No.32 Scope mount

[Charlie]

This mount appears to be original but I'm not sure. At any rate it has be altered. it looks like the original S/N was removed with an end mill and a new number (AM 7421 ?) was added. Any idea what the hash marks under the rear ring represent ? How about the partial number under the front ring ? I assume the cut out in the rail was to accomodate some scope other than a No.32. The cutout is well done mill job not a bubba hack saw special. Any thoughts ?

Information

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[Peter Laidler]

The hash marks you mention ARE the original numbers roughly barred out and usually the second or subsequent number would be placed near here. Why it would be placed near to the front thumb screw is a mystery but it has been milled out with a small milling cutter mounted into the pantograph engraving chuck, then the last AM number engraved at the same time. THEN commercialised by having a chunk taken out - none too carefully, with a grinding wheel that needs dressing off! What makes you say that it's a well done milling job? It looks awful from here!

[RJW NZ]

It could be worse, lol, thats a fine professional job compared to out here in bubba land! Any chance that was to fit a military scope while in service?

[Peter Laidler]

I was just thinking about silver soldering (hard soldering.....) a section into the recess to bring it back to normal. But........... Has anyone out there in forumland got any experience of hard soldering cast impure wrought? Will it distort at that temp.........?

Any thoughts out there........ JM....? Breaky?

[bigduke6]

Has anyone out there in forumland got any experience of hard soldering cast impure wrought? Will it distort at that temp.........?

Was it wrought Iron or low carbon mild steel ?

This is something I was looking at a bit a go regarding a casing for a lathe. (see link below )

MIG Welding Cast Iron

[vintage hunter]

My Dad is a retired welding Engineer and upon seeing the pictures of the bracket in question his advice was that if it's useable as is leave well enough alone. Silver soldering cast won;t work, the solder won't flow or bond well to cast. If the attempt were made to repair the ground out spot JM's brazing method would be best, but it's not an easy thing to do. The first thing to be done is to heat the part hot enough to burn out any grease or oil that has been absorbed, about 900 degrees. Easiest thing to do is make a bed of coals in the BBQ grill and clover it up for 10-15 minutes. Next, clean the area to be braised with a sandstone grinding wheel or a rotary file. If possible it would be good to make up a jig to keep the bracket rigid while the rapair is done and as it cools off. After jigging the entire bracket needs to be heated to a uniform temprature close to the melting point of the brazing rod, after the repair is complete heat the bracket uniformly again without causing the weld joint to come apart. Now cover it again with the hot coals and let it all cool down together. Good luck.

[vintage hunter]

Bigduke6, I read the link on MIG welding cast, the guy did a good job but I think he had a lot of luck on his side. His decision to braze it was a good one but MIG welding it with stainless wire ( 309L) would have worked too if done correctly. One thing he did'nt do was heat the part long enough to burn out any oils that were absorbed by the cast, thats why he had pits and holes in the brass joint. When I make a repair of this type, providing the part isn;t too big, I have a bed of coals handy to emerce the part in until it stops smoking, that tells me all the oils been burned out. If I'm brazing it I try to fill the whole crack in one pass, when arc welding it I peen the weld after each pass. Peening stress relieves the weld joint and reduces the chances of it cracking. An important thing to remember when repairing cast objects is to keep the whole thing hot the entire time the repair is being made, then when done immediatly cover it again with the coals and let everything cool down slowly and evenly. If it has'nt cracked by the time the coals burn out it's not likely to ever crack.

[jmoore]

Brazing will work, My uncle used to do it, but it WILL distort at least a little. Enough to render the bracket US? That depends!

[Peter Laidler]

Big Duke, the material spec for the original brackets is malleable whiteheart (PURE) or blackheart (impure) cast iron.

I seem to remember during my apprenticeship that you can braze it (that's why I was thinking hard silver solder might be suitable....) providing that the whole item is deep cherry red. The metallurgy labs explained why........

I remember it being discussed at some length overcracked/snapped/broken MGB GT V8 exhaust manifolds but that's going off the subject a bit I suppose

[jmoore]

Big Duke, the material spec for the original brackets is malleable whiteheart (PURE) or blackheart (impure) cast iron.

I seem to remember during my apprenticeship that you can braze it (that's why I was thinking hard silver solder might be suitable....) providing that the whole item is deep cherry red. The metallurgy labs explained why........

I remember it being discussed at some length overcracked/snapped/broken MGB GT V8 exhaust manifolds but that's going off the subject a bit I suppose

I reckon the MGB exhaust manifold repair is directly relavent. Near as I can tell the brackets could be a form of nodular cast iron, but have never felt like sacrificing even little bits for analysis. (It does machine like cast iron, as I had to repair an oversized spigot locating hole once. Didn't save any swarf, though...)