angled drilling?

I have to make some 1-1/4x.120" wall cable stair railing posts. The stairs go up at about a 36 degree angle. The tubes have to be drilled at that angle. Well, either that or I have to drill both sides and carefully lay out the holes. I figure it's faster to drill at an angle. I'm going to do it on the Bridgeport, with the tube clamped in the mill vise and supported on both ends by machinist jacks. I'll slew the head around to the correct angle. This much I've done a bunch of times.

The holes will be 3/16" in diameter.

Here's the hard part. How can I drill the hole without having the drill walk around on me? Normally I use a screw length bit and it goes in correctly. But a

3/16" stub length bit isn't long enough to reach the back side at an angle, and a jobber's length bit will walk around on the inside edge of the backside randomly, giving me hole location errors. Is there any solution to this?

I guess I'll have to drill one side, flip the part, reverse it end for end, and drill the other side. Carefully.

Is there any way around this?


Reply to
Grant Erwin
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Stab it with a 3/16 flat bottom endmill to create a flat for your drill to start on. The endmill will likely create an oversized hole, but it will stay on location.

Reply to
Dave Lyon

Proly not, unless you can find a long 3/16 em, and mill very slowly thru the other side. Even then, at that length, there'd proly be walking.

How bout, with the tube laying normal/flat, *center drill* one side , then do the math, and center drill the other side at the correct corresponding positions. Then angle-drill each side. Location error should be minimal if the trig is correct. Probably more of a problem w/ tube *rotation* when shifting the tube, than misalignment of the angle itself. However, this rotation issue would be a problem even for one-sided drilling at no angle. I solved this on a cnc mill by having the stub drill itself move/drag the pipe once the vise jaws were carefully loosened. Making the gas pipe for pizza ovens. :) In this case, after the first pair of opposing holes are drilled, you might slide stiff 3/16 rod thru, and visually align the rod w/ marks on the spindle, proly keeping the rotated angle +/- 1-2 degrees. If the wall thickness of the pipe is suff, mebbe a pin fixture in the vise would fix the orientation.

-- Mr. P.V.'d formerly Droll Troll Party Nominee, IPPVM Independent Party of the Proctologically Violated®© (M)asses "That's proly not a hemorrhoid you're feeling.... " entropic3.14decay at optonline2.718 dot net remove pi and e to reply--ie, all d'numbuhs

Reply to
Proctologically Violated©®

Cobble together a dedicated bushing?


Reply to
Ken Davey

Good idea. A two part drill fixture, one part fits on the outside of the tube. After drilling through one wall, the other part, a round bar with an angled hole through it, would be slid into the tube, located with a pin through the first hole and clamped in place. Take off the first fixture and drill all the way through the internal fixture and opposite side of the tube.


Reply to

"ff" wrote:in message news:PG8%g.23134$

^^^^^^^^^^^^^^^ The jig is a good idea, but your procedure is too complicated. I would make a two-piece drill jig that clamps onto the tube. Weld the halves to a pair of vise-grips or a C-clamp.

Reply to
Leo Lichtman

I have 192 of these angled holes to drill, 384 if I have to drill both sides. I tried angle drilling with a stub drill and also angle plunging a 2-flute end mill. Both took about the same length of time and gave similar hole appearance. In neither case did I get much tool wander.

If I could find a 1/4" center-cutting end mill with 2" LOC that would probably work for me. Can't find one, though.


Reply to
Grant Erwin

Very good idea! Now if we take that fixture and have two drilling guides (one at each side). Clamp it onto the tube and drill by hand on both sides. Will be fast, the drilling guide avoids wandering off of the bit.


Reply to
Nick Müller

Drill top holes. Make jig using a locating pin that goes through first set of holes to index tubing for the second series of holes. You will have to flip the part but who cares.

