What to look for in Geometric die head?

I've been looking into buying a die head, but there's too many variables for me to know what to look for. One of my main concerns is availability and compatibility of chasers. Can you tell me what chasers fit which heads? Any other brands/models of die heads use Geometric chasers? Any unique features on different heads? Thanks.

The Geometric D type heads are the most common and so are the chasers for them. There are a few copies, mostly German, that take the same chasers. The German heads are just as good as the USA heads, but look a little bit different. The D heads come in 5/16, 9/16, 3/4, 1, 1.25 and other capacities. Each capacity head takes chasers that only fit that head. For instance, a 5/16 D head uses 5/16 D chasers, which are available in thread sizes up to 5/16" or 8 mm. Geometric made other heads, like the K, but the chasers are harder to find.

My first die head was a Geometric 9/16 D that had a 1900 patent date stamped on it. It is probably 100 years old now. It took brand new chasers and I made hundreds of parts with it. These things were made to last.

Look in a tool catalog (MSC, for instance) that lists chasers to see what is actually available new and what they cost. Genuine Geometric chasers are USA made, but I have a few good quality import versions that work fine and cost less. You can usually find lots of Geometric D chasers on eBay. Learn to recognize when they have been reground so many times that they are not worth buying. Yes, they can be sharpened with a surface grinder and a holding fixture.

There have been a number of other die head designs made over the last 120 years. They all worked fine when new, but most have become unpopular, resulting in difficulty finding chasers. I think there are a few companies that specialize in chasers for screw machine shops and probably have some of the less popular types.

I have seen a lot of eBay listings for die heads where the seller called it a "geometric," but it was actually one of the old designs that does not take Geometric D chasers. Most would be almost worthless. You need to study the pictures so you can tell what is being sold.

Larry

stick with the D type heads D, DS,DSA all use the same chasers in there head size ken

Make sure it is geometric and not what some say "geometric style". The only time I've ever trouble

buying them is when the base is out of alignment with head due to a crash. Depending on what your running them

on they also come in alignable or non alignable. Sizes are 5/16 9/16 3/4 1" 1 1/4" Depending on what your doing

one large diehead will do it all, although the larger dieheads tend to shave the threads on smaller brass and aluminum

threads. I had a 1" geometric on a turret lathe that a roughing lever on it which would allow you to make a roughing pass

then go right back after flipping lever and do a clean up pass which worked great on larger course threads. Also I would buy chasers

from someone who makes them like "Quality Chaser" they will give them the proper hook for the material your running. ususally in the

$125 range , most dieheads I have bought at auction are in the $200 - 300 range but its been a while. RD

You can also get chasers (standard and projection) from these guys. Sometimes NOS and regrinds. Good to deal with. Complete heads too.
Detroit Automatic Tooling, Inc

Here's one of many old posts on the subject.

http://www.practicalmachinist.com/vb/general/geometric-die-head-ds-dsa-187997/

I think today unless you get all the chasers you will ever need with a different brand, that a Geometric DSA is the most practical unit to own.

smt

A while back, I picked up a Jones & Lamson 1" shank die head for a good price (under $100) that came with a set of 3/8" coarse chasers. It's in top shape, low miles, still had the original box, and works like a champ.

But, J&L chasers basically don't exist- and those that do, are for something like a #21 (or whatever) and mine's something like a #19L. I've never seen another 19 (or whatever the size is, it's been a while) and haven't been able to find any extra chasers, regardless of thread pitch.

So yes, if you're going to get a die head, get a real Geometric. Or barring that, something that is known and verified to be 100% compatible with Geometric chasers. I understand Geo is expensive- that's why I bought the J&L, though that proved false economy- but they're worth the cost. I picked up a 5/16" unit, and it paid for itself the same day it arrived.

Doc.

A lot of great info here. I did notice the D heads seemed more prevalent. I didn't know that the chasers were a specific size though, so that probably saved my butt right there. A couple of more questions. How do I identify one with a roughing lever, and what's the difference between a D and a DSA?

A few quick comments.

D and DS chasers are compatible up to 1" heads. At 1-1/4, the D and DS chasers are totally incompatible. The 1-1/4 DS chasers are the same blank size as the 9/16 D/DS chasers, while the 1-1/4 D chasers are the same blank size as 2-1/2 C chasers and a bunch of other large sizes.

The A in DSA supposedly stands for "aligning", meaning you can stick it in a dodgy turret hole and correct it to match up with the spindle centerline.

Rubometric is a really good German clone of Geometric.

Many eBay sellers have absolutely no fucking clue what brand, style or size of die head they are selling. The rule of thumb seems to be "every die head is geometric" (even if it is clearly labeled Landis!) and "if the diameter of the head is 2-1/2, this must be a 2-1/2 die head." It does not help that Geometric's original markings were often very faint right out of the box.

If you read the link I posted above, the S refers to a scale on the side of the head, for adjusting the size of the thread. (thread fit/class). A -D- head does not have this scale.

