75% is for brass (or aluminum) but you should use 50% for the cast iron tappings. Also, use cutting oil liberally for cast iron because its brittle. Free-machining brass is somewhat self-lubricating, but I use oil anyway because I hate when it squeals.

 

Interestingly, I did find this chart from the American Screw Company showing that 12-20 was a standard thread for some companies in 1916.

That's great, thank you. It shows what I meant about it being an evolving standard-note the odd sizes, 7 & 9, and how it goes way beyond #12. What surprises me is that there's no #1 or #0. I thought they were there from the get-go. (The 00, 000 and so on are very recent extensions.) I'm also surprised that this standard wasn't more buttoned-down by 1916. But notice that this table has only numeric sizes. The question I'd really like to know more about is when and why this numeric machine screw standard got wedded to the fractional sizes inherited from Whitworth to form what we now know as UTS. I might have to go to an actual library to research that.

 

By all means, please report back if you do find an answer to why we use the numeric designations rather than fractional sizes. I have been unable to find any references to why the standard evolved that way only that it did so around WWI.

I did read somewhere that the UN thread pitches are defined such that there is a 15% increase in mechanical advantage for a particular size going from UNC to UNF and from UNF to UNEF. Maybe that defined correlation falls apart at smaller fractional sizes without introducing odd number pitch sizes? Just a WAG, I have absolutely nothing to back it up and don't have time to dive into the calculations to see if it proves out. Though it does sound interesting and may do so at some point…

 

I'm glad I've found someone who finds this as interesting as I do, because, y'know, when you start talking about it at cocktail parties…

 

Knob and tote rod thread diameters for my older planes, all pre 1888. All seem to be cut threads, nothing rolled.
Comma separated if you want to manipulate…

0.2095, 0.2070, cut, type5, No4
0.2070, 0.2050, cut, type5, No4
0.2090, 0.2090, cut, type4, No4
0.2070, 0.2085, cut, type4, No4
0.2215, 0.2205, cut, type2, No4
0.2195, 0.2195, cut, type2, No4

0.2085, 0.2110, cut, type5, No7
0.2050, 0.2060, cut, type5, No7
0.2060, 0.2060, cut, type4, No7
0.2070, 0.2065, cut, type4, No7
0.2065, 0.2040, cut, type2, No7
0.2085, 0.2080, cut, type2, No7

 

Awesome Mike, glad you have that many early examples Could you tell whether they were all 60 degree thread forms or if any were 55 degree?

 

Sorry, no, my eyes aren't that good.

I did just look at a type 13 (1925-28) rod, and it looked rolled.

 

Nothing to add, but thanks to all who added to this thread, some useful info here.

 

I'm really curious about the No 79 and 98/99. Is it really 27 tpi? Mine is, and even wierder, my thread gauge has a 27 tpi blade.

 

That is weird Mike. Unfortunately I don't have any of those planes to check. I was curious about the 27 tpi though since the only threads I knew of with that pitch are tapered pipe threads.

So, first stop, the gearing chart for chasing threads on my lathe:

Low and behold, there is a 27.

So, stop #2 is my shop bible aka The Machinery Handbook (28th edition). Table 1 in the threading section:

Also a 27 there.

So I combed through Table 3 in the Handbook and found there are a handful of UNS (s=special) threads with 27 tpi listed. However, nothing smaller than a 1/4"-27. So your #10-27 is indeed an odd duck. Or, perhaps it's a 3/16-27? Who knows.

If you need to chase those threads though, I found you a tap. Of course just buying a new plane would be cheaper ;-)

 

Knob and tote rod thread diameters for my older planes, all pre 1888. All seem to be cut threads, nothing rolled.
Comma separated if you want to manipulate…

0.2095, 0.2070, cut, type5, No4
0.2070, 0.2050, cut, type5, No4
0.2090, 0.2090, cut, type4, No4
0.2070, 0.2085, cut, type4, No4
0.2215, 0.2205, cut, type2, No4
0.2195, 0.2195, cut, type2, No4

0.2085, 0.2110, cut, type5, No7
0.2050, 0.2060, cut, type5, No7
0.2060, 0.2060, cut, type4, No7
0.2070, 0.2065, cut, type4, No7
0.2065, 0.2040, cut, type2, No7
0.2085, 0.2080, cut, type2, No7

- drsurfrat

Thanks. Did you happen to measure the diameter of the unthreaded portions of the rods? I'm curious about the stock they used.

 

whoa. Fortunately, they are in good shape. I am sure somebody with a 79 or 98/99 will chime in.

 

Added bare rod diameters

0.2095, 0.2070, cut, type5, No4, 2065
0.2070, 0.2050, cut, type5, No4, 2050
0.2090, 0.2090, cut, type4, No4, 2065
0.2070, 0.2085, cut, type4, No4, 2040
0.2215, 0.2205, cut, type2, No4, 2080
0.2195, 0.2195, cut, type2, No4, 2075

0.2085, 0.2110, cut, type5, No7, 2090
0.2050, 0.2060, cut, type5, No7, 2045
0.2060, 0.2060, cut, type4, No7, 2060
0.2070, 0.2065, cut, type4, No7, 2055
0.2065, 0.2040, cut, type2, No7, 2055
0.2085, 0.2080, cut, type2, No7, 2070

The No 4 type 2 stands out, but doesn't look rolled to me:

 

Awesome Mike, glad you have that many early examples
- HokieKen

I really enjoy holding a tool that was made a couple years after the Civil War (even tho made by Yankee Carpetbaggers). Cast in a foundry before personal deodorant, ground flat by a master craftsman, exotic wood from far away countries piece-worked at 3 cents per, when coffee cost $1.20/lb, and there was a 3 cent nickel minted for postage…
I hated history in school, but have an unexpected fondness now.

