1929 Sport Coupe Rear Window Trim Screws

[Conaway2]

I need to find a source for the trim screws in the rear window frame.

These are 1” long pan head screws. They may have been nickel plated originally- hard to tell now. I’m missing three screws…..

I don’t know what size the threads are - NC-40 is too small; NC-28 is too big. My tap and die set has no in-between sizes.

Does anyone know what size the threads on these screws are ? Or, where I can find replacement screws ?

Many thanks - Jm

[rotorwrench]

They are usually oval head slotted drive screws with 5-40 thread. This is an odd thread size since most sources have 4-40, 6-32, etc progressing in even numbered sizes. The odd numbered sizes aren't anywhere near as common but tooling like taps & dies are available. One inch seems a bit long but they can be cut or ground to specific sizes if too long.

I had a conversation with member Dknapp recently and he found some 5-40 screws on Ebay that were 7/8" long for his oval port windows on his 29 business coupe. He had to purchase like 100 units so he has more than he needed and offered them to me. You might send him a Private Message and tell him I sent you if 7/8" will work on that frame. I guess in might depend on how thick the replacement glass and setting tape might be. There are 16 screws on those frames since they are larger than the roadster type frames.

[Conaway2]

Originally Posted by rotorwrench

They are usually oval head slotted drive screws with 5-40 thread. This is an odd thread size since most sources have 4-40, 6-32, etc progressing in even numbered sizes. The odd numbered sizes aren't anywhere near as common but tooling like taps & dies are available. One inch seems a bit long but they can be cut or ground to specific sizes if too long.

I had a conversation with member Dknapp recently and he found some 5-40 screws on Ebay that were 7/8" long for his oval port windows on his 29 business coupe. He had to purchase like 100 units so he has more than he needed and offered them to me. You might send him a Private Message and tell him I sent you if 7/8" will work on that frame. I guess in might depend on how thick the replacement glass and setting tape might be. There are 16 screws on those frames since they are larger than the roadster type frames.

Rotorwrench - this is great info ! Thank you !

Jim

[Synchro909]

Hi jacking a bit here but I need a similar screw for the back window in my 1930 CCPU. At least, I think it is similar, I have no idea what the screw sizes you guys are talking about are so you can imagine the chances of me finding one.
What is the significance of those numbers?

[rotorwrench]

I just checked Bratton's and they list a rear window frame screw set for the CCPU but they are 10-32 and come with square nut hardware. Other sources should also have those.

The cars with cloth tops use the frames that attach to the top material like the Sport Coupe & Business Coupe. Most of these have two piece formed steel frames with a few having solid aluminum frames. Open cars had smaller glass and frames. Most were solid aluminum. To reduce weight, they made them as small and light as practicable. The screws threaded into fittings that were spot welded inside the steel outer frame. The cast aluminum ones were threaded in the casting of the outer frame. The screws were always on the inside of the car.

Under the SAE or Society of Automotive Engineers, numbered screw thread sizes were used and still are in aerospace and for replacements. They generally start at #4 with 40 tpi or threads per inch. The system actually started at #1 with odd and even diameter numbers through #5. Above that they are even number through #12. A person would have to Google an SAE numbered screw chart to see all the sizes with National Fine and National Course threads used on them. It's different than the old brittish association screw system but did the same job. Metrics changed all that unless you restore old American cars.

[jack backer]

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Those screws clamp the window frame halves and pinch the top material. I used Harrtz stay fast fabric on my top, it was challenging to catch the threads

[rotorwrench]

The book "The Ford Model A As Henry Built It" has two cross sectional diagrams of the two styles of frames and a chart that lists the glass and frame dimensions used on the different cloth top cars. It also lists the type of finish on the frames. What it doesn't list is the thickness of the glass and the top material. It mentions nothing about the fasteners either which is kind of disappointing.

[Synchro909]

Originally Posted by Synchro909

Hi jacking a bit here but I need a similar screw for the back window in my 1930 CCPU. At least, I think it is similar, I have no idea what the screw sizes you guys are talking about are so you can imagine the chances of me finding one.
What is the significance of those numbers?

Anybody?

[dave in australia]

Originally Posted by Synchro909

Anybody?

They are gauge size screws. The first number is the diameter in gauge, and the second is the TPI. So, a 5-40 would be 5 gauge 40TPI. As with wire gauge, the bigger the number, the smaller the diameter.

[Synchro909]

Originally Posted by dave in australia

They are gauge size screws. The first number is the diameter in gauge, and the second is the TPI. So, a 5-40 would be 5 gauge 40TPI. As with wire gauge, the bigger the number, the smaller the diameter.

Thanks, Dave. That sounds a bit "screwy" to me.

[rotorwrench]

There is no gauge to the old United States Standard. It is an old standard that was updated by the SAE and ASME. The numbers represent fractional inch sizes below 5/16" using 60 degree threads. The numbers begin with smallest to largest right along with the sizes. The numbers have no correlation with the fractions. They just start with the small numbers representing small fractions getting larger numerically as the fractions get larger.

During WWII, the old inch systems were unified between British and American systems so that there would be commonality in production and repair parts.

Steel and wire have gauges and they do get smaller numbers as thicknesses gets larger. Numbered drills follow that pattern as well but they stop at #1. From there on, only fractional and alpha lettered drills continue above that size.

These system standards aren't perfect but they do work as well as any other. They are still in use in aviation and aerospace here in the US.

[Synchro909]

The gauge system seems un necessarily complicated to me. If you guys caught up with the rest of the world, you'd be using the metric system. They have no gauges for screws or wire. It is all straight forward diameters and the thread counts work in the right direction too. A small number is a fine thread whereas, TPI works the other way. Puzzling why a country like the USA hasn't changed over.

