This is why you fully inspect your new rifle...

[tatou]

Awesome, thank you guys for the great explanations. Wont make me a better welder but it does help a lot in understanding what is going on.
Cheers

[Surpmil]

The other advantage of brazing is that the lower temperature of the brazing metal means there is usually no possibility of actually melting or distorting the pieces being joined, as there is in arc welding, nor the kind of instant contraction / "pulling" that makes it a bit of an art to maintain the relative positions of pieces being arc welded.

I'd have to disagree slightly that the depth of weld is limited to the depth of the weld pool, unless one means in each pass over the joint; one usually makes several passes over larger or deeper joints.

Or that welding inherently involves only fusing together the original metal of the parts being joined: only forge-welding does not involve the addition of new metal to the joint.

Brazed or gas welded joints are also generally much neater, and less obtrusive or likely to require treatment with a "welder's eraser".

[bombdoc]

The other advantage of brazing is that the lower temperature of the brazing metal means there is usually no possibility of actually melting or distorting the pieces being joined, as there is in arc welding, nor the kind of instant contraction / "pulling" that makes it a bit of an art to maintain the relative positions of pieces being arc welded.

I'd have to disagree slightly that the depth of weld is limited to the depth of the weld pool, unless one means in each pass over the joint; one usually makes several passes over larger or deeper joints.

Or that welding inherently involves only fusing together the original metal of the parts being joined: only forge-welding does not involve the addition of new metal to the joint.

Brazed or gas welded joints are also generally much neater, and less obtrusive or likely to require treatment with a "welder's eraser".

The point I was trying to make was that in brazing, the fusion between the original parts and the braze material is a surface alloying process whereas in welding, the metal of the original part has to be melted and becomes part of the joint. This has two consequences, in that in a braise, the physical structure of the original part is only slightly affected (you can still get distortion!) but that the surface of the joint can be much larger due to the jointing material flowing by capillary action through the joint. In a weld this does not happen as the surface tension of the liquid in the weld pool keeps it local, and the depth of fusion in the weld is not much greater than the depth of the pool. As you point out, this is why, where a deep weld is required, multiple passes are required. A weld always results in the physical dimensions of the original part being changed, both from heating effects and as a result of liquification of the original structure..

It is possible to create welds without adding filler, known as "autonomous welds" but only in a limited number of weld types such as outside welds in thin metal or where a weld can be run along the edge of a double flange. Autonomous welds are sometimes designed when welding exotic materials where adding a different filler metal would be an issue.

Most of my welding is using TIG, which I consider to be the best method for gunsmithing. It is as precise as gas welding, but without the need to give houseroom to acetylene, which often upsets insurance companies! You can also use TIG for brazing, although the filler rods are expensive. The only better technology is laser welding, which is a bit outside my budget!

Most common weld fillers for steel are low carbon. eutectic alloys that end up as fairly soft mild steel. You end up with a reasonably tough join, however it can be a bit soft for bearing surfaces. If you are doing welds to build up worn or damaged surfaces you might want to think about using one of the more specialised fillers or case hardening after dressing the weld.

[Surpmil]

I've just picked up a TIG, so it's going to be interesting to play around with. A garage sale here just yielded a full mid-sized bottle of acet., an O2 bottle, hoses, and and a nickel-plated Smith's oxy-acet torch, all for a tenner. Less than the deposit on one of the bottles now; though have no need of either I'll use the acet. and take them back for the deposits. I should get some propane tips really, especially for tasks like burning off powder-coating and stubborn accumulations of paint and dirt. A touch of air burns all such stuff off beautifully, but when one has to pay for the gasses it gets expensive quickly!

"hard facing rod" was what they used to call the sticks for wearing surfaces here.

' Enjoyed the chat.

"Let sleeping insurors lie" I always say.