Drag link thread size
 

What is the thread size on a 1936 Ford drag link end or coupling sleeve? Thanks, Art

Re: Drag link thread size
 

From memory I think it is 11/16-18. It is a non-standard thread but taps and dies are available. Left and right hand threads are used.
Hopefully someone can confirm.

Re: Drag link thread size
 

It is 11/16-18. Speedway has the taps. I made the tie rod and drag link for my hot rod from 7/8 OD x 1/8 wall steel tubing. You should be able to get that from a local metal supplier or Amazon.

I had a problem getting the tap started concentric with the tubing. I solved that by cutting a short piece of the tubing (about 3/4" long) and pressing a similar length of 1/2" copper tubing used in house hold water systems. The ID of the tubing is perfect to hold the shank of the tap. I passed the end of the tap through the new bushing and C clamped it into the end of a length of angle iron. I then clamped the piece of tubing to be tapped into the angle iron and the tap was perfectly aligned.

Re: Drag link thread size
 

Taps and dies this thread both L & R hand thread are available on Amazon.

Re: Drag link thread size
 

I've NEVER understood why Automotive engineers use oddball diameters and threads like this??? Why not 5/8-18 or 3/4-16? Same with 7/16ths and 9/16th diameters!!! Stupid, ALL not used in the civilized industrial world!!

Re: Drag link thread size
 

Pete: Thanks for sharing your thread alignment technique.

Re: Drag link thread size
 

A lot of companies used "House, or Captive" thread sizes so that when you needed a replacement part, you would buy from them. Brown and Sharp used the same system, but used standard thread sizes but higher thread profiles. I worked for Merrow Machine Company, a manufacture of high speed over-seam industrial sewing machines. All of Merrow's threads were their own sizes, and when people needed replacement screws there was a lot of profit to be had.

Re: Drag link thread size
 

Here is my version of a tap guide. As @PeteVS mentioned is important the tap goes in straight when tapping the deep holes when making tie rods and drag links.

Used it for many years until my son got a big lathe; now we just chuck the tube up and put the tap in the tailstock. A whole lot easier on the shoulders.