin. I have 2 mushroom button type valves for the air supply instead of using the one on the impact itself.

Also, what is a captive drawbar?

Here is a picture of the mill it is going on and also a picture of the air valves.

valve the action so that it does not start until the socket is on the draw bar.
Any suggestions on how to valve that way and still only have to press one button?

My only complaint with mine is that it spins up right away.

MY DRAWBAR (http://www.knifewerks.com/images/equipment/Drawbar/Drawbar.htm)

Yours is very nice my friend.
You spent a substantial amount of time and money on it, and it looks good.

One suggestion.
If you find it lacking balls due to back pressure in the air line like I did, save the hours of time and frustration I spent troubleshooting.

Quick exhaust air valves from McMaster-Carr (6646K31) solved my problem.

You can see them mounted on top of the wrench on some of my pics.

Brian

Exhaust valves are one of the items I am waiting to arrive. At first I didnt think about it but then I realized that because some of the check valves that I am using the cylinder would expand but then not release so I ordered some exhaust valves.

In terms of getting the cylinder to expand before the impact starts spinning, I changed how the air goes into the system. The incomming air goes through a "T" fitting but goes straight towards the air cylinder and the air has to make a 90 degree turn to go toward the impact gun. So hopefully this will give me a slight delay allowing the cylinder to activate first.

I am going to mount it and do some tests today, so I will let you know how it works.

Vince

Just finished mounting it to the machine and gave it a test run. It works great, the only thing that I may change would be to have a stronger air cylinder but it works fine with this one.

Also my idea of how to plumb the air lines works great as well, the cylinder expands then the impact starts to spin.

Here are a couple of pics of it on the machine.

Vince

BigVinney & HayreAss,

1st; Vince, a captive draw bar is forced to stay vertcally stationary while it forces the taper to break lock.

HayreAss; By design your power drawbar has all of the elements required to valve the action so that your motor does not spin until the socket has seated. In the attached picture you can see where I'm using the ram of one cylinder as a valve to control a secondary cylinder. The primary ram is the index locking pin which must be out prior to the indexing cylinder being actuated.

Good Work Guys,
Servo

Wow those are nice looking pieces. I am sure I could think of a way to keep the drawbar locked from going up but it seems to work fine so far, so if it becomes an issue I will draw up some plans to keep it in place. As for the socket grasping the drawbar, there had been no issue with it not seating properly yet. I dont have the means of taking a video of it working but from my first tests, the cylinder actuates and about a half second later the impact starts to spool up at 90 psi.

BigVinney,

Sounds like it fits in the "If ain't broke then don't fix it" category.

Servo

I'll agree with that servo, seems to work fine so I will leave it until it malfunctions, or I am bored and feel like making something, which happens to be all the time :)

I never touched a mill before 4 months ago and now I cant stop customizing and playing with it. Now only if I could just win the lotto and get nice little haas vmc.

Here is a picture of the mill it is going on and also a picture of the air valves.

Your mill has belt drive right? Does your power drawbar interfere with changing the belts at all? How do you flip the top open?

BTW: The type of mill you have is my personal favorite for the size. Really neat to see that you CNC'ed it. Did you detail the conversion any where?

The belts and pullies sit about 1" below the cover so the drawbar does not interfere. I have latches on the side of the lid to make sure it stays shut when using the power drawbar, but I can unlock them and flip the top open if needed.

I did post a the final conversion pictures in another thread a few months ago but I did not go into details about it. Just do a search for G3102 and you should see it. If you have questions just let me know.

a captive drawbar is a normal drawbar that has a collar on top of it to stop coming up when it is undone, anyway if the
air cilinder that pushes the nutrunner down is big enough it will hold the drawbar down while it unlock the taper on the tool
again
good job
rasta