How on earth do these die holders work?

[HollowpointParticipant @hollowpoint]

Hi guys.

I picked up these die holders with the purchase of a lathe some time ago. I don’t know if I m just being dumb but I can’t understand how they work? The mechanism doesn’t make much sense to me? They have a toothed clutch at the front and a ramped notch at the back.

They came with a Boxford and I believe they are a genuine Boxford accessory.

[BazyleParticipant @bazyle]

The front dog clutch works when it is being advanced onto the work but quickly releases when you stop feeding it. Then reversing the machine will pick up on the rear one. The ramp ensures the rear clutch  cannot pick up when running forward.

[Julie AnnParticipant @julieann]

Same principle as the tap and die holders on the Britan repetition lathe. Very fast in operation, two or three seconds at most per thread.

Julie

[Martin Johnson 1Participant @martinjohnson1]

Every day is a school day.  Never seen one before, but a good method for small batches for those that can’t justify a Coventry die head.

Martin

[Clive FosterParticipant @clivefoster55965]

A DIY version of would be a nice article for Model Engineer and Workshop. A tap holding version would be nice too.

I have one of the moderately common commercial “slide on a pin” die carriers which work well enough when I don’t have the appropriate chasers for the Coventry head but a tap carrier working on the same lines would be of serious interest.

I imagine there is sufficient subtlety of design in the relative sizes of clutches and ramps for truly satisfactory operation that straight off the drawing board success is not guaranteed.

Clive

[Julie AnnParticipant @julieann]

On the Britan the same style of dog clutch mechanism is used for both dies and taps, just a different holder screwed onto the front:

The sequence of operation is as follows, first dogs driving:

Once a stop is reached the dogs at the point of release:

The dogs slipping, ie, the tap/die just revolves with the work; no feed:

Dogs reversing the die/tap after the spindle rotation is reversed:

I’ve used the tapping function for making hundreds of custom nuts. The die facility is far less used as I prefer to use the Coventry diehead.

Julie

[Clive FosterParticipant @clivefoster55965]

Lovely pictures Julie.

Maybe I do just enough tapping on the lathe to make it worth while designing a DIY friendly version. Most likely I’ll still be muttering after 3 more moderately frustrating tapping in the lathe jobs.

Mr Pollards tapping heads on drill or mill effortlessly handle most of my tapping work.

Clive

[HollowpointParticipant @hollowpoint]

Thanks for the explanation, it helps a lot. I think I will have to have a go. See how well it works. 👍

[Nigel Graham 2Participant @nigelgraham2]

I have the die-holder itself for one of these – had no idea what is missing until this thread appeared!

It looks as if meant for a turret feed: the turret is advanced as far as a pre-set stop, when the die will then run on until the pins disengage. As far as I can see the spindle then has to be reversed while easing the turret back to withdraw the die from the work.

[bernard towersParticipant @bernardtowers37738]

All the education boxfords I have worked on had these as std accessory

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