For those with milling machines - annular cutters.
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If you’ve not got a set of Annullar cutters, you need to get on eBay and buy a set.

These things punch through material in no time and make a hole that looks close to a bored finish.
I measured woth telescoping hole gauges, and the holes were all +/- .001” (0.025mm) - two perfect to size, one was .001” over and one .001 under.

It took under 30 sec to go thru this 1/2” alloy plate using the quill handle. It’s best to ‘peck drill” them to avoid the massive bunch of thin chips that’s created by the many cutting surfaces.

Any links to the ones you bought Dave? To help avoid shit quality ones.

Phil.

WWW.TURBO-MINI.COM

These look good 👌

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

Three different brands here Phil - the 1-7/16 is Wansui Probor, the 1-1/4 and one 1-3/16 was Steel Dragon, and the last 1-3/16 was AC tool. All Chinese obviously, but I can’t tell them apart in quality.

I’m still in awe of how amazing these are....

FYI I’ll be using them to bore out the valve seat throat on RV8 heads; 1-3/16 and 1-7/16 are absolutely perfect sized for the typical oversize valves giving 88% on inlet and 85% on exhaust. I’ve got to take out so much material that this will be more effective than hand cutting. I’m going to make a mandrel to pilot them in the guide and mill them, but given how accurate they are made, and the number of cutting surfaces; I bet these could be adapted very easily to use with a mandrel piloting in the guide (or guide hole) to hog our a lot of material fast and easily using only a cordless hand drill...

Might be worth you experimenting with...

Edited by TurboDave16V on 7th Apr, 2021.

These are also called rotary broaches ?

I used one ( came with a kit ) to drill a hole in my sump years ago. Tiny pilot hole, and then as you say, cuts a super clean hole through the material.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I’ve never heard that term; the only other term I’ve heard then described as is a ‘slugger bit’.

Not sure if what you’re talking about looks more like this, I discovered these from the electricians at work Who use them for putting holes in panels. They make an absolutely perfect cut with no deburring - I certainly can’t say that about the old school hole-saw type.

Edited by TurboDave16V on 7th Apr, 2021.

I think broaching is a general term for a type of machine cutting, of which rotary broaching is one method that uses this type of tool. There is also linear broaching that is used for things such as cutting teeth on a gear, or a slot such as a keyway.

Edited by metroturbo on 8th Apr, 2021.

I brought back a set of these when working out in South Korea a few years ago, I was amazed how well they cut a hole over your typical Starret hole saw, I've also used them in the lathe before for roughing/facing when I didn't have a flycutter to hand.

These annular cutters do appear to be similar/same as what you'd use in a Rotabroach/Magdrill, good results tho.

On 7th Apr, 2021 TurboDave16V said:
I’ve never heard that term; the only other term I’ve heard then described as is a ‘slugger bit’.

Not sure if what you’re talking about looks more like this, I discovered these from the electricians at work Who use them for putting holes in panels. They make an absolutely perfect cut with no deburring - I certainly can’t say that about the old school hole-saw type.

That's just a variation of a holesaw, albeit looks like it has carbide tips in it for hopefully a cleaner cut. As regular HSS holesaws are pretty terrible.
Haven't actually tried one of those yet.

First google of "rotary broach" brings up this, drills for mag drills. Or the term "rotabroach" is also common.
Seems there are lots of variations, or rotary broach can mean something different altogether.

https://uk.rs-online.com/web/p/magnetic-drill-bits/5067430/

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will