Mount Trapezium

[Sanjay F]

Thank you both for your replies, yes they are made from brass which is 3mm thick and I think you are right about screws (see diagram). The build log suggests fixing (using screws) the vertical to the base before soldering and I think the diagram shows this? I originally thought the diagram was showing the holes to fix the guides to the cylinder top, but I may be wrong.

They are suggesting 8BA which seems quite large in a 3mm plate so may have to go with the 10BA as suggested by Jason

[Jasonb]

I would say those two 8BA holes are to attach the guides to the square plate that sits ontop of the cylinder. How do their positions compare with those in the plate.

One other thing to mention when silver soldering brass & GM is not to have too much clamping pressure on anything as you are getting close to it's melting point and it will become a bit soft and can be bent by clamp pressure

[Sanjay F]

I think your right, see diagram of cylinder top. In which case I should make the silver holdering holes where the blue arrows are in my photo; the red dots are the cylinder fixing positions.

I've now got the verticals fitting through the base slots and they protrude out slightly which is I think is okay as once I have screwed them in place then silver soldered them I can lightly mill the surface flat

[Sanjay F]

It's a dumb question, but just to make sure I'm silver soldering around this joint on this side, not underneath, right?

[crueby]

Either way round would work, as long as the solder flows into the joint. I would put flux on both sides to help the flow. It might be easier to have it the way you show in the more recent post, though you may want to prop it up to make sure it doesn't blow over.

[Jasonb]

Screws as the arrows and as Chris says prop it upright then you canb see the solder flow around the joint as it forms a small fillet.

[Sanjay F]

Got there in the end ......there's an additional hole in the guide on the right where the 10BA drill bit broke; I never have much luck with tiny drill bits and I was careful, not heavy handed and used cutting oil 

I ended up using an 8BA and just got away with it although there is some rippling of the metal, but that's on the inside so won't be seen.

Silver soldering next, actually there is a small to be made at the top of each guide, I can use that for support to prevent it blowing over

[Jasonb]

Should the tapped holes not be central to the foot? Or are you going to move them in further on the cylinder top?

[Sanjay F]

That's interesting, if you take a look at the 2 photos the guides are positioned differently with the foot facing inside or outside. I think you may be right and the screws should be centralised in which case some filler needed, however, is the foot in or outward facing .....?

Let me check the length of top connecting pin, that will confirm

[Sanjay F]

Drawing says foot faces out

I've just realised I've had a stroke of luck, I can use the 8BA tapped holes which I made temporarily for silver soldering to fix the guides to the cylinder...... just need to fill in the other holes with a bit of weld and no one will know

[PaulR]

Facing out looks right, facing in looks weird!

[Sanjay F]

I think I'm finally making some progress with silver soldering. The setup looks precarious, but it allowed me to get the heat underneath, I added some washing up liquid to the flux which seemed to improve the consistency, used correction fluid to limit were it flowed and as soon as I touched the solder it ran (like all the videos I have watched and never managed to achieve!)

There are few dots (bubbles) where the solder hasn't flowed and underneath has not got solder all the way around the joint.......however, better than the mess I was creating before!

[Michael S.]

You did a great job. 👍
You could close the small hole with soft solder.
Electronic soft solder, used for circuit boards, is particularly suitable for this. Heat the part and close the hole with the thin solder. If the brass part is clean and free of grease, you don't need any solder paste.

Michael

[Sanjay F]

Thanks Michael, I never realised you could use soft solder top of silver

[Jasonb]

Not much wrong with that, it's quite satisfying to see the solder run around the joint.

Soft after silver is OK but the lead in soft solder causes problems if you do it the other way round.