Power Drawbar Build for PM-728VT

J

jlchapman

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Apr 4, 2017
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Well, its time for me to build a Power Drawbar(PDB) for the PM-728VT. It really sucks using the two wrenches. I like the idea of holding the tool as I release it. I also want a foot pedal to operate the PDB.

This may not be a fast build, but I will share all the information I have and look forward to all my questions being answered. Thanks in advance.

So far I have watched a ton of videos. Franco, CNC4XR7, CRUDCNC, etc. Lot of good information out there.

I have ordered the same 3 stage air cylinder that Tormach uses, CQ2100 X 12-3. Really easy to order. Should be here towards the end of the week. Contact White Wu at email address: ppyz8@xinyipc.com.cn. He creates an order line for you at Alibaba. You can use Paypal so there is not any credit card concerns. It was $267 shipped by FedEx. If you just buy off Alibaba you pay alot higher price.

So to start, I needed to create a drawing for the threaded bolt holes on top of the mill. I only need the holes on the top right to hold a bracket. On this bracket would be standoffs going up to the plate on the air cylinder and an air valve mounting on the side of the mill. I also have to keep the encoder mounting in mind. More on that later.

I did the drawing and 3D printed a template to see if I the drawing was correct. Not a perfect fit but it will work for building the PDB. The bolt holes line up, but may adjust the fitment of angles, bigger diameter around pulley, and such. I'm a beginner to advanced at Fusion360 so my drawings suck. They will get better over time. I'm a Computer Programming Manager with a passion to machine parts and build things, electronics, cars, etc.

TopOfMill.jpeg


Stay tuned, more to come.
 
I have also ordered some needed parts to build the drawbar from McMaster Carr. I ordered the following:

Belleville Disc Spring - 9712K436

Threaded rod for the Drawbar - 98957A807

Coupling Nuts - 90977A190

I'm building the new drawbar similar to what I saw in the videos from CNC4XR7 and from Jim Kramer. I'll create some drawings to show what I'm building.
 
I got all the parts I ordered yesterday. The air cylinder is a monster.

I measured the stack of Bellville washers at .712. So, I turned one of the coupler nuts down to .453 for 1.1". I also turned the bottom portion of the nut using a 5 degree angle for 1/4". The picture of the nut doesnt show this. This barely leaves any material for the turned portion with a 7/16" threaded drawbar. I may consider taking the Bellvilles out to .5 or buying some with a 1/2" id. The id of the spindle is .50". I will need a 1/2" sleeve on the threaded rod to take up the slack between the draw bar and the id of the spindle.

CouplerNuts.jpeg


NutsBellvilles.jpeg
 
I also removed the spindle. If you wondering how to remove the c-clip, just push down on the spring cup and slide the c-clip out.

spindle.jpeg
 
Any followup? Very interested.
 
I recently got a PM-728VT. I was going to make my own power drawbar. I had looked at the one from Priest Tools... hmm.. not impressed at all. So, I looked around for DYI plans and found this impact gun. I ordered it just to have on hand for when I got around to making the power drawbar rig. No need! I just put an 11mm socket on it, put it on and use the paddles for F and R. Because it's impacting, you don't even need to have a spindle brake. $60 and done. Easy.

Found it on amazon: NEIKO 30088A 3/8" Drive Butterfly Impact Wrench | 75 Foot/Pound Torque
 
feral_cat said:
I recently got a PM-728VT. I was going to make my own power drawbar. I had looked at the one from Priest Tools... hmm.. not impressed at all. So, I looked around for DYI plans and found this impact gun. I ordered it just to have on hand for when I got around to making the power drawbar rig. No need! I just put an 11mm socket on it, put it on and use the paddles for F and R. Because it's impacting, you don't even need to have a spindle brake. $60 and done. Easy.

Found it on amazon: NEIKO 30088A 3/8" Drive Butterfly Impact Wrench | 75 Foot/Pound Torque
Click to expand...

Very interested in this. Can you pls post photos of your set-up? Thank you

I also had the 11 mm socket on top, but life got complicated when I also wanted to attach an Omron encoder. I put the encoder on top and used an open wrench but that was slow and annoying.

So I got a Priest PDB (the entry level one with a single stage air cylinder) and works well. He uses a quality MAC air solenoid. I can post photos of my setup if there is interest.


Sent from my iPhone using Tapatalk Pro
 
I'll bring my video recorder tomorrow and I'll make a video. This is so painfully easy. I might build some stuff to hold it someday, but you still have to reach for the in/out buttons. Grabbing the impact wrench is like 10% harder so it's hard for me to justify spending any more time on it.
 
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