By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale July 23rd

odd thread

All Topics | Latest Posts

Search for:  in Thread Title in  
Philip Burley03/04/2019 12:12:31
114 forum posts
3 photos

I am having problems with a fine thread , the dia is 0.156 inch ie 5/32 The pitch fits on my metric gauge marked as 50 , which I assume is 0.5 mm pitch, but seems finer than that , too fine to count till I borrow grandsons microscope . The screw is an adjuster in a model aeroplane engine ,

any thoughts ?

Ian P03/04/2019 12:21:35
2116 forum posts
89 photos

Rather than trying to count the threads to find the pitch, Just measure haw far the adjuster travels over say, 10 turns. Simplest is with digital calipers because you can set zero over the whole assembly (exposed end of screw to opposite side of engine or carb.

No requirement for the manufacturer to use a standard thread size (although they probably did) but establishing the pitch accurately will give you the answer.

Ian P

Lambton03/04/2019 12:28:55
675 forum posts
2 photos


0.156"= 4.0 mm

4.0 mm diameter X 0.5mm pitch is a standard metric Fine thread. Yes it will look very fine.

I find it is best to avoid any confusion by sticking to either imperial or metric dimensions.

Best regards


Hopper03/04/2019 12:57:15
3651 forum posts
72 photos

Or could it be 5/32 x 50tpi?

What make, vintage and country of origin model airplane engine is it?

Might give a clue as to whether it could be metric or imperial.

JasonB03/04/2019 13:02:20
15787 forum posts
1663 photos
1 articles

Yep M4 x 0.4 is standard needle thread, I had to buy a suitable tap when I used an OS needle on the carb I made for my Firefly

Philip Burley03/04/2019 15:48:53
114 forum posts
3 photos

hello Jason yes its for a old Bluebird 45 engine , the needle valve . I have one for a pattern . I was told by an "expert" that it would be an AF , I could have a try on the lathe but sure to need a die to make a clean finish

Thanks every one for information

Philip Burley09/04/2019 18:16:24
114 forum posts
3 photos

made one , and it works !!! amazing !!

Jon Lawes09/04/2019 20:06:59
313 forum posts

Well done Philip

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
TRANSWAVE Converters
Meridienne Sept 2019
Eccentric Engineering
Eccentric July 5 2018
Advertise With Us
Allendale Electronics
Subscription Offer

Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest