A historical thread curiosity

[Snakeoil]

I'm reading Vol II of The Winchester Single Shot Rifle. The book is loaded with original Winchester engineering drawings. I've made screws for my High and Low Wall rifles. Most were for tang sights or to plug holes where tang sights go. I've measured them and they normally measure 0.185 and have a 36 TPI thread pitch. I've always thought that they were simply 10-36 screw threads and the 0.185 diameter was just manufacturing tolerance.

Well, one of the drawing shows the specs for the screw threads used for most of the screws in the original 1885 Winchester. The size on the Winchester drawing is .185-35-1/2. Yup, that's not a typo. Thread pitch is 35-1/2 TPI. My South Bend cannot cut that thread. My Machinery Handbook does not list that pitch. My Grandfather's American Machinists' Handbook, originally published in 1908 and the one I have is a 3rd edition published in 1923, is packed with info on threads, but nowhere lists a 35-1/2 thread pitch. It lists 35 and 36, but not 35-1/2.

I guess Winchester wanted to make sure nobody else could make their screws. Would require specialized gearing for their screw machines.

 

[Ian]

There's a little free program called "ride the gear train" on line that will calculate change gears for you. It is really a comprehensive program capable of figuring ratios for your particular setup, or a custom gear/banjo setup. If you're REALLY interested in cutting correct screws, I'm sure you can figure it out. You'll almost be guaranteed need a super spacer and a milling machine with arbor and full set of the correct gear pitch cutters to make it happen, but it can be done.

 

[Missionary]

That is certainly a unique discovery ! I wonder how other models fared ?

 

[Petrol & Powder]

That’s weird. Considering the relative abundance of machine tools in Connecticut in the second half of the 1800’s, one would think they would use a standard thread pitch. I wonder if there’s more to that story.

There would be little to be gained from a proprietary thread pitch for screws; particularly in that age. Could it be the machinery used to cut the threads were sourced from some British (Whitworth) or European (metric) supplier and simply set up as close as they could get it to the desired pitch? Or maybe the machinery was reused from a prior application? That machinery would have been expensive, maybe they just used what they had. The drawings could have been made to correspond to the machinery on hand? I don’t know but it is some interesting history.

 

[Snakeoil]

From my limited experience, many companies came up with proprietary specs back then. Singer Sewing machines used oddball threads. From what I have read about Winchester, they were not the kind of company to use hand me down machine tools. They were known for their commitment to precision. I just bought a tang screw from MVA for my High Wall. For $10, was too lazy yo make it. Well, the thread was a 10-36 and I had to "relieve" it a bit to fit the rifle.

 

[Petrol & Powder]

There’s no doubt that a lot of oddball threads existed on equipment made in that era, I’ve certainly encountered that on old items. My guess is it was done to improve some aspect of manufacturing expediency.

It is not as if some oddball thread pitch was needed to protect your patent rights or company reputation in those days. The effort to make a forgery in those days wouldn’t hinge on a screw thread.

I suspect there was some minor manufacturing efficiency to be gained by using an oddball size. Perhaps some long lost peculiar coincidence of a change gear that was exactly half or twice the needed value for some other operation? Or some raw material source that was just easier to incorporate into the process with an oddball size?

The reasoning may be lost to history, but it is interesting.

 

[Bret4207]

It entirely possible Mr Browning (think he designed the Hi Wall) had a tap and die set that turned out to be 35 1/2 TPI and that that was what the guy drawing the blueprint was told to put down. Tap and die making back in the day wasn't quite as "precise" as it was a decade or 2 later. Or maybe the guy doing the measuring didn't get down the right tread pitch. Things like that aren't unusual.

 

[Charles Graff]

I recall some weird French threads used on Krag rifles and Singer sewing machines. I suspect these Winchester screws have Euro origin.

 

[KeithB]

I have read that some manufacturers of equipment such as guns used oddball diameter/pitch combinations so that an unhardened hardware store screw couldn't be used as a substitute. I personally think there are a number of reasons why a proprietary thread might be used.

With CNC it doesn't make a damn bit of difference. Change a couple numbers and POOF! any thread you want.

 

[Glaciers]

I order a Marbles tang sight for my High Wall 38-55. This is a second year Winchester. The sight came with recommended screws which didn’t fit. Ordered the optional screws offed by Marbles. Didn’t fit.
Call Marbles and talked to someone who is supposed to be in the know about this stuff as he’s been there forever. After explaining what the problem was he informed me that I was mistaken and one set was obviously going to be correct.
Well that was good to know but he was wrong. Neither screw set was right, almost right but after a turn would come up hard.
Well I gave the better fitting but not quite fitting screw set a little more encouragement and fortunately the screws were a softer metal than the tang threading. Went in with lubricant and tang threads were clean but the screws were recut. I would not have continued if it was going to damage the threads of the rifle.

 

[RBHarter]

One thread pitch just dia changes . Make a 100 each #6,8,10,12-32 , reset cut 4,6,8-40 .
May have just been gear slop .

 

[Bret4207]

I order a Marbles tang sight for my High Wall 38-55. This is a second year Winchester. The sight came with recommended screws which didn’t fit. Ordered the optional screws offed by Marbles. Didn’t fit.
Call Marbles and talked to someone who is supposed to be in the know about this stuff as he’s been there forever. After explaining what the problem was he informed me that I was mistaken and one set was obviously going to be correct.
Well that was good to know but he was wrong. Neither screw set was right, almost right but after a turn would come up hard.
Well I gave the better fitting but not quite fitting screw set a little more encouragement and fortunately the screws were a softer metal than the tang threading. Went in with lubricant and tang threads were clean but the screws were recut. I would not have continued if it was going to damage the threads of the rifle.