Both mine are DSA's so what has not been completely clarified in previous posts is whether the adjustment exists on a D, but absent the scale; or whether a D is non-adjustable. I tend to think a die head would have to be adjustable, but maybe someone else with a D only head can comment further.

My personal feeling is that unless all the work pieces will be held as a second op in a floating holder, an A type (adjustable shank) for centering in a turret is the only sensible option. Yes, it takes a moments checking and set up, but then it will cut on size non-tapered threads repeatable due to being on center and not deflecting from being up/down/or sideways.

smt

stephen thomas said:

If you read the link I posted above, the S refers to a scale on the side of the head,

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Was that to my address? I discussed the "A", not the "S".

what has not been completely clarified in previous posts is whether the adjustment exists on a D, but absent the scale; or whether a D is non-adjustable.

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I'm pretty sure all my D models are adjustable, although I can't sure that applies to all sizes of D. At least one of my D's has a witness mark and rude scale scratched in by a previous owner.

sfriedberg said:

Was that to my address? I discussed the "A", not the "S".

I'm pretty sure all my D models are adjustable, although I can't sure that applies to all sizes of D. At least one of my D's has a witness mark and rude scale scratched in by a previous owner.

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I was responding to Forestgnome who said

A couple of more questions. How do I identify one with a roughing lever, and what's the difference between a D and a DSA?

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Thanks for the clarification that a D can be adjusted for thread fit/dia/class. That seems to mean the S only refers to having a factory inscribed +/- scale but that either are adjustable. I did not comment on A because you already addressed it in your separate answer to ForestGnome.

smt

Just to add to the confusion, I've seen a couple of photos of a 1-1/4 DD Geometric with scale, but with no witness mark. (Possibly the head was disassembled and then reassembled with the front at the wrong rotation.)

Forestgnome said:

How do I identify one with a roughing lever?

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At the tail end of the die head, just in front of the shank&mounting plate, there's a small metal rod that can swing out. On some heads, the roughing position is marked with a stamped 'R'.

sfriedberg said:

D and DS chasers are compatible up to 1" heads. At 1-1/4, the D and DS chasers are totally incompatible.

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What I wrote is probably confusing. Below size 1, all Dx Geometric die heads use compatible chasers. At size 1 the D, DD and DJ heads use one size of chasers, while the 1 DS and DSA heads use a very different size of chasers. This pattern continues for 1-1/4 and larger Dx heads.

I've found this document, Geometric Style Die Head Capacity Chart, very helpful.

stephen thomas said:

If you read the link I posted above, the S refers to a scale on the side of the head, for adjusting the size of the thread. (thread fit/class). A -D- head does not have this scale. smt

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Sorry, somehow I missed that. All of the responses have been thoroughly helpful!

I was digging through some old books today and found some interesting stuff about Geometric die heads in Screw Thread Production to Close Limits by Howard Adt, The Stirling Press, 1920. Despite the title, the book is 60% by page count "why you should use, and troubleshooting of, Geometric die heads." At the time, the main models were D, DD and C. The photos of the D and DD models show size adjustments and scales. The D was the basic model, with fixed pull-off trip. The DD had a floating shank, like a reamer holder, which is a bit different from an adjustable shank which has a fixed alignment once you lock it down. The DD also had an adjustable pull-off trip, carried outside the die head body, which is a familiar feature on more recent DS and DSA heads. The D head was available with a roughing lever as an option, which opens the chasers 0.01" from the finishing size, while the DD did not have this option as it was intended for use in automatic screw machines (thus no one there to throw the lever on two turret strokes).

I find this especially interesting:

Where such parts cannot be efficiently threaded by the Style D Die-Head, the conditions are special and a die-head is designed to meet them. This is known as the Geometric Style C Die-Head, and, as in every case it is made to meet special conditions of threading, these die-heads are made only to order.

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What I knew from other reading is that they made C heads in sizes from 1-1/4 to 8, all of which use the same chaser blanks as either the 1 D or 1-1/4 D heads. But I had no idea all C heads were special order (at least in 1920).

"Screw Thread Production to Close Limits by Howard Adt"

Nice find! Lots of good info there. Free to download.
Screw Thread Production to Close Limits: Manufacturing Methods of Threading ... - Howard Elsworth Adt - Google Books

I can’t find the link where I downloaded it, but I have a 71 page .pdf copy of “Geometric Standard Screw Threading Manual” Covers all their Die & Tap heads. Any suggestions on where to upload it so others can download a copy?
Here are some other related links:
Downloads
http://www.akon-werkzeuge.de/doc/brochure Rubometric.pdf

Forestgnome said:

I've been looking into buying a die head, but there's too many variables for me to know what to look for. One of my main concerns is availability and compatibility of chasers. Can you tell me what chasers fit which heads? Any other brands/models of die heads use Geometric chasers? Any unique features on different heads? Thanks.

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i bought one of the 1-1/4 geometric heads that has six chasers. and idea where i can get chasers for it? it is a 1-1/4 ds model. b80226