anybody know how to use this centerdrilling

tool on eaby?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category%274&item824691219 &rd=1
This isn't my auction, but I have one of these that's been sitting on the
shelf for want of some brilliant way to use it.
Thanks, DOC
http://www.robot-one.com
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Your question got split between the subject line and the body of the message. (Subject: Re: anybody know how to use this centerdrilling)

    Auction #3824691219
    I think that the auction description gives a quite adequate guidance as to how to use it.
    But to paraphrase:
1)    You put it against the end of a shaft.
2)    You adjust the rollers on the arms until they contact the OD     of the shaft.
3)    You stick the centerdrill (of a size to fit the hole in the     device, and therefore of appropriate size for the shaft size     range that the arms will handle) through the hole in the device,     and drill.
4)    Remove the device, and mount the now center-drilled shaft     between centers on the lathe.
    Note that this is at its best on round shafts. Hex shafts will probably work fine, but square will not work at all. You will have to use one of the many other means for locating the center to center drill your shaft. (But for round ones, this looks as though it would be quicker and less subject to error than most of the other methods.
    Enjoy,         DoN.
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Hi Don:
Thanks for the help.
I guess it would be more obvious if I had a better idea of how a turret lathe is set up.
Thanks also to Jim Sehr also replied off group and mentioned that this works in a manner similar to a steady and said that the bolt that you see in the side of the tool is there to secure the centerdrill in the tool. (in a collet)
I guess this saves having to secure the work piece in the spindle twice.
Jim also mentioned that he used an adapter on one of these to fit the tailstock of an engine lathe. That way he could turn smaller diameter round stock without having to centerdrill.
Regards, DOC
| Voice (all times): (703) 938-4564

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DoN. Nichols wrote:

I never used one but I'm guessing that a center drill get mounted inside the hole and is held in place with the square head set screw. I would think the center drill is positioned to protrude slightly. The device gets mounted in the turret (or tailstock) and is advanced closely to the end of the work piece. Then the rollers are moved inward by means of the thumbscrew, which causes the end of the bar to run true. Next I would think that the turret (or tailstock) is advanced forward to drill the center hole. I could be totally wrong; maybe it is completely automatic in the closure of the three arms holding the rollers. In any case I doubt that it is designed to run statically as Don describes although it seems possible that you could use it that way.
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Most commonly used on turret lathes or automatic screw machines, 1 1/2" shank says #3 or larger machine. Center drill goes in the hole in the center of the device, the rollers are brought into contact with the work using the large knob, usually snugged by hand on each piece in the turret lathe, locked into postion in an automatic. Round work only, (Sorry, Don) but will center within a few tenths if in very good condition, a thou or less for most work.
It's a production device, fine if you have a bunch of shafts to center, not worth messing with for only one piece. Normally used in the turrets or automatics after the turning has been done with a box mill in contrast to the normal of centering then turn from a center. (ie: turn, center, other operations as needed, cutoff, instead of: center, turn, other ops, cutoff) Nice when piece will be ground, the center being concentric allows leaving less stock for the grind operations. Good for production work, boat anchor for anything else. (Not cheap when new, either.)
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Don't know for sure, but it looks like you'd mount the tool into a stationary portion of the lathe (tailstock?), mount a center drill into the middle hole, and then mount the stock to be center drilled using the rollers (similarly to using a steady rest) so that you'd hit as close to center as you could adjust them... Neat little tool, it looks like.... Might have to try to make one.
Centering new stock is always a pain in the butt for me. It just seems to be one of those skills that I'm doomed to forever buy oversize stock in order to compensate so I can turn it down.
Which brings me to the obvious question that I should have asked long ago -- what is the best "field expedient" way to center round stock for drilling assuming that you don't have a steady rest in the first place, and assuming that the stock is too long to be simply chucked up? I've used the marking tool, and then started on the cross marks with a small punch and worked up like it says in the books, but I'm always a couple thou (or more) off.
Thanks all!
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On 08 Jul 2004 11:34:01 GMT, snipped-for-privacy@aol.com (Enders Epilogue) wrote:

You and everyone else. In the shop I work part time in, if we have to hold dead on concentricity, oversize stock and grind is the normal procedure.

Assuming you mean you're using a center head from a combination square, if it's within a couple of thou, you're doing pretty good. ONe way of hitting a little closer, when you scribe the end, make four lines, 90 degrees apart so you end up with a tiny box in the center. Sorta compensates for stock that isn't perfectly round or a center head that isn't perfect, and none of them are. Maybe not of much help, but if I have something too long and large to go through the spindle, I'll clamp it to a universal right angle in the mill, indicate to center and center drill there.
Other devices available, one resembles a center punch with a conical "skirt", the center punch in the middle, but it depends on the end of the stock being square, if it isn't, your punch mark won't be centered. It also depends on being able to hold the device perfectly alighned with the piece, not too likely to happen either. Quick and dirty, but I don't remember seeing one much larger than being able to mark over an inch or so. (Doesn't mean they don't exist, means I haven't seen one.)
Hermaphrodite calipers works too, just takes a little practice before "what looks easy" becomes easy. Lennie the Lurker
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