Very poor large hole result

I would use an annular cutter, use a 3/4" R-8 collet to hold it, I use them all the time in various steels and they fly through steel plate and rod. Run around 300 RPM, use continuous feed pressure do not peck at the work. Use some cutting oil. I get very close tolerances using them, but if I need an exact ID. I cut the hole slightly under and then for an exact ID I finish with either a boring bar or boring head. I would not use that Harbor freight cutter, a decent annular cutter is much more rigid. Once you start using them, you will never go back to regular hole soles in most applications.

Hougen Rotabroach 12136 1-1/8" X 1"
CHAMPION RotoBrute XL100 or XL200 1-1/8"
 
On something as rigid as a mill or even decent pillar drill, and with the work clamped, the pilot drill "guide" isn't needed and a hole saw will work well, though will give a ghastly surface finish in many cases. The pilot drills are really for hand held use. Even better, and the "right" tool for the job is an annular cutter.
 
An annular cutter might be the right tool for the job, but you use what you have. The guide pin approach takes away alot of the wandering that a holesaw does when it first starts cutting.
 
I did a similar job for an overhead gantry. We used a boring head.
 
mattthemuppet2 said:
couple of tips. One, go slower, 300rpm is pretty quick for a hole saw. Two, drill a pilot hole to match your holesaw pilot drill. Then swap out the holesaw pilot drill with a blank rod the same size (ie. 3/16" rod for a 3/16" pilot). That stops the holesaw wandering when it starts the cut.

An annular cutter would be the bees knees, but holesaws are waay waay cheaper.
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I have used solid pilots as you suggest, with good results; I use dowel pins rather than soft stock. is nor more rigid than soft, but lasts longer without getting chewed up.
 
I have cut numerous holes in steelplate with holes saws. If the work is securely clamped to the mill table you shouldn't need the pilot drill. In my experience, the saws don't run true to the arbor which means they don't run true the the pilot and you end up with eccentric holes. If you remove the pilot and allow the saw to find its path, you should cut relatively clean holes. If it is necessary to use a pilot, I predrill and replace the pilot with a dowel pin, The dowel pin is more rigid and fully engages the pilot hole. Another trick is to use a slug from a previous hole to act as a centering device, This helps to ensure that the saw is concentric with the pilot. Better yet, turn a slug on the lathe for a close fit to improve concentricity.
 
Jake M said:
A proper annular cutter is an amazing thing. Still not "precision diameters" by some standards (Pretty good by my standards....) but they give you a beautifully cut and very round hole.
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mattthemuppet2 said:
An annular cutter would be the bees knees, but holesaws are waay waay cheaper.
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This is one of life's tragic issues. I have had, like many of you, lots of trouble with these hole saws, but annular cutters are as Jake M says, truly amazing, so nice to use. I'm slowly acquiring them as need arises.
 
Slow...slow...slow!

We drill with same type saw, 3.5 ich diameter in 1.25 inch plate with no pilot.

Back gear to get speed as slow as you can go.

Oil as needed and Peck, lift to clear chips

Saw should stay somewhat cool, if not you are too fast.

Sent from my SM-G781V using Tapatalk
 

mattthemuppet2 has it exactly right in post #10. I have done literally hundreds of holes up to 5" diameter using this procedure with hole saws. Also, as John York said, use a hardened pilot. As others have said, the annular cutters are better, but they're pretty pricey.​

Ted
 
Like many others I have cut hundreds of holes in similar material with a hole saw. I use the procedure outlined by matthepuppet. Depending on the thickness of the material you may have to back off and clear the swarf. If you don't it will clog the gullets and result in an odd, shaped hole. Another thing that might help is to drill a series of holes slightly smaller than the outside diameter of the saw. They will help evacuate the swarf.

When using my old worn out chicom drill press I don't have the luxury of anything lower than 200 rpm. The holes still turn out within spec if I take my time. They're much easier to do at 90 rpm on the mill with heavier down feed, lots of cutting oil, and occasional swarf removal.
 
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