CA-ON Small Fasteners

[Blondihacks]

Problem is, if for a model, they will be way oversized.

This is very often true, but not always. For example, I find the brass hex head bolts at small sizes (3-48 ballpark) look great. However nuts don't scale down well at all. The manufacturers alter the aspect ratio on them dramatically below 1/4" so they look totally wrong. So for stud-and-nut situations, I think it's well worth making the nuts from hex bar (which really doesn't take long anyway). More power to those who make every fastener from scratch (RIP Cherry Hill) but it certainly adds a lot of time when you start doing that.

Another factor to consider is maintenance. On my A3, I originally used scale hex bolts on the cross head rails because they looked nice. I was quite proud of myself until the first time I had to take it apart again. It was very nearly impossible to get any kind of wrench or nut driver in around the finished valve gear. I managed it, but it took about an hour and I immediately replaced them with slot-headed screws which can be removed in seconds.

 

[Mcgyver]

It was very nearly impossible to get any kind of wrench or nut driver in around the finished valve gear.

What is the across the hex for the 3 48 nuts you mentioned? The ME sized hex in a 3 48 thread is 5/32 I believe or .156. No idea who set the standard, I gleaned it from old Coles and Power Model Supply catalogues ..... afaik it was fairly universal and considered about the right size for a scale appearance. Those folks were advanced model engineers and so when I was a begiinner it was natural to following along as I think gives the right asthetics (and they easy to source!).

I don't know the specific tight quarters you were up against, but I made BA and ME nut drivers that often save the day. Case hardened with a thin wall, they fit in tight places and take the frustration out of it. You also occasionally end up making the odd wrench for those impossible locations.

I'd rather buy fasteners as its not the greatest use of shop time, but it can be a PITA finding them and they get expensive from England. Last requirement was for some 7BA counter sunk screws. Just felt like too much money bringing them in ..... it helps of course to have a small turret late . You spend time setting it up then its easy to knock out several models worth

 

[Blondihacks]

What is the across the hex for the 3 48 nuts you mentioned? The ME sized hex in a 3 48 thread is 5/32 I believe or .156.

I just checked, and the brass hex bolts I have are .183 across the flats (probably 3/16" nominal). They look great to my eye, but I'm not a real model engineer. I only play one on YouTube. Of course, the truth is I think most things should be stud-and-nut anyway so if I'm going for best possible appearance, I'm going to try to make that work regardless. Pretty much every prototype steam component I've looked at up close is always stud-and-nut, likely for ease of maintenance.

Nuts are a whole different ballgame. All the commercially made ones at small sizes look terrible.

 

[Mcgyver]

Agreed on the nuts and studs.

If you make model engines, you're a model engineer . Ages ago I did an article on making the hex drivers, and I found the table I put together. These are the ME sizes for imperials threads I found from various catalogues. From what a scaled size would be they're obviously rounded to a nominal hex for convenience so the rivet counters might not like that, but I think it sensible approach. otoh, where are you going to get 11/64 hex stock nowadays?

 

[trevj]

What is the across the hex for the 3 48 nuts you mentioned? The ME sized hex in a 3 48 thread is 5/32 I believe or .156. No idea who set the standard, I gleaned it from old Coles and Power Model Supply catalogues ..... afaik it was fairly universal and considered about the right size for a scale appearance. Those folks were advanced model engineers and so when I was a begiinner it was natural to following along as I think gives the right asthetics (and they easy to source!).

I don't know the specific tight quarters you were up against, but I made BA and ME nut drivers that often save the day. Case hardened with a thin wall, they fit in tight places and take the frustration out of it. You also occasionally end up making the odd wrench for those impossible locations.

I'd rather buy fasteners as its not the greatest use of shop time, but it can be a PITA finding them and they get expense from England. Last requirement was for some 7BA counter sunk screws. Just felt like too much money bringing them in ..... it helps of course to have a small turret late . You spend time setting it up then its easy to knock out several models worth



View attachment 65066

Those are pretty nice!

One of the best iterations of a purpose built tool for confined spaces that I have seen in person, was a nut holder/starter wrench that a fellow at the Estevan Model Engineering Expo had made to deal with just this problem.

