JIS Threads

[derekg]

Howdy folks,

Been a while. I'm doing more stupid automative things, this time with a 1966 Datsun 411. Italian body design, MGB engine copy, using mostly SAE sizes. An oddball for sure. The issue I have now is finding some teeny, tiny screws that hold the old knobs onto the shafts of old switches. The thread does not fit my SAE or Metric gauges with an M3 being the closest diameter, but none of the pitches will work. They all bind. So, I am thinking, because these switches were used on other less oddball cards (like the Datsun Roadster), that the thread just might be JIS. The problem is that I cannot find a JIS blade style gauge and really don't want to shell out for the ring gauges just to be proven wrong. The thread is different than a standard 60 degree vee (more like a Whitworth - yes, another fun thread):

http://www.ring-plug-thread-gages.com/ti-Article-JIS.pdf

As such, not sure how I would even cut it on a lathe, besides being too small and fine for my ham-fisted work.

My question is whether any of you have seen thread gauges for JIS as I cannot find them online. McMaster-Carr has M3 JIS screws, but given their gold plated shipping charges I'd like to be sure first.

Many thanks, Derek

[MattiJ]

Howdy folks,

Been a while. I'm doing more stupid automative things, this time with a 1966 Datsun 411. Italian body design, MGB engine copy, using mostly SAE sizes. An oddball for sure. The issue I have now is finding some teeny, tiny screws that hold the old knobs onto the shafts of old switches. The thread does not fit my SAE or Metric gauges with an M3 being the closest diameter, but none of the pitches will work. They all bind. So, I am thinking, because these switches were used on other less oddball cards (like the Datsun Roadster), that the thread just might be JIS. The problem is that I cannot find a JIS blade style gauge and really don't want to shell out for the ring gauges just to be proven wrong. The thread is different than a standard 60 degree vee (more like a Whitworth - yes, another fun thread):

http://www.ring-plug-thread-gages.com/ti-Article-JIS.pdf

As such, not sure how I would even cut it on a lathe, besides being too small and fine for my ham-fisted work.

My question is whether any of you have seen thread gauges for JIS as I cannot find them online. McMaster-Carr has M3 JIS screws, but given their gold plated shipping charges I'd like to be sure first.

Many thanks, Derek

To me the JIS standard looks like just a copy-paste of metric(including withworth pipe) and american unified.

Maybe yours is BSF.
Or if thread pitch doesnt make any sense in metric or per inch try BA:

https://en.wikipedia.org/wiki/British_Association_screw_threads

[Sun God]

JIS is Metric. I would bust out the calipers, and do a very close comparison to the BA standard threads, a BA5 or BA6 probably. BA was used in electrical components not infrequently back in the day, especially those made for Commonwealth markets.

[J Tiers]

Seems like JIS may be one of the "alternate standard metric" versions, where some of the size/pitch combinations do not agree with anyone else. But with screws such as you mention, it may be an oddball that you will have a hard time finding.

The smaller sizes are standard. its the 8mm and above where the trouble starts.

https://www.boltdepot.com/fastener-information/measuring/metric-thread-pitch.aspx

[754]

My lathe does not care what pitch of thread form as long as it's in the gearbox.
What pitch is it ?

[CCWKen]

If it were me, I'd be tapping the threads to something I CAN get my hands on. Even if it was a point car, I guarantee no judge will be checking the knob screw threads.

[JRouche]

Howdy folks,

Been a while. I'm doing more stupid automative things, this time with a 1966 Datsun 411. Italian body design, MGB engine copy, using mostly SAE sizes. An oddball for sure.

Many thanks, Derek

What caught my eye was the Italian body. I had a fiat, 69 and it spec'ed out some threads in the shop manual. The JIS is what caught my eye. What is that spec? Japanese market or a variant of threads.

I did what this guy said. JR


CCWKen

If it were me, I'd be tapping the threads to something I CAN get my hands on

[Peter S]

Derek,
Have you got any of the screws or do you only have the female thread? If the former, tell us the screw diameter and its TPI or pitch using either an inch or metric screw pitch gauge and someone here will find it.

