Slotted nuts vs. Castle nuts, when was each first produced?

[28anut]

I was studying a brass car and noticed a mixed usage of slotted and castle nuts trough out the car.  Which  is correct for the period?  Did the slotted nut come first?  or is the slotted nut an easier / faster to produce replacement for the castle style?  What is the history of these two styles?

[1937hd45]

The Model T Ford is full of castle nuts, the "slotted nuts" came later, for some reason I first noticed then on tie rod ends. 

[Shootey]

Should cotter pins be bent straight or should they be be also curved around the circular part of the nut?

[mechanician]

https://www.raa.ca/magazine_pdf/tech articles/Cotter Pins.pdf

[wayne sheldon]

The next level of discussion is whether the "cut" through the "castle" should be "squared" or "rounded" at the bottom of the cut!

Believe it or not, that question has been debated among the model T crowd, and serious researchers have spent hours in the Benson Archive trying to find "the answer!"

Apparently, at several times during the model T's production, as early as about 1912, Ford did in fact specify which way the "cut" was to be made! The kicker is that Ford specified each way at different times, and that specification went back and forth over the years. In addition to that, empirical evidence (very original surviving cars) were at the time found showing all castle nuts on a given engine to be the opposite of what was found to be specified at a given time. Clearly, Ford used both square bottom and round bottom castle nuts pretty much throughout model T production.

Henry Ford was an early proponent of standardization! He was one of the founders of the SAE in the early 1900s. He demanded that hardware be uniform and fully interchangeable. He probably did try to have the castle nuts done one way, and maybe tried several times? But the reality was that his demand was so great, that several major manufacturers combined could not keep up with his needs. A hundred thousand cars in a year with each one using nearly fifty 3/8-24 castle nuts?  That was a lot of nuts! And that was just the beginning! By 1916 they were producing nearly a half million cars in a single year!

 

Most other automobile manufactures were also using mostly standardized hardware by about 1910. Most of them likely did not care whether the castles were square or round cut. Both styles were fairly common by then.

With the vibration of most cars at the time, castle nuts with cotter pins was the one sure way to make certain that things stayed tight. What we consider so common today, the cut spring lock washer did exist back in the day, and were being used on many things by the mid 1910s. However the spring steel wasn't such a sure thing then. And lock washers had a bad habit of breaking and falling out. So if it was important? Castle nuts and cotter pins were preferred.

 

Ever seen a course thread castle nut? Ford used six of them in the brass era and late 1910s model Ts. Anyone care to guess where? (I bet Bob knows?)

[TAKerry]

Now that I see I have been installing the pin incorrectly, can someone clarify the difference between a castle nut and a slotted nut? I think I know what a castle nut is.

[AHa]

I guess most guys know modern slotted nuts are course thread and the castellated nuts are fine thread, at least at my local bolt and nut supply.

[wayne sheldon]

TAK, I think what you are asking is a matter of semantics. The "true" castle nut is the darker single in 28anut's photo. Notice how it is "cut in" around the top circumference. Notice also that the dark one is somewhat taller than the two "bright" ones in that photo. That was how nearly all castle nuts were made back in the day.

The two "bright" ones are modern facsimiles, and not quite exact. They are in fact cheap knockoffs, wherein a standard height nut is run through a machine that simply cross-cuts the slots. Functional, but not as strong as a properly sized nut.

 

Most of the shorter knockoffs are post-WW2, although I have found some on machinery from the 1930s that appeared to be original. 

A lot hardware stores around here call the shorter knockoffs "castle nuts". I don't think the people working those places know the difference. The real thing can be ordered (I think still?), but tend to again be pricey. I usually try to buy a box every few years, although I don't have many on hand again. Putting together two model Ts pretty much wiped me out. Again, on occasion, I have made my own when I only needed a few.

 

AHa, Most modern "slotted" nuts I see are in fact fine thread. Course thread can be ordered through some hardware supply stores in some sizes. 

About thirty years ago, I needed a few course thread castle nuts for something old and odd. When I found out what they were going to charge me for a handful of course thread slotted nuts, I bought a few extra tall standard course threaded nuts and cut my own slots with a hacksaw.

I wonder if your local supply keeps those for a specific customer that may need them occasionally?

[PWN]

Are these correct? Restoration Supply.

