Modify screwplate from Swiss to Elgin?

[LittleWatchShop]

Screws...the bane of my existence!

I have a nice set of Elgin taps and have watched some videos about making die. It is a lot of work to cut the main hole, then the relief holes and the slots...

This morning the wild idea came to me!!  Take a Swiss screw plate and drill out the screws and re-tap with a larger Elgin tap.

I think it is a good idea, but to make it work, I believe that the starting screw plate must be annealed.  To be done properly, I need an oven with controlled temperature ramp.  Even then, I am about 99% clueless in the world of metallurgy.  Then, after the threads are tapped, the plate needs to be tempered back to its original hardness.

I will continue to ponder.

[MechanicMike]

i'm gonna assume the swiss thread plate is a donor/scrap? if it is, then no problem. experiment away!

just my two cents-something as small as a screw plate I don't believe you'd need to have something expensive as such to ramp and regulate temp control. whenever I'd have to draw, anneal, harden or temper something in the shop, depending on the size of the piece I would use an oxy/acetylene brazing tip or rosebud tip, or something as small as a pop torch(portable hand torch)or even as small as a butane hand torch for soldering. The main thing is watch your color. a good dull to cherry red will draw whatever hardness the screw plate is. after, do a test hole-see what it sounds/feels like. If you smoke a drill well, you know its still got some hardness in it. repeat. 

when it comes to hardening, back up to a dull to slight cherry-to-orange red, then quick vertical dunk into some old heavy oil for a decent depth harden or quick cold water dunk for a decent case hardening. and even further I'd then run some surface colorless heat over the part, then air cool to seal the deal. 

I like this idea. cuz watch screws, actually threaded anything on a watch is a pain in the a$$.

9 hours ago, LittleWatchShop said:

I have a nice set of Elgin taps

I've got one too, in pretty good shape, box and all. Ever seen or do you have a set of Walthams? That seems to be a whole different story. 

[LittleWatchShop]

1 hour ago, MechanicMike said:

I've got one too, in pretty good shape, box and all. Ever seen or do you have a set of Walthams? That seems to be a whole different story.

Nope never seen Waltham taps. I have several extra Martin Fils plates...one of them would be the candidate.

[MechanicMike]

2 minutes ago, LittleWatchShop said:

Nope never seen Waltham taps. I have several extra Martin Fils plates...one of them would be the candidate.

Nor have I. Not. Even. One. I've been looking but not a single listing or even history of a listing. Hey let us know how your screw plate turns out. I'll be watchin. 

[Waggy]

My main concern would be the plate warping during the hardening process, as it is not a uniform shape the heat dissipation during quenching will be slower in thicker sections (and vice versa) leading to temperature differentials within the plate which will be 'locked' in when it finishes cooling. Even slight warping would be catastrophic for something like a watch plate where fractions of a mm can make or break a watch working. You may get lucky, but I think the odds of this are vanishingly small.

[nickelsilver]

Supposing you managed to fully anneal the plate, you still have the holes with cutouts to make the cutting edges (most of the time, some older plate have no cutouts and just forced the metal into a thread shape, some had one cutout, some two). Drilling and tapping would be next to impossible. 

 

 

Gazeley's excellent book Watch and Clock Making and Repairing has a great description of how to make a die, pic below. One issue with his method, he plugs the threaded hole with a piece of threaded steel before filing through the boundary between the two side holes and the tapped hole... but how do you make the piece of threaded steel? Though- it's a little more work, but you could make a simple die like the above old screwplates, with no cutting edges, and make your threaded plug with that.

 

I make dies when I need them, there aren't really good ones available any more except for rolling dies, but those aren't always useful (but they are great). Some pics of a couple home-made next to an old commericial die. 8mm outside diameter on the die.

 

A useful trick an old watchmaker friend taught me if you need a die quickly, is to drill and tap a bar of steel, whatever diameter is convenient for the bar, harden it and temper to a straw color, then grind back the end of the bar at a 45 degree angle until you just break through the thread. That break-through is now a cutting edge, and you can thread a number of parts before it dulls. Then you just grind some more. The limit is the depth of thread you made in the bar. Image is 4mm bar with a 0.60mm thread.

 

Edited February 24, 2023 by nickelsilver

[LittleWatchShop]

Ok...message received! I like the bar idea. I am gonna try it. I have lots of 01 bar stock. Will report back.

[nickelsilver]

1 hour ago, LittleWatchShop said:

Ok...message received! I like the bar idea. I am gonna try it. I have lots of 01 bar stock. Will report back.

O1 is perfect for this (well for pretty much everything watch related). When you grind, be careful not to draw the temper more. And you want the "business" end, the part ground away that will do the cutting, to be a full thread ideally. If it's not, you can grind back the face until it is (usually a bit of back-and-forth).

 

If you grind the angle at more than 45 degrees, or further into the thread, the material being threaded just tends to climb out of the notch. But when you get it all right it does work.

Edited February 24, 2023 by nickelsilver

[MechanicMike]

On 2/24/2023 at 10:16 AM, nickelsilver said:

A useful trick an old watchmaker friend taught me if you need a die quickly, is to drill and tap a bar of steel, whatever diameter is convenient for the bar, harden it and temper to a straw color, then grind back the end of the bar at a 45 degree angle until you just break through the thread. That break-through is now a cutting edge, and you can thread a number of parts before it dulls. Then you just grind some more. The limit is the depth of thread you made in the bar. Image is 4mm bar with a 0.60mm thread.

oh now I like that idea. basically a reusable single point die!