Discussion of Fastener Sizes and Scale Equivalents

pakpaul

Western Thunderer
Today there are a large number of general arrangement and detail drawings available to help us build a model, and these tend to specify fasteners by their size, usually without quoting dimensions such as across flats in the case of nuts or bolts, or head sizes in the case of rivets or coach bolts.

These dimensions are available from standards, but I do not recall much detailed information on relevant standards in the modelling press and publications, and in this thread I will try to set out dimensions from some relevant standards, as well as scale equivalents, initially for gauge 0 7mm to one foot, gauge 1 at 1/32nd or 3/8" to one foot, and gauge 3 at 17/32" to one foot.

To start the ball rolling I will set out the Whitworth Standard which would cover nuts and bolts used for the construction of locomotives and rolling stock for British railways from middle/late victorian times to the 1960's. The tables below do not have all of the standard sizes, but can easily be expanded if this is felt necessary (the 1/16th sizes have been omitted as the do not seem to appear on the railway GA drawings I have looked at). There is one area I would like assistance on these as the washer sizes are guesstimates based on other standards as I do not have access to original Whitworth ones. For this reason they are shown in italic script.

I am initially showing tables for full size in inches, gauge 0 and 1 with scale sizes shown in both inches and millimetres as this may assist someone in making scale fasteners, depending on their machine tools units .

Apologies for the quality of the tables but we are still working on a means of getting a table from an excel file directly visible on the forum.

Any comments on format, scales needed and additional information would be appreciated. We could then modify this and then have it as reference material for the forum.



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Regards

Paul
 

Steph Dale

Western Thunderer
Paul,

I seem to remember we had a thread on the subject before, but this looks to be much more thorough and easily presentable than we had. I like that you've imported the data as images so it's easily readable; I'll have to see how I get them printed for the workshop.

One small thing - if you can centre the text/headings in the columns they'll all line up and be a little easier to read; MSExcel defaults to putting text to the left of each cell and numbers to the right...

Steph
 

pakpaul

Western Thunderer
Steph

I can upload the original excel files as Adrian has switched on this facility in the forum, the only problem is you cannot read them directly and have to download them. I can easily reformat them, and think my printer head needs cleaning.

Paul
 

pakpaul

Western Thunderer
Jim

Thanks for the link to your thread, I am interested in CNC machining and from a quick skim there is much for me to learn there. I have been experimenting making hex sections, and the photos below show some recent efforts at 34, 41 and 46 thou a/f using a 3/8" end mill as a cutter on a Sherline mill. I will write it up and post it when I can be sure of consistent results.
hex1.jpg

hex3.jpg

The results surprised me.

Paul
 

JimG

Western Thunderer
Paul,

Those machined bars look excellent. I haven't tried machining hex stock - I've concentrated on nut and washer detail, like on my cylinder covers, or on bolt head and washers on wagon detailing. The only bit of bar stock milling I have done was a length of octagonal wooden bar for a 4mm scale model of a yard crane and that worked quite well in the end, although I had to take quite light cuts to avoid deflection of the material under the cutter. I've got an "A" axis available so rotating stock to any angle is fairly straightforward.

I do a lot of work milling styrene but small detail, like nut and bolt heads, doesn't work too well on this relatively soft material. However, on brass, small detail works very well. I use carbide cutters down to 0.5mm diameter since these cutters work with best styrene and prevent melting at the cutter end. I'm limited to a certain extent by the top speed of my spindle with small diameter cutters. Its top speed is 7000rpm so feed and depth of cut in metal tends to be slow and very careful. :) It got a bit expensive in cutters at the start and I still get the occasional "plink" as a cutter decides it's had enough. :)

And I sympathise with you on achieving consistency. I find that results can vary from one day to the next when all the variables seem to be the same. The beauty of CNC is that you can do it again literally at the press of a button which helps a bit at the time, but it would be nice to guarantee a result. I suspect that it is because we are working cutters outside the manufacturer's specifications.

Jim.
 

