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Advice on annular cutter for 3" hole please

I've used hardware store Milwaukee and DeWalt HSS hole saws many times to "trepan" up to 1-1/4" mild varieties of steel plate successfully up to 5" in diameter without trouble, of course it's usually in my Radial arm drill or Cincinnati mill where I have flood coolant, but I've used the Bridgeport clone mill too. First you MUST have a (several if possible) "drain" hole(s) for the oil and chips drilled right in the path of the blade. Then enough oil to keep it lubricated and flushed. My oil can pumping fingers got a real workout during one of those particularly thick slugging jobs on the BP mill. I used the quill rather than the knee, but the other way might work just as good, I haven't tried it yet.

Speeds and feeds.... Slow as you can, smoke is bad, way too hot. Patience will pay off big, impatience will cost you days of regret and repair. Chips Should be pretty small, just barely large enough to be individually recognizable. Remember there are a LOT of cutting edges on a hole saw, each one grabbing steel, there's a lot of pressure there for your mill to overcome.

I've never had an annular cutter so I can't compare them. But then with bigger machines one rarely has need of any type of slug cutter, just pop in the 3-1/4 AMEC drill, hit the power feed and relax for a couple minutes.

The most cuts made with a single hole saw was around 20 in 1/2" a36 plate. Dad made custom washers on the Radial arm drill a few years ago on a rush job. I still have the cutter and it's still sharp.

We had a video somewhere, I wish I could remember where.....
 
Thank you Wile E. Coyote.
Any super genus will make sure the set screw goes on the flat.
Even if you have to face off the holder.
A basic machinist knows that.
I hope.

-D
The guy already said he has the proper R8/annular cutter adapter, so why not just use the purpose built holder he already has?
 
I do have a Hougen R8/annular cutter adapter. That was also another reason I was strongly considering going with a Hougen annular cutter. It fits their cutters nicely and provides good tool holding.

I mentioned it briefly in my first post, probably pretty easy to miss that detail.
 
The guy already said he has the proper R8/annular cutter adapter, so why not just use the purpose built holder he already has?

Randalthor said he has an R8 to 3/4" Weldon adapter. A Weldon adapter is a single set screw holder. Why are you asking dumb questions on the internet ?​


-D
 
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With a hole saw you will need to peck at it to clear chips. Once the teeth are completely below the surface of the workpiece, there is nowhere for them to go. An anular cutter is typically designed with fluting to carry the chips out, reducing the need to peck. However, you will probably need to feed quite hard to produce chips large enough to be carried out. Either way, lock the quill and feed with the knee. You will need good control of the feed rate to make a consistent chip and not allow the cutter to grab and twist it off the shank (which the hole saw arbor is prone to do)
 

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I have used 3/4” copper head carbide annular cutters many times and they work good and last, but a 3” might be a different story.
If you try a hole saw which I think will work as mentioned drill relief holes for the chips to dump.
And don’t even think about using a keyless chuck with a hole saw, it will tighten itself so tight it ruin itself.
 
That big- torch or plasma cut then mill clean, or just have plasma cut by steel supplier.
Second would be hole saw- no holes on the edge. I have done a number of 4 1/2 thru 1/2 inch plate with a brushless cordless drill. Pre-drill pilot hole. The cordless has lots of torque and doesn’t jump to faster rpm as you relax pressure.
If for some reason you are set on hougan (the big ones have never worked for me (2 1/2 is max I have had success with) get the right holder with ejector.
Burn it or hole saw. Annular cutter is more money, more risk, and zero gain if it does work.
 
I had a job cutting holesaw holes in big diameter pipes and bends,the holes were mostly offset ,some tangent ............I made up extension pieces for the holesaws,and had them tig welded together..........The job was a breeze in the radial drill ........The engineer had specified the holes be cut with solid milling cutters ,that would have cost a fortune.
 
...The job was a breeze in the radial drill ........The engineer had specified the holes be cut with solid milling cutters ,that would have cost a fortune.
The engineer should put a size with a tolerance, a geometric callout with a tolerance, and a surface finish callout with a tolerance on the print.
The engineer should not tell you how to do the job.
Else people get pissed off because someone stepped out of their lane.

-Doozer
 

Randalthor said he has an R8 to 3/4" Weldon adapter. A Weldon adapter is a single set screw holder. Why are you asking dumb questions on the internet ?​


-D
I'm sorry I misspoke. I was trying to describe the tool holder, and didn't put a lot of thought in how to describe it, so described it incorrectly.

This is actually what I have.
 

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Thanks to all for your comments. Unless I've missed it, so far I've not seen any comments that someone has cut a 3" hole with an annular cutter on a Bridgeport. But I've read lots of warnings in this thread that it may not work, so I don't believe I'll try it.

Smaller annular cutters do cut very nicely on a BP and don't make it growl like larger drills do, but, as many point out, 3" is a big hole.

I try the hole saw route again. Thanks especially for all the advice on how to cut holes with a hole saw.
 
Btw, a couple people have mentioned having the hole plasma cut, slightly undersized, then finish it up myself. That would be the way to do it, but the customer already has the blank made and wants me to machine some various holes, some threading, a through slot, and a blind slot. I could take it back to someone to plasma cut the 3" hole, but consensus here seems to be that a 3" hole is pretty doable with a hole saw. So I plan to give that a try.
 
I'm sorry I misspoke. I was trying to describe the tool holder, and didn't put a lot of thought in how to describe it, so described it incorrectly.

This is actually what I have.
When you mentioned annular cutter, and Weldon adaptor for it, in the same post, I figured that was what you had. But Doozer seems to enjoy any excuse to act like an asshole. Another one to add to the ignore list.
 
Why not a trepanning tool? Like this...

Cutting a 5" hole in steel. An annular cutter is one size, you can vary the hole (slug) size with a trepanning tool when you have to do a different size hole on the job you get down the road.

 
When you mentioned annular cutter, and Weldon adaptor for it, in the same post, I figured that was what you had. But Doozer seems to enjoy any excuse to act like an asshole. Another one to add to the ignore list.
I don't think you know what a Weldon adapter is.
People come here to give and receive help.
You seem to be picking the fly shIt out of the pepper.
If you have a Rotobroach holder great.
If you need to modify a Weldon holder to make it work,
also great. Looking for a problem with people trying to
contribute, not so great there fella.

-D
 
Why not a trepanning tool? Like this...

Cutting a 5" hole in steel. An annular cutter is one size, you can vary the hole (slug) size with a trepanning tool when you have to do a different size hole on the job you get down the road.

Something like this work on a BP?

 
If you can grind that scoop-out toolbit geometry
you could make one of those pretty easy.
Positive rake and making the chip curl is the key.
It is like a mini-gooseneck planer tool. If the edge
digs in, the flex forces the tool to unload some force
and this prevents chatter.

-D
 








 
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