Annular cutters

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Re: Annular cutters

Post by ChipMaker4130 » Wed May 20, 2020 7:42 pm

Quality annular cutters, properly held, will make a very accurate hole. No need to start with 1-7/8 and bore unless you need a tolerance measured in single-digit thousandths. Hand-held drill, no. Gooddrill press or mill, yes.

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Re: Annular cutters

Post by NP317 » Wed May 20, 2020 9:01 pm

Just figure out how those blind holes were drilled in granite in ancient ruins in modern Egypt!
Then replicate...

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Re: Annular cutters

Post by jcfx » Thu May 21, 2020 12:37 am

SteveM wrote:
Wed May 20, 2020 5:44 pm

That would probably not be much different than step drilling.

If you actually needed a ring shape milled into something, like if a tube needs to go inside something and have the material both inside and outside the tube, an annular cutter would work.

I guess it would depend on the size holes with step drilling, or did you mean using a
step drill on thin materials ?
Annular cutters give you round very clean accurately sized holes, quickly but at a price.
Just had to do some light deburring of the sharp edge on that prop elevator call button
panel I posted previously.

The baby versions of them are Blair Rotabroach, excellent for sheet metal.

The kerf on the annular cutters are pretty big, random measuring of the few I have
are about .1940" so if you have tubes that have that wall thickness it's a perfect match.

John Hasler
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Re: Annular cutters

Post by John Hasler » Thu May 21, 2020 7:30 am

if your tube wall is thicker than that you could use an annular cutter to save time by roughing with an annular cutter and finishing with an end mill. That's a rather esoteric application, though. I can't think of any reason to design such a feature, other than to make machinists hate you.

armscor 1
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Re: Annular cutters

Post by armscor 1 » Thu May 21, 2020 3:55 pm

Rota broaches make excellent end mills, laying up a ship in Indonesia I was running low on sharp end mills but had heaps of rota broaches, they worked well on removing metal on the mill.

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