Re-babbiting big end bearings

[Colin Reed]

Some further info that has been emailed to me tonight:

“This thread started by Greig and added to by various people has landed at just the right time for me and has already answered some of my questions.
Attached are a couple of photos of the Con-rod re-metaling mould / jig I made.
This idea really started with some idle time in the workshop, a conversation and nothing else to do.
As can be seen from the photos it is basically in two parts.
The Base, this is a piece of Ground Stock Bar 9x1x3/8”there is a ½” diameter “Gudeon Pin” fitted to one end. The pin was reduced to 3/8” and screw-cut to BSP with an undercut at the shoulder. The bar was threaded to match with a light ½” counter-bore. I use a Tapping Attachment to ensure it is exactly square. Obviously a guide block or drilling machine could be used. The idea behind this was to use it as a check and make sure the con rod was not bent. By putting the cleaned rod onto the Pin and allowing the rod to lie against the base it can be easily seen if it is true and adjusted to suit before any further work.
The Mould, the main part of the Mould is made from Cast Iron. I used an old window weight for material. It is usually an open grain “dirty” material and they can be found at most joiners workshops. The idea for using Cast Iron is the Babbitt is less likely to stick to it. I made two 1 ¾” flanged pins 1- 3/16” diameter keeping the flange ¼” thick and milled them to the exact centre line. These were screwed to 2 mild steel plates 2-3/8 x 1-1/2 x 1/8”with the big end bolt holes accurately pitched. The main reason for making 2 parts and machining to the true centre line was to make it easier to find the centre of the big-end for machining ie not oval on assembly. Also both halves can be poured at once.
On assembly, before using my intention is to dust the Cast Pin with Graphite powder or rub over with a joiners pencil to prevent sticking. It will be seen that the base is not absolutely necessary when in use, but my thoughts were, it is a secure way of holding in the vice with a piece of insulation under the Cast pin to minimise heat loss.
I am working on a way to machine the sides of the con-rod after building the sides up. Obviously it must be central and true to the rod axis. I think we are almost there!
Now for a question, what flux to use for tinning my thought was Baker Fluid (Killed Spirits)
I hope the above ramble makes sense and may be of some use.
Tod”

Hi Ruairidh,
How are you planning to flow the metal around the sides for the side thrust,
I would use Tinning powder and no killed spirits, the powder is rubbed in with a wire brush                  

And once tinned dip in molten tin this gives an indication of how good the tinning has been done
Having a substantial jig helps keep the heat in it needs to be about 250 degrees C

Cheers Colin