Drilling angled holes through tube?

[Eric C]

I need to drill 12 accurate (+\- 1/32) 7/16 dia holes through some 2" x2"x 3/16" square tube.
The hole will be at a 36 degree angle and go all the way through the tube. The part is made already so it has to be done in place. Any suggestions?

[tapwelder]

how 'bout a template and round file. Or Is it possible, to insert a tube with that id and tig around it. , then grind flat.

[Eric C]

Hum- sloppy hole with a accurately placed tube, welded in and sand flat? Sounds like a good idea.

[Garauld]

Use a Bridgeport with a 3/8" end mill to rough it out and then clean it with a 7/16" end mill for size. Any drill will walk on the inside face and you'll lose your tolerance..

[Tool Maker]

If you can get a couple drill guides ( small hardened steel tubes to guide a drill) you can make up a little jig that you can clamp onto your tube and run a drill through it Or better yet use a long milling cutter in it. By doing it this way you can cut the holes completly accurate with a drill motor. Mac

[puddytat]

Hi Eric, make a simple hinged box jig with two angled holes that clamps to the tube and you drill from both sides alternatively at the reqd angle, finally using a long drill to go through the two angled holes to just clean up any burrs.

I had to do this many years ago on round pipe.....the pipe was upright in the ground but the holes were angle to allow for another smaller pipe to pass through it, part of a rail guard on a sloping path.

The jig (hinged in two halves) had bushes at an angle that supported the drill with about three times the diam in the length to stop deflection of the drill point.

If you want a sketch, just ask.
Ian.

[Eric C]

Originally Posted by Garauld

Use a Bridgeport with a 3/8" end mill to rough it out and then clean it with a 7/16" end mill for size. Any drill will walk on the inside face and you'll lose your tolerance..

The tube is already in place on a railing.

[OPUS FERRO]

Eric C - Who thought of this, and what is the budget - Opus

[kidtigger24]

Originally Posted by Tool Maker

If you can get a couple drill guides ( small hardened steel tubes to guide a drill) you can make up a little jig that you can clamp onto your tube and run a drill through it Or better yet use a long milling cutter in it. By doing it this way you can cut the holes completly accurate with a drill motor. Mac

x2 on this idea. This is what you need:

http://woodworker.com/18x38x12-drill...s&searchmode=2

Drill your 36 degree angle on a piece of hardwood, and press these into the hole. Clamp to the tube, drill. Done.

These bushings work awesome. We have them in a piece of plywood for drill shelf pins for built in cabinets. They are hardened and impossible to kill. We have remade the jig a dozen time cause the wood falls apart, but the bushings are still going. This is after 10+ years and probably over 10,000 holes! These will work for your propose.

kidtigger24

[Eric C]

Originally Posted by Tool Maker

If you can get a couple drill guides ( small hardened steel tubes to guide a drill) you can make up a little jig that you can clamp onto your tube and run a drill through it Or better yet use a long milling cutter in it. By doing it this way you can cut the holes completly accurate with a drill motor. Mac

I made a jig, but a normal 7/16 bit didint want to start real nice at 36 deg.

[shortfuse]

Originally Posted by Garauld

Use a Bridgeport with a 3/8" end mill to rough it out and then clean it with a 7/16" end mill for size. Any drill will walk on the inside face and you'll lose your tolerance..

First...I AM NOT a machinist and have no access to a Bridgeport. But I am curious; could one use a 16" drill press with a drill press vise and or jigs/clamps and a 3/8" end mill to bore the holes? (sort of a poor-boy approach, but ya use what ya got)

[Eric C]

Originally Posted by OPUS FERRO

Eric C - Who thought of this, and what is the budget - Opus

Normally it would have been done on the drill press before assembly, but the guys built the rail before I gave them the layout. They thought it would be easy to drill with a 1/2" drill motor and just "waller the holes out", some times its hard to get them to understand what high end means.