It's possible those screws were removed and lost 100 years ago and someone else used an "almost right" plug screw. You might have been hitting HIS buggered threads at first. I've seen similar things a buncha times!

 

[Snakeoil]

It's possible those screws were removed and lost 100 years ago and someone else used an "almost right" plug screw. You might have been hitting HIS buggered threads at first. I've seen similar things a buncha times!

This is always a possibility with ancient things mechanical. I have a few Brit motorcycles from the 60's and they tend to be a variety of various British threads. Of course, you could not buy replacement screws/bolts/nuts at the local hardware store so the next closest thing was used. There was one SAE thread that was just about identical to a Whitworth thread. Pretty sure if was 5/16-24. I found two of them in a front fork slider and using the correct Whitworth threaded bolts and some patience was able to save the threads in the fork.

That said, I think it is safe to say that Marbles and all the other outfits that make stuff today assume the screws in High Walls are 10-36 as I did. So, if the screw is made to the upper end of the tolerance, it will bind as it did for Glaciers and for me with my MVA screw. The nominal major diameter of a #10 screw, regardless of thread pitch is 0.190". The Winchester screw is 0.185". 0.005 is a big deal with a screw that small. Hence it may start but then bind because the pitch is off by 1/2 TPI or if the new screw is a bit under 0.190, it will go in quite a ways and then begin to bind. To make mine fit, I simply chucked in the lathe and ran a 3 corner file along the thread for a few light passes and it was fine.

I might call MVA to ask the question about thread size just for fun. They advertise that all the parts for their actions will fit in the originals. The word "fit" is open to interpretation.

 

[RicinYakima]

It's possible those screws were removed and lost 100 years ago and someone else used an "almost right" plug screw. You might have been hitting HIS buggered threads at first. I've seen similar things a buncha times!

The other reason is the action is case hardened. If clean, it will act as a die for the soft modern screws. That is what happened when I needed to replace the screw the barrel tilts on with my Steven's Tip-up 35 Stevens rifle. After messing up the first screw, cleaned the threads and used lots of Moly-Tap fluid. Complete in about three minutes.

 

[Glaciers]

This ^^^^

 

[Glaciers]

The threads on the tang are clean and sharp. I was surprised that the Marbles screws were so soft. Pleased mind you, I would not have continued with the screws if they weren’t showing signs of being recut. If there was any indication of upset of the tang threads I would have stopped.

Edit:
I will not bugger an original Winchester in original condition ever. I love early Winchesters.
And one or two other brands I would have to put in that category as well.

 

[Snakeoil]

My guess is because there are no probably no engineering or maching books that list a .185-35-1/2 screw thread, anyone measuring an original screw would simply assume it was worn or within the tolerance range for a 10-36. I measured the threads with a pitch gauge and until seeing that dwg, would have bet that it was 10-36.

 

[Petrol & Powder]

There’s also the possibility that the drawings in the book didn’t come from Winchester, regardless of what the included text indicates.

The drawings could be from someone measuring the parts of the rifle and making a drawing from the rifle and not the rifle from the drawing. Just because the publisher or author includes the drawings, doesn’t mean his source was authentic.

As for the screws from the Winchester factory – If they were making their own screws, they didn’t care if those screws matched some standard. They only care that the screws work in the products they are assembling.

Standards are not needed when you are making all your own parts. The parts just need to work in your application. I sort of like the idea that Winchester’s screw dimensions were a bit oddball but Winchester just didn’t care because they were making all the parts. No standard outside the factory is needed.

 

[Snakeoil]

The dwgs. are from Winchester. They are from the collection in Cody.

I disagree that they would not care. If they could save money buying standard tooling, they would have. I truly believe it was to secure as much repair and parts business as possible. It allows them to charge a premium for their parts as well.

 

[KeithB]

If anyone needs the dimensions for a non-standard/proprietary thread let me know. I have a program called ME Threadpal that will calculate all the dimensions for at least five thread forms (UN, ACME, etc) and any diameter/pitch combination. Be glad to post the data like the .185-35.5 thread mentioned here:

Inch Units
EXTERNAL
0.1850-35.5 UNS-3A
Allowance,0.0000
Major Diameter Max,0.1850
Major Diameter Min,0.1794
Pitch Diameter Max,0.1667
Pitch Diameter Min,0.1645
Minor Diameter Max,0.1545
Minor Diameter Min (Ref),0.1462
Root Radius Max,0.0041
Root Radius Min,--
Flat At Root,0.0070
Thread Height (Basic),0.0173

INTERNAL
0.1850-35.5 UNS-3B
Allowance,--
Minor Diameter Min,0.1550
Minor Diameter Max,0.1617
Pitch Diameter Min,0.1667
Pitch Diameter Max,0.1696
Major Diameter Min,0.1850
Major Diameter Max (Ref),0.1920
Flat At Root,0.0035
Thread Height (Basic),0.0152

Pitch,0.0282
Lead,0.0282
Starts,1
Lead Angle,3.079

Included Angle,60.0000