some screw cutting tools, used or best place to get them new?

try chronos tools, ive always used them

about 4/5's of the way down
linky

or greenwood tools

linky

[Edited on 13/11/09 by liam.mccaffrey]

They are called Taps & Dies
Taps are for internal threads, dies are for external threads (ie bolts)

For cutting new threads on bolts you need what are called split dies.
For just cleaning up bolt threads Hex dies are the best -- they aren't split and have hex heads so you can turn them with a spanner.

Taps for cutting threads come in a set of 3 basic types which are used one after another.
(1) Starter --- ie fully tapered to start cutting the thread
(2) Intermediate --- ie Partly tapered
(3) Plug or Parallel ie --- Parllel for full length to go down to the bottom of a blind hole.

In practice for repair work you don't need a full set of 3 taps of each type. A basic cheapy set like this ebay item 250528470513 to keep in the workshop will get you started, and you can buy extra better quality items when and if you need them.

For cleaning up existing internal threads either use a plug tap or a "Chaser" tap. A chaser tap is designed to repair and clean the threads rather than cuts new ones usually this is the type of tap used to repair spark plug holes.

[Edited on 13/11/09 by britishtrident]

Depends what you mean by screwcutting.

Screwcutting to me means turning a thread on a lathe. You use a 60 degree bit for this.

I have used Chronos and RDG Tools, both excellent service.

If you mean doing it manually, then Taps and Dies are what you are after

sorry I assumed you meant lathe thread tools.^ wot he said

I did mean screw cutting tools for a lathe!

I've lost my 60deg bits somewhere(in a mates garage!) and need some more.

got to make up a car m19x1.5(inch long) going to m20x1.5 so I can fit an extension plate to run a remote filter on a hayabusa engine as the oil filter uses a bloody m20x1.0 thread! So i'm taking the suzuki one out and fitting my own.

Tracy Tools are good for cheap taps & dies (a Google will find them). If you just have one or two threads to cut then their cheaper carbon steel tools are fine, otherwise invest a little extra to get HSS (high speed steel).

As above, sorry if I've caused confusion.... i'm after lathe turning tools not taps and dies as i've a few custom bits to make.

Make your own lathe tools. You can have whatever size, shape, angle etc. Cut up an old file, braze it to a holder and grind to suit. Is that Locost enough?

I guessed right with lathe tools!,

tracy tools are good though for taps and dies

My girlfriend's Dad has just retired and is selling lots of tools. He is going to check what screw cutting tools he has tomorrow. I post and let you know, if you're interested

Andy