The most tedious repair/machining job I've done...

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Leonardj
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The most tedious repair/machining job I've done...

Post by Leonardj » Sat Nov 16, 2013 7:49 pm

Reading Graham's thread on the FAS604 rear sight repair brought back memories of this tedious little repair/machining job from a few years ago.

A friend of mine who also does airgun repairs had been enlisted to repair a Hammerli 480K, which had ceased to function.
He discovered that someone had already tried to repair the gun on their own, causing substantial damage to some very tiny parts.

My friend does not have any metalworking machines, thus, he enlisted my aid in doing the machining of the parts.
In the top pic, the regulator piston shaft had broken off inside the piston head. A previous attempt to drill out the broken shaft had resulted in breaking a drill off in the hole, rendering any possibility of salvaging the piston head impossible. The new piston and shaft that I made up are in the lower portion of the pic. Graham will appreciate this - the threads on that shaft are #0-80. I did not have any Metric taps or dies that were small enough to be used for this job, so the #0-80 was substituted. The .177 cal pellet will offer some perspective on size.

The lower two pics are the inlet to the regulator IIRC. I decided to salvage this part by fitting a stub to it, and machining that to size. The through hole in that end piece was only something like 0.018" diameter. A very tedious drilling operation. Again, a .177 pellet gives some perspective to the size of the piece.

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Tank
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Re: The most tedious repair/machining job I've done...

Post by Tank » Sat Nov 16, 2013 9:20 pm

Hi Leonard and thank you for your post, some jobs really are a challenge. I really love the people who say "but it's only a little part". Looking at the the first job, the piston, as a starting point you would need a lathe, an assortment of cutting tools AND some brass - the right size to get you started.
Then you get to the Hexagonal bit at the end.
All you need to do that is a Milling Machine and an Indexing Head, Mill will cost you £500 and anywhere north of that and the best price I can get for a Rotary Table with Indexing plates is £133 from Arc Eurotrade (and you would need a Collet chuck and some tooling). I could do it on the lathe, using a spirit level on each side of the jaw of a three jaw chuck as the index and scraping the flats on. But I usually break something doing this :D
Then there is the slot in the head of the regulator shaft, a slotting saw is going to be needed for that. Bloody nasty things.

But doing things like this, I find them refreshing and a challenge, it is not my full time job and it is a refreshing break from other stuff I have to think about.
Half of the problem, in the Challenge sense, is how to work out how to hold the workpiece in the first place. The FAS 604 sight I am working on right now, I scrapped my first attempt. I had made a mistake on the outset of that attempt and painted myself into a corner. Scrap was easier and start again.

However, now that I have made the rear sight element the next one can be done in a fraction of the time (if i can remember the sequence :D ) and of course I now have the right Tap/Die combination. It is easy to assume that because I am making a new unit the thread direction would not matter. Of course this is totally incorrect as the ball detent still needs to work and the element is not symetrical so I wasn't going to work out the offset in a completely different direction too!

Next up is going to be the actual adjustment screw for this sight. The good part about this is I don't actually have one to copy from :D
graham.
I’m going off to go find myself. If I’m not back by the time I return, keep me here.
https://tamesidepistol.club/

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