Thread: A 12-20 tap & die set

Hi Ian - I have also been looking for a 12-20 tap and die for a while (same reason - Stanley planes, of course), but have not been able to find one available. Does Alkahestic sell these in numbers, or were you simply lucky enough to get the one and only set available? Cheers, Bruce

The latter I'm afraid, oldB.
They are available here - & finally back in stock after being out for almost 2 years. Both tap & button die are quite good quality and reasonably priced - the problem is getting them here at reasonable cost. If you know someone going to the States who could pick some up for you, or use one of the commercial forwarding agents, it would be much more attractive.

They are the sort of thing you only need occasionally, but when you do, you can't just wander down to Bunnies & pick them up....

Cheers,
Ian

Hi again Ian, and thanks. Damn. I suspected as much (re: only one available). And I have tried Victor tools a couple of times over the last year, but so far I have not received any response to emailed inquiries - maybe because they were out of stock at the time??? I guess it costs nothing to try again. Just for info, and maybe as a lateral suggestion to others with the same problem, I have been managing male threads to date with an adjustable vintage 1/4-20TPI Whitworth die: the sliding cutter type. If you tighten these incrementally, they do an acceptable (not great) thread in mild steel which will work for Stanley rods. I found mine at a swap meet for $5, and have since seen a couple more locally on EBay for $10 or less.

Bruce, there are a couple of somewhat crude ways of getting 1/4" studs to fit the 7/32" thread. You can spin a length of 1/4" all-thread in a drill or lathe & file it down a bit 'til it screws in. It's not completely satisfactory, but it can get you out of a hole (or into it ). The studs in old planes, particularly the rear tote stud, are almost always a sloppy fit because they only have about 2 1/2 turns of full thread in the sole. (If you do use all-thread, I advise filing off the unwanted thread between top & bottom sections as much as you can because it tends to catch inside the handles when you are trying to slip them on or off).

Stripped or badly-damaged studs seem to be all-too common, so the 12-20 die was the part I most desperately wanted, though the tap will do its fair share of duty. The tap from Victor is a full-taper tap, and not much use in it's raw state for cleaning out the shallow stud holes on planes. I ground the sharp point off mine to get a bit more thread in the nut I made, and it could probably stand to be shortened a bit more if it only ever gets used in brass & cast iron (which will be the case with mine).

The die is probably the more important member of the team for me, I seem to strike more stripped studs than damaged nuts, but nuts do get damaged or go AWOL occasionally, so if anyone is desperate for a part like a new tote stud or brass nut I'm happy to make the occasional part (I'll review that offer if the demand exceeds my limited gear & time.. ). I have a pack of bullet-head nails that are just a few thou under 7/32", & perfect for studs, so a few dollars worth of nails can make a lot of studs. Brass seems to be chasing gold prices these last few years, so I'll have to charge a few cents for nuts...

Cheers,
Ian

Hi Ian. Great idea about using 1/4 threaded rod, but so far my compromise method to make handle rods (by over-tightening a sliding 1/4 Whitworth die) has had reasonable success. But my main requirement for a tap is to be able to repair the threads in the body, rather than making replacement brass nuts. I have had a run of planes I have been asked to repair/salvage, where the rear handle stud/rod has been snapped off just level with the body, and of course they are rusted in - which is likely the reason they were snapped off in the first place. I have not had much success with easy-outs or left-handed drill bits - even with heat and penetrating oil - so have had to resort to drilling out the centre of the stud (using a small mill/drill, and the plane inclined at 27 degrees), then attempting to peel the threads out of the rear handle boss. And of course, there is often some damage to the softer, cast iron female thread in the process - hence the need for a tap. Yes, I could drill out (and re-tap) to 1/4" 20TPI, and make a custom stud to match, but the challenge (for the rarer, older planes) is in returning it to as original as possible.

Originally Posted by oldBruce

Hi again Ian, and thanks. Damn. I suspected as much (re: only one available). And I have tried Victor tools a couple of times over the last year, but so far I have not received any response to emailed inquiries - maybe because they were out of stock at the time??? I guess it costs nothing to try again. Just for info, and maybe as a lateral suggestion to others with the same problem, I have been managing male threads to date with an adjustable vintage 1/4-20TPI Whitworth die: the sliding cutter type. If you tighten these incrementally, they do an acceptable (not great) thread in mild steel which will work for Stanley rods. I found mine at a swap meet for $5, and have since seen a couple more locally on EBay for $10 or less.

There is a Guy at Yandina Saturday Market's that sells loads of tap's & dies, but he only goes there every other week.

Originally Posted by Camelot

There is a Guy at Yandina Saturday Market's that sells loads of tap's & dies, but he only goes there every other week.

Worth a look, but I think you'd be extra lucky to find a 12-20, it's just not a size used for general engineering. If I'm up that way on the right week, I'll certainly sus him out - there are a few other sizes I wouldn't mind having to fill in the gaps in my metric & Imperial sets...
Cheers,

Not a cheap option but I spoke to a local bolt shop 20 years ago and we were discussing the option of making a set for a requirement I had for an “old thread” in the end the thread turned out to be a pipe gauge thread and taps we available off the shelf.


