What are the screw thread sizes on .020 and .049 engines?

[Daligh]

Well folks.

I am undertaking some experimental work which will require me to drill and tap components to suit .020 and .049 engine
threads.
Trouble is they will be Imperial sizes, possibly UNF, or are they some weird US only specification?
So I shall need to buy the correct drills, taps and Imperial Hex Keys.

I find it difficult at my age to get my head around anything that is not Metric!

Thanks,
Dave.

[Levent Suberk]

Daligh, here are my reference pages for propeller and backplate screws:

https://coxengines.ca/propeller-screws/

https://coxengines.ca/backplate-screws/

[Daligh]

Flipping heck Levent.
I am obviously getting becoming stupider as I get older!

I have been on the COX.CA website so often and never thought to look at the screws to see if the thread size was quoted.

Thanks,
Dave.

[sosam117]

Flipping heck Levent.
I am obviously getting becoming stupider as I get older!

I have been on the COX.CA website so often and never thought to look at the screws to see if the thread size was quoted.

Thanks,
Dave.

Daligh,
I feel your pain.
I worked for Caterpillar for 46 years (retired 3 years ago - age currently 64).
When Cat was going "Global" I had to learn to change from the standard "inch" (imperial) sizes to metric.

For a while I did the conversion from metric to "inch" (25.4mm = 1 inch).
But after a while I learned and embraced the metric system. I used the metric system for 34 of the 46 years with Cat.


Now it is tough to think of nothing but metric. It is so simple!
Everything is by 10. (100mm = 10cm, ect.)
Though I still do remember the "inch" sizing. But not as easy as when I was younger.

I remember when the USA tried to change over to the metric system in the late 1970's early 1980's (it didn't work!)
So, we have both metric and inch tools, and fasteners.

Mike McIntyre
2nd generation Irish
(grand-mother from County of Leitrim)

[Iceberg]

The thread size is 2-56 inch. Not sure but don't think there is a metric thread that is same there is a very close one but stick with 2-56.

Iceberg

[EXModelEngines]

Well folks.

I am undertaking some experimental work which will require me to drill and tap components to suit .020 and .049 engine
threads.
Trouble is they will be Imperial sizes, possibly UNF, or are they some weird US only specification?
So I shall need to buy the correct drills, taps and Imperial Hex Keys.

I find it difficult at my age to get my head around anything that is not Metric!

Thanks,
Dave.

Prop Screws
020: 3-48
049: 5-40

[happydad]

Flipping heck Levent.
I am obviously getting becoming stupider as I get older!

I have been on the COX.CA website so often and never thought to look at the screws to see if the thread size was quoted.

Thanks,
Dave.

Remember anonymous “something happens when you get old, but I can’t remember what it is”. His famous quote from the past. I think he was from Ireland, LOL.

Happydad      

[Daligh]

Thanks for all your posts.
I certainly will not try to fit metric threaded parts with imperial items!

Flipping heck Levent.
I am obviously getting becoming stupider as I get older!

I have been on the COX.CA website so often and never thought to look at the screws to see if the thread size was quoted.

Thanks,
Dave.

Daligh,
I feel your pain.
I worked for Caterpillar for 46 years (retired 3 years ago - age currently 64).
When Cat was going "Global" I had to learn to change from the standard "inch" (imperial) sizes to metric.

For a while I did the conversion from metric to "inch" (25.4mm = 1 inch).
But after a while I learned and embraced the metric system. I used the metric system for 34 of the 46 years with Cat.


Now it is tough to think of nothing but metric. It is so simple!
Everything is by 10. (100mm = 10cm, ect.)
Though I still do remember the "inch" sizing. But not as easy as when I was younger.

I remember when the USA tried to change over to the metric system in the late 1970's early 1980's (it didn't work!)
So, we have both metric and inch tools, and fasteners.

Mike McIntyre
2nd generation Irish
(grand-mother from County of Leitrim)

Hi Mike.

Nice Irish clan name.

It is not very surprising that you, and millions of other people around the world, are descended from Irish stock! The main Irish export has been people since 'The Great Hunger' (1845 to 1849) until the early 1960s, when it was less than half what it had been in1841. After 1973, when Eire joined the EEC, the economy has grown really well and people have found employment within the island. In a few years it will reach the 1841 level again.

I read somewhere that over 80 million people worldwide are descended for Irish emigrants.



As to  changing from Imperial to the Metric system.

My own experience was good.

In 1966 I began a Student Apprenticeship with Laycock Engineering in Sheffield. From 1966 to 1968 I attended a Technical College to study ONC Mechanical Engineering. Everything was Imperial, and performing Mech. Eng. calculations in feet and inches plus trying to cope with poundals and slugs was a pain. But I still managed to achieve examination results good enough to go to university.