You know how you would, on a full size machine, hold the nut between thumb and forefinger, place it on it's stud, and hook a finger around the nut and pull gently to run the nut down in to contact? This wrench was used to do this on #2 and larger nuts, you would place the nut in the holding end, which IIRC, used rubber and friction, then you slid it into alignment with the stud, and started spinning the little handle with your off hand, resulting in the rubber gripper moving away from contact, extending it's reach, akin to the mechanic's finger, then drawing back and in as the handle was turned, spinning the nut down into contact, or indeed, if reversed, you only had to break the tension of the nut, and you could walk the nut off the stud with the same tool.

I wish I had taken more pictures! LOL!

I recal reading that the BA series lend itself well to scale use, as the sizes of the hex stock used are calculated as a ratio, across the size ranges, and thus scale well, where the Unified series Fasteners, got arbitrary sizes assigned to them, based in part, on not wanting to have to introduce dozens of new sizes of hex stock into the system, so they were arbitrarily assigned a stock size that varies from scalable direct comparisons.

 

[Mcgyver]

Thanks, agreed, BA is ideal, it's the relative scarcity of the taps and dies that keeps me away. I've some BA as all the Stuart models are BA, but if I have to supply the fasteners I go imperial. You could just as go metric and figure out a similar table, I just have a lot more imperial cutting tools

 

[Blondihacks]

I recal reading that the BA series lend itself well to scale use, as the sizes of the hex stock used are calculated as a ratio,

That would explain their popularity in model engineering. Interesting! The imperial stuff seems to have a floor on across-flats size, possibly to keep it at 1/4 wrench size or something. Below some size, the AF distance stays the same but the threads keep getting smaller so the aspect ratio quickly turns ridiculous.

 

[Blondihacks]

Here's a stud-and-nut arrangement with 3-48 threads and nuts made from 3/16" hex bar. I like the look, but now I am curious what .156 would look like since that seems to be the accepted standard.

Apologies for the slotted screws still present and the alarming amount of cat hair that was not apparent at normal viewing distance. This engine lives on Sprocket's favourite shelf.

 

[trlvn]

Here's a stud-and-nut arrangement with 3-48 threads and nuts made from 3/16" hex bar. I like the look, but now I am curious what .156 would look like since that seems to be the accepted standard.

The table I use, from David Croft's article (A Steam Engine for the Novice) says that the "correct" size of hex for 3-48 or 3-56 would be 0.149 inches. (Fastener diameter times 1.5.) The table says that the nearest hex size is 5/32" -- not a size I've ever seen listed. However, 4mm would be 0.157" so that might be another option for something that 'looks proper'.

Craig

 

[trevj]

The table I use, from David Croft's article (A Steam Engine for the Novice) says that the "correct" size of hex for 3-48 or 3-56 would be 0.149 inches. (Fastener diameter times 1.5.) The table says that the nearest hex size is 5/32" -- not a size I've ever seen listed. However, 4mm would be 0.157" so that might be another option for something that 'looks proper'.

View attachment 65071

Craig

This diagram draws my attention to one detail that can really make a scale project shine, which is that in full size practice when most of the engines being modeled, were just normal working tools, the ends of studs were rounded over and reasonably finely finished, presumably to reduce the snaggy points in the systems, and to my point, if you look closely at the drawings of the bolt head and the nut, they both got a slight rounded champher, which indicated in the nut's case, the flat side went towards the machine, while the rounded off edge also reduced the snaggy factor markedly.
Very often the full size washers were also champhered on one side, determining their installation direction as well.

It may be a bit 'rivet-counter' to say it, but the details make a well done model into a truly excellent one, IMO.

 

[Blondihacks]

I agree that finishing the ends of the studs adds a lot, as does getting the stud lengths all the same (which I’m bad at )

 

[gerritv]

proper nuts have a washer face. Easy to do with a lever cross slide

Tapping is done using a UPT and a M3 nut tap

 

[gerritv]

 

[YotaBota]

The pic shows in order the BA nut, my 4-40 nut and a standard 4-40 nut. The BA and mine are almost the same size but the standard 4-40 almost twice as big, way out of scale for the Stuart 10V. Most of the standard 4-40 nuts won't even start to thread on the stud because there isn't enough room for them on the model.

