Hello Jeffrey M and welcome to the forum!

The thread size for both nuts should be 5/16". 7/16" is the wrench size needed for those nuts.

Keep in mind, that a "normal" 5/16" nut will use a 1/2" wrench. However, these Ludwig nuts have a narrower profile than a normal 5/16" nut, so they use a 7/16" wrench, (which is used for a "normal" 1/4" nut).

The best way to replace the nut (if you have a vice and workbench) is just to cut a 5/16" coupling nut in half. Then you can replace both nuts and be done with it. A 5/16" coupling nut is narrower than a normal 5/16" nut, so it will use a 7/16" wrench. A new 5/16" coupling nut should be less than 50 cents at your local hardware store.

Double check your thread sizes, but that's generally the simplest solution. While you're at it, you may want to replace the carriage bolts as well (the screw with the smooth, rounded head and a square shaped "collar" underneath the head that the nuts thread on to). Sometimes those can get worn or bent from years of use. Take the carriage bolts with you to the hardware store to double check thread size and length. I am guessing they are both 5/16" thread, and in your case one had a "normal" nut and they other was a coupling type nut.

V

Thanks V,

As it turns out the two carriage bolts are a different diameter as the upper and lower holes are different sizes. As you guessed, the threads are ratched up and one is bent so off I go for two carriage bolts and 7/16 nuts. I like your idea of cutting one down but would prefer to buy without having to get more than needed.

I appreciate your input.

Now to find a source.

Great info there V.

Thanks for sharing.

Wayne

I repeat:

The nuts/screws are NOT 7/16". They should be 5/16". The WRENCH Size is 7/16". If your carriage screws are two different sizes, one is most likely 1/4" and the other is 5/16". The squares that the carriage bolts fit into will most likely be slightly different in size too. I assume the bigger (5/16") size is on the screw that actually adjusts where it is on the rail (not the angle/L-arm adjuster). Again, take the old carriage screws to the hardware store with you, so you can be sure of the thread size and length.

That's the case for me on a few MIJ (Made In Japan) kits. I made everything 5/16" (instead of 6 mm) just so everything would be uniform, and so that my Ludwig consolette hex wrenches would work. It's not terribly difficult to slightly enlarge the square. Five minutes and a file equally spent on all four sides of the square should work.

If you want to stick with the two different sizes (and not do any modifications), consider replacing the nut that adjusts the angle and L-arm with a stop or locking nut. If it's 1/4", it will use the same 7/16" wrench as the 5/16" screw with a coupling (Ludwig) nut, because again, the Ludwig coupling nuts are smaller in diameter than normal, so that's why a 7/16" wrench will fit both a 1/4" "regular" nut and a 5/16" coupling nut.. It's much more secure that way, and usually, once your angle is set, you typically don't adjust it that often.

You can buy the 5/16" hex nuts on ebay for a few dollars plus shipping. Or you can just cut a 5/16" coupling nut in half and have two for less than 50 cents. Better to have one extra for some small change (less than 25 cents each) than to pay 20 times as much (or more once you factor in shipping) to get one from ebay.

V, Good clarification. I was able to replace both sets for $5 from a local specialty supplier. I chose stainless over coated, based upon appearance. One caution is that stainless has a low strength rating. I utilized the original washers as they were a bit thicker than the replacement version.

For anyone interested, here are the size spec's

5/16-18 x 1-1/2 UNC Carriage Bolt

5/16-18 UNC Hex Nut

1/4-20 x 1-1/4 UNC Carriage Bolt

1/4-20 UNC Hex Nut

Both of these need a 7/16 wrench or the drum hex key.

The earlier had the two different size carriage bolts and hex nuts, I think they came with both the same larger size carriage bolt and hex nut in 65 on.

Thanks Ludzil

Jeffrey,

Vyacheslav gave you great advice.

Just one note: keep the originals. Should you decide to sell your precious set, a purist will want all original hardware.

Josh