Scale nuts and bolts

[Paul BoscottParticipant @paulboscott25817]

Scale nuts and bolts

I would appreciate some help with the scale model of an industrial machine that I am about to start.

I the past I have made many model engines (type JaguarB into youtube to see some of the better ones) these have been from existing designs or not to scale for my next model I intend to make an original with the data coming mainly from a set of photos. I am now in the process of drawing the machine up 1:1 in AutoCAD. From the dimensions I have so far it is looking like one inch to the foot is a practical scale as I will be able to make the largest part on my 10 in atlas lathe.

Now for the Question

What thread type should I use and where do I get the information on A/F sizes for scale nuts and bolts?

For example what would a 1/2 whitworth become at 1/12 scale to look right?

I can see that the diameter would be 0.041″ this is close to 14BA or 1mm but information on the AF sizes of these threads is conflicting and I know that sometimes what is right on the calculations does not look/feel right in practice.

I also notice that some suppliers have different size bolt heads to nuts for the same thread in the sizes below 8BA

Thank you for your time.

[Paul BoscottParticipant @paulboscott25817]

[JasonBModerator @jasonb]

Whitworth AF sizes

 

BA etc AF sizes

 

Amazing what google can find in 10 secs

 

Jason

[Martin WParticipant @martinw]

Paul

 

There is a fair bit of data re thread sizes plus other very useful data at :

http://www.oldengine.org/members/diesel/Tables/mech1.htm

 

 

The host site oldengine.org seems to look interesting as well as it contains many links/articles to old engines etc.

 

Hope this helps

 

 

Martin W

 

Edited By Martin W on 12/12/2009 16:58:42

[D.C.ClarkParticipant @d-c-clark]

Posted by Paul Boscott on 12/12/2009 14:07:34:

 

I know that sometimes what is right on the calculations does not look/feel right in practice.

 

That’s the crucial point.  A model has to look right, and the human eye is not calibrated.

 

I’m working on a 1/12 scale animated model of Fulton’s steam boat engine.  Working from period drawings and sketches, even scaling photos of a reproduction built in 1905. Visiting museums and their archives to study the hardware and fittings on engines and other mechanisms of the period.  It still comes down to what looks plausible.

 

It helps a lot to solid model in CAD, then print out full scale.  My model will be almost 36 inches long, so I go to a print shop with a large format printer.  Even this doesn’t always ensure that the model will look right, though.  So, I’ve made a prototype, and several design studies of component parts.  Been at this over a year, and have yet to make the first part for the museum-grade model.

 

David Clark in Southern Maryland, USA

 

 

 

[Sub MandrelParticipant @submandrel]

Hi Paul,

 

You can lie awake at night worrying about this!

 

I’ve found that the BA series really helps, because the 0.9-times step bewteen sizes means that there is always a size within 5% of the correct size. The thread scales with the size of the nuts, so it always looks right, even if it isn’t scale pitch

 

Many folk suggest that BA fixings with reduced size heads look best. The one pain in the neck is that the ‘one size smaller hexagon’ BA fixings can be hard to track down, and don’t seem to exist below 8BA with 9BA hex.

 

Another reason for variation is that some suppliers can’t get hold of proper BA hex stock, and use the nearest metric size instead.

 

Interestingly, though, looking at some old engravings the full size BA hex scales pretty well.

 

So my advice is use the nearest BA size and get a good nights rest!

 

Neil

Edited By Neil on 23/01/2010 21:33:01

[Paul BoscottParticipant @paulboscott25817]

Thank you Neil

 

I am going along that track. I have drawn up in autocad the full range of BA nuts and bolts fron 14 to 0 in actual size the scaled them by times 12. I am now using these drawings in comparison with the phoros I have, to draw up the press in full size then when I scale the drawing inch to the foot the BA sizes will return

 

see http://www.boscott.co.uk/drawings.html

 

Thank you agian for the conformation of the data

 

yours Paul Boscott

[martin leslieParticipant @martinleslie67699]

Paul

 

I wish you the very best of luck in what is obviously a marathon task.

 

Martin Leslie

[Sub MandrelParticipant @submandrel]

That’s a very different modelling subject!

 

Best of luck.

 

The draughtman needs a haircut though!

 

Neil

[Nigel McBurney 1Participant @nigelmcburney1]

hi  pre 1940  whit nuts and bolts had a larger hexagon,sizes were reduced during the war to save material,  eg  half inch whit prewar was  .920 ins AF  and reduced to  .820 ins AF  which was made the hex on whit and bsf the same, A lot of early machinery ie pre ww 2 ,used square headed nuts and bolts,

[Sub MandrelParticipant @submandrel]

I drew a lot of circles for the BA sizes in Corel, and matched them up against a scale a 1″ 1′. These were the best matches for some standard screw sizes:

 

0BA – 2 3/4″, would serve for 3″

1BA – 2 1/2″

 2BA – 2 1/4″

3BA – 2″ (slightly small)

4BA –  1 3/4″ (slightly small)

5BA – 1 1/2″

6BA – 1 1/4″ (slightly large)

7BA – 1 1/4″ (slightly small)

8BA – 1″

 9BA – 7/8″

10BA – 3/4″ (slightly large)

11BA – 3/4″ (slightly small)

12BA   – 5/8″

13BA – 1/2″ (10% large)

14BA – 1/2″ (slightly small)

16BA – 3/8″

18BA – 1/4″ (slightly large)

 

The matches in bold are very close – within a few percent of nominal size. 13BA is a better match for 1/2″ than 14BA, but much harder to source. Otherwise, the pairs of large and small are probably more or less equally good. Screws smaller than 1/4″ are unusual on engines, so I think the BA series covers everything from holding down bolts for baseplates to minor fixings pretty well.

 

Neil

[JasonBModerator @jasonb]

Could have saved all that trouble and just looked in the “model engineers handbook”  It has a table that gioves the same data

 

Jason

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