Update On My Hole Saw Arbor And Results

[JoeLee]

Pressing a 3/4" shank over the original three sided arbor help reduce the noise and chatter by quite a bit. It even helped tighten up the tolerances of the holes and the repeatability is even better.

There is still a little squealing but I'm not sure if I can do anything else to reduce it. Obviously there is give or deflection somewhere causing it.

My press on shank did not slip nor did the shank slip in the collet. But these were 1 1/2" holes I just cut. Have to do some 2" ones next. Keeping my fingers crossed.

The only thing left that I can think of is the plywood that is clamped between the strip and the table. I made sure that piece was flat and had no waviness or low spots that would allow the sheet to be pressed into when force is applied. The only thing I can think of now is to try something more solid under the strip like either a piece of high density particle board or an aluminum bar which would have to be face cut flat on both sides since bars usually are slightly concave in the center.

One other thing I thought of was to slightly grind the tips of all teeth except for two of them leaving those two opposed so the hole saw would basically be turned into a trepanning tool. The other remaining teeth with their cutting tips being ground a few thou low would act as a safety to prevent the cutting teeth from biting in too deep and snagging or breaking, etc. But the draw back there is if I loose a tooth I can toss the cutter. I actually think there is too many teeth giving too much tooth engagement.

Any thoughts ??????

JL...................

[metalmagpie]

Drill a 1/4" hole tangent to the inside of your circle. The chips will self-clear out the hole and the cutting will be much smoother.
They do make cutters that are infinitely more suited to that job. Here's an example:



metalmagpie

[JoeLee]

No need to drill a hole for chip evacuation as the material I'm cutting is only .100 thick and the hole saw gullets are about a 1/4" deep. After about .050 in I raise the cutter and brush the chips out and then finish. Works fine. In this instance drilling a hole would mess up the finished product.

JL...............

[nickel-city-fab]

X2 use something high-density under the material to be cut, and clamp the snot out of it. Your setup looks similar to some of my experience with annular cutters on mag drills. Can you slow the RPM way down and use some tap magic? That always used to work the best for me, a very slow RPM (about 200) , peck feeding, with tap magic against an extremely solid surface.

[The Metal Butcher]

That type of cutter may just chatter and squeal. They were designed for hand drills where they always operate in a chatter regime. Sucks but.... An annular cutter would be better for your use case.

[john b]

One of the things that you can do that I know that works. Is to grind a fair amount off the od of alternate teeth then grind id of the other teeth. What that does is reduces the chip load by quite a bit. Yes I have done this before on much larger sizes than you are cutting. And watch your tool geometry when you grind.

[JoeLee]

X2 use something high-density under the material to be cut, and clamp the snot out of it. Your setup looks similar to some of my experience with annular cutters on mag drills. Can you slow the RPM way down and use some tap magic? That always used to work the best for me, a very slow RPM (about 200) , peck feeding, with tap magic against an extremely solid surface.

The faster it turns the worse the squeal becomes, slower is the answer. My BP won't go slow enough in back gear, slowest it will turn is 85 R's so I put it on a VFD and got it turning at about 50 R's and that helped some more. With chatter I've found that faster is never the answer.

About the only thing left to try is a different sub surface. Glad I don't have to do a lot of these.

JL................

[JoeLee]

One of the things that you can do that I know that works. Is to grind a fair amount off the od of alternate teeth then grind id of the other teeth. What that does is reduces the chip load by quite a bit. Yes I have done this before on much larger sizes than you are cutting. And watch your tool geometry when you grind.

I can see how that might help, reducing the tooth width and staggering them. Less engagement per tooth. But that's a lot of messing around. I could do the OD but the ID would be more difficult. The saw is cutting just fine and holding out pretty well. Tolerances are good also, it's just the noise.
It may just be the nature of the cutter.

JL................

[The Metal Butcher]

How hard are you feeding it?

[CalM]

How hard are you feeding it?

Think about it, there are likely more than 20 cutting edges in the work at the same time.

Lots of PRESSURE is required.
Dinging alternate teeth , as suggested is a good idea! I've even cut out groups of teeth. (leave four, cut two, leave four cut two, all the way around.. Seems to work just fine!)

[The Metal Butcher]

Think about it, there are likely more than 20 cutting edges in the work at the same time.

Lots of PRESSURE is required.
Dinging alternate teeth , as suggested is a good idea! I've even cut out groups of teeth. (leave four, cut two, leave four cut two, all the way around.. Seems to work just fine!)

I wasn't going to suggest less pressure.

From my use of a 3 3/8" annular cutter, slow speed and high feed is good. I will occasionally stall out my drill press at 18 RPM.

[J Tiers]

Think about it, there are likely more than 20 cutting edges in the work at the same time.

Lots of PRESSURE is required.
Dinging alternate teeth , as suggested is a good idea! I've even cut out groups of teeth. (leave four, cut two, leave four cut two, all the way around.. Seems to work just fine!)

yep. I was trying to use one of those hole saws back a while, to core out a big (2.75") hole in 1" thick aluminum. I couldn't get it to even cut.... took WAY more pressure than what I could/wanted to apply. I was using it on a lathe, and the tailstock took major effort to make it cut aluminum at all. I went another way with the hole.

Grinding off some teeth would have worked OK. I think there were more like 30 teeth trying to engage at once, since it was a larger saw, 2" or 2 3/8".

[JoeLee]

How hard are you feeding it?

Just what it takes to cut and not much more. This of course is going to vary with different dia. saws. Loading it too much produces a lot of heat. The material is only about .100. It doesn't take long to cut through.

JL....................

[JoeLee]

Think about it, there are likely more than 20 cutting edges in the work at the same time.

Lots of PRESSURE is required.
Dinging alternate teeth , as suggested is a good idea! I've even cut out groups of teeth. (leave four, cut two, leave four cut two, all the way around.. Seems to work just fine!)

I had mentioned "dinging" the teeth leaving maybe 20 of them opposed basically turning the saw into a trepanning cutter. But as I said if I loose those teeth, the cutter is done.

If this was going to be an ongoing job I would be looking at other methods.

JL...............

[JoeLee]

yep. I was trying to use one of those hole saws back a while, to core out a big (2.75") hole in 1" thick aluminum. I couldn't get it to even cut.... took WAY more pressure than what I could/wanted to apply. I was using it on a lathe, and the tailstock took major effort to make it cut aluminum at all. I went another way with the hole.

Grinding off some teeth would have worked OK. I think there were more like 30 teeth trying to engage at once, since it was a larger saw, 2" or 2 3/8".

I have to cut about ten 2" dia. holes.
I understand that is going to require more feed pressure. I have to play it be ear. It's all feel.
If it becomes too difficult with the 2" saw I will try dusting off the tips of some of the teeth by a couple thou. Those teeth will also serve as a depth protection tooth as the will limit the tooth engagement in the work so the others won't become too aggressive and snag or break.

These hole saws were basically designed to be used in a hand drill. That's why the arbor they make for them has a 3/8" shank with three flats.

If your using it in a hand drill odds are you won't be holding it dead square to the work like it's being held in my mill. You'll be rocking it from side to side using half of the saw or less to cut without even knowing it.

I still don't know why they make such a precision saw to be used in a hand drill...... .005 + .000 and they do call it a precision saw, in the mill yes it is, in a hand drill...... doubt it.

Note: I'm not using the 3/16" pilot drill in the arbor, not needed in the mill.

JL...............