chaser grinder jig

[lug lordParticipant @luglord]

[lug lordParticipant @luglord]

having a play about with this today what kind of grinder do i need to make it work and do i only need to grind the throats to just sharpen them up a bit

[lug lordParticipant @luglord]

[lug lordParticipant @luglord]

[Anonymous]

Posted by lug lord on 10/10/2017 16:20:56:
having a play about with this today what kind of grinder do i need to make it work and do i only need to grind the throats to just sharpen them up a bit

Ideally a surface grinder, although some T&C grinders, like a Clarkson, can be used.

As I explained in my recent PM as well as the throat you need to grind the flat face so that the cutting tooth reaches the arbitrary number engraved on the chaser set when measured with the tapered "rules". This is because the axis of the teeth is not aligned with the axis of the screw thread but crosses it, so the front tooth cuts and the rest act as a guide. If you only grind a thou or two off the throat then you may get away with it, but after that you'll need to grind properly.

Andrew

[lug lordParticipant @luglord]

I'm thinking i bit of more than i can chew with this item but it looks good to look at .It seems the more i do is like a chain reaction need this for that and that for this it seems to never end . I can see now why i need a surface grinder to keep all the angles the same .

I think i get what your saying if i grind the throats the rakes need to be ground to match and this is where the tapered rules come into play .

ian

[lug lordParticipant @luglord]

I can attach the jig to my vertical slide on my myford super 7 and crank it up on full speed then i would only need to find a suitable grinding wheel and make light pases using the carriage wheel how does that idea sound do you think it would work

ian

[lug lordParticipant @luglord]

I can attach the jig to my vertical slide on my myford super 7 and crank it up on full speed then i would only need to find a suitable grinding wheel and make light pases using the carriage wheel how does that idea sound do you think it would work

ian

[roy entwistleParticipant @royentwistle24699]

I would personally keep grinding wheels as far away from my Super 7 as I could

Roy

[lug lordParticipant @luglord]

Posted by roy entwistle on 11/10/2017 17:04:46:

I would personally keep grinding wheels as far away from my Super 7 as I could

Roy

yes i think that is best was thinking about all that grit on the bed and getting in the workings not the best idea

[Anonymous]

I've been having a discussion via PMs on grinding Coventry diehead chasers. As well as grinding the throat the front of each die needs grinding. This is because the threads are not radial to the work but cross the axis at an angle. This is so the cutting is done up to,and including, the first full tooth, the rest acting as a guide.

To help grinding the front face each set of chasers has an arbitrary number on it, which has to be matched against a tapered rule. Here's a picture of one for ½" RH chasers, the key number for this chaser set is 51:

The numbers seem to increase linearly with diehead size, so in theory one long rule would cover all dieheads. I've measured the angle as between 2.6° and 2.7° across several rules. Unfortunately these items seem to pretty rare; probably because a toolroom would have had only one set to cover multiple dieheads. They come in assorted sizes, for different size dieheads, and RH and LH are different. I can't remember where mine came from, but probably mostly Ebay.

Andrew

[lug lordParticipant @luglord]

Cheers I might try measuring the intersection see if I can work out what the number is my chasers have no 54

Maybe it's 5.4mm or its some kind of percentage of an inch measurement

Ian

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