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View Full Version : Ancient history: half drilling vee for tailstock. Why??



Arthur.Marks
06-04-2013, 09:03 PM
First, I understand the entire tailstock drilling vee thing ( = "crotch center" ), but why make one with half a vee? I can't come up with a reason. picture (http://www.ricardo.ch/kaufen/buero-und-gewerbe/metallgewerbe-und-schlossereien/zubehoer-und-teile/reitstockeinsatz-mk2-mit-halb-v-ausschnitt/v/an713612060/?ABTestedFeatureKey=59)

CCWKen
06-04-2013, 09:21 PM
It may be shop modified. The only reason I can think of is for clearance of some protrusion on the backside of tube or rod.

RussZHC
06-04-2013, 09:27 PM
If the "half" were actually not quite half, it would allow one to drill completely through a tube/pipe/rod with a larger diameter than would be the "norm"...or at least I would assume that the width of the "V" of the crotch sort of controls how large a bit can go entirely through before touching the sides of the "V".

I also agree with CCWKen, might have been for a very specific purpose/reason.

The other thing I thought of, though I don't know how valid it is, it would give a flat edge to measure from...

Fasttrack
06-04-2013, 11:24 PM
I've never seen a drill pad or "crotch center" before. Could someone give me a short primer on the purpose/operation (or point me towards some good reading)?

Thanks!

Jaakko Fagerlund
06-04-2013, 11:46 PM
I've never seen a drill pad or "crotch center" before. Could someone give me a short primer on the purpose/operation (or point me towards some good reading)?

Thanks!
You put that in tailstock, drill in the chuck and your workpiece (usually round) in that V and advance it against the drill with the tailstock to get a hole in the workpiece.

Edit: This is easy way to drill on center holes in pipes and small rods.

Paul Alciatore
06-05-2013, 01:41 AM
You put that in tailstock, drill in the chuck and your workpiece (usually round) in that V and advance it against the drill with the tailstock to get a hole in the workpiece.

Edit: This is easy way to drill on center holes in pipes and small rods.

Yes, since the head stock and tail stock of a lathe are supposedly accurately aligned, this is a quick and accurate way to drill round stock (rod or tube) through the center without any additional set up as you would need if using a Vee block in a drill press or vertical mill.

Sun God
06-05-2013, 04:05 AM
If it were me, I would have done it if I needed to repeatedly drill a cross-hole - for example, for a cotter pin - through a turned part, whereby the cross hole is referenced off a shoulder on the part.

So, you would butt the shoulder on the part up against the ground away face of the V-centre, which gives you the right distance away from the shoulder, and cross drill - to make a a second-op simpler. You could do the same op on a drill press or a vertical mill, but perhaps it was more sensible for the creator to do that op on a small lathe, perhaps with a lever tailstock.

Fasttrack
06-05-2013, 10:58 AM
Thanks guys!

Forestgnome
06-05-2013, 12:12 PM
It would seem a little dangerous if the part wasn't supported on both sides of the hole being drilled. A recipe for binding.

Arthur.Marks
06-05-2013, 03:42 PM
That was my thought too, Forestgnome. Sun God's thoughts seem the most practical. At least if there was a shoulder that would aid in supporting the workpiece cross-wise to the vee. Even so, I feel like it still makes no sense, and it is a manufacturer catalogued item:
http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/Schaublin%20items/Vedepercage_zps1d99f073.jpg (http://s771.photobucket.com/user/Arrak_Thumrs/media/Schaublin%20items/Vedepercage_zps1d99f073.jpg.html)
Unfortunately, the catalog provides no more detail. It is called, quite literally, "drilling vee, half." Bizarre.