Threading in a turret lathe

I have a W&S #2 and I need to thread the stem on an End Brush (see link) to 1/4-20. The stem is about 1" long.

I guess I need a Geometric Die Head. I know little about them or other methods. What size head should I be looking for? What inserts do I want? Is there one on someone's shelf gathering dust?

I need to do about 200/hr. The threading will be done before the cup is filled with wire.

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Reply to
Tom Gardner
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5/16 or 9/16 goemetric die head will do the job just fine. You want D-Style self opening. Chasers are plentifull and cheap on ebay, new ones can be had for 9.00 plus shipping. Do not buy used chasers, most have been sharpened to thier limit and are worn out. You can expect to spend anywhere from $25.00 to $100.00 for a die head. The chasers can be resharpened many times on a surface grinder, geometric made several types of fixtures just for sharpening.

You can download a old geomeric manual here:

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Be advised geometric is out of bussines. Repairs and support is available from 3rd party vendors only.

Best Regards Tom.

Reply to
azotic

If I had to do it at that scale (200/hr), I would look into brand new stuff, well supported by dealers and manufacturer. Not into some old stuff with hard to find parts.

i
Reply to
Ignoramus30725

External thread, I presume.

For 1/4" threads, if you aren't planning to go much larger, the

5/16" die head would be the best choice, but you could probably use up to a 3/4" die head as long as you aren't going any smaller. A 1/2" would be pretty reasonable if you can find them. Some sizes are hard to find these days, and as I got all of mine from eBay auctions, I don't know about commercial availability.

For a turret lathe (not to be confused with an automatic screw machine, with which I have no real experience), you would likely need to make an adaptor collar from the shank of the die head to the socket in the turret. Mine has 1" turrets, and most 3/4" die heads come with 1" shanks already.

The die head has "chasers" not "inserts". It looks like a 4-jaw chuck, except that the faces of the jaws are formed to cut threads.

Depending on the material, you will want a different grind on the chasers (rake and taper at the entry), and if you are going into serious production, probably a second set of chasers (per thread you want to cut), and a sharpening fixture for the chasers to be used on a surface grinder.

The four jaws are closed to the cutting diameter by a lever, usually hand operated on a simple turret lathe, or operaed by cams on automatic screw machines, and fancy power-cycled turret lathes. When the chasers contact the spinning workpiece, they start cutting the threads, and pull the head and the ram of the turret in at the proper speed, until you hit a stop set for that station on the turret. At this point, the shank stops, but the chaser part of the hed is pulled a bit forther in, releasing a lock which allows the hand lever to spring to the "open" position, and the chasers to withdraw from contact with the workpiece. This allows the turret to withdraw the Geometric die head while the workpiece is still spinning. (There are also versions which have a push to trip setup, if there is room for something for it to hit in the lathe. Some can be converted fairly simply between the two release techniques.

The force needed for that pull by the threads is the primary limit on using smaller threads in larger die heads. The force required scales with the heads.

Note that above I said that it was closed to the proper diameter for the threads. Some have a small lever to switch between a roughing and a finish pass, so you feed it on twice. These are useful if you have a tougher material to machine. (Or, if you have stations to spare on the turret, you can have one set to roughing, and another set to finish to operate successively on the workpiece.)

I don't know what else you may be doing. I'll assume that the workpiece will start out a bit oversized for the thread, so you will want a roller box tool on the preceding station, to turn it down to the proper diameter (just barely oversized) to accept the Geometric die head. (You start off a little oversized, and you can check the settings for pitch diameter by simply measuring over the completed thread, because the thread form is complete.

Oh yes -- the chasers can have a shallow taper if you don't need full threads up to a shoulder, or can have a much sharper taper if you do need the full threads. When you buy the chasers, a good source will ask you for the workpiece material and other things so they can supply chasers sharpened to work optimally with that material.

The chasers are changed by pulling out a spring-loaded stop pin, and allowing the closing lever to move past its normal stop, at which point all four chasers can be slid out of their ways. (The ways and the chasers are numbered, and *must* be installed in the proper places to produce a proper thread.)

I think that it could handle that -- with a good fast chucking system. An automatic screw machine could certainly do it.

I use mine (most often) on brass, involving turning down a bit, knurling the part not turned down, threading 5/8-27 on the turned down part, drilling the center, and tapping for a center mounting thread, and then parting off -- and I have to stop and reverse the spindle for the tapping at least, and I get about thirty to forty in a couple of hours, with brass bar stock fed through a collet. You are just threading (as far as you have said), so it mostly will be a function of how quickly you can chuck and unchuck the workpieces.

Looking at that, I'm assuming that the major turning is being done on another machine. A proper collet to accept the cup (ideally with a stop to keep the depth consistent) would work well -- but you would have to stop the spindle for the change of workpiece.

Good Luck, DoN.

Reply to
DoN. Nichols

Another Excellent die head is "H&G" Can be had cheaper than Geometic and brand new dies are still somewhat available.

Gunner

Reply to
Gunner Asch

Tommy..contact Leigh at MarMachine in Costa Mesa California. He had a literal Shitload of H&G chasers as well as Geometric in all sizes. Most of the chasers were NOS

Tell him Gunner said to give you a good price.

Gunner

Reply to
Gunner Asch

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