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How would you cut angled hole.

snowman

Diamond
Joined
Jul 31, 2004
Location
Southeast Michigan
Material is 304 ss tube, 10” diameter, 1/8” thick.

I need to drill a 4” hole so that the centerline of the drill meets the centerline of the 10” diameter tube at a 45 deg angle.

Precision is pretty important. It’s a tig welding fit up...so while I have room, just not a lot.

In a perfect world I’d have a 4” annular cutter, but my max is 3 3/8”.

Right now I’m thinking about just making a wooden buck to support the pipe from the inside, then starting with the 3 3/8 and then using boring head. This doesn’t sound like fun.

Any other ideas likely to be found in a traditional shop?


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Starting with the largest plunge cutting endmill or annular cutter then finishing it out with the boring head was exactly what I was going to suggest. Doesn’t sound all that painful really, maybe if you needed to do this in volume.

My only other realistic suggestion would be to make a template of the cross section of the smaller tube where it will intersect the larger, transfer the outline onto the tube and then just plasma is out. Unless you’re relying on a precision bore so you can save time on weld fixturing, the hole shouldn’t need to be super tight tolerance for a TIG fitup. What’s the application? What’s the length of the 10” tube?

Edit: if it really is that critical or you have to do these in quantity, just order your 4” cutter and be done with it. If your 10” tube is short, you could possibly fixture it in a rotary table but that’s over complicating things.

Edit 2: $2000 for a 4" annular cutter :eek: glad I don't need one!
 
I'd try making an annular cutter from a chunk of short steel stock, but this is based on your having a machining center or robust radial arm drill, I wouldn't try this on a Bridgeport. And you have to fixture the steel tube rigidly, if it can flex then you'll inevitably get a heavy bite that causes unpleasantness.

And this presumes angling the (presumed short) steel tube. If tube is long a big R.A.D that can tip the head would be ideal.

1) Figure out actual desired ID of hole, cut ~3" long section of steel scrap to that diameter, minus a touch for clearance. Since you're likely to get some rubbing anyway that will leave behind some smeared metal, probably best to use a matching stainless for this body. Make a steel (regular steel is fine here) drive end that can be pressed, welded, or screwed in, whichever's easiest (turning from solid is cool but more work). At least 1" OD, bigger is better if you can mate your drive to it. Turn a Morse taper on the drive end if you're using a R.A.D. (hopefully it's set up with a keeper of some form, cut drive to suit).

2) Mill at least eight axial slots around this core of the annular cutter, each of the slots being sized for 3/8" brazed carbide L or R turning bits. Cut access flats next to each slot to allow drilling and tapping for 5/16-24 set screws (unless you're English or Australian, in which case you're a grubby bugger). Think beefy fly cutter, but with bits arranged around the axis of rotation, not perpendicular.

3) Set the brazed carbide bits into the slots, whichever rotation direction you intend on driving will determine which bits you need. Stick each bit out just enough to ensure waste stock cannot hit the cutter body. You want to have them at the same stickout within small errors.

4) You need to prep the tube with a plasma cut hole to a rough ellipse leaving ~1/4" waste stock for finishing with the cutter, then drive cutter though at slow RPM and controlled feed. Patience and cutting oil will help.

5) Or %$*(@ all this and find a waterjet shop with a five-axis head, have them cut the damn ellipse to size. If ID damage is a worry you can try to fit an inside barrier plate to take most of the exit stream.

Let us know what you wind up doing.
 
Might also do a test hole at 1/4" dia. at first to make-um sure you are on location ??
Sounds like spendy shit
Quantity of parts dictates strategy
if one or 2,,sounds like you got a plan that will work already
 
Well...you don't say how many holes...but since you say 'an angled hole' let's assume it is only one.

Since it's only one, I'd use of of those angled hole programs that allows you to print out a pattern that shows you what the hole looks like when laid out in 2 dimensional form. Then, I'd position it on the 10"SS, trace around it, then go to work with cutting it out. Maybe a plasma cutter to get close, then a die grinder to finish it.
 
