Subject: Re: Johnson slot forges. Resistance heaters

From: [email-masked]
Date: Thu, 12 Sep 1996 10:08:05 -0600

>[email-masked] wrote:
>>
>> In a message dated 96-09-10 15:42:34 EDT, you write:
>>
>> >Johnson 'slot' forges
>>
>> These are high pressure production gas furnaces.  They are used to heat LARGE
>> numbers of pieces to temperature and use LOTS of gas.  Production forgers
>> might line up 20 or 30 cut bars in the slot, heat them all to temperature and
>> forge them all in drop die hammers within a few minutes.

The idea with a slot furnace for production work is to time the heats so
that you just keep working. You don't want them all ready at once but one
ready at a time, do your operation, cut the part off, pick up a cold one
(or re-insert in furnace if bar work) and start over again. Do this eight
hours.

I worked in a forge (made plow bottoms) in Illinois back in the early
seventies. There were guys there that had been there thirty years. There
was a large horizontal upsetter that was used to upset the front end of the
"Land Blaster" plow share. The guy running it had been running it for
around thirty years.

He had worn a groove in the concrete floor walking from furnace to upsetter
to shear to cart to furnace all day, every day. He worked through his
vacations and made double pay cuz he had to be in that groove.

Bob

---

From: [email-masked]
Date: Thu, 12 Sep 1996 18:05:26 -0400

In a message dated 96-09-11 18:56:38 EDT, you write:

>Mike,
>	I'd like to know more about these resistance heaters,
>and I figure it would fit in with the discussion on new improved
>ways of heating metal....something tells me they are out of my
>price range, though.
>	Thanks!
>	George
>
Hi George, 
The resistance heaters that I have seen are all fairly complex and designed
to do a very specific task, like heat 2 or 3 thousand 1-1/8 inch diameter x 8
inch long pieces of bar stock (one at a time) to a preset forging temperature
of say 1850F.  The precut pieces are fed magazine style into a fixture which
holds the individual piece, contacts move in and meets both ends of the bar,
the juice flows, the piece get bright yellow and the forger grabs the piece
with his tongs, sticks it in the drop hammer box and forges the part, and
meanwhile, the next bar is being heated. I takes a few seconds, no scale to
speak of is developed, and it makes a nice clean surface on the part.  I
can't see any of us doing that volume of work of any one part, unless you're
a lot stronger than I am.  This is production stuff, although the principle
of resistance heating makes sence if scale is a problem on the part that you
are forging.  You can also induction heat the part, but this type equipment
and its operation is very costly, and not in the budget of the average smith.
 So, if you get an resistance heater, then you'll need a production hammer,
do dah, do dah.
Think coal,
Mike Schermerhorn