Thread sizes Optimus and Svea

Ill try it out tomorrow and let you know.

 

I have some answers, maybe even difinitive ones.

Firstly, the re-engineered burner I fitted to the Enders 9061D will NOT fit on the Optimus 8R! Therefore, the thread on an Optimus burner is NOT 12mm x 1 as i first thought.

Secondly, both the 7/16 BSB and BSCY taps fit easily into a genuine 8R burner... by hand, no force needed whatsoever.

Thirdly, of the two, the BSCY 7/16 is just a tad more snug which I assume is due to the thread angle, as BSCY uses a 60deg thread angle, therefore the BSB does not completely 'fill' or mate properly.

Therefore, in my opinion, the Optimus burner thread is 7/16 BSCY.

Now for some photos...

 

My Optimum 8R with the burner removed.



The 7/16 BSCY tap screwed into the Optimus burner.



The 7/16 BSB tap screwed into the Optimus burner.



For comparison, here are the two burners side by side, Enders adapted burner on the bottom, and original 8R burner on the top.

Just to be 100% clear, absolutely no force was needed or used when screwing the two 7/16 taps into the Optimum burner, they both slipped in with that satisfying feeling of a perfect fit.

Hope this helps.

 

Thanks Colin, we are making progress.
Now it would realy help if you would tap a piece of scrap with the 7/16 BSCY tap and try it on the Optimus burner thread. To prove it fits both ways.

 

I - can't find such 7/16 - 26 taps in Ukraine. Found only 7/16-20. If someone has the opportunity to send them to me, I will carve in detail. And I'll give you a set of a silent burner, converted to 8R, 99, Svea 123R. Respectfully to all

 

so far, I'm only doing clone 8R-stove PT-1, no problem, thread 12/0.75 (metric). I make nozzles on PT-1 according to the factory drawing.

 

Ah, so the Russian 8R copy used a 12mm x .75 metric fine.

I can certainly get a 7/16 x26 BSCY tap in the UK and it doesn't cost very much, but getting it to you might be a problem maybe? If you PM me we can discuss.

 

@ROBBO55 I will try to find some spare material and cut a thread as you suggest. When i fo, ill post the results.

 

I made this threaded steel sleave and tapped it 7/16 X26 BSCY. Unfortunately it needed a 10.3mm pilot hole but I only had a 10.5mm drill so the threaded hole is not perfect. I couldn't get it to fit and being steel I didnt want to force it and ruin the original Optimus thread



I'll try to find some aluminium and try again, but given that the tap fits perfectly in the burner, I'd be happy with that.

 

I will say again.
Not a good policy to use a tap to check thread size.

 

@snwcmpr
I agree, using a tap isn't the best option. It can remove material and damage a thread. Also once material is removed you then can't be sure if the original thread was 55 or 60 deg. If a suitable bolt and nut is available it is a preferable option. Making a bolt or nut would be the next option.

@Colin Geer Just because the taps entered the thread on the bell doesn't mean it is the correct thread. If the pitch /TPI is correct a slightly smaller male thread will screw into a larger female thread and appear satisfactory. But a slightly larger male thread won't screw into a smaller female thread. Thats why I asked if you would make a nut to try on the burner male thread. For soft material you can get away with a 10mm drill for the initial hole. Having used a 10.5mm drill the nut should have still fitted if the outside diameter of the tapped hole is correct. Your result suggests the thread on the burner is larger than 7/16".

 

If it is larger than 7/16 x 26tpi it might well be a special, possibly even proprietary to Optimus.

Anyway I've done all the tests I'm prepared to do, so without any manufacturers documentation that specifies what the thread actually is, all you can reliably say is, it's pitch is 26tpi, OD greater than 7/16" or metric equivalent.

 

Colin.
There is no valid argument to use a cutting tool to measure with. A tap that fits is no better than a straight pin fitting into a hole.
A thread gage has 2 features.
One to go, limited slop.
One to no-go.
That validates the min/max.

A bolt that fits with minimal slop will NOT cut so as to not damage the old, classic, stove part.

 

As the dolphins said when leaving planet Earth (Hitchhiker's Guide)... 'So long, and thanks for all the fish.'

I shall continue to use the tools at my disposal in any way a see fit so long as its safe to do so. The only material difference being that I will no longer be a subscriber or user of CCS.

 

Why's that?

 

Thanks @Colin Geer for your input, it has been helpful and appreciated.

 

Friends, we are all different, but the question is one, and not resolved. I hope it will be interesting for many to put an end to this issue . The carving was invented by people and it's hard for me to believe that it can't be repeated. There is a war going on in Ukraine and I can't find non-standard taps. But the search continues and I hope we will find the answer together. Regards and best wishes to all

 

Duane, Any feedback from Gary?

 

Yes, within a short time he replied back and also asked I reply back with results. He even sent me links to tools which he didn't have to do. Waiting for stuff to arrive on Tuesday. Have never had issues with a fuel cap before and was surprised that my external pump caps that a pump attaches to had two sizes. Will have to look into them.
Duane

 

@hikerduane

Looking forward to hearing the results.