Slat grill Top bow pivot Thumb screw

[Ladislav]

What is the correct length of Slat top bow pivot Thumb screw ? The diameter is 5/16"-24NF, right?
Thanks, Lad.

[Chuck Lutz]

Yes, they are 5/16" NF but I don't have one to measure. However, I see no problem in using the later 3/8" NF thumbscrew to make one....turning it down and threading it should be possible. As far as the LENGTH of the 5/16" compared to the 3/8" goes...I see no reason to suspect that would be any different. Just be sure you have an original 3/8" and not some out-of-spec piece of repop crap to do that transformation with!

[cor]

I think you mean this. Early thumb screw, brass, length 0,75 inch (unf)

Cor

[Chuck Lutz]

Except.....neither Ford nor Willys used a BRASS thumbscrew. Those are repops or French Army or something. So I wouldn't count on the length of the threads to be correct either!

...and, if the pivots are marked A-3719 then they would have been 3/8" NF from the factory....so again, if the pivot is brass it is not Ford/Willys.....and if it is 5/16" NF it should be marked A-2901 and not A-3719....

[cor]

The pivot is original, no changes made afterwards, No Copy, I am not sure about the screw but the length fits perfectly and that is what the question was about.

[Darcy Miller]

Chuck, a little clarification.
Thumbscrews:
From the original Willys drawing the thread for the Thumbscrew is 5/16 – 24 and then changed to 3/8 – 24 with notation, I will try to find a clearer drawing to check actual dates of the change but one would assume it changed when the thread in the pivots changed.
Pivots:
From the original drawings, the pivots except for the very first are always marked A-3719 because A-3719 is the casting number not the pivot part number. The A-3417 was added to the drawing 3/4/41.
The drawing states the following:
A. ASS'Y #A2901 CONSISTS OF ASS’Y #A3719 PAINTED LUSTERLESS OLIVE DRAB. QUARTERMASTER’S SPEC E.S.4745.
F. ASS’Y #A-3417 CONSISTS OF ASS’Y #A-3719 PAINTED LUSTERLESS OLIVE FOREST GREEN (W.0. CO’S #A326).
A & F are the actual drawing change letters.
Change F refers to a Marine Corps number.
They refer to A-2901 and A-3417 as assemblies because in automotive production even painting a part turns it from a raw casting into an assembled part.
There is also change letter E referring to the Thumb Screw Thread that changed from 5/16 – 24 to 3/8 – 24 dated 3/5/43.
There is also a note on the drawing that the Pivot part # was AE-2901 before becoming A-3417.
The very early Top Bow pivots were marked A-2901 then the new casting was marked A-3719 and that change is dated 3/4/41.
The Top Bow Pivot casting part mainly carried the casting number A-3719 and the catalog part number was determined by the paint color.
All the drawings call up the material as Malleable Iron, I have never seen a drawing where Brass were specified.
M.V. Spares makes all their parts to original drawings where possible.
Hope this helps.
Darcy

[Chuck Lutz]

Hmm...

I would agree that the manuals I have show the PIVOT as "A-2900" and the PIVOT ASSEMBLY as "A-2901". However I have never seen a pivot marked with "A-2900" on it. I have seen many with "A-2901" on them and they were all 5/16" NF.

I have seen many with "A-3719" on them and none were 5/16" NF, they were all 3/8" NF.

I've not seen a part numbered "A-3417" before but I have an inkling that would be the BRACKET, PIVOT, THUMBSCREW and BOLT/WASHERS as a complete assembly. Perhaps someone with a Master Parts List can check if that is true?

In checking my GPW manuals...which basically are cloned from Willys manuals...

