Some questions about die head chasers

[Brian CorrieParticipant @briancorrie54124]

Hello all

I have quite a few good sets of chasers plus some which are not in sets or where one or more in the set are damaged. This leads me to ask a couple of questions:

Assuming all the other factors are the same, can (say) a good No.3 chaser from one set be used in another set with a damaged No.3 ? I would imagine they would all have to be ground the same.

Is there a work around if some teeth are damaged on one chaser in a set, or does it effectively scrap the whole set?

Thanks in advance

Brian

[Brian CorrieParticipant @briancorrie54124]

[vintagengineerParticipant @vintagengineer]

I would assume that you could swap them, as when they are sharpened you only grind the top of the dies.

[JohnFParticipant @johnf59703]

Brian, in answer to Q1 its no, each set is numbered when manufactured and individual chasers form one set are not interchangeable with another set, I don't mean the sequence number 1-4 its a unique set number the same on each chaser in the set.
Q2 chasers can be re-ground but you need a jig to do it, they appear from time to time on ebay etc but you need to be careful to get one suitable for your particular die box size — there are some jigs that will do several sizes as well providing they are complete. You also need a surface grinder.
John

[Anonymous]

I agree with JohnF, you can't swap individual chasers between sets. The arbitrary number on each die in a particular set is used in conjunction with a tapered jig to set the height of the cutting thread after the throat has been ground, like this:

I think this is required because the ground threads are not in exactly the same place axially from set to set.

Here are some grinding jigs. Those specific to one diehead, and specific to RH and LH dies, are to the left. Then some angled plates to set different throat angles. Then the generic jigs that cover both RH and LH and a range of diehead sizes. Finally some tapered measurement jigs:

Depending upon where the damaged threads are located it may be possible to rescue a set of dies. The throat can be ground a considerable way back, about half the width of the die before the dies become unusable. If that isn't clear, say so and I'll take a picture of a die so ground tomorrow.

Andrew

[Brian CorrieParticipant @briancorrie54124]

Thanks for the answers.

I have a die grinding jig suitable for most of the dies – I think, but not one of the tapered gauges as shown in the top photo from Andrew. The grinding jig is a Herbert No.1 and has markings on the ends which I thought referred to the type of head that the chaser fitted, but I evidently need to read the f'n manual again.

At least I have some scrap sets to practice on it seems

Cheers

Brian

[Howard LewisParticipant @howardlewis46836]

You could always make up a holder, (drawings have appeared from time to time) and use individual chasers to chase particular threads. Either hand held, or in a toolpost, with the gears set to match the thread of the particular chaser

Howard

[lug lordParticipant @luglord]

I guess if you can salvage chasers from mixed sets and set them up in the jig and grind with a surface grinder all will be good as you have then created a matching set so long as the grinder takes a skim off all the chasers correct me if i am wrong please.

[JohnFParticipant @johnf59703]

Lug Lord, sorry you are wrong you cannot mix chasers from different sets. Even if you re-grind them the thread profile will never match — that means the start point of the thread on each chaser will not be compatible with the others in the set.

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