Nerdy wheel question

[Christoffer Ahlfors]

It appears that the screws and nuts on the wheels on Bovington's tiger 131 are different size. I have come to the conclusion that the nuts are 32mm and the screws only 25,6mm. A difference of more than six millimeters! Am I on the right track here?

There flat ring where the screws and nuts sit, has its edges very close, so a slight size error will be quite noticable.

I managed to stock up on screws and nuts with a s/w of 5,35mm, which is extremely close to the 5,33mm that corresponds to 32mm in reality. So far, so good, but the screw heads would need to have a s/w 4,27mm. It has not been possible to find a reasonable match of this head size - especially since I have already tapped for M3...

So, I figured maybe I could machine the 5,35mm screws down to size?

This is the result. One machined screw of 4,27mm and the other 5,33mm from the bag. The difference is quite visible, but is it right?

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[Adrian Harris]

A 7BA bolt would be 4.37mm across the faces. A 6BA bolt with a "one size smaller" head would have a 2.9mm diameter thread but a 4.37mm head.
I don't know if it would fit an M3 thread though. Maybe with enough Loctite

The other question is whether the bolts in the Tiger wheels are still the originals from 1940s or more modern ones which have been swapped out at some time. They only seem to have been seriously interested in restoring it from 1990 onwards.

Three of the bolts in this picture have RIBE 8.8 markings on the heads, the other three are unmarked.

Adrian.

[simon_manning]

Remember Adrian we had 7BA Hex heads with a 3 mm Thread made at EKP, for general use on the models, they give a better visual effect and are more to scale, wheels especially, The bolts with numbers on are probably not original, regards simon.

[Christoffer Ahlfors]

Thank you Adrian for this perfect photo!

It makes me think that my machined screw is too small. I got the 25,6mm from a full size to 1/6 conversion chart that was published here some years ago. When I look at DIN and ISO thread tables, M18 s/w 27mm is a possibility. That would be 4,5mm in 1/6th. I will try that and see if it looks better.

I agree with the danger of relying on museum vehicles. It's quite likely that the screws have been replaced, but with a different thread? That would have been so much more work than ordering M size screws from abroad, if not available locally. My bet would be that some of the screws are indeed new, but with the same M size and a head size similar to the original.

Just for fun, I tested a BA6 screw in an M3 nut. It works, but is very loose. I would have to go through the same machining process anyway, so I might just as well continue with the M3 screws I have enough of. Besides, they are stainless....

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[Christoffer Ahlfors]

The bolts with numbers on are probably not original

I was thinking that, too. Suits me well, because I am unable to replicate those numbers...
Thank you!
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[Chris.Marshall]

Hi All,

I can't find the specific date..... BUT, the bolts marked 8.8 are to the ISO material standard ISO-898-1 - I can easily trace previous versions back to ISO/R-898-3 - in 1969 - That is as early a I can easily find. Suffice to say, my understanding is that any bolt with a material grade marked on the head is post war... Unless anyone here knows of earlier standards on this.... Being a true NERD too... I get very interested in standards.....

As to model bolts... The most accurate patterns for tis period are the machined BA bolts, model engineering standards like those supplied by EKP and similar. And very useful are the " one size smaller " where a 5Ba thread has a 6Ba head size. I use this almost exclusively on my large scale locomotive work...

Interesting thread.... Lets see where this one goes

Chris.

[Christoffer Ahlfors]

Suffice to say, my understanding is that any bolt with a material grade marked on the head is post war...
Interesting thread.... Lets see where this one goes

Thank you Chris!

If I read your mind correctly, this thread is taking the direction you just predicted: I just couldn't help trying s/w 4,5mm (M18 s/w 27mm) to the right... And I adjusted the photo angle to better match Adrian's photo of the prototype, for easier comparison:

What do you think?

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[Jerry Carducci]

Ahhhh scale bolts, one of my favorite topics! For years I've spent a substantial amount pursuing nuts and bolts that 'look right'.

