What are these drills called?

I am looking to buy another few of these drill bits, they are self centering and have a very steep helix.

Any ideas what they are called?

Edited By Chris Denton on 30/01/2015 13:33:42

Edited By Chris Denton on 30/01/2015 13:34:36

Spotting Drills?

Martin

Who is selling and price?

I've always known them as slow spiral drills.

Available here (and many other places I'm sure).

http://www.drill-service.co.uk/Tools.asp?Tool=020240000000

I'd say a slow spiral as well, definately not a spotting drill.

The angle on the end is greater than 118 degrees, rather than less, looks like a stub drill meant for sheet metal to me.

Neil

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How strange ... I would have described something with a large "pitch" as having a fast spiral, not a slow one.

Might be wrong though ... must check.

MichaelG.

Definitely slow spiral; intended for hard materials, as the cutting edges are stronger than standard helix drills, or for materials that tend to 'snatch', like brass. Presumably if it is self-centring it is 4-facet ground, although that is not clear from the picture.

Andrew

Here you go Michael, slow and fast

Talking of drills I was looking through the box of stuff that came with my lathe for a 12mm drill came across a Dormer drill still in it's red sleeve it was a 21/32 don't know why but opened it up and was surprised to find it contained a 3 flute drill never seen one before what would be it use /

H

.

Thanks Jason

Happily corrected

MichaelG.

Sounds like a core drill that's designed to follow a pilot hole and produce a nice true and size hole without the web snatching that would probably occur with a twin flute.

They aren't even slow spiral, they are slow helix. A spiral is only 2-dimensional

Neil

I remember buy some years ago for drilling brass.

For the pendantic maybe (same as a helix staircase?) but for everyone else they are spiral

**LINK**

Roger

It used to be possible to buy straight flute jobbers drills specifically for brass.

Never mind pedantry, if we're being mathematically correct a helix is simply a special case of a three dimensional spiral. There's nothing that says a spiral has to be two dimensional, or indeed limited to Euclidian geometry.

Andrew

Good for brass or possibly tough materials as Andrew says. Saves having to square off the leading edge of a normal steel cutting drill with a slip stone, which many people consider a clever trick.

I also have some for drilling aluminium which have a "faster" helix than normal. They came in a mixed bag of drills from Tracy Tools back in the 70s. I was disappointed at the time, as I thought I'd paid for a "set" of drills. However, they are great when used for their intended purpose and they refunded my dosh when I complained which worked for me, being a Scottish-blooded Yorkshireman.

Murray

I suppose that if you stretch a point a helix is a spiral on the surface of a cylinder.

Isn't there a version of a spiral that links the two 'poles' of a sphere?

Yes

Neil

Interesting link Neil but be careful, someone will be along soon complaining that the OP only asked what that drill is called

Russell