What are these drills called?

[Chris DentonParticipant @chrisdenton53037]

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?

[Chris DentonParticipant @chrisdenton53037]

[Chris DentonParticipant @chrisdenton53037]

 

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

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

[Martin KyteParticipant @martinkyte99762]

Spotting Drills?

Martin

[andrew winksParticipant @andrewwinks64215]

Who is selling and price?

[Roger Provins 2Participant @rogerprovins2]

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

[JasonBModerator @jasonb]

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

[Neil WyattModerator @neilwyatt]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 30/01/2015 16:09:49:

I'd say a slow spiral as well,

.

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.

[Anonymous]

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

[JasonBModerator @jasonb]

Here you go Michael, slow and fast

[Harry WilkesParticipant @harrywilkes58467]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 30/01/2015 16:53:05:

Here you go Michael, slow and fast

.

Thanks Jason

Happily corrected

MichaelG.

[mickParticipant @mick65121]

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.

[Neil WyattModerator @neilwyatt]

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

Neil

[Brian Rice 1Participant @brianrice1]

I remember buy some years ago for drilling brass.

[Roger Provins 2Participant @rogerprovins2]

Posted by Neil Wyatt on 30/01/2015 18:17:02:

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

Neil

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

**LINK**

Roger

[Anonymous]

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

[MuzzerParticipant @muzzer]

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

[Neil WyattModerator @neilwyatt]

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

[Russell EberhardtParticipant @russelleberhardt48058]

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

Russell

[Rufus RoughcutParticipant @rufusroughcut]

Hi Gents

Surely a two dimentional spiral / helix is merely a zig-zag line, unless of course its dimentions where away from you then it could apear to be a stright line.

sorry to pedantic

[Chris DentonParticipant @chrisdenton53037]

Thanks for the link Roger that was exactly what I was looking for.

[Bodgit Fixit and RunParticipant @bodgitfixitandrun]

A Spiral starts at a centre point and flows away from said point in a circular path with a progressively increasing radius on a flat plane so is two dimentional.

A helix starts at a point on a circumference and rotates around the circumference at the same radius, if it is a parallel helix, moving forward with a given pitch eg. a screw thread. It can also move out with a progressive radius as on a cone. With the cone, when viewed from the tip, you can see a spiral in two dimentions but you won't see the helix as the always have effectively some form of forward motion.

Also, just in case someone notes, a helix can also have a variable pitch but I don't know why you would want one.

Spiral staircases are so called because of how they look from the plan view where the tread appears to rotate out around a given centre point ie the column. which geometrically is actually a cylinder with a very very deep thread with an equally deep pitch wrapped around it therefore a helix.

Edited By Bodgit Fixit and Run on 31/01/2015 15:48:43

[Anonymous]

Posted by Bodgit Fixit and Run on 31/01/2015 15:46:57:

Also, just in case someone notes, a helix can also have a variable pitch but I don't know why you would want one.

See here for some examples:

**LINK**

Andrew

[Author]

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