OzzyO

Western Thunderer
Hello Paul,

now that you have the Hex. heads have you thought about how you are going the M/N the "shafts"?

If you can do the turning on the same M/C I'd do the shafts first then the Hex. Then all you have to do is the parting off.

Granny and eggs time, if your A axis is at the L/H side of you M/C if you index it so that it turns ant-clockwise you should only have one large rag to clean up. The other thing is are you cutting along the length of the stock or across the stock? To some this may sound daft but it can affect how the job reacts.
If your coming in from the back (using the cross slide) this can try and lift up the free end.
If your coming in from the front (using the cross slide) this can try and push down the free end, with the result of a small second cut as the rear of the cutter crosses the face.
If your coming in from the free end (using the longitudinal travel) depending on where you have the cutter C/L can affect the job. If the cutter is set to the front of the M/C it will tend to push the job down with the rear of the cutter taking a small amount off.
If the cutter is set to the rear of the M/C it will tend to try and lift the job into the cutter. So that all of the work will be done on the "in" cut.
If the cutter is set on the "dead" C/L it should not move the job too much.

Some very nice milling going on there, but you can get brass bar that is drawn to the following sizes, 0.75mm, 1mm and 1.5mm. But to hold it and then turn it takes a very good lathe and chuck.

KUTGW

OzzyO.
 

pakpaul

Western Thunderer
Jim

I have also done some work on styrene, but using a CNC engraver with a carbide parallel engraving cutter, and with this I have achieved consistent results and made some 1/32nd scale 3/4"nuts of 0.041" a/f, plain square ones, square with washer and hex with washer.

Engraving cutters are D bits, and the parallel cutter I used was .060" in diameter. The cutter itself is 6 1/2" long with a shaft diameter of 11/64", which is held by a collar at the top of the spindle, and a collet at the bottom about 1/2" from the tip. For styrene with this size cutter, the speed is around 10,000 rpm. The styrene is held onto the bed of the machine with double sided tape, and the cutter must not pass through the styrene and contact the tape or a mess will result!

The photo below shows carefully selected finished product sitting on a metric ruler:

nut1.jpg

Below is the engraving of a square nut followed by a hexagonal one both with washers.

nut3.jpg

nut2.jpg

The problem comes in trying to cut the items from the styrene. For those with a washer the solution found is the press and tool below which has about a 50% success rate in getting an acceptable washer and nut.press tool 2.png

In the case of the square nut a modelling knife was used with a success rate of around 15%. I have not made a successful hex nut yet.

Most of this work was done about 3 years ago and I have not had a chance to get back to it to progress it further, hopefully this will change in the next couple of months.

I think the use of engraving D bit cutters is better with styrene than two flute milling cutters, they are more robust, and can be sharpened. In the event of a mishap they may possibly be salvaged as well. They are also excellent for cutting out coach panelling. Please be patient with me and I will start a thread on my experiences with these cutters, and the results than can be obtained.

Paul
 

pakpaul

Western Thunderer
Hi Ozzy O,

You have hit the nail on the head, the hex machining is most definitely the last act prior to parting off the finished item, those three little pieces of hex material cannot be machined without risk of them bending or breaking.

They were simply made to see what was possible, and started off as 1/16" plain hard brass wire. This was placed in a collet and the last 0.35" turned down to 3thou greater in diameter than the cross corners dimension of the hexagon. This was placed in a specially made pin chuck with a hexagonal body and put in the mill vice, and 2 thou cuts were made with the base of a 3/8" end mill with the mill at maximum speed. After each cut the pin chuck was rotated 60 degrees, and the next cut made, after 6 cuts the feed was increased another 2 thou and the process continued until the correct size was reached.

I am trying to refurbish my workshop but that particular day a few weeks ago was too hot for building a cupboard, 38 centigrade if I remember correctly, and the workshop has corrugated iron roof!

I have seen 1mm hex advertised, but as you say holding it for machining is the greatest issue, which is why my trial was based on using collets, and an accurate pin chuck. The wire was also plain brass, not leaded, and so when there is time I will try again but using 1/8" leaded extruded brass, but in the correct order to make something.

