Coventry die head question

[MuzzerParticipant @muzzer]

Some stuff here about the various models.

My 3/4" die head is marked "20DS" on the side of the body (and in the steel box). The 20 refers to the metric equivalent of 3/4" and the DS is the style of body. A "12DS" would be a 1/2" version etc.

[Anonymous]

Posted by Phil P on 18/08/2016 17:13:00:

Posted by hth on 18/08/2016 13:45:40:

what more can I say . You guys cannot understand plain English ..

I am not too impressed with your attitude to people who are trying to help you.

Quite so!

One can lead a horse to water……………unfortunately some horses not only won't drink, they're daft enough to fall in and drown.

Andrew

[JohnFParticipant @johnf59703]

hth – Mike, those dies [photo] are pretty near useless you will at best get a very poor thread, they all should have the same thread teeth, they have also been sharpened several times and not to the correct spec. The taper on the front should be similar to that on a round split die, to maintain this profile there is a particular way of sharpening them and to do this properly you need a jig for each size of die head.

Some jigs will do more than one dies size — a little hazy now some years since I used the jigs.

Regards John

[MuzzerParticipant @muzzer]

JohnF – see the link in my post at the top of this very page….

[Anonymous]

There are three stages to re-grinding a worn Coventry die set. One, the throat angle needs to be ground to provide fresh cutting edges. The rake angle then needs to be ground at the appropriate angle to return the cutting edges to their correct position with respect to the work rotation axis. Third, after a number of regrinds the start of the throat angle needs to be ground away to remove non-cutting material. Here's a selection of Coventry die grinding jigs:

On the left are a selection of the old style jigs, two separate ones for each size of diehead, for RH and LH dies. These were intended to cut the standard 20º throat angle. For other throat angles, commonly 15º, 33º and 45º, the jigs could be mounted on angled plates, centre left. Centre right are two sizes of the new jigs (as per Muzzers link) each of which can grind dies for a range of diehead sizes, for all throat and rake angles, and for both RH and LH dies. Finally far right are some angle gauges. Those familiar with die sets will know that each set has an arbitrary number engraved on it, which is the same for all dies in a set. The angle gauges have a numbered scale corresponding to these numbers. When regrinding the rake each die is tested in the gauge until the first tooth stops on the scale opposite the number engraved on the die. This ensures that the tooth is in the correct orientation with respect to the work to cut properly.

Andrew

[Nick HulmeParticipant @nickhulme30114]

Posted by hth on 18/08/2016 09:59:51:

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 .

Definitely two teeth short of a Die Set

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