Power Drawbar Issue/Question - new Atrump Mill

Not too happy right now with Atrump. In process of getting my new mill running - its mostly set up now. The PC has a hardware issue and I am waiting for the replacement unit. It still works but I have to manually turn the PC on as you can't change the bios. Not too good for a brand new machine.

Tonight I put air on the power draw bar for the first time. It did not go well. Essentially the drawbar was semi-seized to the spindle. When I engaged the air, the spindle was spinning and I could not hold it with my hand without major effort and the air motor was laboring real bad.

I took the power draw bar motor off to inspect it. The unit is a Maxi Torque-Rite. Did not see any visual issues but the bar was pretty much stuck. I messed with it quite a bit and it is now a lot looser but still not right. Without a holder, it takes a couple seconds of the air motor spinning before the motor does not labor at all.

I have never used a power draw bar before. I am used to a Bridgeport drawbar where the bar can be removed from the top without anything holding it.

This bar does not move vertically - acts like it is locked in place - is this normal? If it is normal, any idea how to remove the drawbar?

Was hoping to be able to make some progress with this tomorrow but if necessary will wait till Monday when Atrump support is available.

Any suggestions or feedback?

It's clearly not right (you knew that) - the bar should spin freely under air without the spindle moving much at all.

I've only had mine apart once, and don't recall the drawbar itself being stuck to the spindle in any way, but it was awhile ago.

bryan_machine said:

It's clearly not right (you knew that) - the bar should spin freely under air without the spindle moving much at all.

Click to expand...

Yup - the question on the table is whether the drawbar is supposed to come straight out (like I'm used to on my Bridgeport) or is it captured and there is a trick to get it out.

My gut feel is that its stuck. And no way am I (or anyone else) going to put a hammer to it to drive it out. If it is indeed stuck, I think the best bet is to drill and tap the top of the drawbar, put a stud in it and pull it out against the inner race of the support bearing.

I did verify that the drawbar height is set correctly against the manufacturer's instructions.

I hope that the damage is confined to the drawbar or I will be quite mad..........

Thoughts?

What spindle taper?

converterking said:

What spindle taper?

Click to expand...

It is a BT30 taper.

On a 40 taper mill there was a roll pin in the nut on top of the drawbar. You had to remove the roll pin, unscrew the nut, and the drawbar came out thru the bottom of the spindle.

Ordinary "Bridgeport style" heads of all breeds generally don't have a drawbar retainer. Fixed heads and VMC heads frequently do.

Maxi-Torque Rite instructions and parts books make no mention of a retainer either so odds are it hasn't got one. However the plain portion of the drawbar between the spline drive and drawbar paper is a pretty close fit in the spindle bore. Be unsurprised to find grot and grunge in there sufficient to make it too tight and hard to extract.

Clive.

Thanks for all the replies!

I have confirmed with the vendor that the drawbar is not retained so it should slide right out. I got it to the point of rotating, but it is totally stuck vertically.

I'm off on a business trip for 2 weeks. When I get back they will send a service guy to work on it.

I know this is not a million dollar machine, but its very frustrating to have so many issues on a brand new machine. Maybe I was naive, but I expected better. In addition to the drawbar and PC issue, there are several attention to detail issues that I have to correct. However, I am taking a real liking to the software so I am still quite happy with my choice of machine.

Mach-1 Systems - R8 Quick Change Tooling for Knee Mills & Bed Mills

this would of fixed your issues, we have five of them

solidworkscadman said:

Mach-1 Systems - R8 Quick Change Tooling for Knee Mills & Bed Mills

this would of fixed your issues, we have five of them

Click to expand...

Does it work with a BT30 taper?

What problem does that solve on a BT30 machine - it's already quick change!

Maxi torque is hardly quick compared to these. No air nessary to boot

I had a 30 taper quill machine (yes, cnc) with an air powered drawbar. Had a Kurt setup, using a 3/8" air impact to drive the drawbar. To fix when things needed adjustment, I just removed the cover of the assembly, disconnected air, removed maybe 4 cap screws, then lifted the assembly off the top of the head. Then the drawbar lifted out. Don't know if this helps or not....... Sounds like your setup might be more agony......

Update - its fixed (at least temporarily till they send replacement parts).

They put in a R8 spacer on my BT30 drawbar. The R8 spacer has a shoulder that goes into the spindle. The BT30 does not use a shoulder. When the air motor hit the bar, it drove the shoulder into the spindle and locked it up because the shoulder OD was 0.012 inches larger than the spindle ID.

When the spacer shoulder was driven into the spindle, it drew the shoulder against the drawbar and spindle. The reason I got it somewhat loose was because it wore a groove in the drawbar. We tapped the top of the drawbar and pulled it out - it fought us all the way out.

We chopped the shoulder off the spacer and cleaned up the drawbar. Works great now. They will send a new spacer and drawbar.

Changed the PC and all was good till the battery died. New battery and is ok now.

Got my fingers crossed that all is good now and finally ready to cut chips........