14BA die and 15 thou split pin.

I was at a local steam rally at the weekend. Whilst adding to my collection of taps and dies I noticed a 14BA die. I was tempted to buy it just to see if I could cut a 14BA thread.But I stuck to my shopping list. 12 BA is the smallest I have cut, initially this was a challenge, but I mastered it with practice. Is 14BA a bigger challenge?
In the latest model engineer, I was intrigued by the mention of making 15 thou split pins (I have always called them cotter pins) from the wire in plastic bag sealing ties, to use through 12 BA. Which got me intrigued, what drilling setup would you need to drill the holes for these pins.

You can buy cheap boxes of very small drills off of the net. This is one used for drilling holes through a carburettor jet. 0.34mm (0.013" approx)

Do the 'cheap boxes of very small drills' actually produce holes??

Tony

Thanks

It wasn't really the drills, more the setup to do the drilling without breaking the drills.

Keith

No, the boxes are what they keep the drills in.

I'll leave now.

I've used the smallest 0.3mm one from a cheap set with no problem drilling for gas jets. The 0.8mm gets used the most for 1/32" split pins. Smallest split pins I have made were 0.5mm dia.

Like any other hole I tend to use my mill for drilling, nothing special except running as fast as it will go and pecking to clear swarf..

14ba isn't a thread, it's a surface finish!

"Surface finish"? My reference book on threads gives one set, I forget the standard's name and diameters, up to well over 200tpi !. I think it is a watch-making size - literally so.

I read that article too, and wondered how sharp a scriber and what pressure to engrave a groove 0.007" deep in mild steel! Still, it obviously works......

File Handle -

These are "Split Pins".

I think it's American practice often copied by shops to call them "cotter pins".

A cotter pin is a different beast, a type of wedge whose action tightens the joints and with it, its own grip inside the hole or slot.

Examples include the round-section cotter in a bicycle pedal-arm, and the flat-section one (a little like a Morse-taper tang drift) typically holding a piston-rod into a cross-head.

Engine connecting-rod big-ends with split brasses were often held together, and adjusted, by a tapered, rectangular-section cotter working against the mirror-image wedge face of an insert called a "glut", to present opposed parallel faces to the appropriate surfaces of the bearing block and big-end. Often, a threaded tail on the cotter allows it to be tightened with a nut acting on a bracket.

I've had no end of arguments over this "cotter pin" name with people who should know better - I'm with you 100%

Rob

Looks like it might be one of those “which side of the pond” issues : **LINK**

https://en.wikipedia.org/wiki/Cotter_(pin)

which [Heaven forfend!] may lead to debate about ‘English as a living language’

< sigh >

MichaelG.

To answer File Handles question on the best method to drill very small holes through small pins or bolts I have found it is best to make a simple drilling jig from a small piece of MS. Even brass will do if the number of holes is to be small.

I use the cheap drills 61-80 and have found those supplied by Proops to be among the better.

Split Pins are easily made from wire scraped to half round section before cutting to length and bending into a pin - one leg slightly longer than the other of course

Here are some pics of those done for the governor pins on the Waller Engine

The drill jig and pin. Pin hole is about 20 thou

The wire is clamped tight to a piece of steel

and scraped to a half section using a piece of HSS tool blank

The pin is approx 2mm diameter, the split pin is 1/64 silver steel (yes that is right)

16 BA is the smallest I have threaded (the nut is 10 BA)

The parts all together. All six pins on the linkage have turned washers and fitted with split pins

All realtively easy to achieve so hope that's of interest to the OP and others

Best - Tug

Oh yes, a split pin is a split pin, a cotter, as said, is a totally different beast but that's our American cousins for you

Edited By Ramon Wilson on 14/08/2023 22:21:48

And I thought that drilling a 0.036" was bad enough to take a 1/32" split pin

Hi, the smallest tap and die I have is 1mm. Below is a trial I did quite a while ago on a piece of 3mm diameter high melting point silver solder, as that is what I had to hand. A short length was turned down and threaded, then at the other end a 0.75mm hole was drilled into the end about 15mm deep and was tapped, this was then turned down to about 1.4mm and cut off about 3mm long. Quite a fiddly job.

The bottom photo just shows that the 3mm long piece does screw onto the threaded piece.

The smallest BA size I have on a chart is No.24, which has an OD of 0.0114" (0 .2895mm) and has 323.6 TPI, tapping drill size is 0.22mm.

Regards Nick.

25 BA is listed as 0.25mm diameter ( 0.0098" ) 0.07mm pitch ie 363tpi and a tapping size of 0.18mm - but whether it ever existed outside of a British Standard I am not certain.

Edited By Nick Clarke 3 on 15/08/2023 08:28:07

Coincidentally, I spent a merry hour on Sunday morning replacing a nut on my reading glasses that had totally disappeared with no obvious trace.

This is what it should look like

This is what I made as a replacement:

Tube nut OD was 2.4mm, thickness was 1.4mm and tapped M1.4 which is definately the smallest I have ever done.

However it fades into insignificance to some of the work shown here, deeply impressed!

Simon

my Bergeon tap and die set goes down to .3mm; biggest is 1.2mm

One of our club members did hs apprenticeship at Mercers the instrument makers. A task for them was making the taps used in the works in these BA sizes.. The lathe they used for this had a system for correcting leadscrew errors which must have worked down in the tenth of thous region.

My set would make an interesting study because the drill grinds are all over the place! Down to 1.5mm, the bigger diameters are almost all OK, but as the diameter drops, an increasingly high percentage of the smaller drills are ground asymmetrically. Something like a third of the smallest diameter in my set are acceptable, the rest are junk.

I got value for money out of the set because it was delightfully inexpensive, but sure is an annoying time-waster to have to check drills with a loupe before using them. Not keen to try another set - they're too inconsistent.

Dave

Cheap drills can be used by grinding them flat and then putting the cutting edge back on with just one stroke on the stone on each side to get near-enough equal flutes. If it doesn't look right under the loupe then grind ftat again (rather than trying to correct with little strokes)

Sheer curiosity, but how on earth do they do that?