Coventry die head question

I recently got hold of a Coventry die head , model CHS , I think it is the 1" version.

Do the actual dies change over from one size die head to the next size die head ? Or do you need a set of dies that are dedicated for each sized head ?

Thanks Mike

Hi Mike, dies are sized according to head size so are all different.

Emgee

Dies for each size head.

OK thanks .. seems like I need to look around for some dies !

Forgot to add. The Coventry die head manual is available for free download here

http://pounceatron.dreamhosters.com/docs/index.html

Here's a guide I did earlier:

Andrew

Thanks Andrew

I think there are other brands of dies that will fit the Coventry die heads , these brands are clones or copies of the original brand . Sutton , a tool company here in Australia , is one such brand. Must be many more out there.

My only set of dies

I'm pretty sure that Alfred Herbert no longer make Coventry dies, so all new die sets will be clones. I've bought new sets in the last year or two, which must be clones, and they work fine. Even in the heyday of Coventry dieheads there were alternative manufacturers. I've got some sets made by Robertson of Bedford, probably made in the 1960s looking at the style of the packaging.

Andrew

The leftmost die seems to be missing its cutting teeth?

Andrew

The manual explains that the teeth only guide the dies , they behave like a nut, the actual cutting is done by the angled section before the teeth .

Really? Think about it! If none of the teeth cut how is the thread formed. If you look at a die end on, at the teeth, you will note that the teeth are not parallel to the axis of work rotation but angled. It is true that the teeth at the rear of the die are in front of the rotation axis and do indeed act as a guide pulling the diehead forward and eventually opening it when a stop is reached. The cutting is done by the partial teeth on the throat (angled section) and the first full depth tooth to give the full thread form.

Andrew

The first one has lost a couple of teeth. It's not supposed to look like that!

What the book says , the teeth guide the die , they don't cut

If you say so. Did he charge you extra for it?

It was absolutely NOT made like that from new. It has been made like that by someone after they have damaged the teeth. It is not uncommon to see this sort of thing on second hand dies. I have drawers full of them.

The book also says that the cutting is done on the the throat AND THE FIRST FULL TOOTH as already explained by someone else.

Phil

Its lucky they are 1" Whit chasers, any smaller and the work head and or head would get pushed to one side as the other three chasers try to do the work resulting in a wonky thread.

The cutting edge of the dies, is defined by the throat and the first tooth flank .. look at the line on the diagram , it explains it clearly . The text was written by the manufacturers themselves ...what more can I say . You guys cannot understand plain English ..