Of course, in the middle of 1968 the UK went Metric so when I got to university all engineering calculations were in the MKS system (Metre/Kilogram/Second). How much easier it was working with millimetres and Newtons. What was really good was that we students were younger than our lecturers and we picked it up more quickly than they did. I was great fun taking the pi55 out of them when correcting their errors!

[sosam117]

Thanks for all your posts.
I certainly will not try to fit metric threaded parts with imperial items!

Flipping heck Levent.
I am obviously getting becoming stupider as I get older!

I have been on the COX.CA website so often and never thought to look at the screws to see if the thread size was quoted.

Thanks,
Dave.

Daligh,
I feel your pain.
I worked for Caterpillar for 46 years (retired 3 years ago - age currently 64).
When Cat was going "Global" I had to learn to change from the standard "inch" (imperial) sizes to metric.

For a while I did the conversion from metric to "inch" (25.4mm = 1 inch).
But after a while I learned and embraced the metric system. I used the metric system for 34 of the 46 years with Cat.


Now it is tough to think of nothing but metric. It is so simple!
Everything is by 10. (100mm = 10cm, ect.)
Though I still do remember the "inch" sizing. But not as easy as when I was younger.

I remember when the USA tried to change over to the metric system in the late 1970's early 1980's (it didn't work!)
So, we have both metric and inch tools, and fasteners.

Mike McIntyre
2nd generation Irish
(grand-mother from County of Leitrim)

Hi Mike.

Nice Irish clan name.

It is not very surprising that you, and millions of other people around the world, are descended from Irish stock! The main Irish export has been people since 'The Great Hunger' (1845 to 1849) until the early 1960s, when it was less than half what it had been in1841. After 1973, when Eire joined the EEC, the economy has grown really well and people have found employment within the island. In a few years it will reach the 1841 level again.

I read somewhere that over 80 million people worldwide are descended for Irish emigrants.



As to  changing from Imperial to the Metric system.

My own experience was good.

In 1966 I began a Student Apprenticeship with Laycock Engineering in Sheffield. From 1966 to 1968 I attended a Technical College to study ONC Mechanical Engineering. Everything was Imperial, and performing Mech. Eng. calculations in feet and inches plus trying to cope with poundals and slugs was a pain. But I still managed to achieve examination results good enough to go to university.

Of course, in the middle of 1968 the UK went Metric so when I got to university all engineering calculations were in the MKS system (Metre/Kilogram/Second). How much easier it was working with millimetres and Newtons. What was really good was that we students were younger than our lecturers and we picked it up more quickly than they did. I was great fun taking the pi55 out of them when correcting their errors!

Daligh,
My grand mother came over to the United States as an indentured servant.
Had to work as house keeper/maid for 3 different homes. This was in the 1920's to 1930's
My mom (only child) was shuffled off to different boarding schools while grandma worked.
Mom said she knew how Ebenezer Scrooge (in his younger part of his life) felt as everyone went home from boarding school for the holidays and mom stayed there.

Mike McIntyre
(Shanley - grandma's / mom's Irish last name / McIntyre - my dad's)

[Oldenginerod]

Dave.  I get completely baffled by the # sizing used in the USA.  The quoted 5-40 is simply 1/8" UNC.  Tapping drill 2.65mm.
3-48 is a UNC thread as well. Not sure of the fractional diameter. https://www.engineeringtoolbox.com/unified-screw-threads-unc-unf-d_1809.html
Rod.

[GallopingGhostler]

.

[sosam117]

In 1966 I began a Student Apprenticeship with Laycock Engineering in Sheffield. From 1966 to 1968 I attended a Technical College to study ONC Mechanical Engineering. Everything was Imperial, and performing Mech. Eng. calculations in feet and inches plus trying to cope with poundals and slugs was a pain. But I still managed to achieve examination results good enough to go to university.

Excellent, just want to say that you are not alone and among those who understand that

E = MC/I

I graduated in 1981 from the University of Hawaii, College of Engineering with a Bachelors in Mechanical Engineering. Back then US was still heavily entrenched in the English system of pounds, feet, inch, mile, etc. Most if not all of my engineering classes were still using the English (or should I say ahem, ANSI, SAE, etc.) system. All HVAC (heating, ventilation and air conditioning), thermodynamics, material science, etc. equations and figures were in the American system. Reason for this is much of the time in the current day US industrialization, metric hardly scratched the surface back then.

My work history proved that out through aerospace during the 1980's, and even in facility and construction contract administration until I retired in 2012. US is still heavily entrenched in the American system of weights and measurements for facilities construction.

Well,
If your company went "Global" like Caterpillar Inc. (formerly Tractor) did, they would have to shift to the metric system.
If you look at Caterpillar's Logo over the years, it started off as a tractor, then a "C" with pie sections, then a CAT over a pyramid, to their current logo which is a Globe.