I will report on further progress, but better make my next posting more in line with this thread.

Paul
 

JimG

Western Thunderer
Jim

I have also done some work on styrene, but using a CNC engraver with a carbide parallel engraving cutter, and with this I have achieved consistent results and made some 1/32nd scale 3/4"nuts of 0.041" a/f, plain square ones, square with washer and hex with washer.

Engraving cutters are D bits, and the parallel cutter I used was .060" in diameter. The cutter itself is 6 1/2" long with a shaft diameter of 11/64", which is held by a collar at the top of the spindle, and a collet at the bottom about 1/2" from the tip. For styrene with this size cutter, the speed is around 10,000 rpm. The styrene is held onto the bed of the machine with double sided tape, and the cutter must not pass through the styrene and contact the tape or a mess will result!

Paul,

I've been using carbide slotting cutters for nearly all of my work and I get on with them very well now. When cutting styrene, the parameters seem to have a wide range and I find that the main criteria is the strength of the glue in the double sided tape and the propensity for the styrene to distort before the cutter if you push things too hard. The carbide cutters give very long life cutting styrene and I am now learning when to tell that they are starting to get too blunt and need changing.

the cutters I have had a lack of consistency with are fine carbide engraving cutters - typically 20 degree/0.1mm. I have been trying to use them to engrave planking on styrene and some days I get excellent results with very clean grooves, and other days I get rather untidy results which need a bit of cleaning up to get rid of edge on the grooves. I'm trying to ascertain what the problem might be. I've tried brand new cutters out of the box and get the same inconsistencies so it doesn't seem to be the sharpness that's a problem. The only other consideration is that the cutters I have obtained quite cheaply from Ebay and they could be at the poorer end of the Chinese standards of production. But I don't have a good enough microscope to inspect the cutting ends to see what they are like. But they do scar well - I've still got a mark on the base of my thumb where one gashed me. :)

The problem comes in trying to cut the items from the styrene. For those with a washer the solution found is the press and tool below which has about a 50% success rate in getting an acceptable washer and nut.

In the case of the square nut a modelling knife was used with a success rate of around 15%. I have not made a successful hex nut yet.

I haven't tried to cut items as small as that but I do agree that getting them out of the material is a major consideration. The smallest parts I have done in brass, I cut from clock plate brass sheet and arrange two or more tabs to the main sheet so that they don't detach during the last cut through and get damaged or break the cutter. I then cut them out of the sheet with a piercing saw through the tabs and clean up the residue of the tabs with needle files. With larger styrene parts I rely on the double sided tape to hold them. With smaller styrene parts, I use tabs or try to leave a thou of material around the part on the final cut which lets me break it out of the sheet easily, then clean up the part with a knife blade or file.

I think the use of engraving D bit cutters is better with styrene than two flute milling cutters, they are more robust, and can be sharpened. In the event of a mishap they may possibly be salvaged as well. They are also excellent for cutting out coach panelling. Please be patient with me and I will start a thread on my experiences with these cutters, and the results than can be obtained.

I had a thread on here four years ago (was it that long ago? :) ) using the milling machine to cut panelled coaches in styrene.

http://www.westernthunder.co.uk/index.php?threads/re-rolling-stock-for-banavie-road.700/

I got good results after a bit of messing around at the start and I finished up by incorporating full 3D cutting to do the bolections round the quarterlights.

Jim.
 

OzzyO

Western Thunderer
Why not use brass, then you can solder the nuts and washers to the base plate and then cut them all out of the plate that is the correct thickness. If you see what I'm saying.
 

pakpaul

Western Thunderer
OzzO

I do see what you mean, it's a good idea, you only forgot to add that the nuts would be already tinned after separation from the base plate. It will be a while before I get the chance to use my engraver; at 4pm today the temperature in my workshop was 40 centigrade. The next post from me will provide some data on coach bolts.

Paul
 

pakpaul

Western Thunderer
Coach Bolt Head sizes

Coach bolts are usually found on wagon strapping, with the head on the inside, which by its shape reduces the possibility of damage to a load, compared to a hexagon head for example.

