Linkert idle bleed slot question?

[T. Cotten]

Folks,...

I have asked previously, on several forums, if anyone has solid evidence as to how L&L produced the delicate idle bleed slots.

One source swore that they used a "dental drill". That's nice, but even today, .008"-.0015" endmills that will cut .030" deep do not exist.
Just producing the cutters to produce a million slots would be an achievement that exceeds the rest of the venture.

Punching seems reasonable, but that's still an engineering feat, to produce no signs of burring or distortions.
How do you make punch guides that narrow and that deep? And wouldn't they have to be punched before they were finish bored?
Hardly seems practical.

The reason I bring this back up is because a rare pre-War Linkert came in where somebody had a "better idea" and ran a 1/16" drill bit through the large hole, about twice what it should be.

If I close the hole back up, I must then somehow re-cut the delicate .009" idle slot.

Thanks for any real help in advance,

....Cotten

[Robert Luland]

If I were going to bang out a zillion of these things? Most likely the piece is stamped. Way to much trouble to drill two holes and the run a mill end across. If it was stamped in a precision die. You wouldn't have burring or distortion. Keep in mind, it's soft brass. Bob

[T. Cotten]

Well, Robert,..

These two M51s show that the holes were performed in a separate operation, and this M74B aberration shows that a piloted punch would have had a hard time to miss by that much.

All I have gotten over the years is arm-chair conjecture, for a feat as mysterious to me as the building of the Egyptian Pyramids.

Just look at one Folks.
That's ~.030" of bronze that has been slotted without a booger, pucker or bulge, and down deep in a hole.

Even modern reproduction attempts with EDM were sloppier.

....Cotten

[pisten-bully]

Cotten, understand you're searching for how it was originally done and I can't help you there, but I dunno... to effect your current fix what would happen if you used something more maleable, such as lead to fill the hole, then you could cut the slot with an exacto knife?

[T. Cotten]

Harry!

Soft solder and a feeler gauge cut with saw teeth has been my crude approach before, but I constantly try to improve.

Think about it, Folks,...

A punch for a .008" blade (the thinnest I have recorded; .009" for many) would not only require an extremely precision guide that threaded into the hole to exactly the same index each time, but an equally precision anvil with just as accurate and indexed female hole to accept the slug that is punched.

Literally hundreds of thousands of Linkerts were produced with remarkable precision, for well over three decades.
Yet just six decades later, we do not know how.

The lost History still stings.

....Cotten

[Robert Luland]

Tom, even if they went the long way. Once you have a jig in place, you can pump it out all day long. Drill a hole, slide to next station. Mill slot. If they can do this on watches. Then this is a piece of cake. Bob

[T. Cotten]

Tom, even if they went the long way. Once you have a jig in place, you can pump it out all day long. Drill a hole, slide to next station. Mill slot. If they can do this on watches. Then this is a piece of cake. Bob

Easy for you to say.

Hold one in your hands and look closer.

Seriously.

...Cotten

[MMasa]

Maybe it was done with some sort of precision keyseater? (It's like a shaper) Bobs reference to watch parts is valid. The technology existed back then to make some very small and precise parts.
Mark

[T. Cotten]

Maybe it was done with some sort of precision keyseater? (It's like a shaper) Bobs reference to watch parts is valid. The technology existed back then to make some very small and precise parts.
Mark

Mark!

A shaper would have to work from the inside of the carb bore, as no conventional tooling is going to fit in a 5/16" hole, 3/8" deep, and then cut through .030" of bronze.

As far as Bob's cavalier notion of just milling the slot, making the cutters themselves would be a feat un-matched today; .009" endmills are available for cutting circuit boards, but not .030" long.
Nor could a mill be long and thin enough to cut as close to the wall as the botched M74B example I posted.

I can only imagine that it was a reciprocating saw.

....Cotten

[MassHarley]

Maybe some type of precision wire saw?

This PDF describes the cut as a "lapped finish"

Just and Idea

http://www.princetonscientific.com/rsc/pdf/Wire.pdf

Mike

[MassHarley]

One more thought. How about a jewelers saw blade.

http://www.sloanswoodshop.com/scroll_saw_blades.htm (Scroll almost to the bottom)

Drill the two holes then insert the jewelers blade using a deep throat coping saw. With a steady hand and some time you could get a fairly straight cut.

Mike

[exeric]

I think they would have used a broach and support fixture that would would make the slot between two holes. As Bob said, watch manufacturing was far more sophisticated than this.

[BigLakeBob]

Mark!

A shaper would have to work from the inside of the carb bore, as no conventional tooling is going to fit in a 5/16" hole, 3/8" deep, and then cut through .030" of bronze.

As far as Bob's cavalier notion of just milling the slot, making the cutters themselves would be a feat un-matched today; .009" endmills are available for cutting circuit boards, but not .030" long.
Nor could a mill be long and thin enough to cut as close to the wall as the botched M74B example I posted.

I can only imagine that it was a reciprocating saw.

....Cotten

I doubt they were available then, but I can buy a .009 x .030 long endmill nowadays.

[T. Cotten]

So Bob!

You have a spindle to drive such a hair-thin endmill down in that hole?
How many do you expect to break? How would you even expect to index down in that hole?

Mike!

I don't see any scroll blades that are only .009" wide; The Princeton Scientific sounds hopefull, but I cannot view it until I get home to a PC with Adobe....

And Exeric!
A "brooch" basically gets us back to a feeler gauge with saw teeth, and one that would insert through a .052" hole.
Making the indexable guide to produce hundreds of thousands of carbs would be the hard part. (But it wouldn't explain the M74B anomaly.)

Meanwhile, digging in my watchmaking tools, I have retrieved a handle, and now must make a saw from a feeler gauge.

Fluxing only the big hole with a capillary pipette seemed to work, as the #70 hole was easily finger-drilled.
Locating the big hole required more patience, but I am now atleast up to Schebler design.

Now to bring it back to Linkert specs.

How sad that so much History has been lost and forgotten.

....Cotten

[harleytoprock]

If they used a punch and die, then how did they make the male punch and the female die? Just stirring the pot a little. Remember, no edm, laser or cad back then.