Webley Senior piston repair?

[ggggr]

I have a problem with a Webley Senior piston. The holding face where the sear engages is worn and rounded, probably due to cocking link wear a long time ago.

ive got 2 ideas for a "fix" and would appreciate views about how to go about it.

(1) get the front of the piston machined down and then fit a new front end , holding ring and head onto it.
I think the problem with this is how much "meat" is behind the holding ring---IE- how deep the piston is drilled for the mainspring.

(2) Get the ring welded up and then cleaned up. Is this possible? Use Mig or Tig?


Im hoping Edbear might see the "Edbear signal"

[trajectory]

I think if you are filling in a ring/groove then it's probably Mig rather than Tig that might be best. Don't really think Tig will fill anything like Mig as Mig uses a filler 'rod', just choose a filler metal with similar characteristics to the steel the piston is made from. Ok, sounds easier than it might be to do well but think that's the way I'd go. Hopefully you will get some other advice & be able to choose which way you tackle it.

[trajectory]

If it would still work & function safely with a wider groove what about truing it up on a lathe rather than trying to build it up with weld?

I don't know how or what the pistons were made of but it will probably mess up any hardened bearing surface it had....maybe someone can advise you on that. Welding will mess it up too.

[ggggr]

A bit of a bump up for this please

[Vic Thompson]

Firstly a link to a Dealers Website that shows a picture of a Webley Senior Piston : https://www.airgunspares.com/s3weble...tolpiston.html

Secondly, I don't know the extent of the damage to the holding ring but is it possible to just trim back the "rounded off edge by a few thousands of an inch" and then re-harden it to avoid problems with "skin hardening". Having thought about it a few times, if it works it might save a lot of trouble and time over other ways of tackling the job.

Just a thought and apologies if a useless one.

Vic Thompson.

[DrGunn]

Depending on how badly worn / rounded the holding face it it may be possible to just skim it to square it up again, this would be by far the simplest option.
If its badly worn then it should be possible to build it up with weld and machine it back, it may be difficult to to achieve the right level of hardness though so the new holding face will wear faster.

[ggggr]

Thanks to Vic and Matt. I've had the skimming done in the past with a Mk1 piston and it seems to have worked. However on this piston, the ring is not very thick (wide) and fairly rounded as well. Taking it back would mean it would be like a razor blade.

I hope our welding genius Edbear ( who could probably weld spaghetti to string ) will see this and advise.
Another option would be to machine a new head from the holding ring forward and fit that after taking the exisiting bits off. A simlar idea would be to take it down to a core and then fit a sleeve and re machine.

[trajectory]

Looks like the truing it up option seems to be the front runner at the moment, providing there is enough meat on the piston to work with & allow it to still function. There's still the re hardening issue to tackle though. As I said I am not sure what the pistons were made of so can't really advise you on heat treating (if appropriate).

When you asked about welding I went down the Mig route....Tig could work with a filler rod but as there may be more Mig set ups in sheds than Tig ones I thought Mig was a fair bet.

I suppose if it's kaput at the moment then truing it up (& heat treating?) to see if you can get the required hardness might be an option. If it didn't work then taking off a few thou might not effect the possibility of welding, shaping & heat treating as a follow up?

Atb