 

 

[George K]

[1937hd45]

Somewhere there is a video of the nuts being produced.

[Jeff Hansen]

Does the term "marsden nut" apply to either a slotted or castle nut?  Or is that another type of nut altogether?

[wayne sheldon]

3 hours ago, Jeff Hansen said:

Does the term "marsden nut" apply to either a slotted or castle nut?  Or is that another type of nut altogether?

I wasn't familiar with the name, so googled it to make sure I knew what you were asking about. Those have slits cut down into them from the top. Either by machining or by pressing, the internal threads are slightly tapered. If using on a nice clean new thread bolt or stud, they may or may not be able to be started upside down. Starting from the "un-slit" end they start easily, and should become more difficult to turn as they run farther onto the bolt. The slits allow the narrowed end to "spring" out somewhat and in turn hold tight so that the nut doesn't loosen from vibration.

They were an improvement over earlier "locking nut" designs that usually had the sides "punched" inward causing a "burr" on the threads inside. The problem with the burr on the inside was that they often damaged the bolt threads badly enough that the bolts, and often the nuts, could not be reused. Sometimes, the damage to the bolt or stud was severe enough that the locking nut would eventually back off slightly and the damaged threads were not sufficient for the nut even with its burr to stay in place. The slots in the Marsden nuts tend to be more gentle than the punched burrs. However, they still have a tendency to damage threads, and still occasionally can work loose.

 

Personally, I don't trust them. I know several engine rebuilders that swear by them and use them exclusively on connecting rods. Me? I plan to stick with castle nuts and cotter pins.

[AHa]

I want to reply to my earlier post. My local bolt/nut supplier is a small company with nine locations in the southeast. They have warehouses full of bolts and nuts of all descriptions at each location and deal primarily in bolts and nuts and washers with a few other automotive fasteners. They have a counter out front where customers can walk in and buy one, two, three, or any number of anything they sale; there is no minimum. It is a real blessing to have this company 6 miles from my house.

 

Last year I walked in to ask for a course thread castle nut and was informed castle nuts only come in fine thread; slotted nuts come course thread. I tried a couple of other venues and found the same thing to be true. Obviously, some of you guys have different experiences. I know the SAE supposedly standardized threads on nuts but in my experience, with antique cars, you can find nearly every thread imaginable. In fact, some bolts and nuts on my 1989 Dodge Dakota are Metric. My experience has been there is no such thing as standard but this company claims slotted nuts come in course thread, so, there you go.

[Jeff Hansen]

18 hours ago, wayne sheldon said:

I wasn't familiar with the name, so googled it to make sure I knew what you were asking about. Those have slits cut down into them from the top. Either by machining or by pressing, the internal threads are slightly tapered. If using on a nice clean new thread bolt or stud, they may or may not be able to be started upside down. Starting from the "un-slit" end they start easily, and should become more difficult to turn as they run farther onto the bolt. The slits allow the narrowed end to "spring" out somewhat and in turn hold tight so that the nut doesn't loosen from vibration....

 

Thank you for that, Wayne!  I now understand the difference between the three types of nuts.

 

Jeff

[Frank DuVal]

15 hours ago, AHa said:

In fact, some bolts and nuts on my 1989 Dodge Dakota are Metric.

Normal. For every manufacturer in the US since the mid 70s.

 

Well, actually since waaaay back, since most spark plugs are metric (exception is pipe thread types) and the Schrader valves.

[wayne sheldon]

4 hours ago, Frank DuVal said:

Normal. For every manufacturer in the US since the mid 70s.

 

Twenty years ago, I had a 1988 3/4 ton Chevrolet Suburban (my then tow vehicle). The day came when I needed to replace something (I think it was the power steering pump?), which I don't think had ever been removed from the vehicle before.

There were five different bolts holding that silly thing onto the brackets and  motor. And it took five different wrenches! (Not counting the hydraulic fittings.) Three of them (if I recall correctly?) were USA threads and heads, while the other two were metric! All five different head sizes!

[Gary_Ash]

Marsden nuts:  I think the original Marsden nuts had tapered flanks so that a tool, almost like a socket, placed over them and tapped down would squeeze them against the bolt threads.  I did a Google search for the tool but came up empty.

 

Edited May 25, 2023 by Gary_Ash (see edit history)