April 1942 GPW Parts Manual and the March 10, 1943 GPW Parts Manual lists:
GPW 1153142 - PIVOT - top bow A-2900 Quantity TWO
GPW 1151270 - PIVOT - top bow-assy. A2901 Quantity TWO...... (includes two 3/8" x 5/8" bolts, two washers, two lock washers, two oval head spring washers)

A separate listing for a thumbscrew:
355470-S2 - SCREW 5/16-24 A-2473

My September 1942 GPW Parts Manual lists:
GPW 1151270 - PIVOT - top bow assy. A-2901 Quantity TWO.......(includes two 3/8" x 5/8" bolts, two washers, two lock washers, two lock washers, two oval head springs)
355470-S2 - SCREW 5/16-24 A-2470

So....I checked the SNL....it lists:
GPW 1153142 - PIVOT - top, front bow A-2900
GPW 1151270 - PIVOT, top bow assy. A-2901 Quantity TWO........(includes two 3/8" x 5/8" bolts, two washers, two washer, two lock washers, two oval head springs)
GPW 1150498 - SCREW, thumb, 3/8" x 24 NF (top bow) A-2214)

Now...from your post, the item "F" is an ASSEMBLY for USMC jeeps (A-3417) so that means the PIVOT assembly A-3719 is painted Forest Green and becomes assembly A-3417. Let's leave the USMC numbers out of this for the time being...

So.. According to the SNL, if you needed a 3/8" x 24 NF PIVOT you would ask Supply for an A-2900 or a GPW 1153142 if I follow the SNL nomenclature parts numbering system. While that part number is shown on page 275.....it is not shown in your post above as a viable part number.

Now, as to the A-3719 being a "casting number not the pivot part umber"....while the A-3719 is not listed in the SNL, the A-2900 certainly IS listed! You can't have it both ways, one being a casting number and one being an actual part number you can find in the SNL! To me...both those are Willys part numbers!

Furthermore....your post says "F" ASS'T #A3417 CONSISTS OF ASS'Y #A-3179 PAINTED LUSTERLESS OLIVE FOREST GREEN".....from that I take it to mean "Forest Green" is USMC paint spec. yet the date for that "F" notation is 3/4/41? Sounds a little early for a USMC contract but some Willys guy can comment on the date of the first Willys contract better than I can.

So....what is my take on all this? Confusion reigns Supreme here yet again!

If one simply believes that an "A-2901" or any other part on an MB is the WILLYS PART NUMBER which is found in the manuals as is "A-3719" and notes that the two items are different in that they are a finished part, one with 5/16" NF thumbscrew holes and one with 3/8" NF thumbscrew holes...they could easily enough go to any Supply Depot and order the one they needed without having to get the pivot, bracket, bolts and washers.

My theory is this....they screwed up. The plain, bare PIVOTs were the A-2901 and the A-3719. The ASSEMBLIES were A-2900 and perhaps A-3417.

You posted that the very early pivots were A-2901 and the change to the A-3719 was dated 3/4/41....March, 4th, 1941? That would mean by the time Willys got around to making the MB, there should have been NO jeeps with a pivot numbered A-2901 on them.

You posted the pivot CASTING numbers were mainly A-3719 and catalog number was determined by paint color....Yet AFAIK, the SNL does NOT list any USMC Forest Green painted items and yet they list the A-2900 PIVOT by itself and the A-2901 as an "assembly"?

Again...if one steps back from the paperwork and looks at what was produced and the markings on those items....the paperwork makes less sense the more you look at it....unless you reverse the part numbers and go with A-2900 as the assembly and A-2901 as the pivot by itself for the 5/16 x 24 thumbscrew and A-3719 as the pivot by itself for the 3/8 x 24 thumbscrew!

Nabholtz notes that in March 1942 at MB 125809 Willys changed to a top bow pivot with 3/8" NF threads....

I'm not doubting your reliance on the Willys drawings....I'm doubting the veracity of the drawings themselves.

