Kurt drawbars

[MrWild]

I see eBay has several auctions for new and used Kurt automatic drawbar kits. Many are for R8 collet equipped mills. I've asked the sellers of the new drawbars how much one for a rigid ram BP1 with nmtb30 tooling would be, and have been quoted several hundred dollars more than the R8 styles. Because I've never held one in my hands before, I don't know what the differences are except for the drawbar length and diameter.

Can anyone tell me the differences between the R8 style and the nmtb30 style if there are differences? If the changer itself is the same, with just a different drawbar being used, I think I'll buy a used or cheap new/used R8 style and buy the required nmtb30 drawbar from Kurt. Limited budget and all that, ya know.

[machintek]

In theory, there were 2 different styles. One was a lever type and one was a push button type.
The lever type was the most simple, typically used on a S1STD. The push button type when used on a S1STD had a mechanical/pneumatic interlock that fit on the FWD/REW switch so it would not work when the spindle was ON.
The push botton type on the CNC usually tied into the air line to the brake cylinder (BOSS 8, BOSS 9, V2XT, some BOSS stepping motor CNCs) and had a pneumatic delay which allowed the spindle to stop and then the drawbar to operate.
The older CNC and EZTRAKS that did not have the pneumatic brake used a variation that had a electric solenoid that would disable the draw bar if the spindle was turning.
These extra parts raise the price. See exactly what version he is selling.

George

[MrWild]

Thank you,

Machinetek you are the holy Grail of Bridgeport knowledge. The seller of new Kurt drawbars on eBay claimed that he had no idea what the differences were and that he had never opened a box to see. I have to admit that warning flags jumped up high at that bit of information.

This old iron I'm working on has a pneumatic brake (with broken actuating arm), and a bank of electro-selenoid air valves. I recieved an air vise with the machine, but several of the air valves are unused and should(?) be able to operate the air cylinder for the brake (even if I have to wire in a switch).

I just hope the rest of the machine isn't as trashed as the table. When I went to look at the machine the table had a layer of mung on it. I sit in a wheelchair so couldn't see the surface well. Upon getting it home and getting my new stand-up wheelchair, I've been cleaning what seems like 20 years of crud. Upon getting to the surface of the table, I'm appalled at how chewed up and bashed in it is. It actually looks like vises were clamped down on top of chips bunging up the table surface. Animals shouldn't be allowed to be machinists.

[machintek]

Consider a "stevens plate" for the top of the table. That is what it was called way back. It was an aluminum plate with evenly spaced threaded holes of about 1 inch thick. It would cover the neglected table. Of course your piece of aluminum needs only counterbored holes to mount it and some way to mount a vice or vices to it.
These were great for mounting fixtures, etc.

As a side note, I was just restoring the geometry on a 2 month old CNC horizontal boring mill and had to stone the table so my granite square would sit flat. They also had clamped pieces down to the table without good housekeeping. On a 3/4 million dollar machine! Oh, yes, I was doing this because they crashed it.

George

[MrWild]

Well, I guess it is time to step up and accept the dumb a$$ award. The one new thing I got with the mill was an aussi draw bar in a much mangled and dirty box. Before I hit the hospital this last time I had given it a cursorary glance and thought it was the old style mechanical hand lever, up high at the top of the mill head. The last owner had told me about the "new" drawbar he had bought, but when I did my glance, the new drawbar in the box was the 7/16 style for R8 collets and the meat hound had tried to use it with the 1/2-13 nmtb tooling. Naturally a few threads were buggered. I didn't look further after that...

My plan was to buy a Kurt automatic and sell the Aussi mechanical. Looking at it tonight, I see the Aussi is a brand new automatic. What I thought was the mechanical actuating lever was really the mounting bracket for the regulator/oiler/valve assembly. All I need to make it work is a new drawbar for the rigid ram/nmtb30 tooling. Any idea where I might find one, or a blue print of the length and diameters for machining one from 4130? Talk about lucking out and saving bucks!