First it was for my 1/10 scale work- finding nuts and screws for so many Panther models, some 768 per tank just for the outer circumference (why did I begin with Panthers!) and first using Metrics, then SAAE then reverting to metrics once reliable sources of SAE types dried up. They cost a fortune.

I thought once I made the leap to 1/6 the screw issue would be a thing of the past... but noooooo! I have set up my indexing head on my mill with a fixture so I can mill down the heads on commercial screws so they 'looked better' to me. Madness.

My one consolation is that the late J Littlefield once told me sourcing proper nuts and bolts for his Panther's wheel rebuilds was a disproportionately expensive process...

I agree with the others' assessment that stamping (ISO, IATF, SAE, ASTM, ASME) standard identifiers on bolts is a relatively recent development. I won't lose sleep over that one. Perhaps it matters if you're building a modern machine model.

I also agree that museum vehicles are not always the best source of bolt and screw detail. Even out here I've seen some hideous misuse of modern bolts as nothing else came to hand.

Jerry

[Bernd Schöllhammer]

It is very bad if you use Allen or Phillips screws in the visible area on WW2 tanks
Bernd

[Christoffer Ahlfors]

Thank you Jerry!

I was worried that I might be a real nerd, but now I realize that I am only a fraction of a nerd (1/6th maybe?). Sure feels better to be more of a moderate kind (cough, cough!)!

While waiting for opinions on size (is the bigger one actually better looking?), I am troubled with the fact that the chamfer on the real thing is circular, while mine was hexagonal. My primary purpose was to remove the burrs, as not to get splinters in the skin. I have heard, that can be a real problem... My deburring tool is 45 deg. The commercial screws seem to have a chamfer of maybe half of that or max 30 deg. Being somewhat of a nerd (...), I was so curious I decided to try a circular chamfer with the 45 deg tool I have (center):

Looks way more okay than I thought - yay!
But I still need your opinions on if the 4,5mm looks right (as opposed to the 4,27mm on the left) or if I should aim for something else? Maybe someone knows the exact dimensions?

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[Marco Peter]

Circular chamfer looks perfect!

[graham pipe]

All German WW2 bolts were stamped Ribe, Verbus or, towards the end just 8G. Having restored Wehrmacht vehicles since 1996, one is only too familiar with these makes.

As an aside, there is great demand from restorers for such bolts and nowadays they command good prices. I recently sold a huge bucket of "scrap" bolts from SdKfz 7's, Kettenkrads, Panther, Kubelwagen and RSO's for a ridiculous amount. But sandblasted and re-plated, chemical blackened or painted black, they are the Holy Grail to ensure absolute authenticity. The originals were black zinc electroplated.

And in reply to Jerry's post above, I supplied all the wheel fixings for the late Jacques Litlefield's Panther back in 2002. The bolts were modern M14 and we had to remove the 8.8 and manufacturer's name using sanding flap discs on angle grinders. Hours of fun...

The wheel rim nuts are M14 nyloc but the taller T profile rather than the normal P profile. The Germans used this pattern but with a fibrous anti rotation insert unlike our modern day nylon plastic. The bolt heads did not show as they were on the inside of the wheel and held from rotating by use of pressed U section lock plates. We had to make over 1000 of these for this project by laser cutting then forming in a special press tool. The cost Jerry refers to was undoubtably the airfreight shipping price from the UK to San Francisco. We loaded the crate into the UPS truck using a fork truck but the poor collection driver was at a loss to know how he'd unload at the airport by himself!

Best regards from Normandy

[Christoffer Ahlfors]

Thanks Graham! Learned lots there!

Looking at Adrian's picture, I get the feeling that my screw heads might be a bit thick? I decided to have a go at thinning it slightly and that makes it appear bigger as well. The "flattened" screw is to the far right:

I think I'll go with this unless someone chimes in with better size information. 48 plus spares.

If you're into watching the machining, look into my Youtube channel! Ha ha, I always wanted to say that!
https://youtu.be/pIs4_bCBSfM
https://youtu.be/GdKb2iA6tn0
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[Jerry Carducci]

I personally would leave them as is. But that's just me..

Jerry