 

I agree Mike. It is very cool to think of the history of some of these old tools when you put them to task. Every time I chase a thread on my South Bend lathe, I think "wow, somebody made a screw the same way nearly a century ago on this same machine" )

For rolling a thread that size, the blank rod would typically be .004-.005" smaller in diameter than the major thread diameter. For a cut thread, you expect the rod size to be the same as the major diameter. Of course threads also take some deformation when tightened and some corrosion can increase the measured diameter too. So, if those were new rods, I'd say they were rolled based on the measurements. But being 150 years old, who knows. Rolled threads would have been uncommon in the 1800s outside of shops only making fasteners though. Stanley had their spoons in a lot of bowls though so it's entirely possible they had the tooling somewhere. It's also possible that they purchased the threaded rods rather than producing them in-house.

 

The ones where the rod diameter is between the major & minor diameter are textbook rolled. Cutting only removes metal, while rolling raises the threads by pushing down the valleys. Technically this is called forging. It moves metal instead of cutting it away.

I honestly don't know what to make of the ones where both the major & minor diameter are bigger than the rod they started out with. I've never seen anything like that except, back in the dark ages when I used to work on Volkswagens and Porsches, some of the Porsche engines and the type IV VW engines had these cylinder head studs that were thicker at the threaded ends than in between, but this had to do with reducing thermal expansion while retaining anchoring strength. Planes don't operate at those temperatures, so I'm really at a loss.

I suspect all these threaded rods were made in house. Fasteners were their bread and butter, and if Stanley was making drills for the home market at the same time, they would have had dies for drawing wire in all the fractional sizes from 1/16" to ¼".

 

I'm tempted to walk into Home Depot, plunk down $36.97 for a brandy-new No 4 smoothing plane so I can take off the plastic knob and tote and see if they're still using these same threaded rods. Then I could get some measurements that would pretty much remove field wear from the equation. With a little work I might even be able to make a decent plane out of it.

 

I m tempted to walk into Home Depot, plunk down $36.97 for a brandy-new No 4 smoothing plane so I can take off the plastic knob and tote and see if they re still using these same threaded rods. Then I could get some measurements that would pretty much remove field wear from the equation. With a little work I might even be able to make a decent plane out of it.

- HapHazzard

I can't say for sure, but I'd expect to see 'oval head' machine screws rather than threaded rods with barrel nuts on later Stanley planes.

 

I can t say for sure, but I d expect to see oval head machine screws rather than threaded rods with barrel nuts on later Stanley planes.

- poopiekat

It'd be just my luck if they finally got around to using metric.

Turns out the only way I can get this is to order it, so I can't check it out in the shop first. $36.97 isn't a lot, but I already have a Buck Bros. No 4, so it would be somewhat redundant.

 

Some interesting stuff in this blog post I stumbled across from WayneC. According to his info, Record planes used Whitworth thread forms (makes sense being made in England) for the knob and tote rods.

...
I honestly don t know what to make of the ones where both the major & minor diameter are bigger than the rod they started out with. ...

- HapHazzard

I think Mike's measurements are the major diameter of the threads measured on both ends of the rod rather than major/minor diameters.

 

Some interesting stuff in this blog post I stumbled across from WayneC. According to his info, Record planes used Whitworth thread forms (makes sense being made in England) for the knob and tote rods.

Whitworth was also widely used in the US in the late 18th century. It was the first widely accepted standard, and served as the basis of Sellers's proposed standard.

I think Mike s measurements are the major diameter of the threads measured on both ends of the rod rather than major/minor diameters.

- HokieKen

Oh, that does make more sense. Whew. That was making my brain hurt.

 

Whitworth was also widely used in the US in the late 18th century.

I meant 19th. Only off by 100 years.

 

Yeah, I knew where you were going ;-) Record didn't start making planes until well into the 20th Century though, around 1930. So had they been in the US, it would have been odd for them to use Whitworth at that time. But being an English company, I guess it wasn't that abnormal to still use those threads even at that time.

 

I m tempted to walk into Home Depot, plunk down $36.97 for a brandy-new No 4 smoothing plane so I can take off the plastic knob and tote and see if they re still using these same threaded rods. Then I could get some measurements that would pretty much remove field wear from the equation. With a little work I might even be able to make a decent plane out of it.

I've got a new-old (NOS) global #3 or two. The rods for the knob and tote were threaded 12-20 (or 7/32-20) with barrel nuts. I routinely replace the rods with 1/4-20 all-thread after running a tap through the female bits.

They're model 12-163, if that helps. Cost $37.50 new in blister-pack, shipped from Canada.

 

Yeah, I knew where you were going ;-) Record didn t start making planes until well into the 20th Century though, around 1930. So had they been in the US, it would have been odd for them to use Whitworth at that time. But being an English company, I guess it wasn t that abnormal to still use those threads even at that time.

- HokieKen

Somewhere, it was said that Stanley dumped tons of parts on postwar England to build planes with, all of their surplus stuff and leftover junk, just to get the Brits going on their reconstruction period.