Sunday, 16 November 2014

How I Learned to Like My Bending Iron (or, The Return of the Betterizer)

Hi friends,

I was bending ebony soundboard edge-bindings for a new batch of lutes this week, and realized again how much I like my little bending iron.  It wasn't always this way--when I first got it, probably about a dozen years ago, I didn't care for it very much at all.  Over the years, though, I've modified it in a few ways to really make it work for me. 
The bending iron is one of the standard ones you can get from a guitar making supplier, like Luthier's Mercantile or Stewart Macdonald (I forget which one I bought it from).  It came a bit raw out of the box, a bit unformed.  The first problem I noticed was that the sides of the iron (which, incidentally, is not made of iron, but of aluminum) were really pretty wobbly, not straight at all, which didn't help the results of my attempts at bending.  I gave it a good workover with some files and sanding blocks, and got it to the point where the faces were reasonably true.  Making good bends, especially with wider material (like for 9- or 11-rib lute backs) became a whole lot easier.

I also screwed a plywood base to the thing, so I could clamp it more conveniently and securely to the work bench. 
The main thing that I disliked about the bending iron was the way it sets up to bend small strips of wood, such as edge bindings or rib spacers.  It comes with (or maybe you have to buy these separately) a pair of aluminum hoops that fit around the bending iron, one on top of the other, which you tighten in place by means of a nut and bolt.  This is what they look like when they're not on the bending iron, which they haven't been on mine for a few years.  (I didn't care to put them on just for the sake of the photo op, so here they lay, lifeless.)

There are a couple of problems with this setup, the main one being setting the width between the hoops.  To work best, the hoops need to be very evenly spaced apart, and the distance needs to be just ever-so-slightly wider than the material you're working with.  If it's not (and this is the way it usually went for me), then on one side of the iron the material will be pinched, while on the other there will be too much wiggle room.  I had real trouble adjusting these hoops accurately--you can hold them in place, but as soon as you start tightening the nut, they'll move.  A small, but constant, source of frustration.   

A second problem arose when I first began building lutes in batches, because occasionally the rib spacers for one back would be a different thickness from the spacers I was using on the other.  This meant as I went back and forth, fitting ribs alternately on the molds, I would need to adjust the space between the hoops back and forth too, to accommodate the different sizes.  Frustration multiplied.  It was clearly time to call in--the Betterizer!

I have found that when I'm stumped about how to modify a piece of equipment, it sometimes helps just to take things apart and have a look at the insides.  That's what I did with the bending iron, and found that it's basically hollow--just a teardrop-shaped aluminum tube with a small heating element that plugs into it.  All that space gave me an idea.
I flattened the top surface of the iron and drilled a couple of holes into it, then threaded the holes and screwed a couple of 1/4" bolts up from the inside.  Then I drilled slightly larger holes, the same width apart, into a couple of pieces of 1/8" brass stock I had on hand.  I shaped these pieces carefully on the bench grinder so they were the same teardrop-shape profile as the top of the bending iron.

Then I drilled holes into some other pieces of brass stock, of various thicknesses (to be exact, the thicknesses were 0.2mm, 0.4mm, and 0.8mm).  I also shaped these pieces on the bench grinder, but I made them a little smaller than the 1/8" pieces--about 3mm smaller, all the way around.  (I stacked these pieces and clamped them together for shaping on the grinder, so they would all turn out with the same profile when I was finished.)

Here's what I made, a veritable Roman hoard of brass shims (or perhaps a beautiful school of brassfish swimming by.)   You can see the two larger 1/8" pieces at the bottom of the photo:
 Stack up some of the smaller shims on top of the bending iron, and here's what you get:

 Put a larger 1/8" piece down on top.
Add yet more smaller shims on top of that--
And another 1/8" piece.  Screw the pieces down tightly with some wingnuts--
And there you have it, a bending iron with grooves built in for bending ebony edge bindings (shown here), sycamore rib spacers, or just about anything else your heart desires.  Need to adjust the depth of the slot?  Just remove the wing nuts, add or remove or stack a different combination of shims so that the slot is just that tiny bit wider than your material.  Are you building multiple lute backs that use different widths of spacers?  No problem--this set up gives you two slots that you can set to whatever depth you want.  No muss, no fuss, no guesswork, no switching back and forth, just... calm.  Peace.  Oneness with the universe.   Betterization accomplished.

I usually have a few spacers left over, so I just stack them on top before screwing down the wing nuts. 

I really like this setup.  I feel that I've taken a tool which, when it came from the supplier, was really not that well made or well-designed for the job, and turned it into a piece of equipment that's essential to my professional workshop.  For any builders out there who have experienced the frustrations I have, I recommend this fix.  And I wish you well in your own adventures, shaping your tools to your needs.  Do let me hear about them, if you like... and Happy Betterizing!