Coventry Die Head Chasers

I’ve got a couple of sets of chasers for an 1 1/4” die head that I use quite regularly but are starting to blunt off now and affect the finish of the threads. I don’t have any proper grinding machines, only a pedestal grinder. Can anyone recommend a company to touch up the chasers? They aren’t chipped or damaged, just blunt!

Cheers,

Dan

Try these I don't know for certain if they do Coventry Die head cutters but it is worth a call.

https://www.abbcotooling.co.uk/

David

I'd try these people:

Wiseman

I've not used them for grinding dies as I have the capability to grind my own, but have bought spare parts from them. Look under PDF price ists for Coventry Die Head Chasers. Prices seem very reasonable.

Andrew

I have both the Alfred Herbert No1 and No2 Fixtures that should do up to the 31/2" dies though The info for the No2 does not mention 11/4", only listing 3/4", 1", 21/2" and 31/2" FT dies. It will regrind the throat and also the rake angle if needed.I have the height gauges. May be some one can answer the question as to IF this device will do your dies. If yes then we are part way to solving the problem. The device is new and I have never used it ! There is a No3 I believe. Noel.

I do not know if it will answer, but Wiseman have a section on grinding the chasers:

https://www.threadtools.com/uploads/pdf/technical-specs/coventry-chaser-grinding.pdf

The book of the Coventry Diehead is available here:

http://www.vintagemachinery.org/pubs/detail.aspx?id=21649

DC31K, thanks I have the Alfred Herbert book on the coventry die heads, there were many editions, the early ones did not cover the later device for regrinding. The wiseman section I will look at. Thanks. Noel.

PS, just looked at the wiseman site it is a copy of the later Herbert book and has answered the question ! You need the No3 device to do 1 1/4" die head chasers. Thanks again.

Edited By noel shelley on 08/08/2022 22:59:03

Thanks for the replies guys. Out of interest should it ever be necessary to regrind the flanks of the chasers? Or would grinding the rake and face normally be good enough to bring the quality of the finished thread back?

Cheers,

Dan

To clarify, you need more than just those grinding fixtures.

You also need a surface-grinder or tool-&-cutter grinder to use them on.

Mine, marked "3/4 RH" on top and with the Alfred Herbert name embossed in a recess underneath, definitely is. It does not appear to have a number though; just size and thread-hand.

The idea is to grind the set of 4 as a unit. It may be possible to make some form of grinding-jig to sharpen them one at a time on a bench-grinder; but it is vital that the grinding is accurate enough for the set still to work together. Each chaser must pick up exactly a quarter-pitch beyond where its previous one left off.

Hi Nigel, The chaser jig you have sounds like the early style, No1,No2 and No3 were the later style. The throat is done with the 4chasers clamped together and if the height number is not the same when checked in the height gauge then the 4 chasers can be ground on the rake laid flat in the jig. If need be the chasers can be cut back as well to bring things back to the right number. I have a couple of Clarksons to do such work. As has been mentioned the Herbert book is very interesting.Noel

Dan, The tapered entry (throat) is ground first. If on checking the height as stamped on the chasers it is found to be incorrect then the rake(top face) can be ground. and finally to get even more life out of them if not chipped or damaged they can be cut back ! Noel.

Edited By noel shelley on 08/08/2022 23:57:30

Edited By noel shelley on 09/08/2022 00:02:03