MAC 65522 Specialty Tool – What is it for? An aviation tool?

[Leviton]

Found this last week. Trying to figure out what it is used for.

It is 15.6-inches long, has a 3/4" twelve-point box end on one end and a 0.476-inch diameter hole on the other end. Looks like it might once have been cad plated.

Stamping is:

MAC
SABINA, O.
U.S.A.
65522

and

3/4 (at the box end)

I looked in the MAC catalogs on ITCL and could not find it.

I found a couple of these wrenches on eBay that look the same but don’t identify the purpose of the tool.
However, there was one ebay ad that shows a similar one and says it is a WRIGHT AVIATION WRENCH TOOL USAF (see thumbnail below). Their version is a NOS that does not seem to have a “WRIGHT” marking but does have the same part number as my MAC version. Even though I don’t always trust eBay identifications, the seller does list quite a few aviation tools.

I plugged the part number into the current Wright website and came up empty. I checked the 1956 and 1989 Wright catalogs on ITCL with no luck. Most of their part numbers only have 4 digits.

Any ideas?

(I thought about posting this in the Mac thread, but since it might be made by more than one company, I figured I’d post it here first and then if it gets identified I’ll also put it in the Mac thread.)

Thanks.

 

[BrandonV]

It's a cylinder base nut/hold down wrench. The hole is for a turning bar.

 

[BrandonV]

Here is a catalog image from a P&W listing on eBay.

 

[BrandonV]

 

[Private Lugnutz]

...there was one ebay ad that shows a similar one and says it is a WRIGHT AVIATION WRENCH TOOL USAF (see thumbnail below). Their version is a NOS that does not seem to have a “WRIGHT” marking but does have the same part number as my MAC version.

The seller may have been referring to Wright, the aviation company, of Curtiss-Wright, and Wright Aeronautical, not Wright Tool & Forge. I am skeptical, though. All Wright aircraft tools had a 5-digit 8xxxx series number in the 40's. I suppose it could be later. But I suspect they are just guessing.

 

[Leviton]

Here is a catalog image from a P&W listing on eBay.

Thanks Brandon! You nailed the type of wrench. How did you know this? I'm just curious because am always trying to improve my sleuthing skills and I'm trying to figure out what else I could have done.

It looks like the PWA 186 had a 9/16" service end. Some initial searching shows that 3/4" wrench sizes were used on Lycoming and Continental engines.

 

[Leviton]

The seller may have been referring to Wright, the aviation company, of Curtiss-Wright, and Wright Aeronautical, not Wright Tool & Forge. I am skeptical, though. All Wright aircraft tools had a 5-digit 8xxxx series number in the 40's. I suppose it could be later. But I suspect they are just guessing.

Thanks Lugz. You saved me from going down the wrong rabbit hole. I'm going to keep trying to find some documentation related to the 65522 number.

 

[Provincial]

This sort of wrench was commonly made by various tool companies in the 1930's and 40's both for both the engine manufacturers and under their own names. Often, it was used for cylinder base nuts on air-cooled engines, but also for other, hard-to-reach applications. These were intended for field repairs, since the use of a "Tommy Bar" did not allow precise torque control. Even torque on cylinder base nuts is absolutely necessary to avoid "progressive stud failure" that occurs when one nut is looser than it's mates and transfers part of the load it is supposed to carry to them. These become overstressed, and eventually fail, breaking off others like a zipper.

The 3/4' opening implies use on 1/2" threaded fasteners, which puts the use of this wrench in an interesting place. Post-WWII Lycoming engines used this size wrench, but by then, it was required to use a torque wrench on these nuts, because proper torque was critical.

Essentially, this type of wrench is useful for reaching nuts on flanges that are obstructed for access. The "Tommy Bar" design was superseded by square drives in the 1940's, so this is a holdover from earlier days.

MAC specialty catalogs are likely the only chance to identify the use for this wrench.

 

[BrandonV]

This sort of wrench was commonly made by various tool companies in the 1930's and 40's both for both the engine manufacturers and under their own names.

Thanks Brandon! You nailed the type of wrench. How did you know this?

Just like old aircraft. That wrench above looks just like the P&W one used for the engines on the B-24 Liberator.