ArtMetal

For some time now I've faced an ongoing annoyance with my raditional anvil hold-downs - youknow, you get the piece one the anvil, set the hold-down and go to work, only to have the work come loose on the second blow.  By the time you get it clamped again, you've lost the heat and have to start over.  This issue cropped up mostly when I was doing chasing or chiseling work, where the work was hit a number of times in rapid succession.  The traditional figure 7 style hold-down just didn't hold tight enough against repetitive blows or much side pressure.  Clearly, I needed a better solution.

The big advantages of the traditional hold-down are that it is quick to set and it accomodates a fairly wide range of work thicknesses.  I needed any different design to do the same, as well as hold securely regardless of the enthusiasm of my pounding. 

My "solution" to this problem was to design and construct a hold-down that used a cam to lock the tool against the work very securely, yet could be adjustable pretty easily to handle differing work thicknesses.  Naturally, this wasn't going to be a twenty minute forging project like a triditional hold-down, but I felt it would be worth the additional effort.  Besides, just about my favorite activity is making tools.  :-)

Anvil hold-down tool

 You can see that, as with many of my tools, the thing is by no means a quickie to make.  Still, it works amazingly well, holding work securely enough that I can chisel it with an air hammer or set rivets, whatever, and the work never moves.  That alone is worth all the effort for me to make it.  As I work alone all the time, a really effective hold-down is an absolute necessity.

In use, the piece you see on the left handThe bottom anchor piece end is placed at the bottom of the anvil's hardy hole and the stub on the side of it goes into a conveniently-located handling hole in the anvil.  This particular configuration fits my 450# Nimba Gladiator.   My other anvils will require a slightly different configuration.  In order for the clamping head of the tool to be pushed up by the spring when the cam is released, the bottom piece must stay put.  On my Fisher anvil, for instance, I'll probably have to drill and tap a hole under the heel for a small clip to hold that piece in place.  (As I view an anvil as a tool rather than a collector's item, I have no problem drilling holes in them if it serves my needs.) 

Hold-down in place

Once the bottom anchor is in place, the rest of the tool is dropped down the hardy hole and screwed into the anchor.  It is then adjusted for clamping height by screwing the cam handle around to set the distance.  The spring keeps the hold-down open until the cam lever is actuated.  I made the cam with the axle offset from center a bit over 1/4" so the total travel of the cam, from fully open to fully closed, is about 5/8".  The tool can accept workpieces varying in thickness from nothing at all to about two inches in its present configuration.  Adding more length to the threaded portion of the main shaft could easily increase that to as much as four inches, if needed.

Hold-down in action

When the tool is locked down with the cam lever, it holds the work extremely securely.  The amount of clamping force is adjusted by how the screw is set.  A half-turn, more or less, makes a reasonable significant difference in clamping pressure, using the 5/8-11 threaded rod that I had to work with.  A finer pitch thread would make the adjustment even more precise, but would slow down changing the thickness setting.  The way it is now seems to be satisfactory.

The "Gazinta"

One feature that I included in my design is a receiver socket for additional hold-down arms.  This "gazinta", as I call it (because stuff gazinta it) allows me to use auxilliary arms for special situations.  One I particularly wanted was a hold-down arm with split feet to hold plate for chasing.  With the two feet split apart four or five inches, they can hold a larger piece of plate much more securely than a single foot can, and the cam action of this hold-down has plenty of clamping power to handle such a configuration.  The gazinta will accept tooling with 1/2" square shanks.  Since the whole tool can be indexed in the hardy hole in any of four positions, the pressure foot can be located almost anywhere on the anvil face that is convenient.

All in all, I'm really pleased with the success of this concept.  It was certainly a hell of a lot more work than just forging a quick traditional figure-7, but it does a lot more for me, too.  Definitely worth the effort.

Rich