Does anybody know if the pressure gauge thread used by Primus (and presumably Optimus etc.) is a standard one? I have measured it to 7mm x 0.9. Not a standard metric size and it doesn't seem to match any imperial size either. I'm after a replacement pressure gauge for a couple of lamps and it's not likely I'll find an original so need to know what to look for.
Hello Nils It´s the same thread as 991 jet. I think it is W7-28, its the same on Primus, Optimus and Radius. Conny
Yes 28 TPI is almost exactly the same as a pitch of 0.9mm. I didn't think about the 991 jet, but it is the same. What I am wondering is if this thread is the same as the ones found on commercially availble manometers. So far all I can find are ones that talk about a G 1/4 or G 1/8 thread.
I know old thread.. but looking for manometer for my Optimus 200P. Saw that Hytta.de has pressure gauge with M7 thread, can it fit?
Nils, have a look at BSP thread (British Standard Pipe). Yes, if shoes were bolted together instead of laced, there would likely be a BSS thread too. Anyway, in the field of pipes, hydraulics, gauges, there is this category that might apply to your Primus gauge as well. Regards, Mike
So a contradiction, unfortunately not uncommon. Seems an owner of both a Butterfly and an Optimus lamp could tell if they are / not compatible.
Hi all! Forgot to get back with the result. There was no problem getting it in place regarding threads. It works but after some 70 pumpstrokes on a Optimus 200P it only reaches no1 on the scale, it should reach the red line with that pressure. Tank filled around 70%. I simply used a Dremel cut-off disc to lower the Butterfly housing and placed it in the Optimus house and carefully soldered it in place with low temperature solder. Regards Matti
Well Matti, it does look nice, and looks are what you were after for, were you not? And who really needs a (correct reading) pressure gauge? So congratulations with this result! Mike
Nils, I wouldn't think so. The commercial ones I've found or used so far come in standard, common sizes. They are normally available in G1/8, etc(BSPP), R1/8, etc(BSPT), NPT, standard UN sizes and metric medium/fine threads. They are common to pipe and fittings for most hydraulics or pneumatics and gases. The users won't have to search high and low for these parts. As for the Primus pressure gauge size, I have measured 7mm x ~0.9mm or 28tpi too on my 991. Mine's missing the gauge as well but I found that the ones on the Optimus 200 and pre-war Petromax 821(Baby) have the same size and pitch as the Primus 991. They fit perfectly although the diametres of the gauges might differ.
