Hewland dog ring reconditioning.

[jstreet]

Hi all. I have a pile of used MK9 dog rings that are in "so-so" shape. And I recall someone telling me once that there is a shop somewhere reconditioning them. Does anyone know about this process and if you do, how is it working for you?

Thanks for all your help, John Street

[Roger Eade]

We get welded and shaped over here (NZ) so would think that someone would do it there, but they must get it right or they will hang on shfting out or bang going in, the guy I get here has done them for years and has a jig for grinding them back after welding so they are cut correctly.
Roger

[Barry Haynie]

Look in the back of SportsCar for an ad-Can't remember the name and don't have one at work--for a shop that does gear recon etc. Its been in there for years. I'll poke around in an issue at home and hopefully provide a better steer on to the target.

Barry

[Charles Warner]

This can easily be another instance of false economy. Normally the regrinding process removes the hardening from the dogs and I have never heard of any outfit that re-hardens the dogs after grinding. I've forgotten how thick the Rockwell hardness is on the dogs but Craig has the numbers off the top of his head. I tried the reground dogrings one time and they were basically worthless. I am not referring to any specific individual or firm. They were sharp, without the proper radii on the mating surfaces, and broke and flaked very quickly. IMO get new items and "save" money elsewhere.

If they were a viable alternative I imagine Craig would provide the service.

[D.T. Benner]

I use the Webster Dog rings because they are made from an alloy that will purposly wear more than the dogs on the gear sets. The idea is that its cheaper to replace dog rings than gear sets. I agree with Charles that this is not a good place to try to save a buck.

[Charles Warner]

It is my understanding that the dogs on the Hewland dogrings are also purposely softer than the dogs on the gears for the same reason. Rockwell 52C versus Rockwell 48C sticks in my mind for some reason.

[R. Pare]

It is my understanding that the dogs on the Hewland dogrings are also purposely softer than the dogs on the gears for the same reason. Rockwell 52C versus Rockwell 48C sticks in my mind for some reason.

That would more likely be 62C on the gear vs 58-60 on the dog. The Hewland standard (and most likely the same for Staffs and Webster) is a case depth of .060 on the gears (or at least was years ago), and a minimum of .030 on the dogs, though the ones that I've cut seemed to be closer to the .060 depth.

Buy new dogs, and use a diamond file to radius the sharp corners.

[Craig Taylor]

Gentlemen,

1.

[Craig Taylor]

Gentlemen,

1. We do provide dog lug recutting services, but find that it is only economical on gears that have very short lugs, such as the case in the FT200. The FT200 lug is only .100" tall, wear out rather quickly. Virtually all racing gears are made from English EN 36 or 9310 steel, with a case hardened exterior (Interior hardness typically Rc 42, with a 59-61 RC case). Any recutting breakes through the case, so the "new" dogs are only of core hardness. A driver who manages the gearbox well can get a season out of recut FT dogs; one with poor skills can destroy the recut dogs in just one session. The wear limit for the dog lugs is reached when the rounding wear at the dog lug reaches 25% of the dog height. EG when the wear reaches .025" for FT (.100" dog) or .037" for MK (.150" dog) the dog is worn out.

2.

[Craig Taylor]

Gentlemen,

1. We do provide dog lug recutting services, but find that it is only economical on gears that have very short lugs, such as the case in the FT200. The FT200 lug is only .100" tall, wear out rather quickly. Virtually all racing gears are made from English EN 36 or 9310 steel, with a case hardened exterior (Interior hardness typically Rc 42, with a 59-61 RC case). Any recutting breakes through the case, so the "new" dogs are only of core hardness. A driver who manages the gearbox well can get a season out of recut FT dogs; one with poor skills can destroy the recut dogs in just one session. The wear limit for the dog lugs is reached when the rounding wear at the dog lug reaches 25% of the dog height. EG when the wear reaches .025" for FT (.100" dog) or .037" for MK (.150" dog) the dog is worn out.

2.

[Craig Taylor]

Gentlemen,

1. We do provide dog lug recutting services, but find that it is only economical on gears that have very short lugs, such as in the FT200. The FT200 lug is only .100" tall, thus they wear out rather quickly. Virtually all racing gears are made from English EN 36 or 9310 steel, with a case hardened exterior (Interior hardness typically Rc 42, with a 59-61 RC case). Any recutting breakes through the case, so the "new" dogs are only of core hardness. A driver who manages the gearbox well can get a season out of recut FT dogs; one with poor skills can destroy the recut dogs in just one session. The wear limit for the dog lugs is reached when the rounding wear at the dog lug reaches 25% of the dog height. EG when the wear reaches .025" for FT (.100" dog) or .037" for MK (.150" dog) the dog is worn out.

2. The Hewland dogs rings are hardened and cased to the same specifications as the gear. The Webster dogs are drawn back to about 57 Rc, resulting in most of the wear being concentrated on the dog ring, reducing the wear on the dog lug. With extremely abusive drivers who have trouble getting through the weekend on a set of dog rings, we recommend Hewland dog rings. Conversely, with drivers that can properly manage the gearox, Webster dog reings reduce the wear rate of the gear dogs.

Craig

[D.T. Benner]

Well I was almost right? It's not the material,it's the hardening thats different. Gee,I love it when I'm almost right!