size of O-ring for classic spring-loaded desoldering pump

[jkn]

Hi All I have one of the 'classic' (to my eyes) spring-loaded desoldering pumps from the '80s, green in colour, probably bought from RS or Farnell. I don't think the actual model is made any more.

The O-ring on mine has finally failed, and it's a bit too perished to be able to properly tell the original size.

Any old-timers out there might have a reference to the right size to buy?

I'm guessing something like 1.6mm cross-section by 16mm ID, but I'd like to be more sure...

Thanks, J^n

[The Natural Philosopher]

cant you measure the diameter of the piston?

[Andy Burns]

I've got a green RS one stock number 544-516 and a smaller no-name one bought when I was about 12, that's bit lethargic, and a similar sized one to the RS that I borrowed from someone who it happens I never saw again ... Sorry Trevor!)

Mine (starting to perish too) is O/D 20mm, C/S 2mm

[newshound]

One irritating thing about the cheap kits of replacement O rings available from various suppliers is that they are mostly 1.6mm cross section, while rings that I want to replace are typically 2mm.

Once you confirm the size you can often buy a small number for not much cash from eBay.

[jkn]

It's not for the piston, it's for the nozzle (I could have been clearer on that point)

I did measure the diameter of the groove, that's where I got the est. 16mm from

[jkn]

Heh - yeah, somewhere I might have another one and a similar Trevor to apologise to...

Thanks. that roughly fits with my guesstimate.

[PeterP]

Like the one that comes with a replacement nozzle?

Or maybe this one:

[jkn]

Ah, cool, thanks! That looks like the one - I wasn't able to find that for some reason.

I'll check compatibility, I think I might have enough for an RS order in the near future. A new PTFE nozzle would be worth getting after all these years...

J^n

[alan_m]

+1 I have a couple of kits of O rings but all are the thinner cross section.

I've found sometimes fitting two thinner rings solves the problem, especially when one bit screws into another and the O ring forms the seal.

[jkn]

Funny, my cheap O-ring set is the other way round!