Drilling on a manual lathe

"Dan " wrote: (clip) I'm not sure I believe the gravity statements. Gravity affects the

^^^^^^^^^^^^^^^^^^^ Right. If it's flexible enough to sag, it will sag whether or not it is spinning. If gravity were an issue, I would expect gun barrels to be drilled vertically. Anyone ever heard of an artillery boring tower? ^^^^^^^^^^^^^^^^^^^ Spinning the drill and the part probably makes a straighter hole

^^^^^^^^^^^^^^^^^^^^^ If the drill is not symetrically sharpened, all sides of the hole are exposed to both lobes, whether or not the work alone is rotating, the drill alone is rotating, or both are rotating.

When both are turning, the sum of the speeds or the difference is the effective speed of cut. Both turning in the same direction can cancel the cut while the part and drill are turning fast.

Mart>>> "Ed Huntress" wrote: Why are you having trouble with coolant? Most

I'm not following you, Leo. There is only one cutting edge on a gundrill. What are the two "lobes"?

-- Ed Huntress

sporting size firearm

sealing is done, etc.?

The guy uses standard gun drills. As such, they are held in a standard size sleeve type holder built from a bored block of material(around 1 inch, from the looks), that has the feed for the oil , and a couple O rings, and a setscrew to lock it in.

Cheers Trevor Jones

Yup! If it was worthwhile, there would be all sorts of tools available to do that.

Why is it slow compared to a VMC? Crank the revs, push the drill, done!

If you pussy foot around, and try to scrape out 2 inches of hole, the heat will kill you. Pound the drill in, as fast and hard as the machine can run, or at least somewhere near the feed/speed recomendations (do the calculations!)in MH, and run with it. A couple fast pecks will get enough coolant or oil into the hole to make life a little easier, but 2 inches should not be an issue for a one shot, 10 second or less, hole.

Cheers Trevor Jones

Thanks Trevor. I have got to get that video.

sporting size

sealing is done,

The guy uses standard gun drills. As such, they are held in a standard size sleeve type holder built from a bored block of material(around 1 inch, from the looks), that has the feed for the oil , and a couple O rings, and a setscrew to lock it in.

Cheers Trevor Jones

Dan sez: "Spinning the drill and the part probably makes a straighter hole because any inequality in the sharpening of the drill in nullified by rotating it it. "

You are probably right, Dan. AFAIK, commercial gun barrels are drilled that way. It can be done without turning the drill though. It requires a lot of pecking, that's for sure. Several years ago, I drilled a .38" (3/8+) hole, 12 inches into a 1" diameter brass bar using an ordinary twist drill silver soldered onto an extension. It went fairly straight - within 0.010 as I remember.

Bob Swinney

I just drilled two 1/2" holes, 3 1/2" deep through steel with a hand drill! It wasn't fast though. Probably took 20 - 30 min. per hole. I drilled a 1/8" pilot hole 2" deep first without breaking the drills

I'm not sure I believe the gravity statements. Gravity affects the drill because of its mass. Spinning it around doesn't change the mass. ie Turbine rotor sag.

Just my two cents. Probably wrong.

Are you calling me a wus?? A lathe-wus?? :)

Here may be part of the problem, as per some comments in this thread:

The issue of "symmetrical or new drill" came up re chips, and I think I'm noticing a strange Asymmetry to the chip production, sometimes very little coming off one flute at all!! Even on new drills!

Then, just last night, in a 5/16 hole, I saw one nice long continuous ribbon come out, but not two, and realized, that indeed, had TWO continuous ribbons come out on any regular basis, I would not have been originating this thread!

This was from a 118 deg drill, not the 135 deg I buy in sets for cheap from Sam's.

Any tips on how to get two continuous ribbons coming off, vs. chips? All

Use a quality shapening fixture. It's not rocket science.

Agreed, but I was seeing, I think, this asymmetry (chip-wise) on *new* drills. But I'll look at it more closely.

Try to figure the odds that you, among all the guys around, are the one getting ALL the misground drills. :-)

My first bet is that you have an alignment issue with the tailstock. Or a buggered up chuck.

Time spent checking is time well spent!

The drills do the same when used in a drill press? Results that move around from machine to machine may well be attributable to the tooling, but repeatedly getting the same results on one machine and not the others, is rarely the fault of the tooling.

You can get a bit better idea of what is happening, by coating the entire cutting end of the drill with a sharpie or other permanent marker. It should be obvious from looking, which cutting edge is doing the work.

Have fun!

Cheers Trevor Jones

I don't see gravity having a measurable effect on a 3/8" jobber drill. Also the factors in gundrilling are different than ordinary twist drilling, ie different geometry drill, high pressure coolant to force chips out.

I would suggest to the OP to try a drill bit made for drilling aluminum, instead of the ordinary all purpose jobber drill. If your doing production you may consider a drill with oil holes, and oil drill holder, and coolant pump. If you are using a CNC machine, consider adding a peck drill cycle.

But really, drilling a 3/8 hole in aluminum really shouldn't present much of a challenge, even without a pilot hole.

Tony

Are you gettting enough exercise? Try adding another potato.