A New Crucible Furnace

I good friend of mine called recently and told me he had a crucible furnace for me!  Well, it has arrived.  Its a Johnson 510.  If you have any manuals and whatnot, please comment!

Here is the beast.  Note the side chimney.  The gasses have to actually go down and out, like a kiln.  I suppose its good for efficiency, but you can't see the melt or add metal without opening the lid.

 The blower.  I assume the open pipe is where the gas line attaches.  There is a valve right below it.

 Pilot burner/ignitor?

 The furnace has 2 main burners on tangents.  The one visible here is slightly lower.

 Chamber is 9.5" wide and 11" deep.

 Furnace no. 510
Serial no 1012-T
BTU 120,000

The song of the month

Making a Crucible

I needed to make a crucible large enough for some future projects.  It has been a long process, and at no point was a sure I would succeed, but I believe I have.  Coming this far, I think its safe to show how I went about it.

I planned to cast the crucible using a dense castable refractory.  I chose it because of its strength, conductivity and the fact that I have a bag and a half left over from making the furnace.

The first thing to make were the wooden patterns.  

I didn't have stock large enough to turn the outside pattern, which is 10" tall and 8" wide.  Instead, cedar was cut and glued up to form a "barrel."  This barrel was then sanded and carved to shape as it was too big to fit on the lathe!

Below is the internal pattern.  This was composed of glued up cedar 4x4 posts.  I use a lot of cedar.  It is all reclaimed from rebuilding our deck.

Now this was the mold that I cast the crucible in.  It was a wooden box in which I had poured concrete backfill and a plaster face around the patterns.  The plaster would give me a smooth layer that could be sanded and repaired in case the pouring didn't work well.  It came out well, but I'm still happy I used the plaster.  The crucible, after it had set up in the mold got stuck.  Plaster was easier to break away from the crucible than concrete would have been.

With my green crucible de-molded, a kiln was in order.  This is old firebricks stacked up.  Barbecue charcoal is the fuel.

It became rather hot in there...

And the crucible! The patch is from my initial attempt at firing, which I will not speak of.

Ok...I'll tell.  

I tried to fire it in the furnace with the evaporator oil burner.  I'm supposed to be able to control it, but I failed.  It malfunctioned, spat out a huge flame and spalled the crucible a bit.  It hadn't really fired yet, so I patched it. The patch appears to have completely adhered.  

Now for some melting!

I've finally come through with pictures!  The lathe has been mounted since spring break in April.  I have already made parts on it, including siphon burner nozzles for the foundry.  I have faced off a mini anvil paperweight as well to test out the versatility.  An amazing fun machine it is.  These pictures show what will be the permanent home, for now of the lathe.  Since I took these, I have added considerably to my tooling.  I bought from a machinist going out of business and from Fazzio's several large drill bits.  One is 18" long and 3/4" across.  I will use it for drilling my miniature cannons.  That bit realistically needs to be used in a longer lathe though.

I have replaced the belt since this picture and welded a 1/4 socket extension, which fits the 3 jaw chuck, to a handle for a chuck key.  It works great.  I use 7mm hex keys for the 4 jaw.  If anyone knows where to buy real 7mm chuck keys, please leave a comment.

Hope you enjoyed.  I will have lots of pictures of machining and projects coming soon!  School is almost out.

Just showing off another Lathe Picture

I have built a bench and everything for my lathe.  I just need to get around to uploading the new stuff.  Grrrr.  why do I have to be so busy.