tricky hole saw cut

[gft]

Hi everyone. I posted this on another forum but thought of the vast wisdom you guys possess. I'm needing to drill 3-1/4" hole into side of 24" diameter plastic drum off center (not square to side of drum). I've put a longer pilot bit on but think a little less than half of teeth will be all the way through before the rest contact the surface. Has anyone done anything like this? Thinking maybe attach block of wood on inside to keep pilot bit and hole saw teeth boring. I'm inserting 3" pipe into opening, coming into it at an angle with resulting hole somewhat egg shaped. Thanks for any insight or ideas.

 

[andyvh1959]

I had to drill some 3.5" and 2.5" holes in ABS plastic sheet stock to form a dash panel for gauge set I installed in a fairing for my Kawasaki Vulcan 1600 project. Didn't want to spend $35 and more for each size of cup saw and pilot drill insert. So off to Harbor Freight and I bought an adjustable knife style hole saw, the type with a center bit and an arm on which are the cutter heads. With a bit of trial and tests I was able to accurately cut the holes so the gauge panel lined up exactly on the back side of the ABS panel. Since the holes were into plastic I was able to create the cut slowly.

 

[gft]

Thanks Andy, I'll look into that. Are you refering to:

Carbide Tip Adjustable Circle Cutter​

 

[gft]

I have a buddy who is a fabricator/machinist. I'm thinking he could make one of the bits longer, and if i can keep it from wandering, it might work.

 

[gft]

Just realized that's wrong thinking. But slow might be the way to go

 

[no704]

I’ve done this before in SS beer kegs on a Bridgeport with a fly cutter. But you might get away with heating a similar size pipe, thin wall, and melting thru it?

 

[The Cobbler]

if the hole doesn't need to be really accurate you could whittle away at the hole with a saw/file etc. infact for one hole that may be the way to do it?

 

[jack stand]

^^this.
Approximate the pipes entrance into the drum and draw it on, jigsaw, keyhole saw knife and files.

 

[strantor]

^^this.
Approximate the pipes entrance into the drum and draw it on, jigsaw, keyhole saw knife and files.

To further this concept, If you want to get it right the first time you could model it in sketchup or other 3d software and flatten it, print it out, cut it out, and draw it on with the template.

 

[Honch]

I would saddle a 3" cardboard tube or a piece of your pipe to the side of the barrel, outline the tube and use anything but a hole saw to cut and trim to the outline.

 

[jack stand]

The other approach is to sculpt the end of the pipe to the correct angle and direction to enter the barrel. Now you have the pattern for the hole.

 

[gft]

Thanks everyone for your input. I'm going with jack stand's idea: Cut scrap piece of pipe to match side of drum, trace it, and cut with jigsaw.

 

[Spareparts]

drill your pilot hole then replace the bit with a 1/4" rod and cut your hole, that way the bit won't wander

 

[Muckin_Slusher]

drill your pilot hole then replace the bit with a 1/4" rod and cut your hole, that way the bit won't wander

This is what I do 100% of the time anyway.

Drill bits are ****** at being pilots, they bend and the woller. Also, you won't look like an apprentice when your 1/4 inch bit pops through, letting the holesaw grab and **** right off sidewards.

 

[DuluthMachineWorks]

drill your pilot hole then replace the bit with a 1/4" rod and cut your hole, that way the bit won't wander

This is what I do 100% of the time anyway.

Drill bits are ****** at being pilots, they bend and the woller. Also, you won't look like an apprentice when your 1/4 inch bit pops through, letting the holesaw grab and **** right off sidewards.

I second this. That's how I put holes in steel drums with a hole saw. My method of getting the angle right is to piliot drill with a smaller bit square to the curved surface, and then go back at the appropriate angle with the correct size. Seems to work OK for plastic and steel up to 1/8", sometimes you have to angle the bit and cut a little with the side flutes on the drill bit.

As long as you get your pilot hole angle right, it,s not too hard to keep it lined up even if only some of the teeth are engaged. With plastic, I bet you'd have a pretty easy time and it would be a lot cleaner than using a jigsaw. Think about how a tubing notcher works- you only have some of the teeth engaged while cutting. As long as you go slow (slow feed, slow RPMs), you should be abele to cut this pretty easily.

 

[shawhite]

I usually make a jig out of wood and strap it to the pipe I am trying to cut at the angle I desire. The jig will keep the hole saw from wandering.

 

[cannuck]

If you are doing a tangential entry to make flow stay stuck to wall, or anything else approaching such a shallow angle a hole saw just isn't deep enough to do it in one cut. You need to be able to mount the drill and workpiece rigidly and repeatably to complete the cut. So, going with the template, saw and trim with die grinder and COARSE bit (the single cut ones intended for aluminum) should work well.

BTW: don't feel shy about asking such a question. I once had sent a job onto the floor for such an entry for a wood saw cyclone fab job. When I went over at coffee to see how the welder and fitter were doing, they had been trying to figure out how to follow the drawing and do layout for two hours!!!!!

 

[gft]

Follow Up: Just got project to the end. Yesterday I put the sump basin in after enlarging ground hole diameter, allowing me to use a 22-1/2° elbow, that aligned squarly to side of drum, using standard hole saw. Really detest digging but it happens.