Identification of thread form

Advert

New Replies

Report Bug

Help/FAQs

Identification of thread form

This topic is empty.

Viewing 15 posts - 1 through 15 (of 15 total)

Author

Posts
31 October 2013 at 17:30 #7325
Derek
Participant
@derek63019
Saito 2TDR thread sizes.
Advert

31 October 2013 at 17:30 #44714
Derek
Participant
@derek63019
I have measured the threads for exhaust port of my Saito engine and,as far as I am able to ascertain with vernier calipers have come upwith the following measurements :-

Metric: Diameter 6.8 mm Pitch 0.7 mm

Imperial: Diameter 0.0268" Pitch 0.29"

Can anyone enlighten me as to this thread form ?

Derek
31 October 2013 at 18:34 #44716
Bob Abell 2
Participant
@bobabell2
Hello Derek

I assume the dimension of 6.8mm is the actual hole size of the internal thread?

I would say the thread is M8 Fine thread

The pitch of this thread is 1mm

Bob
31 October 2013 at 19:42 #44720
John W E
Participant
@johnwe
hi there

going by the measurements you have given, it is a possibility that this could be a 1/8 bsp thread but the best way is, if you have a small engineering firm near where you live, pop in and ask them if they have a 1/8 bsp tap and also a 8 mm fine tap – and you want the plug taps, just to gently try in the hole. I have had a quick look on the web and there are one or two places I will go back and read on the forums and if I find anything about this steam engine I will come back to you about the thread size.

aye

john

Edited By bluebird on 31/10/2013 19:59:31
31 October 2013 at 21:22 #44725
Tony Hadley
Participant
@tonyhadley
From a 1974 Zeus book here are the details of 1/8 BSP, which doesn't appear to be the thread in concern –

O.D. – 0.383 Core – 0.337 Pitch – 0.357 Depth 0.229 Radius – 0.0049 Effec. – 0.3601 TPI – 28 ODP – 13/32

Tony

Edited By Tony Hadley on 31/10/2013 21:23:40
31 October 2013 at 22:05 #44727
Tony Hadley
Participant
@tonyhadley
Derek,

Further research here – **LINK**

Tony
31 October 2013 at 22:12 #44728
Keith Long
Participant
@keithlong89920
The nearest "standard" thread to your measurements is 7mm FINE (0.75mm pitch). Metric threads are always very slightly under the nominal size. You can best check the pitch by measuring across as many turns as you've got and dividing by the number of turns- much more accurate than trying to measure across adjacent peaks. Alternatively use a thread gauge but I wouldn't be surprised if 0.75 mm pitch is missing. If you wind up having to make the fittings yourself, Tracy Tools can supply taps and dies for 7mm fine taps are listed at £4 and the die at £5. My only connection with Tracy Tools is as a customer and I've bought taps and dies from them and have been quite happy with them.

Any other common size of thread seems to be well away from what you've got. BSP even down at 1/16in. is 28 tpi and other taps listed by Tracy Tools for 36 tpi are 1/4 inch (too small) and 5/16in (to big). The imperial fractional size nearest to the diameter you've got is 17/64in. and that isn't listed in any thread tables that I've seen.

My best suggestion is to recheck the pitch.

Keith
31 October 2013 at 22:25 #44729
David Marks 2
Participant
@davidmarks2
Derek

There is a range of Model Engineering (ME) threads in fractional sizes and available in both 32 and 40 TPI variants.

9/32" X 32 TPI gives an O/D of 0.281" and a pitch of 0.031". 0.281 is the exact conversion from 9/32" and going back to my apprenticeship as a tool and gauge maker, you always make the o/d about 0.005" under size, before screw cutting, which gives 0.276".

There is data re. ME threads on the internet. Additionally as already defied in an earlier response Tracy Tools will be able to supply taps and dies.
1 November 2013 at 09:23 #44731
John W E
Participant
@johnwe
hi Derek this may help you **LINK**

aye

john
1 November 2013 at 13:06 #44733
Paul T
Participant
@pault84577
I believe that Bob has the correct answer to this conundrum, being Japanese the Saito engine is most likely engineered with metric components and as such the M8 fine thread would be the logical solution.
1 November 2013 at 13:42 #44734
John W E
Participant
@johnwe
hi there

with regard to the thread and my earlier typo where I typed 1/8 instead of 1/16 for bsp, and also having read on several forums the most likelihood is that this particular thread is a 7mm fine thread. If the gent wishes he can try an 8mm tap in the hole, but my thinking is he may destroy it… can anyone read Japanese? The following image is of a drawing of the engine with parts – but its in foreign language to which I am not privvy also working on a lot of Airsoft guns from Japan for my son – I know some of these threads can be way off the standard mark.

aye

john
1 November 2013 at 13:43 #44735
Gerald Gardiner 1
Participant
@geraldgardiner1
I don't know about Saito, but some Japanese Metric is different from the rest of the worlds Metric.
25 November 2013 at 16:40 #45244
David Marks 2
Participant
@davidmarks2
Was there a final resolution to this problem i.e. was the thread identified and a matching component manufactured? Someone did suggest a special thread i.e. one with a defined/recognised form to the thread shape but a non-standard pitch. Threads on camera lenses are a good example.
26 November 2013 at 09:47 #45252
Derek
Participant
@derek63019
Hi David,

It was merely a Japanese 7 mm fine thread which is slightly different from British metric thread form but was able to get good enough fit with cutting a thread with British Die.

Derek
30 December 2013 at 11:22 #45940
Giovanni Sorrentino 1
Participant
@giovannisorrentino1
The Saito theads are mm 7 x 0,75 (fine tread).
Author

Posts