3/16" 28 TPI screw, why so hard to find?

[The Artful Bodger]

I am working on something that requires twelve screws that as far as I can tell are 3/16" 28TPI but they seem very hard to find. I would even go up to 6mm and retap but there are inserts ('helicoils'?) in the holes.

I am in New Zealand and do not relish the thought of US$50 to courier a handful across the blue Pacific.

[Rich Carlstedt]

Thats a real odd size !
the closest I know is a British Standard Brass Thread at 26 TPI for a 3/16" thread
for Metric you would need a 4.5-.9 configuration which is nothing I have ever seen
Its always possible it is a custom thread by the machine maker ??
Rich

[J Tiers]

Can you cut 28 tpi?

If so, then you can make them. The major diameter has nothing particular to do with the TPI.

[wierdscience]

#10-28 would be very odd and not something on the shelf anyway. What do the screws come off of?

[ezduzit]

I am working on something that requires twelve screws that as far as I can tell are 3/16" 28TPI...

Almost certainly incorrect. Much more likely either 5mm or #10. Where was the "something" manufactured?

[The Artful Bodger]

I have one screw that I think was original and it appears to be stainless steel. This part is a radar rotator from a ship's masthead but I am using it for something else so stainless is not required.

In theory I should be able to cut 28 tpi as I am sure the required gears will be in my lathe kit, I am thinking of starting with 6mm screws which I think will have enough diameter once I turn the threads off.

[The Artful Bodger]

Almost certainly incorrect. Much more likely either 5mm or #10. Where was the "something" manufactured?

Close to 5mm but the pitch would be 0.9 mm, possible but not likely.

#10 just tells me it is 3/16". I see that 10-28 is listed on some sites but they are too far away for me to access.

The ship the rotator came from was I believe Taiwanese and the electric motor shows Asian script so probably Japanese or Chinese manufacture.

Other sizes of screws match imperial threads.

[ezduzit]

...#10 just tells me it is 3/16"...

No. It is 0.190"

[vectorwarbirds]

That sounds like an Aeronautical Standard Machine Screw. Cessna used them as well as others.

Also this: Screw for Sharps Tang Sight, #10-28 thread, bright steel to mount Sharps tang sight. These screws have a 5/16" diameter head, a overall length of .42", and threaded shaft of .29".

https://www.trackofthewolf.com/Categories/PartDetail.aspx/855/1/SCREW-SHARPS

Also: Lincoln Products 3/8" x 10/28" Brass Bibb Screws

[RB211]

Wow, the Apple of machine screws! Actually they would probably do 27.3 turns so people couldn't even make them easily...

[djc]

Number 10-28 seems to be part of the obsolete ASME (pre-UN) thread series.

I found some references to the thread being used in Juki sewing machines. See:

https://www.amazon.co.uk/kunpeng-10piezas-ss-4120915-sp-Screws-ddl-8500-ddl-9000/dp/B078692HQX

Put "3/16-28 screw juki" into Google and there are numerous hits, in different lengths. You would have to check if they ship to your place.

[The Artful Bodger]

Thanks, there may be something useful in those responses.
John

[Paul Alciatore]

Why couldn't they be shipped via the post office? Does New Zealand add some astronomical charge above US postal rates? Any US company could ship them to anywhere in the world starting for under US$15.

https://www.usps.com/international/mail-shipping-services.htm

I am working on something that requires twelve screws that as far as I can tell are 3/16" 28TPI but they seem very hard to find. I would even go up to 6mm and retap but there are inserts ('helicoils'?) in the holes.

I am in New Zealand and do not relish the thought of US$50 to courier a handful across the blue Pacific.

[The Artful Bodger]

Regardless of the postage questions there seems to be very few online sources in the US for what I seek.

[Doozer]

M5 x 1.0

-Doozer