25-01-2018, 12:07 AM
(This post was last modified: 25-01-2018, 12:12 AM by john williams.)
Further to the photo's of my re-mettaling jig.
This is a jig that was produced for the trade, and I rescued from a Technical college.
Dimensions; The half round casting bar is 1 3/16inch across the flats.
The casting bar protrudes 3/16inch each side of the side pieces.
Distance between side pieces when clamped together 1inch.
Side pieces 1/2inch wide with the internal shoulder 1/4X 1/8 inch
I do not wish to teach "Grandmothers how to suck eggs", but this is the method I was taught 40 years ago.
Firstly the big end assemble must be completely grease/oil free. Wash with degreaser, then soak in mixture of boiling water and household Soda crystals.
Plug oil holes in con rod with exhaust sealing putty.
Coat a thin piece of string in exhaust putty, and place in bottom of side piece shoulders. This will prevent the liquid hot metal running out of the side of the cap/con rod during casting.
Two tubs of heated white metal are required. One is the new metal to be used to pour the bearing. The other is old metal from previous jobs.
Place the con rod bearing end and big end cap into the second tub and heat until the white metal is liquid. this will melt the old metal out of the con rod and cap and bring both upto casting temperature.
For the casting operation, place the assembled casting jig across the opened jaws of a bench vice. This will allow the big end cap to be positioned as shown in the photo's; and when the con rod is placed in the jig the length of the rod can pass down through the open vice jaws.
Pre-heat the jig and casting bar using a blow torch. This is important, because if the jig assembly is cold; the molten white metal will solidify in the jig before it has completely filled the jig.
Remove the cap from the second tub [pointed pliers]. the bearing surfaces can be scrapped clean with a piece of hack saw blade. Tin the surfaces with "Tinman's flux" and solder. Ensure surfaces are completely tinned.
Place cap in the jig, position casting bar. Ladle out new white metal from first tub and pour into casting bar. If everything is hot enough, the hole in the casting bar will fill with molten white metal. at this stage let the whole thing cool, you will see the wight metal in the casting bar hole "go off". Cooling can be assisted with an airline directed at the assembly. When cool, a sharp tap with a light hammer on the end of the casting bar will free it from the cap/white metal.
Repeat the process for the con rod, and remaining con rod assemblies.
Use a small drill to clear the exhaust putty from the oil holes in the con rods.
Remember this process produces LEAD FUMES, so good ventilation and a face mask are essential.
Likewise protective clothing and gloves.
This is a jig that was produced for the trade, and I rescued from a Technical college.
Dimensions; The half round casting bar is 1 3/16inch across the flats.
The casting bar protrudes 3/16inch each side of the side pieces.
Distance between side pieces when clamped together 1inch.
Side pieces 1/2inch wide with the internal shoulder 1/4X 1/8 inch
I do not wish to teach "Grandmothers how to suck eggs", but this is the method I was taught 40 years ago.
Firstly the big end assemble must be completely grease/oil free. Wash with degreaser, then soak in mixture of boiling water and household Soda crystals.
Plug oil holes in con rod with exhaust sealing putty.
Coat a thin piece of string in exhaust putty, and place in bottom of side piece shoulders. This will prevent the liquid hot metal running out of the side of the cap/con rod during casting.
Two tubs of heated white metal are required. One is the new metal to be used to pour the bearing. The other is old metal from previous jobs.
Place the con rod bearing end and big end cap into the second tub and heat until the white metal is liquid. this will melt the old metal out of the con rod and cap and bring both upto casting temperature.
For the casting operation, place the assembled casting jig across the opened jaws of a bench vice. This will allow the big end cap to be positioned as shown in the photo's; and when the con rod is placed in the jig the length of the rod can pass down through the open vice jaws.
Pre-heat the jig and casting bar using a blow torch. This is important, because if the jig assembly is cold; the molten white metal will solidify in the jig before it has completely filled the jig.
Remove the cap from the second tub [pointed pliers]. the bearing surfaces can be scrapped clean with a piece of hack saw blade. Tin the surfaces with "Tinman's flux" and solder. Ensure surfaces are completely tinned.
Place cap in the jig, position casting bar. Ladle out new white metal from first tub and pour into casting bar. If everything is hot enough, the hole in the casting bar will fill with molten white metal. at this stage let the whole thing cool, you will see the wight metal in the casting bar hole "go off". Cooling can be assisted with an airline directed at the assembly. When cool, a sharp tap with a light hammer on the end of the casting bar will free it from the cap/white metal.
Repeat the process for the con rod, and remaining con rod assemblies.
Use a small drill to clear the exhaust putty from the oil holes in the con rods.
Remember this process produces LEAD FUMES, so good ventilation and a face mask are essential.
Likewise protective clothing and gloves.