Power Draw Bar Install on PM TS Style Knee mill

[Kamloopsendo]

I recently purchased a Power Draw Bar for my PM 949 mill which is a TS style with a cam on top to engage and disengage the direct drive when changing speed ranges. I had talked to Matt at QMT via E-mail awhile back and he sold and recommended purchase of the Maxi Torque-Rite unit which I ultimately purchased from KBC not Matt as I'm in Canada and getting the unit from Matt is a significant amount more hassle and the price was the same from our Local KBC store. At any rate the unit should work but I've no real idea how to attach the power head.

Problem I have is that everything I see describes mounting it on a TV style machine. With the TS style head it simply ain't as simple. Has anyone done this and if so what are the tricks. I'm guessing I need to turn (or purchase?) a spacer to go from the top of the bearing housing to the base of the Power Draw bar unit. Even so not sure exactly where attach as I don't think drilling and attaching to the lock nut is a good idea as the ongoing reversing torque from the power head will likely loosen the bearing lock nut with time and the ring that the nut threads into is pretty marginal in radial thickness to attach to.

Any one who's been thru this I'd appreciate hearing how you did it.

 

[davidpbest]

I'm guessing you bought the generic Maxi Torque-rite rather than a version specific to the step pulley machine. Several version are offered by the manufacturer:

I bought my Maxi Torque-rite from the manufacturers rep. His first question was "Do you have a step pulley machine, or the one with variable speed". The step pulley version comes with stand-off studs that position the mounting platform for the unit above the ring on top of the head where the spindle brake and Hi/Low selector levers are located. Proper centering and clocking of the standoffs are both important when positioning for the mounting bolts.

The second question the rep asked was about the specifics dimensions for my mill as shown in this attached drawing (your machine may be different - this is for the PM935). He asked for these dimensions so that the drawbar they supply was made to fit my machine specifically. It had a specific head length that was longer than the factory-supplied drawbar, and the overall length was increased by almost 2-inches.

You can probably make your own stand-offs to mount the generic version of the PDB above the ring as shown in the photos above.

The issue you are more likely going to be troubled by is the drawbar itself. With the pneumatic actuator system positioned further upward, you are going to need a longer drawbar with a head design that brings the top of the splined head to the proper height. You could potentially add a bushing to the shaft of the drawbar to raise the height, but then the drawbar will probably be too short to reach the tooling in the spindle.

You should be able to order a properly sized drawbar through the rep: https://www.maxitorqueritedrawbar.com/drawbar_models.php

Hope this helps.

 

[Kamloopsendo]

David: You never fail to help!! I'm headed out for a bit but will have a better look tomorrow. The drawbar I have will be short, I'd kinda figured that but I really thought the power head had to be mounted to the bearing housing so that it moved up and down with the bearing housing when shifting between low and high range. That does simplify things a bit. I'm going to ***** to KBC as there should be some responsibility on their part to sell the appropriate unit (I hope this'll cover the draw bar cost at least!!).
Mark Jacobs says you do a fair bit of work with 304SS so I may be asking about that too as I've found it quite the challenge to deal with!

Thanks much once again for the help.
Alex

 

[Kamloopsendo]

Just ran out to the shop and realized the draw bar does not move with the cam action so of course a fixed stand-off from the cast housing makes sense. Not sure why the brain fart about the draw bar movement but sitting on the can thinking about it caused me to run out to check! So, really the only real issue is the correct draw bar length and the standoffs both of which should easily be available. THANKS so much again David.