[DSW]

Eric you might have better luck with something like the Dewalt Pilot point or B&D Bullet bits. The bits tend to cut on the outside and leave a little "washer" surrounding the pilot point.

http://www.dewalt.com/tool-parts/dri...ts-dw1909.aspx

http://www.blackanddecker.com/allpro...rill-bits.aspx

[OPUS FERRO]

Eric C - High-end means start over - Opus

[ironmangq]

Make a drill guide and use an end mill, you need something that will start its cut on the perimeter not the center. Dull the flutes some so it wont eat up the guide and go to town.

[hobohilton]

1) Scribe layout lines around the tube. Center punch for pilot holes.
2) Pilot hole, both sides (entrance and exit). Drill it square with the face of the tube.
3) Fabricate a "base plate" for a mag based drill at the correct angle.
4) Use a "hole saw" type bit with a pilot bit.
5) SLOWLY feed the hole saw pilot bit through the hole you drilled as a pilot hole.

I know, to you machinist, you will argue on the slight bit of center line / angle / layout but he gave 1/32" tolerance.

I'd jig up and experiment on some drop off's prior to making the actual holes on the hand rail.

IMHO

Hobo

[Mondo]

Originally Posted by Eric C

I made a jig, but a normal 7/16 bit didint want to start real nice at 36 deg.

This jig should work well, but start the holes with a smaller bit (I suggest 1/8") held perpendicular to the surface first. Don't drill all the way through the first wall, just enough to set a dimple that the 7/16 bit can use to start it's cut.

- Mondo

[Eric C]

Ended up using the small mag drill with a 7/16 X 2" annular cutter. Tried to modify one bit by welding a stub of 3/4 cold rolled to the end of it and grinding the neck down a bit so it would cut all the way through from one side.(couldnt find a 7/16"x3" bit). that worked for one hole, but had too much run out and snapped while cutting the second far hole. We ended up laying it out from every reference point available and drilling from both sides. It took awhile, but came out fine.

[Brett]

Originally Posted by Eric C

The tube is already in place on a railing.

We have success with reamers in that application. But we tend not to have to have extreme accuracy in the hole size and the holes are smaller .
Most of the time this will be for a wire job on a stair (I think wire is a dirty word atm )
Drill hole square, insert reamer , gently angle down to desired slope. Its worth noting that in our application it tends not to matter if we are a degree or two too much only if its not enough.

Brett

[MikeGyver]

Drill a 1/8" hole straight into the tube at both locations. Then drill out to 1/4" while aiming at the other hole. Then drill to 3/8" using a long bit that will seat in both holes at the same time. Now they're pretty much co-axial. Then finish it off with a 7/16" bit.

[brucer]

make a jig like mentioned above, and use a long series center drill to start with, then go to a 7/16 drill. you might have to have two jigs, one for center drilling and one for drilling or make a small bushing for the center drill and swap out to a 7/16 bushing.. i dont know off the top of my head what size shanks will be on the center drills, a particular size might have a 7/16 shank..

[gimpyrobb]

Originally Posted by Brett

We have success with reamers in that application. But we tend not to have to have extreme accuracy in the hole size and the holes are smaller .
Most of the time this will be for a wire job on a stair (I think wire is a dirty word atm )
Drill hole square, insert reamer , gently angle down to desired slope. Its worth noting that in our application it tends not to matter if we are a degree or two too much only if its not enough.

Brett

Originally Posted by MikeGyver

Drill a 1/8" hole straight into the tube at both locations. Then drill out to 1/4" while aiming at the other hole. Then drill to 3/8" using a long bit that will seat in both holes at the same time. Now they're pretty much co-axial. Then finish it off with a 7/16" bit.

Originally Posted by brucer

make a jig like mentioned above, and use a long series center drill to start with, then go to a 7/16 drill. you might have to have two jigs, one for center drilling and one for drilling or make a small bushing for the center drill and swap out to a 7/16 bushing.. i dont know off the top of my head what size shanks will be on the center drills, a particular size might have a 7/16 shank..

Did you see post #18?