Saturday, June 11, 2011

Ferrule Crimping

A gun owner I know brought me this 22 calibre rifle bore brush because it had come apart on him while in use. Extracting the loose brush from the rifle's bore had been a bit trying, and he didn't want to have to do that again.

The ferrule appears to have been well crimped, but not well enough, evidently. I'll clean the pieces thoroughly with lacquer thinner, put it back together and apply CA adhesive. That's likely all that's needed for an effective repair, but I'll add another crimp just for good measure. I want to demonstrate a method for making dirt-cheap crimping dies for ferrules like this one.

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I'll be crimping the top of the ferrule above the existing crimp. The ferrule's diameter there is 3/16". A 10-24 square nut should give me an effective crimping die for that diameter. (I don't have a 'formula' for this; I just go by somewhat educated guess.)

Cut an ordinary 3/8" A/F square nut in two to make a die. You want the die halves to be quite symmetrical to get a good result. Also, mark the nut so you can keep track of its halves' relationship to one another. Then, the trick is to get the ferrule along with the two die halves into the vise with everything in good alignment. That can take a bit of finessing. Here's a way to hold the work at first that's helpful.

Note the two ink dabs for keeping the die halves in correct relation. Now it's into the vise with it.

And here it is in the vise about to be crimped. Take great care with this part of the job to get the die halves aligned as perfectly as possible.

When all looks satisfactory, squeeze for all you're worth and you'll get your crimp. Here's the done deal, with the crimping die pretty much closed up.

And here's the crimped ferrule just out of the vise.

I'll trim away the squeeze-out, give it another application of CA adhesive and it'll be done.

And there it is, well and truly crimped for all eternity.

I first came up with this method when I needed to make a new handle for a flux brush. I used a length of 3/8" diameter plated copper faucet supply tubing. I did the crimps with a hex nut that I had first drilled through to all but do away with the nut's thread. Here's how the resulting crimps look.

This was crimped in two places. It got an initial full-width crimp to form a stoppage point for insertion of the bristle set, then a partial-width crimp at the very end of the tube to close up around the bristle set. I also bedded the bristle set in RTV gasket maker. As flux brush handles go, it's a cut above the usual.

So there we are; quite an effective ferrule crimping die can be had for the price of a common steel nut.

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