[TheForge] Upsetting the middle of a bar

[Shannell Sugrue]

Hey now thats clever! Might have to try that myself, that would work real
well on a fly press or whatever if you get the bar mounted either side well
enough.
----- Original Message ----- 
From: "Bruce Freeman" <FREEMAB at pt.fdah.com>
To: <theforge at mailman.qth.net>
Sent: Thursday, October 28, 2004 10:17 PM
Subject: Re: [TheForge] Upsetting the middle of a bar


> The following is either "book larnin'" or else something I picked up
> from a demonstration or a video - I just don't remember.  But I haven't
> tried it myself.
>
> First, the physics:  If you tie a steel cable tightly between a heavy,
> movable object and an immovable object, then push sideways on the middle
> of the cable, the heavy object can be moved with ease.  The reason is
> that the relatively small force exerted sideways on the cable is
> translated into a large tension on the cable that can move the heavy
> object.  It's rather like leverage, but different.  If you've never
> played with this, try it with small objects and you'll be convinced...
>
> This upsetting technique is sort of the inverse of the above technique
> - a sideways force is put on a slightly bent bar to exert high
> compression force along the length of the bar.  Drop a couple of drift
> pins in your acorn table, separated by a little more than the length of
> the ballaster bar.  Against one of the pins, put a (sideways) "stack" of
> "shims" to reduce the distance between the pins to something a little
> less than the length of the ballaster bar.
>
> Heat the ballaster bar to yellow in the center (preferably with a
> torch, but heating on a forge and selectively cooling should work too).
> Bend the bar slightly at the hot spot, place it between the two
> pins/shims with the bend up, and press (or hammer) the bar down.  Repeat
> this step, adding shims, until the desired upset is obtained.
>
> Bruce
> NJ
>
> >>> irony at epowerc.net 10/27/2004 10:40:29 PM >>>
> Y'all:
> I have a stair and a parapet railing to make with about 60 balusters,
> each having a long leaf forge welded near the middle of each bar.  My
> stock is 5/8 square.  I am looking for a simple way to upset each bar
> for the weld and am not having much luck.  I have used my coal forge
> with a fairly narrow fire on some and on others, a rosebud to make the
> heated area shorter.  I have been using a 2-1/2" depression in a swage
> block as a base and either a 4# hand hammer or a special tool for my
> air
> chisel that is a cup about 3" deep.  Either way the process seems far
> too slow.  If I use the air chisel and keep the rosebud on the stock
> constantly at almost a welding heat it barely upsets the metal even
> after 5 heat/upset/straighten distortion cycles.  Using the hand
> hammer
> seems to be the fastest way, but even that way it still takes 5 heats
> or
> so.  Is there something basic I'm not seeing here?
>
>  Stephen McGehee
>  Publisher of
>  Irony, the sketchbook of an apprentice blacksmith
>  P. O. Box 9822  Pine Bluff, AR 71611
>  irony at epowerc.net
>  (870) 540-0142
>  (479) 643-3299 (farm)
>  You can see a sample of IRONY magazine here:
>
>   http://lametalsmiths.org/news/page4.htm  )
>
>
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