Die Head Advice

[Harry WilkesParticipant @harrywilkes58467]

[Harry WilkesParticipant @harrywilkes58467]

Hi all would welcome some advice picked up a couple of small die heads the other day along with a few chasers (hope thats what there are called). So looking at the end on photo there is the knurled screw then lookinginto the small grove in the end plate there is a small screw what is the function of these two item ? Also there are three very small holes two in the front part and one in the back plate I am assuming these are for a drop of oil ?. Would welcome your comments, advice or links to info please.

cheers H

[Harry WilkesParticipant @harrywilkes58467]

Had another quick look at die head found that in the grove there is a short set of division marks with a circled +/- either end. The the – can just be seen in the second photo to the right of the threaded hole.

Cheers H

[davebParticipant @daveb17630]

The knurled screw adjusts the thread diameter, 0=nominal, + & – = over and undersize. My backplates have a little movement built in, I assume this is to allow the device to centralise. I believe the small holes are for oil.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Harry,

Your device looks like a Coventry Die-Head. I believe they were originated by the Alfred Herbert company.

You'll find lots of useful information via Google, for example here's one I just found:

**LINK** but there are lots more.

There's also an eBay seller who occasionally lists copies of a Coventry Die-Head manual though the copy I bought suffers from low contrast diagrams and the scan not encompassing the whole width of the page!

The Coventry Die-Head comes in lots of different sizes but I haven't yet succeeded in identifying the size of the one I have.

You'll also see lots of listings for sets of chasers for the Coventry Die-Head on eBay.

In your second photo, it looks as though the screw is damaged – is that a camera angle problem?

I hope this helps.

Best regards,

Swarf, Mostly!

[Nigel McBurney 1Participant @nigelmcburney1]

If the chasers are blunt,they have to be held in a special fixture to grind them,the lead in on the chaser is below centre,the centre part of the cutting edge is at centre height and the remaining part of the cutting edge is above centre,the reason for the this is that the last few thread teeth rub rather than cut ,and help to control the pitch when cutting longer screws,

The Coventry die heads were mainly used on capstan lathes.mounted on the 6 way turret.

[Anonymous]

The device is definitely a Coventry diehead, quite an old CH style. Given that the front screws need to be completely removed before the front plate can be removed to change the dies it is probably a 1/4" diehead. It is missing at least one part. In the second picture, next to the minus sign, there should be a short handle to aid in closing the diehead before operation.

Regards,

Andrew

[Harry WilkesParticipant @harrywilkes58467]

Many thanks for all replies, still would be interested in knowing the purpose of the small screw located in the slot in the back plate (photo 3 left hand side) .

Swarf, Mostly! I assume you are referring to the knurled screw will check it out, having only taken a quick look the knurled screw looks to be a screw with a screw !

Andrew it is probably a 1/4" diehead it does contain a set of 1/4 x 28 dies

Thanks again

H

[thomas oliver 2Participant @thomasoliver2]

You should find that the body is in two parts and they are spring loaded when set by the missing lever. When you stop the feed of the turret or tailstock the die will continue to feed for about 1/8th in then release the cutters, when the whole assembly can be withdrawn immediately. The divisions on the adjustment should be in 1000ths of an inch. Male threads are usually a few thou.down on nominal size so do not make the thread full size. A 6BA thread nominal size is 110 thou. but usually only measures 106 thou. However – check with a nut for a good fit..

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Harry, judging by the adjusting screws, I think it may be a 5/16 Coventry Diehead.

Regards Nick.

[Swarf, Mostly!Participant @swarfmostly]

Posted by Harry Wilkes on 29/03/2014 22:20:05:

SNIP

Andrew it is probably a 1/4" diehead it does contain a set of 1/4 x 28 dies

Thanks again

H

Hi there, Harry,

I was going to come back on the size aspect but Nick has largely beaten me to it.

The thing is, as I understand it, that a 5/16" die-head isn't limited to cutting 5/16" threads – with the right chaser set it will cut any thread reasonably within its nominal capacity. But the chaser set has to be compatible with the particular model of die-head.

I suspect that the one I have may also be a 5/16 'CH', I'll have to dig it out and have a hard look at it! Without a positive identification of the model, it would be foolish of me to buy any chaser sets!

Best regards,

Swarf, Mostly!

[Harry WilkesParticipant @harrywilkes58467]

Hi All please bare with me should my post's appear disjointed I killed my win 8 laptop this morning it does not like coffee so have just dug out my old xp laptop and just got it up and running

Had a quick look around the internet for info on the die heads and came across this maybe many of you have already seen it link

[Harry WilkesParticipant @harrywilkes58467]

Hi All just slightly off topic but how does one create the link thus **LINK** I did add a link in a earlier post but couldn't see how to highlight it in blue.

Cheers H

[jason udallParticipant @jasonudall57142]

Die boxes are great..thread rolls are fantastic…
The resultant ( rolled ) thread is beautiful and the whole process ( once set) like magic ( both processes. .)
But then I am biased.
Enjoy your die box..

[Harry WilkesParticipant @harrywilkes58467]

Hi All

Managed to crab a few pic's of the other die head that I acquired it's smaller and slightly different from the other, the adjuster and the back plate which is spring loaded also the bore is closed. I have also added a pic of the two sizes of die's that were included

[Anonymous]

Definitely a very well used 1/4" die head. The smaller of the chasers will fit a 1/4" die head, the larger chaser a 5/16" die head.

Andrew

[Neil WyattModerator @neilwyatt]

Hi Harry,

Only links not in your history are blue. As, I guess, you visited the link before posting it, it shows as black on your computer.

Neil

[Harry WilkesParticipant @harrywilkes58467]

Thanks Neil

Cheers H

[Rik ShawParticipant @rikshaw]

Until now I have always assumed that a 1/4" die head accepted dies 1/4" thick and so on. I have a collection of BA die sets from 0 to 10 BA, they are 5/32" thick but I have never come across reference to a 5/32" die head – have you?

Rik

[Anonymous]

The size of a diehead refers to the maximum thread OD that it will cut. It's nothing to do with chaser size, although of course the bigger the die head the bigger the chasers. As far as I know 1/4" is the smallest diehead available.

Andrew

[MuzzerParticipant @muzzer]

I thought this was quite useful. If you go down to the bottom of the page, you can see the various head sizes available and if you click on a size, the next page shows what thread sizes can be cut with that sized head. Apologies if someone has already linked to this – I haven't reamed through the whole "thread" here.

Murray

[Ian HewsonParticipant @ianhewson99641]

For a very good set of operating notes for Coventry dieheads, go to threadtools.com.

this is Wiseman Threading Tools ltd site, should tell you all you need to know to use your dieheads.

Btw if you drill through the mounting spigot, you can cut longer threads.

[D.A.GodleyParticipant @d-a-godley]

You can download the complete handbook on specs and maintenance for Coventry Die Heads if you visit ;

pounce atom.dreamhosters.com .

He PDF. Is almost at the bottom and it is a bit slow, but well worth it.

Regards,

David

[D.A.GodleyParticipant @d-a-godley]

Sorry , that should be pounceatron.dreamhosters.com

[Anonymous]

For reference here is a picture of assorted diehead chasers, arranged by size of diehead:

Andrew

[Author]

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