3/4 inch thread on ship’s steering wheel – determining and recutting

3/4 inch UNC thread on ship’s steering wheel

In this blog article we would like to report on a very special request from one of our customers. It is about the ship steering wheel thread.

The customer had the following problem: On a boat, the black plastic nut that was attached as a counter to the threaded rod from the steering wheel had broken off.

A new hexagonal lock nut for the ship’s steering wheel was needed. But this time it should be a durable material. No more plastic! Preferably stainless steel. But first the thread had to be determined.

Thread determination: ¾ inch thread on ship’s steering wheel

The thread determination research revealed a UNC ¾-10. The nut was then purchased from a specialty store. But when the customer tried to screw the new lock nut onto the steering wheel thread, it did not fit. Had the thread been determined incorrectly despite our instructions?
This is where the GSR team comes in…

Thread determination by GSR-Germany

The old as well as the new hexagon nut were sent to us for thread determination. On site, we finally had more possibilities to determine the thread with our measuring equipment and also to test it directly. And indeed: The thread for the steering wheel was a ¾ inch UNC thread with a pitch of 10 threads per inch (2.54 mm) and a roughing diameter of approximately 18.89 mm. The thread determination of the hex nut for a steering wheel was therefore correct.

But why didn’t the nut fit on the bolt of the steering wheel?

On closer inspection, we noticed that some threads of the nut were crushed. After consulting with the customer, we then re-cut the internal thread with the appropriate UNC 3/4″ finish cutter at the factory free of charge and sent it to the customer. Problem solved and the customer was happy.

The thread determination is only one aspect. Sometimes simply recutting a defective thread is all that is needed. Similar to our blog post on the refrigerator foot screw.

How to recut a thread – Ship’s Steering Wheel Edition

As a reminder, we have compiled below how you can easily recut a thread and which threading tools you need for this. Of course, the prerequisite is that you have already determined the correct thread. We explain step-by-step what to do using our example lock nut for the ship’s steering wheel. Let’s go!

This is what you need to recut an internal thread!

To recut the thread, you will need the following threading tools – similar to those used for cutting:

The workpiece, in this case the hex nut for the steering wheel.
A vice for clamping the part
A pair of protective jaws, optional to protect the workpiece and the screw jaws.
The appropriate adjustable tap wrench – here in size no. 2 W 5/32″ – 1/2″
The appropriate finish tap or short machine tap UNC 3/4″ or finish tap UNC 3/4″
Lubricant / thread paste

If you are missing some of these tools, we have provided links to our store. If you need to determine the thread first, you will also find special thread determination sets in our store.

Instructions for recutting an internal thread

How to rework or recut a thread is explained step-by-step in the following instructions:

Roughly clean the workpiece and securely clamp it in the vise.
Clamp the single-cut tap in the adjustable tap wrench.
Wet the threaded tip of the single-cut tap with thread paste.
Position the tap with the clamped tap plumb against the drill hole and screw it in lightly
Carefully turn clockwise and recut the thread. Turning back to break the chip is not necessary when re-tapping.
As a test: screw in the counterpart (here: the pin of the ship’s wheel)

Done!

If the thread jams a bit, repeat the thread recutting process.

In some cases, both the internal and external threads are damaged. In this case, you must also recut the mating part. However, it is easier to detect damage on external threads than on internal threads. Detailed instructions for recutting an external thread can be found in the article on the refrigerator base screw.