I'm afraid I'm not an expert Sam but given that no-one else seems to be offering a view – I'll chip in.

First – your idea of just using soft solder doesn't sound a great one to me. I don't know the distance between the two "slots" but if there is enough meat there to do it, one possible solution might be to drill through 'tapping' for the next sized (fine) thread tap you have (first checking that you can actually reach the point you need to with your tap (?). Then tap the whole hole and make a 'plug' consisting of a threaded 'end' but with a 'clearance' body. The idea being that you can fill the unwanted 'hole' with a metal screw but still be able to withdraw the unwanted part by cutting it off. You could also of course, fill the existing hole completely with threaded 'rod' and just re-drill out the unwanted part.

I have done this on a much smaller casting and was also able to 'tin' the threaded bit (I used a hot plate/hot air gun to heat the casting) before I screwed it home. You can then (very carefully) re-machine the casting… You will have to think this through to be sure it's possible in this instance, as it's size is a problem.

Your idea of replacing the whole area is also quite possible and I've done similar work fabricating parts from existing/scrap materials – normally silver soldering them together. I also regularly use scrap steel with pre-existing holes in them that I generally drill out to a convenient tapping size and then 'fill' with screwed rod. This is mainly about the cosmetics of a part but when its machined these bits tend to disappear. For large, shallow holes – I clean up the hole and turn a large 'washer to fit which can be screwed in (using studs which are cut off flush) in place and then machined flat.

None of this is engineering excellence – much more about useful bodges that save money by using available material (or correcting my c*** **s). They often take more time to do than starting (anew) with fresh material but that's a personal decision.

So, I'd be pretty sure your problem is correctable but take your time before you just leap in. Sometimes there's a simpler way to do things that only comes after sleeping on it a while.

Regards,

IanT

PS Can't type fast enough. Martin posted whilst thumping this in. Sounds a good alternative and perhaps better on a larger piece. 

Edited By IanT on 27/02/2017 17:31:33

Why not silver solder? Careful heating, should be OK. I have repaired a port on a gunmetal cylinder block succesfully.

If the engine is to be run on air rather than steam I would be tempted to try filling the hole in the web with JB Weld epoxy filler, simple and comparitively quick. Should that not work then your flat bottomed hole and a plug would be my next choice, I would use Loctite 638 on the plug which would then not need to be a press fit. Give the Loctite 24 to 48 hours to cure before machining.

Jim

I don't think Sam has used anything just yet Old School – so his options are still open.

Kwil prefers silver solder (as do I normally) but I've not attempted to silver solder a lump quite this large (and solid) before, which would require a lot of heat. I have certainly managed to (partially) melt a brass component by applying too much localised heat, so I am somewhat wary where brass is concerned now. There could be some risk of distortion (to the machined surfaces) when applying red heat but I don't know if this would be a problem in practice. I try to machine/tap/thread my fabrications after soldering where possible. Others may have more experience and be able to offer better advice in this regard.

Vintage makes a good point about using solder paste – I'm sure it would help with respect to any soft soldering in this case. Sorry Sam – lot's of "ifs, buts and maybes" here – but hopefully the suggestions will help you find a way forward.

Be good/useful to know what you decide to do and how it turns out.

Regards,

IanT

.

It's also worth noting that both products were updated for 2014

This press-release from Henkel gives a useful summary: **LINK**

http://www.machinebuilding.net/p/p6621.htm

So [despite my general enthusiasm for using old stock]: For Sam's purpose, the later version offers a substantial performance advantage.

MichaelG.

.

Will this help.?

Don't know if it's 'machineable' like normal JB

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Nick