Correcting the Firebox Door

Correcting the Firebox Door is a tale of me getting the design wrong, then amending it before admitting to it.

Original Door Location

firebox door mark 1

I had originally designed the door to be higher up in the firebox. In my wisdom though as I was machining it I lowered the door.

Oh how wrong I was.

I’m sharing the images now, but I just had to wait until I correct the design before I could do this.

firebox door clash
door hinge removed on firebox door

The hinge and door latch were easy to removed, I just chiseled the heads off the rivets.

large door hole machined in firebox

The slot in the firebox was machined 11.2mm higher up. A simple machining operation using a 4mm solid carbide slot drill.

Note how well the part is illuminated with the angel eyes in the milling machine.

firebox door moved, but door aperture too large
The firebox door hinge and latch in new location, but door aperture is just too large.

Infilling the Old Door Aperture

plate to amend the door hole

Machining the plate to fill in the lower section of the new door aperture.

The plate was 3/16 inch thick mild steel. I machined this so that the backing plate was 1/16 inch thick and the door plug was 1/8 inch thick.

Locking this onto the table allowed me to get a very uniform machined surface on the backplate.

door aperture plug

Some filing and the original door aperture was filled once again with mild steel. I now just need to fix it to the firebox and machine the new aperture.

inside the firebox and back of the door plug

Inside the firebox you can see two notches in the plate that accommodate the firebox beams. This meant the plate needed to be machined carefully to fit as it locates between these beams and the lower edge of the old door aperture.

door aperture plug fixed with solid rivets

A number of 1/16th inch solid rivets were used to fix the correcting plate to the firebox. This is a good solid fix. Had considered backing this up with some welding, but think this is likely to make a mess.

I still need to fill in the hole above the door. I think a chamfered edge to the hole will allow a plug to be made that is then flush. Swaging the inside edge to fix it.

aperture machined in firebox door

The correct aperture was then machined in the firebox. This was machined with a 4mm end mill. Then finally the edges were finished with a fine file.

With the door back on it’s hinges and latch in position it all now works, just 11.2mm higher.

Corrected Door Location

Finally assembled with the tender, correcting the firebox door worked.

firebox door
In the hand you get a better idea as the size of this traction engine.

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