Acorn Dies

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lkrestorer

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Does anyone use Acorn dies in their hobby work? I stumbled across them on Ebay and impulsively bought a couple 5-40 size just because I wanted to try them out. The dies were inexpensive but the holders are a larger investment. There is a company or two still making them but it almost looks like a special order situation. They do pop up on Ebay frequently

They worked so well that I have built a fairly comprehensive collection (from 1-80 to 1/2-20 with 1/8" and 1/4" pipe dies thrown in for good measure). I have to admit that I'm not an expert on their original purposes but they were apparently used in the older (before CNC) screw machines. Also, they are supposed to be easily sharpened with a stone in a Dremel tool (I haven't tried that yet). I have seen listings for some very unusual sizes - like 1/4-100.

I use them by mounting the holder in a drill chuck in the lathe tailstock and run the lathe at it's slowest speed. They are very good at self-centering as the holders are not totally rigid and have sliding parts designed to be self-releasing at the end of the thread length that you choose. All of mine cut extremely well and are adjustable for thread depth with a wrench on the holder - very quick and easy. The operation is much simpler than using "normal" round dies.
20200617_075909.jpg
 

LorenOtto

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They look very interesting. I will do more investigating, thank you for posting. I'm a tool junky.
 

SmithDoor

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You adjust for size
But I would stick with just regular dies.
I use 13/16" to 1 1/2" dies for my work.

Dave
 

L98fiero

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Looks like a simplified version of the Coventry die box.
Not really, they are a 'solid' die that can be adjusted for diameter by screwing down the hold down nut, they don't release like the Coventry/Geometric dieheads, they are like any solid die in that the have to be reversed to be removed.
 

lkrestorer

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I just stumbled on them while searching eBay for a standard die and decided to try them out. I've been VERY satisfied with their ease of use and cutting ability. My question comes from the fact that there have been a lot of them listed for sale on eBay. Who is using them and how are they using them? And, why aren't more people interested? I still have the regular round dies and use them for manual threading tasks but for use in the lathe these top the charts.
 

SmithDoor

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The last time I saw the acorn dies for sale was 1960's.
I have never use the acorn dies they just had high cost.
I holders for my lathe for 13/16" and 1" even have a 2 1/2" die holder with #4 morse tapper this holder need to sell since it does fit my SB 9.

You other types of cutters that just did not make the test of time. Most time is just cost that dome the cutter to history.

Dave
 

lkrestorer

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After reading your comment about the Coventry Die system I searched it out. That appears to be a unit with three individual cutters that need to be changed to change thread size. I would compare it to a Rigid brand commercial pipe threading machine. It looks like it wood be a lot more fiddly to use than these Acorn dies for hobbyist lathe work (with much more expensive dies). The Acorn is just one solid (but mildly compressable for adjusting depth of cut) piece that is quickly swapped out if desired.

Both systems look like they are designed for production work. I'm not sure how the Coventry releases but these Acorn holders are made so that they will travel a predetermined length and ratchet out to spin freely. If you need to cut a longer thread you just advance the tailstock as it's cutting. When the die reaches the depth you desire and it ratchets out you simply move the tailstock forward, re-engage the ratchet mechanism and then run the lathe in reverse to quickly back it off. Or, you can feed it forward and shut off the lathe when you reach your depth and then power it off in reverse without using the ratchet function.

For very small items I do not tighten the holder in the tailstock (drill chuck) and turn it by hand. Everything is well centered, the die is self clearing (you don't need to back up to clear the chips) and the cut is made almost effortlessly.
 

lkrestorer

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The last time I saw the acorn dies for sale was 1960's.
I have never use the acorn dies they just had high cost.
I holders for my lathe for 13/16" and 1" even have a 2 1/2" die holder with #4 morse tapper this holder need to sell since it does fit my SB 9.

You other types of cutters that just did not make the test of time. Most time is just cost that dome the cutter to history.

Dave
They are still being manufactured in limited fashion. I do believe they were used extensively in the past in screw machines. New ones are expensive but the eBay sales are relatively cheap. They were apparently long lasting in a production environment and with the ease of resharpening they could be sent back to the tool room to be sharpened quickly and reused. My guess is that CNC machines did them in.

These holders have a straight shank and could be used in almost any lathe tailstock with a little ingenuity. I'll try to take a picture of one in action and post it later.
 

SmithDoor

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Geometric type die head did the acorn dies.
The acorn can be re-shapen.
The Geometric type is simple to re-shapen.
But the downside to Geometric is cost I still have one. Just found the 13/16" work great and cheeper

They are still being manufactured in limited fashion. I do believe they were used extensively in the past in screw machines. New ones are expensive but the eBay sales are relatively cheap. They were apparently long lasting in a production environment and with the ease of resharpening they could be sent back to the tool room to be sharpened quickly and reused. My guess is that CNC machines did them in.

These holders have a straight shank and could be used in almost any lathe tailstock with a little ingenuity. I'll try to take a picture of one in action and post it later.
 

PeterD

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I use them all the time. They are great for quick,short run threading jobs.
I only use the #0&#1 sizes because of the type of work I do but they would be
just as useful in any small to Med size lathe. Very easy to Resharpen , they feed in straight and are self aligning, I am surprised they have fallen off the radar of home shop machinists.
here are pics of the 8&10 mm watchmakers arbors that I modified to accept
their die heads. I hope this helps and Please leave some on eBay for me.
image.jpg
image.jpg
 

PeterD

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The smaller one is holding a 0-80 die .
with a lever tail stock I can run the thread as long as I like and as soon as I pull back, the die head “freewheels” .I then put the spindle in reverse and the tool withdraws off the part.
 

Peter Twissell

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In response to an earlier question, Coventry die heads have a release mechanism which moves all four dies out radially when the holder is pulled away from its mounting, i.e. the tailstock or turret reaches a stop.
There are also two settings on the die head, allowing for a first and second cut.
I used Coventry die heads on Ward capstan lathes many years ago.

Pete.
 
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