Wes S

Reply to


Take a look here, 1/4" endmills available up to 4.25 reach. Their m>>

Reply to
John Sullivan

Hey Grant,

Get a square piece of stock that has sides just greater than the OD of the stair spindle OD. (ie if the spindles are 2", then square stock of

2-1/16 or 2-1/8 maybe. (This "difference" will make the clearance to slide the stair spindles on, and you may do it a different way to get eh clearance. ) Drill your hole size right through the square stock at the required angle and position near to one end. Then chuck and turn the square off to the ID size of the spindles and just turn along to a length that puts the hole at the correct point along the spindle stock. Clear the drilled hole after turning. Weld a piece to the square flat of the jig piece along it's length to a point so that you can drill back through the first hole and through this new weldment piece. Now the spindle pieces should slide on the turned portion and butt up to the shoulder of the square and come to a stop at the correct place to drill. Place the whole "jig" on the drill bit in the drill, press, and clamp the "extra" of the square shank in the drill press vise, and tighten solid. Now you have an outside guide, and an inside guide in perfect alignment with one another, and a piece to grab in the vise. Ready to go.

Want a picture? A jpeg sketch? I'd bet there are at least a dozen ways to get the same idea.

Take care Good luck.

Brian Laws>I have to make some 1-1/4x.120" wall cable stair railing posts. The stairs go up

Reply to
Brian Lawson

Mount the work on a 1 in. dia. bar and drill through the top wall, the bar and the bottom wall. Hold the tube onto the bar with a pipe wrench..., maybe big pliers. Removal could be difficult.


Grant Erw> >

Reply to

My stair posts ("spindles") are made from square tubing.


Brian Laws> Hey Grant,

Reply to
Grant Erwin

Hey again Grant,

Oh!! Sorry. I didn't see that. Well, the jig will work like that anyway's. The "weldment" piece will keep it "flat". Or use square stock milled to ID size (which isn't usually square).

My point was that you get something to clamp in the vise that keeps the alignment correct, depth as required, and guide for the drill bit on both "sides" to keep it from wandering or breaking.

Let us know what you finally work out.

Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXX

Reply to
Brian Lawson

Use a Wood working drill bit - those that are almost full circle with a cutting lip - and internal cutter.

They cut at any angle to wood and rounds - and whatever. The have a sharp outer ring that cuts a nice round hole.

I want to say Forstner is the name.


Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

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Grant Erw> I have to make some 1-1/4x.120" wall cable stair railing posts. The

Reply to
Martin H. Eastburn

I have to make stairs for 3 identical townhouses. For the first house, I'll just top drill the 8 holes on one side using a screw machine length drill, then flip & reverse each post and top drill the 8 holes in the other side. I'll use a work stop and just crank the table 3" between each hole.

I do like the idea of an inside/outside drill jig, but that's a ton of work, and I don't have any way to harden it either. I bid the hours it will take me, and the bid got accepted, so I'll just do it and see what happens.

Indexing the holes isn't an issue on a Bridgeport, 15 fast cranks and a check of the DRO gets you 3" every time.

One thing I noticed when prototyping the procedure today is that the (lossy) oil system on a BP head is leakier when the head is slewed over 36 degrees. Messy!


Brian Laws> Hey again Grant,

Reply to
Grant Erwin

Forstner is correct , and they're usually hss or carbon steel . Not particularly well suited for metal work , and not usually available in sizes that small .

Reply to

Do the holes have to be angled? If you are passing a cable thru them couldn't you just offset set them side to side and let the cable follow that little jog? If that isn't acceptable once the offset holes are drilled maybe slightly small run a reamer thru there to get the alignment you need and that straight shot. As long as the holes are deburred I doubt the cable would be compromised in strength.

Reply to
daniel peterman


Not in a million years.

Stainless cable railings are a bit tricky. Cable hangs up on the slightest interference. Also, it has to look right or it looks awful. These are for high end homes and building the posts wrong would be very bad for me and my fledgling business.


Reply to
Grant Erwin

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