The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

I have just read a description of fitting a part to a rifle in which it states the part should be sweated on.

Now given that the author has probably been dead 75 years I cannot really ask him. So my assumption is the part is soldered as well as being screwed, however the part does fit in a closely machined slot, so it could be that the part is shrunk into place. I am inclined to go with soldering in place however....

Thoughts anyone?

Sweating on is using heat to expand one part and cooling to shrink the other. No soldering required when the parts are mated.

Yes, what Rog said is correct one part is heated the other is cooled then the two parts are fitted together and left to cool.

Sweating/shrink fit works well, the only thing I would say, it's usually a one way ticket. If it goes on a bit skew it's difficult to fix, so easier if you have some sort of locating peg or register to butt it up to. Sweating the ring gear on car flywheels with inertia Bendix starter motors was regular practice in my youth.

Alpha1 wrote:Yes, what Rog said is correct one part is heated the other is cooled then the two parts are fitted together and left to cool.

Thanks Dave. I got it right this time!
Happy Christmas

Yes a good example is the Steyr SSG barrel to action fit.

I have always understood a sweated joint to be a soldered joint.

In "An Armourer's Perspective" By Laidler, the scope mounts on the No4 T are described as being screwed and sweated on with soft solder. These mounts are flat plates.

I cannot see how the mounts would be a shrink fit.

When I worked at Perkins Engines the crankshaft gears were sweated on, this involved heating them in a special oven (that also did great cheese toastier in a couple of minutes at break time!) and once at the correct temp they were pressed onto the crank and left to cool.Once they had cooled they weren’t going anywhere!

Dave FYI you can buy a spray can of stuff that plumbers use to freeze water in pipes where they cannot shut the water off. I have used it and vouch for it being f'ing cold. Mind your hands with it!

glevum wrote:I have always understood a sweated joint to be a soldered joint.

In "An Armourer's Perspective" By Laidler, the scope mounts on the No4 T are described as being screwed and sweated on with soft solder. These mounts are flat plates.

I cannot see how the mounts would be a shrink fit.

as a plumber I have always understood "sweating" to be soft soldering, just go's to show that every trade has its own language.
interference fitting to me was always a mixture of heating the outside item and cooling the inside item, allowing expansion/contraction to alter the dimensions enough to allow fitment, returning to ambient created a solid connection to be made.
anyone who has ever rebuilt the final drive on a BMW motorcycle will have encountered this phenomenon DAMHIK