During WWII, the old inch systems were unified between British and American systems so that there would be commonality in production and repair parts.

If that is so, things have changed back again since. Using pipe fittings as an example, the British and the American system are different - by 1 thread per inch on most sizes. That is just enough for them to be incompatible. I find that crazy.

[cokefirst]

For those of you that think that metric is standardized, think again. There is a European standard and an Asian standard. The head size of the cap screws are different between the European and Asian bolts of the same size and thread.

[rotorwrench]

So much equipment was made under the old systems that it's still needed for maintenance, up keep, and restoration. Well made stuff dies hard.

The meteric system is in use for production here but most of the stuff available now ends up in the crusher and gets recycled. Folks don't want to restore much of it anymore.

Tapered pipe thread is a different standard since it's not a fastener system as much as a plumbing system. It's still in wide use here for steel pipe applications.

What can I say other than we still use what we have always used. Metrics just haven't caught on here. We still have pounds, inches, and miles. It's what we've always used. It still works so why should we change? If it ain't broke don't try to fix it. We're hard headed and just can't justify the need.

During the war unification was an expedient source of supply. Countries lose wars that don't have commonality. In Imperial Japan, they made naval aircraft differently than army aircraft so one comander couldn't take another branch of services equipment. Can you imagine the logistics on that? It's one of many reasons they lost the war.

[dave in australia]

Originally Posted by Synchro909

The gauge system seems un necessarily complicated to me. If you guys caught up with the rest of the world, you'd be using the metric system. They have no gauges for screws or wire. It is all straight forward diameters and the thread counts work in the right direction too. A small number is a fine thread whereas, TPI works the other way. Puzzling why a country like the USA hasn't changed over.

During WWII, the old inch systems were unified between British and American systems so that there would be commonality in production and repair parts.

If that is so, things have changed back again since. Using pipe fittings as an example, the British and the American system are different - by 1 thread per inch on most sizes. That is just enough for them to be incompatible. I find that crazy.

Try being an aircraft mechanic on USA made aircraft in Australia. I put litres of fuel into the aircraft, and then enter the amount in the logbook in pounds. Before that, I was an electroplater, with bath makeup printed in pounds per gallon, then I'd have to convert it to Kg per litre, remembering that it is US gallons and not British gallons.

[katy]

Here’s some old thread size info taken from “American Machinists Handbook”, 1945 issue, I can’t find my 1908 issue, but I assume the numbers are the same.

Size Basic major diameter in inches

0 0.0600
1 0.0730
2 0.0860
3 0.0990
4 0.11.20
5 0.1250
6 0.1380
8 0.1640
10 0.1900
12 0.2160

¼ 0.2500

There should be spaces between "size" and "basic" and between the first numbers 1,2,3, 4,5,6, 8, 10, 12, and the 0.** The computer deleted them for some unbeknownst reason, it seems it doesn't like spaces.

[rotorwrench]

I think they were first published in the 1916 publication "Mechanical Engineer's Handbook". Prior to that, it was referred to as United States Standard or Seller's Standard. The SAE and ASME started to work on the standardization of the old system in 1912. The first metric standards were based on the 60 degree thread pitch design but were adapted for metric diameters and pitches. The British Standard Whitworth system used the 54 degree pitch on the threads with a rounded tip. British Standard, British Standard Fine, British Association, and British Standard Cycle were common to the UK and Commonwealth countries with some exception to Canada since they manufactured a lot of their own stuff. Since most Ford products that were exported to the south Pacific region were from Canada then it likely saw more of the SAE type fasteners for a time but that changed when manufacturing was built up in that region. Historically, countries use what ever is standard to their industrial complex.

I've played around with a few old British cars and motorcycles so I have all the tooling for the old British standard type fasteners. The Royal Enfield Indian motorcycles I currently have date from 1954 to 1960 and my old Triumph 1800 roadster is a 1947 model. The wood body on the 1800 is held together by plow bolts with British thread. I had to make a few new ones due to corrosion.

[Synchro909]

It has been said that we are people separated by a common language. Don't get me started on that!
Seems we are separated by more than language. Weights and measures too, it seems. Don't get me started on that!

[rotorwrench]

We're pretty much separated by two different hemispheres and a whole lot of ocean. When a separate county sheds it's ties with the ruling country well over 200 years in the past due to too many differences to list, it's not uncommon for everything to evolve in a completely different direction. The US shed more than a few ties with the European community as a whole. It had it's own resources to evolve how it wanted to. It's large enough to have it's own economy so it didn't need much from the outside world. That world used to be harder to traverse and communicate with. The world of the modern era isn't as large as it used to be with modern transportation and communication but we still have the wherewithall to do things differently than other parts of the world if we choose to do so. We are not a lot different in most ways but there are differences. We certainly can't change history or why things are the way they are.

I'm still wondering what all this has to do with old Fords.

[31 Woody]

Originally Posted by rotorwrench

I had a conversation with member Dknapp recently and he found some 5-40 screws on Ebay that were 7/8" long for his oval port windows on his 29 business coupe. He had to purchase like 100 units so he has more than he needed and offered them to me. You might send him a Private Message and tell him I sent you if 7/8" will work on that frame.

I know when Dad (DKnapp to you) and I put the rear window in the business coupe we had to do it in stages—different lengths of screws. We started with long screws to get it into position, then progressively shorter until it was in the final position. He may know what the final length was, but I do remember having at least 2 sizes to get the rear window placed and into final position.