Thread help

We are restoring a 1903 Cadillac and are trying to make a part that fits a thread on the end of the main crank. This thread measures up at 1" x 16 tpi.(It is in poor condition). I have machined a 1" x 16 tpi thread on a lathe but the diameter was too large, so I have nugged the lathe cross-slide in, untill the thread fits. It now comes out some where nearer 31/32" x 16 tpi. A look through the engineering books on this side of the Atlantic does not show an obvious thread type, the nearest I can find is 1"-16 UN. But the UN series did not come in until 1948.

I have been told that there is/was a "American National 16 Series Thread" but can't find any data. Can any of you Guys help.....Also is the thread angle 55 or 60 degrees?

What threads did Cadillac use in 1903?

Thanks.....ttfn.....Alistair

Reply to
Alistair Ross
Loading thread data ...

Have you tried 1" x 16 with the tops of the thread cut off? I doubt the crank was made to fit sharp threads.

Reply to
Nick Hull

Is the engine made by Cadillac?

25mm x 1.5mm pitch is close to what you're making.

John

Reply to
John

Machinery Handbook, 22nd Edition Table 3h is for 16 series thread Basic Major Dia 1.0000 Basic Pitch Dia 0.9594 Minor Dia Ext 0.9233 Minor Dia Int 0.9323 Lead angle at Basic Pitch Dia 1Degree 11 min Joe

Reply to
Joe Gorman

I'm a bit unclear, the crankshaft has a female thread and you are cutting a bolt to fit inside?

You are making the assumption that a thread cut in 1903 was cut to a standard. A lot of things did not get stadardized until later. Since the Cadillac is US, I'd bet on something in whole fractions, ie 1" x16TPI would be reasonable but maybe not 60 degree angle. If indeed you are doing a bolt, a 55 degree thread angle will give you the issues you are seeing. Here is an interesting chart, can't vouch for it's accuracy:

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I'd run the current bolt in as deep as possible to verify that you have

16 tpi, then try another at 55 degrees.

Alistair Ross wrote:

Reply to
RoyJ

================== Can't help you with which thread Cadillac used in 1903, but there is indeed a series of American National threads that don't change by diameter, i.e. 8N/12N/16N etc. These were used in boiler construction and now are mainly seen in the petroleum/chemical industry and the oil fields. Thread is almost certainly a 60 degree included angle. Be reminded that in 1903 the sharp V form was still in use, and you may have a 1 inch 60 degree sharp v thread with the tips gone.

See:

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Good luck on your restoration.

Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

Reply to
F. George McDuffee

So, despite the best practice of Joseph Whitworth (yes that limey) some 60 years before, some dimwit thought a sharp v thread was a good idea? I guess it must be an American thing :)

Reply to
Mike

==================== As I read over the responses, all of us are exhibiting MAS [Male Answer Syndrome]

There is absolutely no way to tell what thread you have. In

1903, proprietary threads were popular to insure the company would get all the repair parts business. For all any of us *know* this was a 63/64 X 15_1/2 TPI 57_1/2 degree thread, and the engine before and the engine after may have had a different thread.

You safest course, assuming you don't want to drill and helicoil to a standard size, is to use one of the kits to get an accurate casting of the female thread so you can see what you have, possibly using an optical comparator.

see:

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Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

Reply to
F. George McDuffee

Also keep in mind that anything bolted to the end of a crankshaft might have battered the original threads into a new and unique form.

Reply to
Jim Stewart

I think you will find the US equivalent of Whitworth was the Sellers thread form which did have a sharp root and crest IIRC. Bad for stress raisers. I have seen it mentioned that in practice due to manufacturing issues, tool wear etc the root was often not sharp.

Reply to
David Billington

I am assuming that this is a tapped hole. Buy some low melting point alloy that is used in chamber casting firearms and make yourself a copy of the internal dimensions for measurement.

