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Drilling angled holes

ktai

Plastic
Joined
Jul 22, 2015
Can anyone recommend an efficient method for drilling angled holes in tough material?

We are an architectural fab shop with manual machining capability, which generally is limited to fairly simple operations.

Lately we have been taking more cable railing jobs, and we had one recently that involved drilling 30 degree angles thru both walls of 1-1/2" stainless square tube (1/8" wall). The depth of cut required to do that is essentially 1-3/4", and the angle is too steep for a drill bit to handle without walking. We tried drilling with standard end mills and annular cutters but neither excelled and both made me very nervous about the brittle edge of the cutter as it engaged the material. We ultimately got through this job by drilling undersized thru holes at right angles on the tube and then finishing with them mill head tilted and using an annular cutter. It was extremely time consuming to do it this way.

I'm sure there is a better way to approach this but I don't know what it would be. Would a ball end mill or similar lead to better results? Are there any other approaches that might be worth exploring?

Thanks.
 
I can't think of a better way than an annular cutter. There should be no need to pre-drill with an annular cutter, you ought to be able to just punch it through at an angle in one go. I advise using the mill's power spindle feed for stainless to prevent rubbing and possible work hardening. Use cutting oil.
 
A few years ago we made a set of handrails for a customer which used 1/4" rod instead of cable--same principle
as cable railing but with different material. The holes had to parallel the slope of the stairs so around 45 degrees.
We tried a couple different things but what worked best was a 4-flute, end cutting endmill in the milling machine
with the head tilted to the correct angle . If I remember correctly we used a 3/8" endmill--anything smaller would
have been too flexible over the length required. Using an endmill holder instead of a collet will allow you to keep
the length of the endmill to a minimum.

In the end I don't think there is an "easy" way to do something like this. You just have to be patient and charge the
customer accordingly. In our case the customer was knowledgeable enough to understand that the way we were
doing the job was time consuming and he was willing to pay what it took...
 
I didn't think of that before... What is the diameter of the hole you were trying to make? If it's large enough for an annular cutter to be stiff at the ~2" length, that would seem to be the way to go. If it's small enough for the 2" length to be flimsy, go with the drill jig.
 
A simple drill jig that clamps over the tube with a hardened Drill Bush on each side would do the job quickly, accurately and repeatable. Hole can then be drilled with hand held tools.

LexD nailed it. "when confronted with a problem, make a tool"
 
My uncle and i did a railing like that. built a angled jig for the mag drill then just Had a rod on the jig to locate the next hole Worked okay had to clamp the jig each move and it ate annular cutters we were only getting 30 or 40 holes per cutter before they would shatter I dont know if that was from ham handed drilling or because of the point load of only one tooth at a time in the cut we tried a regular drill but the angle was to steep to get it to start
 
I don't see how a drill bushing is going to help start the drill on the second (inside) side of the tube. There's going to be 2" of drill in there hitting the wall at a thirty degree angle.
 
I do plenty of cable rails and in tube like you are talking about I just offset the holes to be at the correct angle and drill square in on each side. If the cable kinks on the way through, which depends on cable clearance in the hole and the angle, then you can angle drill through the already drilled holes. If you do angle drill through a little testing is needed to get the angle right by adjusting the offset of the holes on opposite sides of the tube.

Isn't about 7/16" the smallest jancy cutter?
 
I don't see how a drill bushing is going to help start the drill on the second (inside) side of the tube. There's going to be 2" of drill in there hitting the wall at a thirty degree angle.

Did you read the bit where I said the jig should have a bushing for drilling from each side? It still won't be easy going but it's probably the most simple solution for the task.
 
Yeah with the drill jig and having bushings on both sides you could probably do this with a hand drill. I would still use the machine though just for the controlled feed - drill will last longer before dulling.
 
Find a supplier with a tube laser. If you send them good prints, or files they will likely be able to do this for you way cheaper and with better results than farting around with different end mills, cutters, jigs and funky setups. Unless you plan on doing thousands these. If that is the case, then you may want to consider investing in a tube laser to have in your shop
 
Do what you are good at and get good at what you want to do. Farming out certain aspects of your projects to shops that are more efficient at those processes will save you time, money and frustration. The hard part is deciding when those processes become a big enough part of your business to justify investment in the personnel and equipment to bring it in house
 
A simple drill jig that clamps over the tube with a hardened Drill Bush on each side would do the job quickly, accurately and repeatable. Hole can then be drilled with hand held tools.

How can you say that?

That's how it was done for thousands of years, "leaf' stone bow drill on sea-shells, pearls, lapis, jade, etc... to high-alloy steel, yet today.

So it must be surely be obsolete ... .somehow ?

Or NOT!

:D

Works a treat if the jig is "there" and the "drill" is actually a plunge end mill.

Annulars can be hard on bushings. "Hole saw" can be easier to guide. That's why I have both.
 
Did you read the bit where I said the jig should have a bushing for drilling from each side? It still won't be easy going but it's probably the most simple solution for the task.

Easiest ?
In a fab shop ?

Handheld plasma is really rare in a fab shop, yesiree !
:nutter:
 
I'm not wild about drill jigs....you're still trying to start a hole with a drill bit that doesn't like to approach the metal at an angle and wants to kick out. If we were talking about drilling a mild Irish cheddar cheese, OK. But SS?

Plus, the far side wall will really not like it as the drill tip is hanging out there, far away from the jig. And most drill bushings seem to include some degree of chip removal issues.

The fact that an annular cutter in a mill - normally a pretty smooth operation - didn't do well speaks volumes about how well a common drill bit and jig is gonna work.


That said, you could try it and see the results. There's no doubt it'd be way faster and less involved than fitting the mess into a mill.
 








 
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