New Drawbar For The Rockwell Mill

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platypus20
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Location: camillus, ny (syracuse)

New Drawbar For The Rockwell Mill

Post by platypus20 »

If I can get the company leaves me alone, I'll actually get the mill, making chips.I've been out of town for the last 2 weeks, working on the installation of a new burner on a boiler and the fabrication and installation, of a new stack damper on another boiler, with 300 miles separating the two jobs.

Today, I was going to cut a 3/16" keyway in a 3/4" shaft, I went to tighten the ER 32 x R8 collet chuck and the drawbar stripped, the thread just rolled right off. So in the morning I'll make a new drawbar, I have a a 12' length of 7/16"-20 B-7 hardened all-thread, with that I'll have to make a nut assembly.
jack
spro
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Re: New Drawbar For The Rockwell Mill

Post by spro »

Oh man. Just what you didn't need. Serious work on the boilers and they rock. Let's say I was close and you guys move the world. Collets, collet heads and drawbars: if it wasn't so evident that they tapped Imperial right into metric, well I saw it. So don't make it evident, go oversize. All the time it is losing the DP. Anyone notice how actual collets and drawbars are flying away. They are used and maybe 20- 50 years old but they still fit together.
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platypus20
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Re: New Drawbar For The Rockwell Mill

Post by platypus20 »

ended up being a simple project, an 11" piece of the 7/16"-20 B-7 hardened all-thread, a 7/16"-20 coupling nut, a couple of 1/8" roll pins and a quick plug weld and it was done.
drawbar 002x.jpg
jack
spro
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Re: New Drawbar For The Rockwell Mill

Post by spro »

That was great and quick too. I'm glad your collets are okay. I was mentioning other type new collets (MT#2.B&S 7). I'm not aware of that problem with R-8. The old bar was low grade and wore out, like you said.
I like a brass or soft steel thrust washer at the top for various reasons.
pete
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Re: New Drawbar For The Rockwell Mill

Post by pete »

We all know that drawbars hardened or not are going to wear out over enough cycles so they have to be thought of as semi replaceable tooling. I've no real numbers to back it up, but learned the hard way on my little Emco machines that lubeing any screw that gets used to tighten a slide or lock a spindle extends there life by a whole lot. I'm guessing, but maybe up to 10 times verses the life of dry threads. Since my ceiling is an inch or two too low I can't just pull the draw bar and lube it's bottom threads any time I want without tilting the head. So any R8 tooling that's going into the mill gets a few drops of oil out of the way oil container onto the female threads once in awhile. Oil and collets for tool shank holding are not a good combination. Being liberal with the oil can create further problems. Anything more than oil just on the collet or tool shanks female threads isn't needed or wanted. So far I've never run across any recommendations for lubeing those threads, but it's mentioned doing so for items like those ER collet chuck nut threads. Once I figured out it helped then it's seemed logical to add some lube those threads.

Most of us including myself probably aren't cleaning our collets in solvent as much as we should. I'm convinced it's the wear particles that are what creates accelerated wear on anything like those drawbar threads. Flushing out those threads of any old oil and those wear particles once in awhile with something like an electrical contact cleaner would likely extend there life even further. Replaceing the drawbar is fairly cheap and simple to do. Replacing collets and other tooling because of worn out threads isn't. I'd doubt any of this gets done in a production shop, but as a hobby then mill tooling is damn expensive so I try and extend it's life as much as possible.
spro
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Re: New Drawbar For The Rockwell Mill

Post by spro »

I used alcohol but the Brake Clean stuff is darn good. Steve M has mentioned ( I agree) the Green can works fine and less toxic. Just don't get any of it on bearings or seals.
pete
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Re: New Drawbar For The Rockwell Mill

Post by pete »

Yep that Brake Clean does work well. Probably because of the problem when any heat might be used for some of them it wasn't allowed in any of the mines mobile equipment shops at any place I've worked at is why I don't use it. By now they may have changed the chemicals used in some types since any heat enough to boil it caused the creation of phosgene gas. But that alcohol would work just as well. I like the spray cans of CRC electrical contact cleaner other than there cost since there so fast and easy to get anything really clean.
spro
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Re: New Drawbar For The Rockwell Mill

Post by spro »

I like that as well. A trace of oil on the threads .
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