[Darcy Miller]

Hi Chuck,
You have spent some time on this.
I don’t doubt you “have seen many with "A-3719" on them and none were 5/16" NF, they were all 3/8" NF”. Unfortunately, that statement indicates you have not seen very many, I have seen many originals and even NOS MB A-3719 marked pivots that were 5/16-NF, indeed I received another original top bow assembly yesterday that still has the original pivots attached with 5/16-NF thumbscrews.
Ref your “you can’t have it both ways” you are incorrect, any base part that receives an additional process, even painting, especially different colors can and usually does get new part numbers allocated, that is a manufacturing norm, take that from a guy who spent the past 50 years in manufacturing.
As for relying on the veracity of original drawings, I do.
I offered the information, I am pleased to see it generate discussion, it can be taken any way you like and the facts can be massaged to comply with any opinion.
Good luck, I will leave any further discussion to others.
Darcy

[Joe Friday]

[Chuck Lutz]

The problem is...

Looking at the LOPN 1, it lists the following:

A-2900 Top Bow Front Pivot

A-2901 Top Bow Assy, Pivot.

Logically one might say that the A-2900 is just the pivot and A-2901 is the assembly with the hardware attached to it.

I would ask Darcy how many A-2900 pivots he has seen in 50 years. The supposition that an "additional process, even painting, especially different colors usually does get new part numbers allocated" is interesting.

Therefore, does a Forest Green pivot magically change it's CASTING number when it gets painted? Uh...No...
Does a pivot magically get it's CASTING number changed when it gets changed from 5/16" to 3/8"? Uh...Yes...that is a manufacturing norm.

Like I said...the A-2901 and A-3714 are WILLYS part numbers, not the mfgers part numbers. Willys changed the number for some reason...Hello, d'ya think it was because they changed from a 5/16" to 3/8" t'screw or was there some other reason to come up with a NEW WILLYS PART NUMBER.

Again...the LOPN 2 seems to list the A-3417 along with many other parts that seem to differ from standard MB parts only because they were possibly painted Forest Green so I don't think that number is relevant to the discussion. (See Body, Outside Rear Corner handle on LOPN 2 and LOPN 3.....same item, different A-xxxx numbers....and those on LOPN 3 are found in the SNL while those on LOPN 2 are not....probably because they are for a different application (painted Forest Green for the USMC perhaps?)


hey, I'll be the first to admit the numbering of the top bow pivots makes little, if any sense if you wanted to order one from Supply.

[George Hollins]

Getting back to the thumb screw, all of my parts manuals show the following part numbers:
A-2473 thumb screw top bow
A-2214 thumb screw windshield

However, I see these part numbers reversed on parts supplier sites and even in the above text.
What is correct?

George

[Chuck Lutz]

George...

Remove one of the thumbscrews from the windshield-to-cowl mounting...that is the A-2214. It is a 3/8"NF.

It has a SHOULDER on it that the hole in the windshield arm fits through to allow for the thumbscrew to be TIGHT and at the same time the windshield can go up/down.
That provision was not needed on the top bow thumbscrews. That will identify them for you...by the say, the photo you posted shows a thumbscrew WITHOUT that shoulder on it so it would be the earlier version. Therefore the tag number on it is correct.

[Ladislav]

OK,

and what was the original length of pivot 5/16" NF thumb screw..??

thanks.

[Christophe Chevalet]

Hi Ladislav
Regarding the lenght for the A-2473 thumb screw top bow please look these pictures I made yesterday.
I join some pictures about the top bow swivel take out a slat grill is south of France is 5/16 UNF and marked A-2901.
But I have already saw in my hand an top bow swivel A-3719 with 5/16 UNF.
Anyway thanks for these interesting information
Ladislav, one question? Why you want the lenght of this thumb screw? It is for reproducing I suppose?
But Darcy Miller from MV Spares made already great reproduction of these thumb screw?
Christophe

[Ladislav]

Thanks Chritophe,

nice pics and clear answer on my question. I know about these from MV spares and I am not going to reproduce them. The reason is I hade purchased in past NOS 5/16" NF thumb screws, these are 3/4 long, so wanted learn if these are ok for my aplication or I will cut them down... It looks the correct length is 1/2".
Christophe, your ones on pics are originals, right?
Thanks!

lad.