Drilling (or burning) large holes???

[grsthegreat]

I'm jumpin in a couple of days late on this post and know the discussion may have changed, but here goes.

I like holes saws. I built traffic signals for a living for 26 years. Most traffic signal poles are 3/8" to 1/2" rolled plate steel. The wire termination cabinets on each pole require (2) 2-1/2" holes for all-thread between the pole and cabinet (needs (2) 1/2" tapped bolt holes also). Another 2-1/2" hole if there's a pole mounted head and depending on the mounting style, possibly another for mounting the pedestrian signals. Most intersections have 4 poles, some only have three. I built somewhere around 1,000 intersections in my carear. I'm going to make a wild guess that I've probably drilled somewhere around 10,000 2-1/2" holes in signal poles using a 1/2" Milwakee hand drill during that 26 years. Well, several drills actually. I think I've worn out my share.:laughing:

Anyway, with patience and practice, hole saws maks a pretty nice hole. I will admit that it would have been nice to have been able to drill flat steel with a drillpress rather than on a ladder or in a bucket truck with a hand drill on curved steel. The biggest trick to drilling with a hole saw is to keep the drill steady with constant pressure and not wiggling around while drilling. If drilling with a hand drill, brace both yourself and the drill in a manor to try to keep it as straight and steady as possible. Even a small amount of movement can cause the bit to grab. If you get tired, stop the drill before moving. Then take a break before starting again.

Ive drilled a few of those over the years....the contractor i worked for had a magnetic mount base portable drill.....was nice. of course a few times we lost power, and that wanst pretty.

 

[EE_Bota]

Ive drilled a few of those over the years....the contractor i worked for had a magnetic mount base portable drill.....was nice. of course a few times we lost power, and that wanst pretty.

I always put a dab of oil near the base so if on an extremely large bit, I could see the oil start to recede under the base before the breakaway could happen (in the event I was pressing down too hard on the handle.) I have had them chase me across the floor, but this is rare. But about anything they do after breaking free is frightening.

I was using one to drill 36 2" diameter holes through a massive slewing ring the last time one chased me, but that was 20 years ago. The drill bit could be useful to the OP if I could find them available, but I can't. It was like a spade bit, but for metal. The actual cutting part was a rectangular, replaceable piece of metal, and there were several inserts to do various sizes, all using the same shank. It was better than a hole saw in my opinion, because they were cheaper, and could be resharpened. But if they were so great, I would be able to find them still, I guess.

Where others seem to be using oil for cooling, I tend to almost always use a "cool tool" type product. I do use oil for tapping sometimes, but I like the cool tool style products for most things.

Others have mentioned using variable speed controllers for a drill press. I might use one for varying the speed around the root speed as chosen by the pulley ratio, but I would not vary the speed widely from the rated speed of the motor, unless the load is very light. So, if a person were using them to drop the lowest speed of the press still lower, it would be smart to at least have it in it's lowest pulley ratio first.

 

[J_J]

This thread has covered all facets of metal working except CNC. Started out about burning large holes, and setting up a fabrication shop. Some of us have some of those items, and some of us have all of those items. Then there are those that wished they had all those things as well. If you don't have it, you have to adapt, or talk your friends in to doing it for you.

 

[grsthegreat]

This thread has covered all facets of metal working except CNC. Started out about burning large holes, and setting up a fabrication shop. Some of us have some of those items, and some of us have all of those items. Then there are those that wished they had all those things as well. If you don't have it, you have to adapt, or talk your friends in to doing it for you.

hay...i have a cnc plasma in my shop. There, now thats covered also:laughing: :laughing: :laughing: :laughing:.

And i definitely love it.

 

[dcyrilc]

hay...i have a cnc plasma in my shop. There, now thats covered also:laughing: :laughing: :laughing: :laughing:.

And i definitely love it.

 

[crazyal]

I've broken way too many pilot bits over the year only to have the hole saw walk across the metal I was trying to drill.

Torches are nice but for me the insurance needed was just too much for me. It's nice to have some heat to bend things but the few times I've needed to over the years I have just gone to friend's shops. Plus if you rent the tanks you get hit with a monthly charge and if you buy them then you've got a lot more than $100 tied up into a set of torches (even if you go with propane).

 

[mefyj]

Plasma cutter with assorted sized patterns.
Cut patterns with hole saw from masonite bd. If you feel you need too... drill a small hole and then you can actually bolt the pattern to the metal. They may be a little rough around the edges until you get onto going in a circle but I generaly sleeve the critical holes anyway and the other's will be close enough.

 

[Taylortractornut]

Heres my 0.02 cents on it. I use a variety in my shop. I have an old tiwan drill press and I drill alor of holes with a hole saw in it. I ve even drilled 1 inch plate with it and a 2 inch hole saw for backhoe bucket brackets. I also make a few templates to mark with soapstone to burn out with the torch. I can check them with the template and finish with a die grinder. I usually use a bushing in them like a pin boss. I used a cable clamp with a 1/4 20 hole tapped between where the legs of the clamp go into. I put a 1/4 20 bolt with a dogleg bent into it and a compss point ground into it. It works good for burning holes. It works good enough to not have to grind with a torch and make a slip fit for a hydraulic pump or motor flange.

 

[deereman75]

Since we have a cutting torch I would just use that, but since you dont I would try using a normal 1/2 inch hand held drill and drilling holes as close together as you can in the outline of the hole you want. Then just take a hacksaw and cut out the little bits left in between. If you want to you can use a die grinder or file to clean up tho hole a bit.

 

[jimcolt]

I don't drill many holes anymore......since I put the cnc plasma in my shop. On very small holes I will cut them undersized and then drill (ream) them with a cobalt drill (due to the nitride hardening that an air plasma creates on the face of the cut).....but on most holes 3/8" and above the holes are acceptable for use as bolt holes...and are accurately positioned by the cnc.

A few pics of parts/holes cut on my cnc (a PlasmaCam cnc machine with a Hypertherm Powermax85 plasma, also have a TorchMate cnc with a Hypertherm Powermax45 plasma).

1st pic, 3/4" steel with 1-1/2" hole. 2nd, 1/4" steel with holes from 3/16" to 3/4". 3rd 3/8" steel with holes from 3/8" to 3/4" Last pic, a bracket cut from 1/4". The tapped holes were plasma cut to .188 then drilled with a .201" cobalt drill (to remove the hardened surface), then tapped 1/4"-20.

Jim Colt