This pic shows the crank on the base. I made the studs a bit long and then used the mill to make them all the same length and then rounded over the studs on the lathe.

 

[trevj]

I agree that finishing the ends of the studs adds a lot, as does getting the stud lengths all the same (which I’m bad at )

You need to learn how to cheat! LOL! Drill deep, if you can, barring that, make the end that is NOT buried down the hole, the pretty end and trim the ugly end as required. Thread the holes, make a calibrated collet style wrench that has a stop that sets the lengths, or simply adjust up and down the now too deep holes, before securing the studs in place with a thread-locker.

Making a special gage to set heights with, which can be as simple as a notch in a piece of scrap, so you have something in hand to compare the height of the stud to, isn't a bad idea either. In my last workplace (CFB Cold Lake Machine Shop @1 Air Maintenance Squadron there) I made innumerable quick and dirty jigs and setting fixtures, most of which I saved, and most which will never be used again, as aids to getting a specific job that repeated, done as fast as possible, and as well as possible.

As for being bad at something, don't ever sell yerself short. Having seen your output, you have done what MANY have not, which is to say, you actually tried (and achieved, IMO!). Was the biggest hurdle to get past in some of the apprentices, who were convinced that we hid all the proper tooling from them, and they would spend hours poking through cupboards and drawers looking for what they had been instructed to make with HSS tooling, not to mention the drama around fear of thread cutting! LOL! I WILL admit to having some pretty thrilled feelings about it when the 'light came on' in a lot of them!

FWIW, deep in the recesses of memory, I seem to recall reading in Model Engineer and ME Workshop magazines, that even the greats like Ms. Cherry Hill, used screws up until it was time for the show, when they would put the detailed effort in and let convenience take back seat. No shame there!

 

[ChazzC]

One of the best iterations of a purpose built tool for confined spaces that I have seen in person, was a nut holder/starter wrench that a fellow at the Estevan Model Engineering Expo had made to deal with just this problem.

You know how you would, on a full size machine, hold the nut between thumb and forefinger, place it on it's stud, and hook a finger around the nut and pull gently to run the nut down in to contact? This wrench was used to do this on #2 and larger nuts, you would place the nut in the holding end, which IIRC, used rubber and friction, then you slid it into alignment with the stud, and started spinning the little handle with your off hand, resulting in the rubber gripper moving away from contact, extending it's reach, akin to the mechanic's finger, then drawing back and in as the handle was turned, spinning the nut down into contact, or indeed, if reversed, you only had to break the tension of the nut, and you could walk the nut off the stud with the same tool.

HeathKit was noted for including virtually everything required to build one of their kits, including some nifty special purpose tools:

such as P18, a Nut Starter:

Soft-ish plastic with the hole just the right size to slip over a 4-40 nut. A semi-flexible verion could be "made" using an appropriately sized short length of heatshrink tubing.

My favorite tool (I have one somewhere), was an assemble-it-yourself magnifying glass to help read values on small discrete components. It consisted of a 3/4" diameter lens and a thin piece of cardboard with a pair of 5/8" diameter holes: fold the cardboard in half around the lens and tape the perimeter to hold it together, et voilá – a magnifier. This was replaced in later kits with a molded acrylic version which was better (had low & medium power lenses), but not as satisfying. I found one of them (2-1/2" OA):

[If you're wondering what item P20 is, it is an IC Puller]

 

[YotaBota]

I wonder how easy it would be to 3DP the nut starter, print with what ever size nut you need.

 

[Mike R]

I bought some BA sockets and wrenches (spanners) from MACC models in the UK.

I was buying a bunch of BA fasteners and steam fittings, and the sockets were really cheap, the spanners a bit more but worth it if dealing with BA sizes.

They have other options but those are more pricey.
https://maccmodels.co.uk/shop/tools...-spanners/ba-socket-set-0ba-10ba-1-4-drive-2/

 

[Ishmael]

Nice models. I particularly like the Rudy traction engine.