Before steel vises, before iron clamps, and before the industrial revolution, before even the fall of Rome, there were holdfasts; innocuous bent iron bars with the potential to hold a workpiece firmly in place while a craftsperson goes to town on it. The holdfast holds a few advantages over modern work-holding tools. It drops into a hole in the top of a bench, giving it an extended reach across the bench top and a 360 degree range of direction. Application is a simple drop and a tap with a mallet, giving it an instant grip. No manual tightening. Release is a simple strike in the back. And a holdfast keeps a low profile; some will lay nearly flat across a workpiece and won't interfere with planing or routing.
I make all my holdfasts at TechShop.
I make all my holdfasts at TechShop.
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Materials:
Mild steel round bar
1/4" plate steel
Oxide patina finish
Tools:
Metal saw
Piper bender
Welder
Angle grinder
Metal file
The bar stock you will start with should be 1/8" smaller than the hole it will fit into. My bench has 3/4" holes so I'm using 5/8" stock. The general formula for measuring how much you will use is to multiply the desired reach of the tool by 1.5 then add the thickness of the bench top it will mount in, then add the maximum thickness of what you would want to be able to hold with it plus a few more inches as a margin of error. The pictured holdfast has a 7" reach, mounts in a 5" thick top and maxes-out at 6" so I started with a bar 22" long. Some holdfasts have a more extreme curve and some make a sharp bend at nearly 90 degrees and will require more or less length.
Mild steel or ductile forged iron are best since the holdfast will need to bend and spring slightly. Do not use brass, cast iron, aluminum, or stainless steel a they are either too brittle or too soft, or both.
Mild steel round bar
1/4" plate steel
Oxide patina finish
Tools:
Metal saw
Piper bender
Welder
Angle grinder
Metal file
The bar stock you will start with should be 1/8" smaller than the hole it will fit into. My bench has 3/4" holes so I'm using 5/8" stock. The general formula for measuring how much you will use is to multiply the desired reach of the tool by 1.5 then add the thickness of the bench top it will mount in, then add the maximum thickness of what you would want to be able to hold with it plus a few more inches as a margin of error. The pictured holdfast has a 7" reach, mounts in a 5" thick top and maxes-out at 6" so I started with a bar 22" long. Some holdfasts have a more extreme curve and some make a sharp bend at nearly 90 degrees and will require more or less length.
Mild steel or ductile forged iron are best since the holdfast will need to bend and spring slightly. Do not use brass, cast iron, aluminum, or stainless steel a they are either too brittle or too soft, or both.
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You know, this age-old Tool can find it's way into Fabber's Labs, soon...
Went to the Blog, see the Robofold there, too.
http://faz-voce-mesmo.blogspot.pt/2013/03/holdfast-dragon-nanoscribe-e-o-robofold.html