Alex

 

[davidpbest]

Always happy to help. Another observation that might be useful. Even with a custom drawbar based on the dimensions I provided, I still felt that the bushing they provided that is intended to absolutely center the drawbar in the spindle hole was a bit loose. This idea came up in my head as I was attempting to diagnose the source of broken end mills and crappy surface finish. That saga is fully covered HERE, and ultimately lead to the complete replacement of the original J-head with a new one. Whether the bushing was contributing to my problems or not, I will never know. Suffice it to say that in my quest to get the spindle and drive system to behave, I turned a replacement bushing that provided a better fit to both the ID of the top spindle bearing race as well as the drawbar shaft so as to guarantee that the drawbar shaft and splined head were centered in the spindle hole, and to ensure the PDB head unit was also aligned correctly (best way to align it I found was to weight down the pneumatic Head onto the splined hex-nut before tightening the mounting bolts). Original (right) and revised shown here:

As installed:

And a reminder once you get the thing installed: the quill must be fully elevated when you actuate the PDB or the head of the drawbar will not engage with the pneumatic drive above. Took me a while to make raising the quill second nature when changing tools.

Yes, I have done a lot of 304 milling. I’m no expert, but would be happy to help if I can. As my dad was fond of saying, “It helps if you have sharp tools and a quiet mind.”

 

[4cyclic]

I installed mine last year. On the invoice there are 2 items:

TR-100 S/P : Maxi Torque-Rite Power drawbar Unit with step Pulley mounting bracket kit
DB-101 : Bridgeport Step Pulley (R8) drawbar.

Hope that helps with your install.

 

[Kamloopsendo]

Definitely helps, thanks for responding. I wonder if the DB 101 is the draw bar designation after they made up one specifically for David Bests Unit? I"m going to talk to the factory and the supplier tomorrow and get the right kit to finish up. Thanks for taking the time to respond.
Alex

 

[Kamloopsendo]

Always happy to help. Another observation that might be useful. Even with a custom drawbar based on the dimensions I provided, I still felt that the bushing they provided that is intended to absolutely center the drawbar in the spindle hole was a bit loose. This idea came up in my head as I was attempting to diagnose the source of broken end mills and crappy surface finish. That saga is fully covered HERE, and ultimately lead to the complete replacement of the original J-head with a new one. Whether the bushing was contributing to my problems or not, I will never know. Suffice it to say that in my quest to get the spindle and drive system to behave, I turned a replacement bushing that provided a better fit to both the ID of the top spindle bearing race as well as the drawbar shaft so as to guarantee that the drawbar shaft and splined head were centered in the spindle hole, and to ensure the PDB head unit was also aligned correctly (best way to align it I found was to weight down the pneumatic Head onto the splined hex-nut before tightening the mounting bolts). Original (right) and revised shown here:

View attachment 307391

As installed:

View attachment 307392

And a reminder once you get the thing installed: the quill must be fully elevated when you actuate the PDB or the head of the drawbar will not engage with the pneumatic drive above. Took me a while to make raising the quill second nature when changing tools.

Yes, I have done a lot of 304 milling. I’m no expert, but would be happy to help if I can. As my dad was fond of saying, “It helps if you have sharp tools and a quiet mind.”

David: I also wonder about spinning up the mill with the drawbar engaged in the Power head. Puts a bit of wear on the air motor and if one extends the quill down with the draw bar spinning the air motor as it disengages one would expect over time to wear the splines. Do you always extend the quill to disengage the draw bar from the power head before spinning up the quill?
Yes the only thing I've realized with 304 is that VERY sharp tooling does cut better. I bought some 303 which machines beautifully - it gives up a bit in the mechanical properties but still pretty good stuff and MUCH easier to machine.

 

[Jackle1312]

I would recommend contacting the manufacturer.
When I installed one on my Kondia I had a issue with the drawbar length. The vendor I used referred me to the manufacturer and they took care of the issue and sent the part out overnight. Cant remember how I talked to but the customer service was topnotch.

 

[Kamloopsendo]

I would recommend contacting the manufacturer.
When I installed one on my Kondia I had a issue with the drawbar length. The vendor I used referred me to the manufacturer and they took care of the issue and sent the part out overnight. Cant remember how I talked to but the customer service was topnotch.

I will definitely be talking to the manufacturer as well as the supplier. Looks to be a pretty simple solution. Thanks to everyone who chimed in.
Alex