Coach bolt heads can in the smaller scales be represented by a rivet press, but with a very shallow indent as the height of a coach bolt head is around 25% of the bolt diameter, whereas the height of a rivet head is around 70% of the rivet diameter. For 1/32nd scale they can be made from modified lace pins.

The numbers below come from an American Standard as I do not have access to a British one. If someone has details of a pre 2nd world war British Standard I would appreciate details so these numbers can be updated. Old bolts in my possession are the same as this American Standard.

posted1.JPG

This has been formatted according to Steph's suggestion and is clearer than earlier posted data.
 

BrushType4

Western Thunderer
All these hex nuts and bolts. You're going to need a spanner.

image.jpg

Bolt head below is 0.5 mm. The smallest I can do on laser. I think I could do better with a different technique which I will try later.
image.jpg

PS. I really must get a proper camera, the iPhone just doesn't quite do it.
 

pakpaul

Western Thunderer
Snap Head Rivet sizes.

Below is a set of tables for snap head rivets, which appear to be the most common type of rivet seen of steam locomotives and rolling stock of the same era. There are other types of rivet head, and if requested tables can be made for these. There is also as with the coach bolt heads table an illustration of the shape, which will be seen to be significantly higher than a coach bolt.

posted1.JPG

A standard issued in 1970 showed a decrease in head hight of around 7% , with the head diameter remaining the same. I tried measuring some rivets purchased from Reeves 5 or so years ago, in the case of 1/8" and 1/16" head height and diameter followed the standard above, with 1/32" rivets I managed to measure the head diameter with a dial gauge and it agreed with the standard, I did not manage to consistently measure the head height holding the rivet in my hands and gave up.

Another area I looked at was to measure the across flats dimensions of some BA nuts in the smaller sizes, and to see what size these represent at the various scales. The across flats dimensions of the 10,12 and 14 BA nuts were within .002" of the standard. I also looked at the diameter of the thread, and what scale dimension it represented at the various scales.

The table below shows the results of this:

posted1 BA.JPG
 

Steph Dale

Western Thunderer
Crackin' stuff, Paul.
I was looking for that rivet information over the weekend and failed to find it, relying on an estimated rule of thumb. I can see I'll have to correct some of the details on my T1 drawing!
Cheers,
Steph
 

Steph Dale

Western Thunderer
Paul,
Sorry, quick follow-up. Would you mind posting the .xls file, please? I note you say in an earlier post that it's possible to do so. It would be handy to have it available in a digital format for when I'm CADding.
Cheers,
Steph
 

OzzyO

Western Thunderer
Some smashing work on the tables Paul, but one or two errors have crept in in the BA size equivalents, as some of the sizes are the same for A/F nuts and the thread O/Ds .

In the 10BA sizes at 7mm; 1' the nut size would be 4.876" (4 7/8") and the screw 2.92" (2 15/16"). For these sizes I've the ratio of 1;43.54.

Hope you don't mind me pointing this out to you.

OzzyO.
 

pakpaul

Western Thunderer
Steph

Snap head rivets.xls file attached for snap head rivets I hope.

Paul
 

Attachments

  • Snap head rivets.xls
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pakpaul

Western Thunderer
OzzyO

Perhaps I did not explain the BA equivalent table clearly enough, all I was doing was multiplying the BA dimension by the scale factor for both the nut a/f and the thread od. In the case of the nut a/f I put in the nearest Whitworth size which corresponded to this number. In the case of the 7mm 10 BA size, the largest Whitworth a/f value I have is for 3 inches so I simply used the greater than sign ">" to indicate it was larger than 3".

In the case of the thread outside dimension, again I was scaling up to see what size this represented which in some cases is different to that given from the nut a/f, the table shows that the smaller the scale, the larger the variation from the nut a/f to the thread outside dimension.

I hope that clarifies my approach, there are approximations, but not material errors I hope. I will check again in the cold light, but very warm air of tomorrow morning.

Paul
 
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