The place for technical discussions about GA and flying.
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By Antair
On my Bölkow 207 the strut valve is a little different to the usual Schrader valve. It has a 13.25mm male thread and requires, I believe, the core to be depressed by a spindle on a special tool. I need to make the tool and would like to start by ascertaining if this valve is likely to be metric, american, bsp etc. Nothing I have tried so far really fits right.
By cockney steve
I'm assuming that Bolkow is Eastern Bloc, therefore likely to be Metric. The thread into the Oleo is likely just that, a standard Metric profile and pitch.
the "connector"end is possibly a different story, but at first glance appears ti bear a marked resemblance to a disposable gas-cartridge connection.

Thread -pitch gauges are available in Imperial, unified and metric sets. rather like a set of feeler-gauges, they have a serrated end-section on each blade. Select a near match and try it in the threads you wish to identify. (or you could manually count the pitch

wrap a clean strip of paper tightly around the projecting threads, rub with a dirty finger and you will transfer a series of lines , corresponding to the threads (think brass-rubbing!)

As almost everything is standardised, I'd take a wild guess that it's a metric pipe thread.

There is bound to be a tutorial on thread- identification , on the net. note the first couple of threads at 6-o'clock have been damaged If a correct connector will not fit, the damage can be dressed-out with a swiss file (ebay,screwfix and many others)
By Antair
Thanks for taking the time to reply cockney steve, I will measure it up, but it seems to be close to a number of standards. I doubt it is exclusive to Bölkow and would be fairly common on other German aircraft.
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By cockney steve
I'd suggest Euro Hydraulics or a similar outfit,such as a heavy -plant repairs/spares specialist.
As you observed, it's unlikely that someone re-invented the wheel when someone's all geared up to make them cost- effectively and robust. but it does happen!