Apologies if this is stating the obvious, (you have confused me with mention of ring gauges), I am wondering if you have the ordinary inch and metric screw pitch gauges that fold out like a set of feeler gauges.

[Arcane]

Well, if you want to spend your time looking to see what thread it might be, you might find it here.

https://www.gewinde-normen.de/en/index.html

[MattiJ]

Seems like JIS may be one of the "alternate standard metric" versions, where some of the size/pitch combinations do not agree with anyone else. But with screws such as you mention, it may be an oddball that you will have a hard time finding.

The smaller sizes are standard. its the 8mm and above where the trouble starts.

https://www.boltdepot.com/fastener-i...ead-pitch.aspx

Interesting. In larger sizes "they" use fine pitch metric thread as "standard" size.
(JIS "equivalent" M20x1.5 is also listed on ISO/DIN standards and available at local tractor supply here)

[Leadfootin]

The pipe and hydraulic threads on most Japanese excavators are still BSP (British Standard Pipe) to this day. Many of the Eastern countries still use Whitworth threads on devices.

My '69 Morgan had a combination of Whitworth, BSF, BSP, UNC, UNF, and metric threads and fasteners! Also an NPT fitting for the oil pressure line from the engine.

[mikey553]

If we are talking about metric thread close to M3, but not the standard M3 x 0.5, it could be M3 x 0.6. Yes, it is non-standard, but taps and dies are available with this thread from Ebay.

If I were you, I would try to measure the thread the best I can. If you don't have any original screws, you can try forcing a wooden dowel into the threaded hole and measure the pitch from thread impression on the wood. You can also make a few trial screws with different pitches on your lathe and see which one fits the best. My 12 x 36 Grizzly lathe allows me to cut a lot of non-standard pitches. This information is not available from the lathe manual, but one smart guy developed a full table for my lathe, listing all possible pitches and corresponding change gears and gearbox settings.

[MattiJ]

The pipe and hydraulic threads on most Japanese excavators are still BSP (British Standard Pipe) to this day. Many of the Eastern countries still use Whitworth threads on devices.

My '69 Morgan had a combination of Whitworth, BSF, BSP, UNC, UNF, and metric threads and fasteners! Also an NPT fitting for the oil pressure line from the engine.

Pipe and hydraulic threads on MOST of anything are still BSP(T) as it is most commonly used international ISO/EN/DIN standard anywhere else exept US.
Yes, even all the "metric" countries use it even if its not really metric... probably some political horsing around compromise to get brits using meTRes. Or ages old traditions

Even DIN 2353 metric tube/pipe hydraulic fittings use Whitworth thread. Hydraulic tube OD sizes are nice millimeter numbers like 6mm, 8mm, 10mm etc but the thread on other end is BSP(T)
I should probably call these tube fittings as the they are is sold based on outside diameter..

[derekg]

I pulled the remaining switches and managed to find one without mangled threads and a good screw. Looks to be a .6 pitch as Mikey553 suggested. Will give that a try (M3 x .6) and if the thread form is different, will see if there is a BA Std equivalent. Many thanks for the responses. And glad I don't have a Morgan after reading that hodgepodge of fastener stew...

[MattiJ]

I pulled the remaining switches and managed to find one without mangled threads and a good screw. Looks to be a .6 pitch as Mikey553 suggested. Will give that a try (M3 x .6) and if the thread form is different, will see if there is a BA Std equivalent. Many thanks for the responses. And glad I don't have a Morgan after reading that hodgepodge of fastener stew...

I think it would be rather difficult to determine the threadform on these small sizes. 55 or 60 degrees are both probably enough close for your use if they just fit.
BA-5 is 0.59mm pitch and 3.2mm nominal OD. Pretty damn close to the M3x0.6 or M3.5x0.6 (M3.5 is semi-common on electrical equipment)
0.59mm vs 0.60mm pitch is really hard to distinguish if engagement is only couple of turns. Over 10 turns and it starts to show up (0.1mm error) and anything over 20 turns is pretty much guaranteed to bind.