I've just agreed to weld a bolt on a mates bodged mauser 98. After welding it I plan on heat treating the cocking cam surface (I can make sure the locking lugs aren't affected). I'll heat the cam surface to just cherry red with the oxy then and quench in oil. I'll then reheat the area to straw colour with a propane torch and stop the heat continuing by putting in water.

I have a couple of questions: Is straw the right temperature? Will this partial heat treating work? Will heating to cherry produce scale?

I welded a bolt handle on a previous 98 and it went great. But I plunge the rear end into water immediately after welding and it made the whole area very hard. I didn't temper and want to do a better job this time

The camming surface is case hardened so after heating to cherry I would quench in water and leave it at that. I don't think tempering to straw is needed.
I have done this a few times in the past but now I'm smarter, I use a buttress threaded copper heat sink and TIG weld the bolt in short goes over 10 minutes or so. Also have the bolt handle pointing up so most of the heat travels up and out of harms way. Heat loves to go up! This way virtually no heat goes into the bolt body and you don't soften anything.

Bodged ? Buggered ?
If the bolt has been altered in any way I would rather see you sent it out to an experienced HT company and HT the entire bolt. That would take care of all HT damage .Remember that wartime HT can be very spotty .

mete, could you please elaborate on what you mean by "wartime spotty HT"?
Thanks.

so water quenching isn't too violent? When I did it like that on my last one it was nice and hard but so was the handle root which made finish very hard (literally). I guess I could cool it very slowly after welding while trying to keep heat minimal (I don't have a TIG and no one does within 200km). Then heat treat later and only have to clean the colour off. How does that sound? Will cooling it slowly help - it won't be quench by the surrounding steel?

Maybe you Americans don't know the word bodged? I guess it basically means bubba'd, but applies to all areas of practicalities! Someone must have leant on the angle grinder so hard when thinning the bolt the back of the bolt around the cam area is blue... Lug's are ok.

oh yeah this is a 1909 argy and the bolt is matching. It was sportered into a single shot 308 when he got it. Shoots pretty well and no set back (yet)

brno you are on the right track, weld the bolt & clean up first. Hold the bolt upright i.e. cam up, just heat the cam to cherry then quench. You will find the heat will not travel very far down if you do it quick.
Water quench gives you a nice hard case. thats what you want.

OK, thanks metal. So I don't need to worry about cracking or scale?

It will not crack. Alloy steels crack, case hardened medium carbon steels aren't in danger of cracking.

It will turn black, but that should clean off pretty easily with a wire wheel. The big part is to do the finish work before you re-heat treat it. It should take minimal polishing after you clean the scale off.

Jeremy

Thanks, good to hear. I'm not bad on my basic metalurgy but I didn't know what sort of steel the bolt was. In fact I thought I heard they were often high carbon that were through hardened, but obviously not.

They are similar in composition to the receivers, but they are harder. They are smaller parts that heat faster, and take a case a bit deeper for the same heating time as a result. At least the couple that I have seen cut up and analyzed showed this to be the situation. One of those was a DWM the other was a VZ24. I cut up the bolt handle for analysis, not the bolt itself.

I have heard that some had nickel in them, but that isn't going to change what you want to do.

Jeremy

For the most part M98s were always case hardened carbon steel ,something like 1020. My M98 ,a military 1943 had variable hardness on the receiver.Some areas dead soft and some propely hardened. I chose to re-HT the receiver and not take a chance of soft locking lugs.
Toward the end of the war things started to change both in design and quality.Mine has all matching part numbers.That became my deer catcher for the next 25 years !

mete, after 15 years of drilling,filing,cutting,welding and grinding on the M98 this is what I have found.It applies to ex mil. 98's from pre WW1 to late WW2,contract Belgian,German,Austrian,FN commercial,either pack or cyanide bath hardened but not including Mark X /Interarms.
They were selectively hardened,i.e. the deep case was only applied to the areas that needed it,lug seats,wear surfaces and the bolt. Most of the exterior was left unhardened and therefore when tested does not record consistently on the Rockwell C scale. This often leads to the conclusion that they are poorly hardened but I have not found this to be the case.
The proof marks and careful inspection tell me that they are plenty hard where they need to be.

Good info thanks !

I hope this isn't considered a hijack of this excellent thread but . . .

Recently I had a 98 bolt shortened to fit a Model B Kurz sporting action. The work was carried out by a reputable smith who has done excellent work for me in the past, including new bolt handles, as good as any I've seen here. His approach was to cut the bolt between the rear lug and guide rib, and tig weld it. He had to re-harden the cocking cam.

I am currently discussing the result with him as although the bolt functions, it is not "slick" and appears to have the slighest bend in it. The bend is apparent more by eye than measurement, a straight edge does show some waviness but nothing definitive.

I now want to have a go myself, I have some friends who are first class machinists who will do the actual work. My thoughts are to try cutting a bolt through the guide rib, index a socket joint from the inside of the bolt and silver solder the joint using the guide rib to ensure alighnment. We would ensure heat applied is minimal and does not reach the ends. I think I would have the bolt handle done first so the bolt doesn't have to get hot again after the shortening process.

I am interested in feedback and other ideas/approaches.

Thanks

Foster

The common method used when shortening the Mod 70 was to socket join the bolt at the extractor collar groove with silver solder, it's well written up in the Gun Digest Book of Riflesmithing by Jack Mitchell. Very neat & invisible.
Whether it's possible to join the 98 bolt with this method I don't know, there are gas escape ports & firing pin lugs in that area but I think it has been done. Maybe one of the Masters can chime in?
I'm not surprised that your bolt ended up with a bow in it, it's a tough job even for a pro. The weld is going to pull the thing every time, you would almost have to set it up crooked and let the weld pull it straight like when I weld S/S pressure pipe in my real job.

quote:

Originally posted by Tentman:
Recently I had a 98 bolt shortened to fit a Model B Kurz sporting action.

What?! I thought you had a gunsmith who was making a new bolt from scratch?

Anyway, I recall telling you that shortening a standard bolt would be 1/100th of the work. I even mentioned the Joe Reid/Jack Mitchel method that "Metal" speaks of(I believe I referenced the book also...).

Any welding on a bolt that has been cut on the body is surely going to cause problems.

If I were in your shoes I would trash that welded bolt and have another one shortened in the extractor grove and silver soldered.

Gidday Jason

Some (not a bunch in my experience) people do what they say they will but most just mouth off and never deliver . . . and the guy who said he could make me a bolt was yet another of them.

I have both the articles mentioned plus a couple of others but they all focus on getting the job done, only Steve's article makes a start on addressing the issues that arise . . . . which was the discussion I was hoping to hear here from people who actually have done one by picking up a chuck key and firing up a torch, or maybe put up the $$$ and commissioned it.

I've found more fertile ground with great contributors elsewhere.

Cheers

Tentman

Regardless of how you have it done I will be interested to see the finished product. Without a doubt you have the best kurz hunting/working rifles that have been shown on this forum.

I hope you will be able to get a bolt that will get your action back into the field.