Help Me… I’m trying to find a Unicorn of the Stanley variety!!!

[Dynamite]

I’m really struggling to find a #12-20 tap and die for matching the thread on Stanley planes for restoration purposes.

Does anyone know where I can buy a bottom out plug tap and a die? I’m guessing that even if there’s somewhere out there, that it’s probably going to be a pretty penny anyway so might not be an option.

Kind Regards..........Rob

 

[ChaiLatte]

Please could you research what the #12 in the thread description represents, Similarly, please research how other imperial threads are described.

Following that research, if asked to state the major diameter of a number 12 thread, what response would you make? If asked to state that major diameter expressed as a fraction (i.e. a/b), what response would you make?

Thus, after having done your homework, if you looked for an a/b -20 tap and die, what could you find?

https://www.ebay.co.uk/itm/184514689059

 

[kinverkid]

I found a 7/32 20-bottoming tap on eBay in the US that looks like it ships internationally. I have both the 7/32 20 tap and die, but I've never needed a bottoming tap at any time. I'm sure, though, someone here will be able to suggest a way that you could use the die to cut a threaded rod, file a cutting groove, and harden it so you can finish off the last few threads in a pre-tapped hole.

 

[ChaiLatte]

I'm sure, though, someone here will be able to suggest a way that you could use the die to cut a threaded rod, file a cutting groove, and harden it so you can finish off the last few threads in a pre-tapped hole.

Sounds like a lot of time end effort for little reward. You can make any tap into a bottom tap by grinding off the end until most or all reduced-diameter threads are removed.

Given that for plane restoration you are only likely to be cleaning out existing threads, modifying the tap straight out of the box is no great harm.

 

[kinverkid]

Sounds like a lot of time end effort for little reward. You can make any tap into a bottom tap by grinding off the end until most or all reduced-diameter threads are removed.

Given that for plane restoration you are only likely to be cleaning out existing threads, modifying the tap straight out of the box is no great harm.

Agreed, but I still can't think of an instance when I've needed to re-cut or clean the threads to the bottom of an existing tapped hole when restoring. Your suggestion of grinding the tap down would be cheaper than ordering one from the US. Just order two from the UK and grind one down.

Edit:
I have made a few brass screw heads for knobs and handles and still didn't need a bottoming tap. I'll see if the originals are bottomed later (which they probably are) but I still think it's one step too far if it works anyway.

 

[rob1693]

https://www.ebay.co.uk/itm/18451468...514689059&rb_pgeo=GB&toolid=10044&var=0&ff=11

 

[Inspector]

Please could you research what the #12 in the thread description represents, Similarly, please research how other imperial threads are described.

Following that research, if asked to state the major diameter of a number 12 thread, what response would you make? If asked to state that major diameter expressed as a fraction (i.e. a/b), what response would you make?

Thus, after having done your homework, if you looked for an a/b -20 tap and die, what could you find?

https://www.ebay.co.uk/itm/184514689059

His research got him to a #12-20 which from a North American seller would be a tap like this.
https://www.victornet.com/detail/TAST-12-20.html
And a corresponding die like so.
https://www.victornet.com/detail/RD-12-20-B.html

Number sizes have been used for a long time here and at one time probably in the UK. I believe they correspond to the number drills used a lot in machining along with fractional and letter sizes. On aircraft number fasteners (screws/bolts) like #4, #6, #8, #10 (a fastener which is close to 3/16"). Fasteners above #10 are fractional 1/4"etc. Other industries/trades etc had their own quirks.

Pete

 

[Amplidyne]

One thing is dead sure, if it's needed, somebody will make it. I forget the thread I needed for an old Schrader adaptor for a garage type inflator that had one end "cup" to go over the valve ("cup" for want of a better term) missing. Pretty fine. 30tpi or something. Sure enough there were taps and dies available. I cut it on the lathe anyway.

 

[Ross Buchanan]

Number 12 gauge is .216", 5.486mm, but the UNC std pitch is 24tpi. Neither Dormer, nor Presto list 12-20UNC taps as a normal stock item. Any 60degree 20tpi thread chase should work for carefully cleaning out male threads, but for female threads, nothing fits. Smallest UN dia /pitch is 1/4"-20, and there's no metric 1.27mm pitch
If you have a bunch of old planes, find a real banger and use the handle screw from that, suitably shortened, to clean out the thread in the better plane that you are restoring.
Or given where you are, maybe contact Complete Tooling Services. They will have a pretty good idea of whether any of their customers are the sort who never throw anything away, and might have a few mad size taps in the back of the stores.
Otherwise, the States is probably your only option

 

[ChaiLatte]

Neither Dormer, nor Presto list 12-20 UNC taps

Nor would they because #12-20 is not part of the UNC thread series. It is not a UNC thread.

It is a thread of UN _form_ with 20 tpi and a #12 major diameter.

As an aside, it would be a very horrible thread to tap into virgin material. 1/4"-20 BSW taps like to snap at the blink of an eye as they are relatively coarse for their diameter and thus have a corresponding abnormally small core diameter. On a major diameter 1/32" smaller than 1/4", this is made worse.

There is a giant spreadsheet of nearly every known thread around (originally by Andy Pugh). It is instructive to add a column to it which calculates diameter/pitch (or its inverse, pitch divided by diameter) and then sort the results. If you were asked to guess what is the coarsest thread for its diameter or what is the finest thread for its diameter and then compared your answers with that sorted spreadsheet column, you would likely be quite surprised. It is quite non-intuitive. For instance 6"-14 BSP comes out as a fine thread for its diameter.

 

[Dynamite]

Please could you research what the #12 in the thread description represents, Similarly, please research how other imperial threads are described.

Following that research, if asked to state the major diameter of a number 12 thread, what response would you make? If asked to state that major diameter expressed as a fraction (i.e. a/b), what response would you make?

Thus, after having done your homework, if you looked for an a/b -20 tap and die, what could you find?

https://www.ebay.co.uk/itm/184514689059

The sarcastic unfriendly response isn’t at all helpful to be honest and absolutely not required!

The research that I did led to me understanding what I stated above. I’m obviously lacking the knowledge and skills in this area and looking for advice from someone who might know where to buy the tool and more to the point, might able to help and share their knowledge and experience - which actually is the entire point of this forum.

Kind Regards… Rob

 

[Ross Buchanan]

The sarcastic unfriendly response isn’t at all helpful to be honest and absolutely not required!

The research that I did led to me understanding what I stated above. I’m obviously lacking the knowledge and skills in this area and looking for advice from someone who might know where to buy the tool and more to the point, might able to help and share their knowledge and experience - which actually is the entire point of this forum.

Kind Regards… Rob

To be fair, he has put a helpful link to an ebay listing for just the item you seek, and at a reasonable price, from someone in Britain.
In engineering circles, No12 and 7/32" are not the same, but in reality 12-20UNS and 7/32x20 are compatible. Certainly in cast iron it will work fine.

 

[Scruples]

Please could you research what the #12 in the thread description represents, Similarly, please research how other imperial threads are described.

Following that research, if asked to state the major diameter of a number 12 thread, what response would you make? If asked to state that major diameter expressed as a fraction (i.e. a/b), what response would you make?

Thus, after having done your homework, if you looked for an a/b -20 tap and die, what could you find?

https://www.ebay.co.uk/itm/184514689059

Well done, mate. And a happy New Year to you...
Let's hope the New Year brings you more happiness than you seem to have at the moment,

 

[kinverkid]

I got the eyeglass out and checked. Stanley do tap to the bottom of their holes - ooer.