I am fetteling an Optimus 300 from the 1930:th, but having problems with the jet, it seems that the jets I try, will not fit. I have both Optimus 300 and Radius 103 parts.What is the thread on these, migth get myself a tap for the vaporieser making sure the thread is ok.
I hope others would chime in on the Optimus jet. Have you tried using a Petromax 350cp, Butterfly or similar jets? I'm not too certain about the Optimus 300 jet but if its the same as the Petromax, then the thread would be M7 x 1mm pitch. There had been early and later versions of the Optimus 300, so its better to seek a few more opinions before you thread the generator with the wrong tap. Its Swedish, so there's a possibility that it might be Whitworth or even non-standard or customized like the Primus jet. Perhaps @Nils Stephenson or @Carlsson would have a better idea on these.
If I remember correctly, all the original Px clones (Optimus is a Px clone) used a Whitworth thread but with a 7mm diameter. It is almost identical to M7x1, but jkust slightly off. As MYN says, pretty much all the Px type jets out there should fit. If they don't then I suspect that someone might have modified the thread for some reason.
I'm pretty sure it's just like Tretrop suggested himself. The threads of the vapouriser has most likely been damaged at some state. It's actually pretty easily done. I have done it myself a couple of times when mechanically cleaning the Preston loop out from the top, but it could also have been done by trying to mount an incorrect jet. Once the thread is damaged at the initial turn, you're generally screwed, so to speak... But not necessarily beyond repair. An M7x1mm tap might fix it even if the original thread was using Withworth standard angles.
No, it was a specially made thread of 7mm diameter but with a whitworth thread type. I don't know who came up with this size first but it could have been Petromax.
Its always inconvenient about the threads of these lantern parts. There're no standard taps and dies that are exact. I believe this was deliberate on part of the manufacturers. 26 tpi Whitworth is still a standard thread size(BSF) anyway. There are no standard dies or taps that you could buy off the shelf having metric diametres but threads that are in inches. However, it could still be threaded in common lathes having such facilities(any non-standard diametres but standard thread sizes only). Still easier than that for a Primus jet with 7mm diametre but a non-standard 35tpi Whitworth(I'm still thinking how to fabricate this one)....
@MYN 35 tpi - you can make it on a Boxford AUD lathe with imperial gearbox. Screwgear 70T and gearbox 28 tpi
Thanks @Salar and Stove. Seems to me that I'll need to find some machine shop with a Boxford Aud lathe first. Unlikely, in my part of the World, but you'll never know what could be available from the numerous shops around here. The Petromax and clones are easier as I could still make a 7mm diametre and thread them exactly in almost any lathe with a Whitworth 26 t.p.i. pitch.
Thanks @Salar and Stove . @tretrop , The standard Metric M7x1 and BSF 9/32", 26tpi are actually the closest match for the Optimus and Petromax. I'll try both on an unused part to check if they could fit 1st.
@MYN May be you will get problems with jet getting loose. 9/32 = 7,14375 mm ! If not the original thread - 7x1 mm will be better!
Thanks again @Salar and Stove . Seems most agree that M7x1mm would be a better option for anyone looking for a standard size. Its easier to obtain that compared to a BSF 9/32; 26tpi tap or die too. 7mm diametre with 26tpi would require me to ask a favour from the machinist here.
