cap iron too short?

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Personally, I'd use some kind of high carbon steel like 1080 or o1 if I were going to make a slab type.....

Why? Wear of the cap-iron is not a problem, there are plenty of 100 yr old planes (like my 5 1/2) with original cap-irons still doing yeoman service. The biggest enemy of a cap iron (apart from folks with files) is corrosion. For that reason, and because it comes with a nice, clean surface & is more readily available to me in 2-2.5mm thick plate, I prefer to use stainless steel when making cap-irons. It's a little harder on hacksaw blades & files, but at least the finished product remains shiny & smooth.

You can do the job quite easily with hand tools. You will need a tap to match your existing screw. The threads seem to have varied a bit over the years, but I've found an M8 tap will often do. It's not a perfect match, but for the turn & a half of thread in a 2mm thick iron, it's usually close enough to a match (try it on a piece of scrap before committing to the real thing, of course).

A single-bend cap iron like the Hock & Veritas is very simple to make. You can make the bend in a vise & clean it up with files. If you use a heavier gauge like 3-3.2mm, strive for the "right" fit, i.e. just enough bend to ensure a close fit against the back of the blade, but not so much it turns it into a banana when you tighten the screw down, like this:
11 cap iron single bend.jpg
By carefully filing & lapping the edge, you can get it to fit nicely without flexing the blade more than slightly. The older, thinner blades are especially prone to flexing.
I think that's why the original caps are made of thin (~1.75mm) steel and have a 'double bend'. The bulk of the CI sits flat on the blade & causes no flexing when tightened up, like this:

12 cap iron double bend.jpg

I've made a simple jig for bending cap-irons:
Cap iron 2.jpg

It's rather Heath-Robinson-ish, and fussy to set up for bending, especially for a skewed iron which this one is being readied for :
8 CI bending 1.jpg
The bend is then made in a vise:
Cap iron 4.jpg

It would be a lot of bother to make a jig like this for just one cap-iron, I think I'd settle for the single-bend type for a one-off. Made carefully, they works as well as the double-bent version.

Needless to say, it's wise to do the bend and finesse the fit before laying out & making the screw & cam slots; that way you have a precise edge from which to work.

Cheers,
Ian
 
because it files and drills cleanly and nicely when it's annealed. And if you choose out of preference to harden and then temper back fairly far out of preference, you can do that. It doesn't really matter, though. If making a slab type like hock, there's no need for anything other than a gradual bend.
 

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