Strange Lyman thread size question.

[Chill Wills]

I measured a Lyman thread on a Lyman powder measure and wondered if it is the same as the 310 tools use?
I measured it as 39/64ths -30. Odd!
Does anyone have a better description of this thread?
I do not have any 310 tools but I do have some old Ideal loading tools with adjustable seater. I an going have to check that tool to see if it is the same.

[Mk42gunner]

I've read that it is a 5/8-30, but also that that is not quite right. I have also read that it is a .605"-30, which is awful close to your 39/64 which figures out to .609375".

The thing to remember is that Lyman decided on these threads long before the SAE standardized thread sizes came about, 1926 IIRC from eighth grade shop class.

Robert

To answer the question, as far as I know the threads are the same. I have not tried the one adapter that I have (came with a #55 powder measure) on a 310 die, but it looks like it will work.

R

[ascast]

it is the same, not 5/8 as people commonly say. the measure wil mount on the old tru-line jr press.
310 tools come in two diameters, one is the standard which works for most cailbers. There is a larger diameter for big bases cases such as 348 Win or 50-70 Govt.

[farmbif]

is that on outside of drop tube that threads into tru line jr. which is the same as 310 dies.. I have 2- 55's an old orange one and a grey one and both have that thread on drop tube. the grey one came with adapter to 7/8-14. someone else posted something about the actual thread size not long ago

[AntiqueSledMan]

Sounds like it's M16-1, not a standard thread.
My chart shows M16-1.5 & M16-2, both would be a courser thread.
I did Google it, taps are available.

AntiqueSledMan.

[Green Frog]

When pressed, Lyman referred to it as .609” X 30 tpi. Dies and taps are available in that size, but tend to be non-Standard, therefore very pricey. For many years, each #55 powder measure came with an adaptor to 7/8 X 14 and it was/is available from Lyman as a separate item. In addition, there was a less well known adaptor in this size available from Herter’s to use the little dies in their presses with extra large diameter threads.

Froggie

[Pressman]

The thread size goes back to the founding of the Ideal Tool Company in 1887 and before. The .6075" x 30 tpi thread was somewhat common in reloading tool usage at the time. Once established in the Ideal hand tool line it was impossible to convert to another thread without orphaning all previous tools. In a time of lower disposable income this would have had devastating effects on Ideal and reloaders alike.

Actually, there are three Ideal hand tool thread sizes, Small: .381"x 30 tpi, Medium: .6075" x 30 tpi, Large: .652" x 30 tpi. The small dies were discontinued and up graded to medium size by 1926. The Large dies continued after WW2 to the point that Lyman made True Line Jr turrets for the large dies. That ended about 1961.

Ken

[Chill Wills]

Okay. Good explanations. I guessed the pre- SAE (Ideal) history might be the answer. I just had no idea what that history it was. Thanks for taking time to explain it.

[GONRA]

Back in ~1960's or so GONRA setup 30 TPI single point threading on my boyhood Sears lathe.
Made an adapter for 7/8-14, stray sizing dies: 7.62x25mm Tokarev, 9mm Steyr, .45 W&S Auto....
from 5/8 water hardening drill rod using boring bars, etc. etc. etc.,

[Bent Ramrod]

It’s at moments like those that you’re glad you kept your messy old hand gear change lathe, instead of upgrading to a nice, modern, convenient quick-change gearbox.

You’ll be a long time finding “30” on the plate on a QC box when you want to make a 310 die blank or stop ring. I made a seating die for the Ideal 225438 in those primed .22 RF cases that Fedarm sells, using the gas-check shank as the “heel” of the boolit. Ran a .22LR chamber reamer into the blank and turned the screw to get the extractor out of the way. I cobbled up a base plate and plunger to push the cartridge case in and out of the die, as I worried that the extractor would pull it apart again. Works like a charm.

[C.F.Plinker]

If you have the 7 inch mini lathe you can get 30tpi using a 40 50 40 60 set of gears. 40 is the top gear, 50 goes on the middle shaft in the inner position, 40 on that shaft in the outer position, and 60 on the bottom shaft. You may need a spacer on the inner position of the bottom shaft.

[alamogunr]

In another #55 thread, Jsm180 posted a link to instructions which include a parts diagram. Number 17 on the parts list is a 7/8X14 Adapter(7392036). This should be cheaper than just about any other solution.

https://www.lymanproducts.com/brands/lyman/scales-measures/55-standard-powder-measure