#12 screw with 20 TPI?

[sploo]

Just wondering if anyone has come across a #12 screw with 20 TPI?

I've picked up a Stanley #71 router plane (with a 1901 patent date). The thread on the screws for the handles are approx 5.5mm external diameter; which looks to match well with a #12 screw (0.2160" / 5.4864mm), but a #12 has 24 TPI, and this is definitely 20 TPI. It doesn't match any UNC/UNF/UNS/ACME thread I can find.

Possibly a Stanley special?

 

[Cheshirechappie]

This does seem to be a common size on both Stanley and Record planes. I'm not sure that anybody really knows why. It may be that the sizes chosen by Stanley when they first started manufacturing planes pre-dated firm screwthread standards in the US, or maybe they inherited the sizes from Leonard Bailey.

Oddly, when Record started making Stanley copies in the 1930s, they adopted the non-standard screwthread sizes too, despite there being established and recognised standards by then. I'm not sure whether they still use specials on their current production planes, though, or have adopted something more standard.

There are taps and dies available from time to time in the US, but not in the UK, unless someone orders some specials. Thus, if anybody needs spares, it's a case of trawling Ebay, contacting the second-hand tool dealers, or ordering from the manufacturers.

 

[AndyT]

For a longer version of CC's accurate answer, try this two part article from the Traditional Tools Group of Australia

http://tttg.org.au/php/ArticleView.php?id=37

 

[sploo]

Many thanks both.

I was aware of the issues of thread pitch vs material (coarse threads for cast iron), but those articles are interesting.

I guess the best answer is "time to buy a metal lathe"

 

[lurker]

I have just checked my 71 against my stash of plane parts.
The screw seems to be identical to the one on 4 & 5 front knobs.

"A bloke" here has the correct die IIRC.
I will alert him to your post.

If you just need one, pm me your mail address and I will send you one.

 

[sploo]

I have just checked my 71 against my stash of plane parts.
The screw seems to be identical to the one on 4 & 5 front knobs.

That would make sense (depending on the age of said #4 or #5).

"A bloke" here has the correct die IIRC.
I will alert him to your post.

If you just need one, pm me your mail address and I will send you one.

Thanks.

It looks as though the knobs on this #71 never had the brass nuts - they don't have a counterbored pocket, but instead a countersunk hole, and they're held onto the body with countersunk 12-20 screws.

Making new countersunk screws might be a bit of a faff (without a lathe), but I guess some suitable metal rod with one end cut with the 12-20 thread would be a solution; I could cut a metric thread on the other end for a pair of modern brass nuts and drill a little more material out of the tops of the knobs.

 

[Racers]

I have a 12/20 tsp and die, what do you need done?

Pete

 

[sploo]

I have a 12/20 tsp and die, what do you need done?

I need you to pop them in a jiffy bag and post them to me :mrgreen: (worth a try, eh?)

A couple of steel rods, each with one end cut with probably 1/2" length of 12-20 thread should do it (I can sort out the other end for some suitable brass nuts - the recent Stanley spares are metric, IRC).

I'll measure up the dimensions of what I need and let you know. Hopefully I should be able to find a rod with an acceptable diameter for the job.

Greatly appreciated - many thanks!

PS From where did you source the tap and die?

 

[Racers]

I got it years ago from bridge city tools they had a batch made specially.

Pete

 

[sploo]

I got it years ago from bridge city tools they had a batch made specially.

Makes me wonder about trying to see if someone would make another batch (assuming I could find enough others willing to buy)!

I've checked the #71, and what I'd need is two 60mm lengths of 5.5mm diameter rod (e.g. https://www.ebay.co.uk/itm/SILVER-STEEL ... 0289973012), each with one end cut with the 12-20 thread to a length of about 15mm.

I have some modern brass nuts, which use a 5mm thread - so I'd be able to shave 0.5mm off the diameter of the other end, and put a 5mm thread on them myself.

I could get the rod and post it to you (plus something to cover your time) or if you got the rod yourself I could supply you with some beer money via Paypal?

EDIT: It seems that silver steel is not great for threading, so perhaps some 6mm mild steel, reduced a bit in diameter, might be a better choice. I couldn't immediately find any 5.5mm mild steel rod.

 

[Racers]

Silver steel is a bit hard for threading, mild steel would be strong enough, I will check what I have got but I don’t think I will have anything the right size.

Pete

 

[sploo]

Pete - I've not been able to find any suitable mild steel rod (someone somewhere must surely sell "#12 diameter stock", but I haven't spotted any yet). I could get some 6mm diameter and try to get the last inch or so down to ~5.48mm for you to cut a thread on?

 

[Racers]

Yes thst should work, pm me when you have it.

Pete

 

[sploo]

OK, so I've just taken delivery of some 6mm mild steel rod... but I've also just got my hands on a used lathe (a Clarke CL300M - one of the many Sieg C2 clones, like Axminster's C2-300).

I guess instead of being given a fish, I should learn how to fish. I mean, it's just jabbing a sharp thing into a spinning thing. How hard can it be? :mrgreen:

 

[AndyT]

Making your own custom spare parts is a perfect justification for owning a lathe, you should definitely get stuck in. There are some good tutorials on YouTube. I like Tubal Cain aka Mr Pete 222, whose many videos cover most of metalworking including lathe usage. https://www.youtube.com/user/mrpete222
Is your lathe metric or imperial though? It might be possible to approximate some imperial threads on a metric lathe and get something which will be ok over a short length, but it won't be as simple as using an imperial lathe.

 

[sploo]

Making your own custom spare parts is a perfect justification for owning a lathe, you should definitely get stuck in. There are some good tutorials on YouTube. I like Tubal Cain aka Mr Pete 222, whose many videos cover most of metalworking including lathe usage. https://www.youtube.com/user/mrpete222
Is your lathe metric or imperial though? It might be possible to approximate some imperial threads on a metric lathe and get something which will be ok over a short length, but it won't be as simple as using an imperial lathe.

It has an imperial leadscrew and half nut; which for my purposes is ideal as I mostly want to use it for making replacement parts for old planes. I've got plenty of metric taps and dies, so don't immediately plan on buying the optional metric leadscrew.

I do need to spend some time learning how to use it, as I can currently think of at least 4 parts I need to make for various old planes. I'm sure more useful ideas will surface in time.

I was reading an interesting forum post about a guy using one (having downgraded from a much larger old lathe). He tried to take a 60 thou cut in steel (easy for his old machine) and didn't do the lathe much good! The manual suggests 10 thou as a maximum cut; which is a bit different from chomping through timber on the woodturning lathe...