• If you like antique engines, vintage tractors or old iron machinery, register and join us. When you register on Smokstak, please give complete answers and fill in all blanks. IF YOU ARE ON WIRELESS, GIVE YOUR CITY AND STATE! NO ZIPCODES! We get hundreds of applications, so there is no time to deal with missing information.

Old vs New tube compression fittings

JoeCB

Subscriber
Last Subscription Date
02/28/2019
So what is going on here? On 3/8" tubing compression fittings, the old fittings have .531- 24 threads (17/32") and the new ones that I have are .558-24 (9/16"). Are these different classes of fittings or just old vs new standards? The old fittings are on a 1916 vintage marine engine water coolant lines, 3/8 brass tubing with compression ferrels.

Joe B
 

JoeCB

Subscriber
Last Subscription Date
02/28/2019
I 'm just bumping this back to the top...Gee, it's not often that a question goes unanswered for a week here on the Stak...
Any ideas on this one?

Joe B
 

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
many fittings were made to manufacturers specs, as there was no standardization of threads and diameters until the late teens/early 20s. Trying to mate up fittings from different manufacturers and even ones made by the same manufacturer can be dicey at beat. On my engine club's Oil City/South Penn engine, you cannot even swop nuts and bolt locations, as each nut and bolt have slight variations! This was especially true of the bearing mount bolts - the bolts must be installed in the hole it came from, they cannot be swopped to another location!

I ran into a similar problem as yours on 2 engines I worked on - one an IHC M, 3 HP with undershot trip, and an undated Charter-Mietz 4 HP Horizontal engine. On both engines, 3/8 compression nuts, fittings and ferrules do not match fittings made in relatively modern times. On the Charter-Mietz, even the pipe threaded fittings were propietary - they were not US Pipe thread:eek: It took a lot of time searching in flea markets for finding closely matching fittings (not the modern squared off Home Despot stuff). Even finding bending temper 3/8" OD brass tubing was a bear! I never did find the pipe thread fitting I needed for the C-M, I had to solder the fitting internally, in order to make it usable.

If you absolutely need to re-use the fittings you have, try using a soft solder to make the joint, wiping the solder lightly into the threads and tightenning the ferrule to give the appearance that it is tight. if your ferrule or nut is split, clean in muriatic acid and solder, seal pipe to fitting as described and install nut with crack to hidden side. Not original, i know, but it will be functional.
Andrew
 
Top