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Custom making sets does not appear to be a cheap option. I found an Australian (Queensland) supplier a few months back (June 2021) who provided me with a quote for a 12-20 set (tap and die): $272.80 (including GST) plus postage. It was hard to justify, for the amount of use I would get from it...

Originally Posted by oldBruce

....... $272.80 (including GST) plus postage. It was hard to justify, for the amount of use I would get from it...

Yep, that's the rub alright, how much use will it get? For the average bloke, very little; you might need it just a couple of times in your life unless you set yourself up as a repairer/restorer of old planes, so spending $300 on a tap & die would be a major luxury unless you have a limitless tool budget! (in which case, you would probably just buy a set of LNs & wouldn't be mucking about fixing old planes. ). There is, of course, the simple pleasure of making a good old tool fully operational again, & having the necessary gear makes that much easier to achieve.

I think I've only come across one plane with a totally stripped thread in the sole and a 12-20 tap could not have fixed that unless the hole was filled by brazing & re-tapped. "Helicoils" can do a great job, but afaik, don't come in a 12-20 size. Taking a brazing torch to a cast-iron sole is a very fraught move unless you really know what you are doing (I don't!) so I'd leave that route to the experts. I've also read one bloke claiming he fixed a stripped stud by epoxying it in, but I have my doubts about the long-term durability of that method. If I were to encounter such a situation now, I'd re-tap the sole to 1/4" and make a stud with appropriate threads on each end, but that's not a solution everyone can apply.

The more common problem I've encountered with studs is severe rusting to the point the stud may be less than half its original diameter (one I remember was so thin it sheared off in the middle when I tried to undo the top nut). Maybe that's more of a Queensland thing, but it's something I've come across half a dozen times or so. But by far the most common problem seems to be lost nuts. Up til now, I've managed to find enough "spares" to get out of trouble, but there's a limit to that source. Now there is no problem, I can make studs or nuts close enough to original specs to fool all but the most discerning type. Very happy little Vegemite....

Cheers,

Ian . What does 12-20 stand for?

Is it the thread is 12tpi and the thread angle 20 degrees? edit. Couldn't be that 20 degrees surely ?

If not what is the tpi and thread angle for those Stanley parts if I wanted to make a male thread on the lathe?

edit . Is it the same as 1/4 " UNC ? as you were saying above in the quick fix but the only difference is its 7/32 diameter instead of 1/4" ?

Sorry to barge in on a question directed at Ian, but the 12 is 12 Gauge (which in bolt terms is .216 inches, or 5.5mm, or near as dammit to 7/32 inch outer diameter). The 20 is TPI (so same TPI as a 1/4 UNC, just thinner diameter). The problem with turning these rods on a lathe is that this is a Whitworth thread (so, 55 degree angle), rather than a standard AF form (60 degree angle) - which means that you need a specially shaped thread cutting tool, rather than the one that comes with several of the basic lathe tool sets. Yes, you can force an AF form thread into the hole, but then you have the problem of the (mild steel) stud/rod potentially damaging the cast iron base of the plane. I think that I have made most of the usual errors when playing this game... and I may have even learnt from some of them.

Thanks, Bruce, a much better answer than I could have given anyway!

For whatever reason, the Yanks use the old 'gauge' system for bolts up to 1/4" much more than the Brits or we do. It used to confuse the hell out of me when I first encountered it. These days it's easy-peasy, Google will very quickly find you a table of the gauges numbers & diameters.

I should add to what Bruce says about turning the stud threads on the lathe, finding the right insert for the thread angle is a major problem for me because the tools for my mini need special inserts that aren't easy to get - only one place within a bulls roar of me stocks that size of insert & they could not get the thread-cutting inserts in that size last time I asked. So I made a handy die-holder that runs on a 16mm SS rod held in the tailstock that works very nicely & keeps the die cutting straight (well straight enough for my purposes, I don't aim for rocket-engine precision!).

TBH, I'm not sure cutting 60* threads would matter too much, if the pitch is correct. They should feed easily into 55* nuts (or is it the other way round that can cause grief i.e. trying to screw 55 into 60 when the tolerances are tight - I forget, but one will go easily & the other won't). In fact, it is probably not a big issue because even the correct studs are often a very sloppy fit in Stanley & Record planes so I suspect the 'wrong' thread angle would hardly be noticeable. However, my fitter uncle would've clipped my ear for even suggesting doing such a crass thing....

Cheers,

Originally Posted by IanW

I should add to what Bruce says about turning the stud threads on the lathe, finding the right insert for the thread angle is a major problem for me because the tools for my mini need special inserts that aren't easy to get

Isn't one solution to that to grind / make HSS tool bits for your lathe with what ever thread angle you like?

Or is it that a die held in a holder, if you have the die is much better way to do it ? It cuts it in one go yeah ?
And the lathe will take 8 ? passes.