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gellfex
01-05-2009, 02:18 PM
Something I build regularly needs a 1/2" stainless rod with a 1/4" bore and a 1/8" hole drilled crosswise 1/8 off center.
http://img.photobucket.com/albums/v358/gellfex/crossdrilledlinkage_editedsm-email.jpg
I've been doing this procedure in what I feel is a half assed way that works poorly, by using a 1/8 endmill real slow after positioning using the vise jaw edge. I often get a hole loose at the top end due to deflection in the off center cut after it breaks through inside. I haven't tried boring the 1/4 after the 1/8, that was on the agenda. Do any of the geniuses or old hands here have any better ideas?

garyphansen
01-05-2009, 02:33 PM
If you do this regularly why not make a drill jig. Drill a larger piece of stock on the center line of the diameter with the same size drill you need for the part. Then bore a hole in that you part will fit into off center. Harden you jig if you are going to use it mor than 20-30 times. Gary P. Hansen

Circlip
01-05-2009, 02:43 PM
Yep, 1/8" first in a jig, then lathe and through drill 1/4".

Regards Ian.

gellfex
01-05-2009, 03:45 PM
If you do this regularly why not make a drill jig. Drill a larger piece of stock on the center line of the diameter with the same size drill you need for the part. Then bore a hole in that you part will fit into off center. Harden you jig if you are going to use it mor than 20-30 times. Gary P. Hansen

Yeah, that had occurred to me, but I thought the deflection of the sloped entry would wear the hole there pretty quickly. I'm not so up on hardening, but wouldn't the process change the hole diameters slightly? Isn't that why things are generally reground after hardening?

Maybe I'll try an unhardened jig. I'm on the 10th reorder and they each take only 2 pieces.

ERBenoit
01-05-2009, 04:01 PM
How many at a time are you making? The two at a time, or a bunch and shelving until they next reorder.

Suggestions:

1) You don't give an AOL, but if theyre relatively short, I'd try plugging the 1/4" thru hole with a hardwood dowel.

Then try:

2) Spot or center drill, (A #1 center drill is 1/8" diameter.)then drill the hole before or instead of using the endmill. If the hole diameter need be accurate, drill a bit smaller then follow with a reaming or the endmill.

3) If insisting on the endmill, since it only 1/8" in diameter, I'd spot/center drill until the spot was 1/8" diameter. That way the endmill would be cutting from the same plane instead of slapping, bouncing around and being deflected by the material on the "higher" side of the hole.

#2 and 3, Yeah, might be a bit more work, in tool changing, but you may get better results.

If you try the drill ideas, I'd suggest using screw machine drills. Thier shorter length will give you more ridgidity.

Scishopguy
01-05-2009, 04:03 PM
Yeah, that had occurred to me, but I thought the deflection of the sloped entry would wear the hole there pretty quickly. I'm not so up on hardening, but wouldn't the process change the hole diameters slightly? Isn't that why things are generally reground after hardening?

Maybe I'll try an unhardened jig. I'm on the 10th reorder and they each take only 2 pieces.

When you build your drill jig plan on putting a hardened drill bushing in the plate that aligns the hole. Lube the drill and a bushing will last for thousands of holes and when it does get a little sloppy you just press it out and press in another one. You can order them for the size of drill you are using for just a couple bucks each from MSC or McMaster.

tony ennis
01-05-2009, 04:53 PM
I don't like drilling on round stock. My first reaction was to get bar (square) stock and drill the 1/8" hole. Then put that in the 4-jaw and bore the 1/4" hole. Then turn it round. Part it.

You could use a typical spaced-hole jig in the drill press to space several 1/8" holes in the bar stock, then assembly-line a pile of these things.

gellfex
01-05-2009, 09:40 PM
I don't like drilling on round stock. My first reaction was to get bar (square) stock and drill the 1/8" hole. Then put that in the 4-jaw and bore the 1/4" hole. Then turn it round. Part it.

You could use a typical spaced-hole jig in the drill press to space several 1/8" holes in the bar stock, then assembly-line a pile of these things.

Sounds possible but a shedload more work! Thanks guys for the lots of ideas. I've used drill bushings but didn't think this jig would be a good candidate, and I always use stub drills where I can.

What about this: I bore a throwaway piece of square stock 1/2, set screw the 1/2 rod stock in there, and drill through both together. That way I get no deflections, and as many uses as I can fit in 1/8 holes along it's length.

HSS
01-05-2009, 09:52 PM
That sounds like something to try, Gellfex. Push 'em in, drill 'em and knock 'em out with a punch. Easy with no deflection.;)

wierdscience
01-05-2009, 09:57 PM
First thing to do is move the decimals on your drawing,otherwise you'll need a longer bit;)

The drill jig would be the way I would go,but I would fill the tube with a piece of aluminum rod before milling.

A-2 is one of the easiest toolsteels to heat treat,not much distortion.