On the old Mauser I'm working on, I've lapped quite a bit (5 sets of 50 bolt turns with the bolt lapping tool installed using 600 grit lapping compound). I went from about 50% contact to 80% fairly quickly. But I'm not noticing much improvement last couple runs. Is this normal? I'm going to send it away to be heat-treated. Do I need to worry about removing too much material? I have noticed the cammed surfaces and am not "counting" that for % contact. I need to decide whether to continue before taking final measurements to determine how deep to ream the barrel's chamber.

Thanks,

Steve

As you lap it you have more contact and therefore the lapping goes slower.I would try for at least 90% contact but I would wait until it's heat treated to make any measurements.You don't need to remove too much since you will carburize and HT it.But HT then check to see that everything is OK then take measurements.

quote:

I went from about 50% contact to 80% fairly quickly.

Please do us a favor and tell us what % of bearing area you have AFTER heat treating.

Mete,

Okay, thanks.

Vapo,

Will do. Are you looking for evidence of warpage?

Steve

More likely you will see that some of the metal that may have set back will pooch back out after heat treating.

quote:

Originally posted by skl1:


Vapo,

Will do. Are you looking for evidence of warpage?

Steve

I've been saying to lap after heat treat. I'm hoping you'll be in support of this as there's no way to heat treat without some small amount of warpage....the question is always.....HOW MUCH!!!

YES is the answer to your question. What case depth are you asking the heat treater for?

Vapo,

I'm going to ask for what Jerry Kuhnhaussen's book recommends (I believe it was .010-.015in). I think I'll specify the bottom of the range (.010, if my numbers are right), because I think he indicated the mode on the receivers he sectioned was .005-.008. I think his hardness recommendations were 50-55C for bolts and 35C for receivers.

Steve

Oh, but on lapping the lugs after heat treating: I thought one of the most important reason for heat treating was to avoid lug setback on lugs that'd been lapped through the case-hardening and left soft?

read this starting with the post by D'Arcy Echols

It's the best writing on the subject I've found yet.

PM me if you want more discussion please.