Wes

Reply to
clutch

Wes and others have the right idea. There is nothing magic about one pitch/diameter compared to another. I'm not trying to say that a

1/2-13 thread will perform the same as a 1/2-20. What I'm saying is that the threads listed in various publications are just standardised threads that are generally used. This makes it easy to buy threaded fasteners. It also makes it easy to measure the threads and to spec. them when custom parts are being made because everyone is using the same standard. Bearings are another common item that mostly conform to one standard or another while at the same time are also made in smaller quantities for certain needs or wants. But threads are often made to an internal company spec. to meet production needs. These needs may be the desire to have a propietary thread so replacement parts must be bought from the original manufacturer. Or the thread may be a special thread like the ones used for compressed gas cylinders to prevent the wrong fittings from being used for safety reasons. In old equipment it is common to find threads that don't match any standardised thread systems. When I'm asked to make a matching threaded part I check the thread to make sure everything will fit. There are several methods to measure the profile of these internal threads. If you have the time you can order some low temperature melting alloys, as others have suggested, for 20 or 30 bucks and use it. This may be awkward to use depending on whether the engine is in the car or not. Another thing that works well is to use epoxy putty and press it into the threads. Make sure to oil the threads! You don't need to fill the hole completely. You can fill the hole just over halfway. This will make it easier to remove. Since you can measure the ID of the hole then you really only need to measure the pitch and the thread form. After removing the epoxy or whatever you should cut through the stuff and then file or sand it to get a good flat surface. This surface should be such that if it was extended as a plane it would run through the center of the thread diameter. Then you can see the exact thread form and if your gauge was made to extend all the way to the back of the hole you will be able to examine the conditions of the threads all the way back. If the threads are really crappy, and if the restoration allows it, you can buy a 1-16 tap and tap the hole out slightly larger than what it is now and you will know for sure what thread to cut. ERS
Reply to
Eric R Snow

Ask and ye shall receive. =============================

Data From American Machinist's Handbook7th ed. (1940) from table 15- American National 16-Pitch Series

[Basic Diameters in Inches]

Major dia. 1.0000 Pitch dia. 0.9594 Minor dia. 0.9188

[Thread Data]

Helix angle at basic pitch dia. 1degree 11 minutes

Basic area in Sq. In. of section at root of thread, pi K 2/ 4 0.6630

Notes: Pitch, p = 006250 inch(*); depth of thread, h = 0.04059 inch; basic width of flat p/8 = 0.00781 inch; minimum width of flat at major diameter of nut, p/24 = 0.00260 inch.

==============================================

Previous to this Table, it indicated that American National form of thread uses 60 degree threads. It has some other formulas and what not but I suspect the above was what you had asked for.

(*)I will note that I double checked the printing in the notes section, there was no decimal point in this entry, so I typed it as it was printed, but I suspect one may be implied.

Reply to
Roger Shoaf

I think the ole' boy who threaded the crank at the factory "screwed" up---so he made a nut to fit it instead of scrapping the whole Crank we're back in 1903, remember ! Jerry

Reply to
jerry wass

I believe the '03 Cadillac was an interchangable part car and one of the first. The first automotive threading standard was ALAM (Assoc. of Licensed Auto Manufacturers), those that bought the Selden patent. ALAM threads are 60 degree included angle threads but tend to be two TPI greater pitches then SAE. i.e. 5/16"-20 instead of 5/16"-18. That said, earlier manufacturers used some odd sized threads. I have a threaded radiator cap on my early White the is 2-1/32" - 16TPI. I would query the members of AACA (Antique Automobile Club of America) as I am sure some of them will know all about your Cadillac. They have a great website but you will have to Google it as I don't have the URL on my laptop and I am 3000 miles from my destop. Leigh at MarMachine

Reply to
CATRUCKMAN

A big THANK YOU to all you Guys for your help and ideas. I suspect that the thread started life 1-16 but now after years of people mucking about now coincidently measures 31/32-16 and parts have been made to match this. The OD measures 0.963". I have cut a test part to 31/32-16 and its fits a sweet as a nut (pardon the pun). If the car gets to Brighton I'll let you know.

Reply to
Alistair Ross

snipped-for-privacy@AOL.COM wrote: .....as I don't have

What - you don't have your favorites file on a thumb drive when travelling? (sound of gentle 'slap' 'slap')

Ken.

Reply to
Ken Davey

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