I'm with Doug, we do this in 11ga stainless (and thicker)all the time, mark and plasma out the majority of the metal, then run a standard bimetal hole saw down the hole to clean it up to size. Stop at several points and break off the remains with a pair of pliers, then continue cutting until thru. We screw the hole saw to a heavy backing plate/40 taper arbor (no pilot bit needed) rather than use the standard hole saw arbors, much more solid.


edit- Oh Yeah, don't try to power-feed it, just feed it by hand!
 
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Not if you go in and whack out pieces when you hit the holesaw's max depth (usually 2"

Lather rinse repeat.

I do not have good experiences with hole saws. I find that I always...and I mean ALWAYS end up with a hole that is too big. Too much runout, with quality arbors. There's a lot of flex in that back plate.

Because that would be my preferred method.

Thank you all for reaffirming that I'm not over thinking the pain in the ass factor on this job. Not overly difficult, just not "easy".

Right now I'm between running the 3 3/8 annular through and then single pointing and using a hole saw at 90, then stretching the hole with a jig saw and die grinder. My biggest concern on single pointing is material flex. Annular cutters do not like non-ridgid setups, and even if I pack the bore with shimmed plywood, I question how rigid I'll be able to make this. I prize my cutters. They are NOT something I can afford to replace, and if it grabs, which is very likely in stainless on a bridgeport, it's over.
 
Well...you don't say how many holes...but since you say 'an angled hole' let's assume it is only one.

Since it's only one, I'd use of of those angled hole programs that allows you to print out a pattern that shows you what the hole looks like when laid out in 2 dimensional form. Then, I'd position it on the 10"SS, trace around it, then go to work with cutting it out. Maybe a plasma cutter to get close, then a die grinder to finish it.

These programs you speak of.

Got a link?

I've always done this work longhand in autocad...and it takes a while to do the geometric transformation. Learned it in high school. Still have to use my high school drafting book as a guide! lol
 
another vote for hole saw or plasma. Bend-tech is the pipe layout software, It can do a lot once you learn it. I use it more for pipe wrappers than cad and the unfold command, because it is so efficient and good--at pipe.
 
I do not have good experiences with hole saws. I find that I always...and I mean ALWAYS end up with a hole that is too big. Too much runout, with quality arbors. There's a lot of flex in that back plate.

I make my own arbors and use a large washer to support the H/S on its periphery, that seems to help.

I have wondered in the past what would happen if I spun the teeth under the surface grinder in an attempt to reduce runout and get to an accurate size, but I don't think it's going to work.

As for the required depth, I've seen some H/S's in the past that have been extended via some tubing and the TIG. Similar application, too. These guys needed some acute notches in 4130 tubing for a Trophy Truck chassis that was TIG'd.
 
I've always done this work longhand in autocad
Here is one I got to puzzle out back in the day. 44" line entering a 338" dia. vessel at an angle and way off center line that needed a insulation retaining ring. It was 60 feet in the air so they were sort of interested in it fitting right now. No complaints
 

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I don't have a link to a program but I once asked for it on this board and someone directed me to it...of course I didn't save it....

I agree on hole saws...I always wonder who is using these to good effect when they produce a larger hole than desired, and the arbors are seldom worth a dang. I guess they might work if you made a good arbor first.
 
I make my own arbors and use a large washer to support the H/S on its periphery, that seems to help.

I have wondered in the past what would happen if I spun the teeth under the surface grinder in an attempt to reduce runout and get to an accurate size, but I don't think it's going to work.

As for the required depth, I've seen some H/S's in the past that have been extended via some tubing and the TIG. Similar application, too. These guys needed some acute notches in 4130 tubing for a Trophy Truck chassis that was TIG'd.

I have a commercially made backing plate that bolts onto the extra holes in the back of a large diameter hole saw to stiffen it up. It does help reduce chatter when running it in the mill. I swear I bought it from McMaster-Carr but I can't find it on their site now. I also make my own arbors to use hole saws in the milling machine and they help by removing the slop that's present in most commercially available arbors.

I have extended hole saws with tubing before for that application as well. 0.065" wall DOM or 4130 works really nicely. JMR used to sell some super deep, fine tooth hole saws for the purpose of notching tube, but apparently their blade material supplier went out of business and they haven't been available for several years.
 








 
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