Mike McIntyre

[Levent Suberk]

A good source:

https://www.rshughes.com/search.html?q=%235-40%20unc&sort=price&fn.1=Thread%20Size&fv.1=%235-40%20UNC

https://www.rshughes.com/search.html?q=%233-48%20unc&sort=price&v=grid

[Levent Suberk]

Greenfield catalogue:

http://www.gfii.com/images/2013_cle_clf_catalog.pdf

From catalogue:

[coxaddict]

United States did go metric. All they did was convert the inch to metric, LOL! 1/4 inch is called 6.35mm.

[Daligh]

Thanks for all the input folks.

I actually managed to get my brain into gear today and remembered I had a Dormer Tap and Die Booklet from back in the 1970s. I found it in the bike shed but it is a bit worse for wear due to water damage.

Anyways up it's all clear now!



I must admit that if I was forced to use Imperial threads I would use UNC. It uses a proper 60 degree thread angle which is far better than the 55 degree of BSW!

Can anyone advise how I get symbols, such as the one for 'Degree', on an Apple MacBook keyboard?

[Levent Suberk]

Daligh, press both Shift and Option keys, then press 8 key for °

If don't work copy and paste this °

[Daligh]

Daligh, press both Shift and Option keys, then press 8 key for °

Thank you my lovely lad.

You look after me like a second son!

[Levent Suberk]

Daligh, press both Shift and Option keys, then press 8 key for °

Thank you my lovely lad.

You look after me like a second son!

[Oldenginerod]

Can anyone advise how I get symbols, such as the one for 'Degree', on an Apple MacBook keyboard?

Depending on your OS, under "Edit" in the top bar, scroll to the bottom and you should have "Special Characters" (older OS) or "Emojy & Symbols" (Newer).

[happydad]

Can anyone advise how I get symbols, such as the one for 'Degree', on an Apple MacBook keyboard?

Depending on your OS, under "Edit" in the top bar, scroll to the bottom and you should have "Special Characters" (older OS) or "Emojy & Symbols" (Newer).

I'm lazy I just type "deg"  I haven't found it yet.    and you are correct. symbols I have never seen or just forgotten.

happydad         I like to fly, USA, really, really OLD

[faif2d]

We were building s missile nosecone in composite and the screws that were used were 5-40. I asked if the engineer had ever used a C*X .049 as a youth and he said he had. I told him that was what the prop screw was, he was astounded. Only other time in my life (75 now) that I had seen that thread used!

[ffkiwi]

The best technical info on Cox engine threads etc is to be found on Martin Hepperle's website:  http://www.mh-aerotools.de/airfoils/cox_frameset.htm [click on 'technical' in the left hand side menu..]

....there's still a few omissions in the table, such as the TD .010 thread data and the TD 15 and Spl 15 cylinder neck thread details-but its a useful list nonetheless...

ChrisM
'ffkiwi'

[Daligh]

United States did go metric.  All they did was convert the inch to metric, LOL!  1/4 inch is called 6.35mm.

We had a similar thing happen at Laycocks when Design converted J Type overdrives to metric. I was still working in Overdrive Engineering and was given the task of establishing which parts had to be changed, such as bearings, seals, nuts and bolts, etc., and the tooling modifications required to handle the metric components. We did not need to change the internals, such as the planetary gear sets, but had to change shaft sizes and housing bores to accommodate metric items.

Anyways-up. The Design Dept. must have had an idiot junior Engineer producing the drawings and an idiot senior Engineer checking them because they, like your example, just changed a 1" x 2" ball bearing and seal to 25.4mm x 50.8mm and the shaft to 25.4mm and the housing to 50.8mm! As you state 1/4" BSW threads became M6.35!!!!

With the agreement of the Chief Engineer I did not just reject the drawings but corrected them using a bright red crayon. The faces in Design were of a similar colour when I returned the drawings.

[Daligh]

The best technical info on Cox engine threads etc is to be found on Martin Hepperle's website:  http://www.mh-aerotools.de/airfoils/cox_frameset.htm    [click on 'technical' in the left hand side menu..]

....there's still a few omissions in the table, such as the TD .010 thread data and the TD 15 and Spl 15 cylinder neck thread details-but its a useful list nonetheless...

ChrisM
'ffkiwi'

Well Chris, as they say in Yorkshire: "That's reight good"

Looks like I have a few happy hours of reading ahead of me!

Dave.

EDIT:

It's more than good it's flipping great! Five minutes in and I am already getting ideas for this thread. Some of the conversions to RC are brilliant!
https://www.coxengineforum.com/t14175-new-020-muffler-kit-2620-it-seems-a-shame-to-open-the-packaging-rc-ideas-for-the-020-pee-wee

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