Need advice for cutting #12-20 threads

[WCraig]

I refurbish pre-war hand planes ...

Do you mean Stanley planes? These planes were designed well before the development of the now-ubiquitous UNC/UNF/UNS thread forms. See discussion here, for example:

OldTools Archive

swingleydev.com

Plus these planes were in production for many decades. The specifications and tolerances likely changed a fair bit from the beginning to the end.

All that said, it seems that for the few threads engaged in the boss on the plane body, 12-20 UNS is good enough in most cases. The retaining nut engages more threads and may not be as forgiving.

Craig

 

[mwebster51]

Yep, I'm familiar with where Arroyo Grande is. My buddies and I go out to Pismo (Oceano dunes) once a year to "play", well it's been almost 3 since we last went.

Yes hobby lathes are very well capable. Some of them like the Chinese 7x that are very popular may need some work to get them working well but there are many resources online to help with all that as well as the mebers here. Or if you spend a bit more money & get something nice like a Sheline you'll have loads of fun.

But as far as turning down a 6" long rod down to .216 can get tricky because of the length & small diameter. There's things that you will need. I won't get into the details as it's irrelevant right now but it can be done.

I'm not familiar with wood lathes. Does the head stock have a through hole? Just thinking if you might possibly be able to use your wood lathe. Mount the rod in a chuck. Die on the tailstock. Use the tailstock to help put pressure on the die to get started. Would also keep the die square.

Thanks I will check into the metal lathes I have never really looked at them since I have only a few needs, but you know how that goes. Once you get a tool you find out all the stuff you can do.... I held off buying a bead/sand blasting cabinet until I retired and even then thought it would be frivolous but.... well I use it all the time with my restoration work. I figured turning down a thin rod would be difficult I have has similar projects on a lathe with wood and flex is a problem. As you suggested it is premature to discuss add-ons, but I assume one would need some sort of support to prevent flex.
Yeah Pismo dunes and Pismo beach are very popular. We retired from the San Joaquin valley to "heaven" a few years back.
I have never thought about using my wood lathe for metal. I modified it a fews back and added a variable speed motor so I would be able to slow it down. I can put a chuck in the head stock (and have one) that could hold a rod. I have never seen how one adds threads using a metal lathe. Seems a little scary to me if a die is used ie too fast or if not aligned exactly right.... . It hadn't occurred to me that one might affix a die to the tail stock, I guess I assumed there was some way to control the movement and depth of cut with a single point to creat a spiral (I don't know what I am talking about of course, we are talking machining.. not woodworking) Not sure about mixing metal fillings/cutting oil and woodturning.....
Thanks for your thoughts

 

[mwebster51]

Starting a die straight is tricky even with a lathe. Since you only need a few studs maybe you could mail the original stud to a hobbyist friend who could make up a few blanks by single pointing the threads to about 3/4s of the depth. Then you could use an adjustable die to finish the threads yourself to get the fit you want.

Thanks for the idea. I appreciate the suggestion

 

[mwebster51]

I have occasionally put a slight taper on the very end of a rod to help get a die started. All that takes is a bench grinder if you're careful.

As far as turning down a larger rod, it may be that only the threaded section needs to be reduced and a larger diameter is acceptable for the rest of the rod?

Actually your right it is only the last 3/4" in each rod that needs to be smaller. There is plenty of room for the shaft when in the wood. As far as tapering the ends, that is what I am doing now with success but it is still "difficult".... just looking for an easier/quicker way

 

[mwebster51]

How about running a 1/4-20 die on your 0.212" rod. That should cut about half depth threads that could then be finished with your #12-20 die.

Hmmmm.... sounds like it might work... I will give that a try... that would help save wear on the #12-20 die that is hard to get Thanks

 

[bill70j]

I live pretty close to you - in Los Osos, so maybe I can help.

FWIW

In case you were to take me up on my offer, I wanted to make sure I could come through - So I just cut some 12-24 threads out of 0.25" diameter O-1 drill rod, which I turned down to 0.2160".

I did it both ways - first by single-pointing on the lathe, then by using a "re-threading" hex die.

Both methods produced acceptable threads, though I prefer single pointing since you can control the fit.

But what surprised me was how well the die performed, considering this discussion. I wonder if your 12-20 die is dull?

Anyway, here are a couple of photos of this morning's activity.

Here is the hex die I used. It came out of a vintage Craftsman set I have had for years. (Sears sold them as thread cutting dies, but many claim they are acceptable only as thread chasers.)


Here is the tailstock die holder. I used it under power, with no problems with engagement or with cutting.


Here is the single point threading set-up


And here are the threads. Not pretty, but they work.

 

[mwebster51]

I’d use a quality hss die and brass stock. Use a lot of tapping lube. I know you are restoring the plane, and the original might be steel but I seriously doubt anyone would look down on a brass threaded rod. Brass is more expensive than the original steel and always looks great in my opinion.
I see you don’t have a lathe but I’m sure if you found a local machine shop.... they wouldn’t charge much at all if you showed up with a few 1’ length 1/4” brass rods and asked them to turn the rods down to .188.
12-20 is really an odd ball which has pretty much been replaced by 1/4”-20.
Brass is a joy to machine.
If you were in my area...I’d do that for you in an instant and wouldn’t charge you anything to turn down a few 1/4” brass rods to .188”
FWIW.... I suggested a few 1’ sections because it’s just easier to turn down than a long length of brass rod. For a long length.... I’d have to rig my follower rest on my lathe. For your needs... I’m guessing 3 one foot rods would last you a while..

Thanks for the input I appreciate the suggestions

 

[mwebster51]

To help start threads straight when using a die, I will turn down a short portion to slightly over the root diameter to act as a guide for the die, when the thread is finished, I cut off the turned down section. Dave's suggestion of starting with the 1/4"-20 die is a good alternative.

Yeah I think you guys are on to something here...Thanks

 

[mwebster51]

I live pretty close to you - in Los Osos, so maybe I can help.

We could pretty easily take your 0.2188" stock down to 0.216" on the ends -- leaving the middle untouched, as FanMan suggests, then thread the ends using a tailstock die holder. My holder can accommodate 1" hex dies and 1-1/2" round split dies.

If need be, we could also turn the whole 6" down to 0.216" - it would just be a bit more work. I have a follower rest and a tool post grinder - plus we could lean on Will for his ideas on successfully doing that.

We could also see how 1018 mild steel might work. As has been said, it would be a bit easier to machine than 01. We could also explore single point threading in lieu of using the die.

Let me know if you're interested in coming over and giving it a whirl.

Bill

Thanks Bill I will save your message and down the road I may take you up on that. I am new to this forum, do you have private messaging for communication like phone numbers and addresses?

 

[mwebster51]

If you have a drill press, and the appropriate die holder, you could use it to guide and hold tension on the die to ease starting your thread. Mike

I do.... another great suggestion, never having done this is seems like even at the slowest speed, the drill press would be turning awfully fast