getting a die to cut

[zeeprogrammer]

Just a itty bitty miffed...

The drawing calls for a 0.157 DIA and #8-32UNC-2B THD.
Material is half hard 360 brass.
Instruction calls for using a Die Holder in tail stock.
After die cutting, instruction calls for reversing the die and cutting the last bit.

I have an 8-32NC die. My understanding is that UNC and NC are interchangeable.
I have no idea what 2B means.
I do not have a Die Holder for the tail stock.
Picture shows a round die...mine is hex.

I got it turned down to 0.157 (maybe 0.158).
Took a run using a die stock (hand holder).

It's not cutting. Nothing. It's like the diameter is too big. It's 0.157 as called for.
Tried reversing the die on a lark. What? The die simply slipped over. (Dead lark?)

??? What's wrong? Bad die? I wouldn't be surprised. Is cheap. But I thought it would do better than it is. Any other hints?

On the up side (what's keeping me from tossing the die across the room)...I made my first tool tonight ;D. I ground down a hack saw blade to the shape of a cut-off tool, snapped off the end using a vise...and made some thread reliefs on the part. First time I've used a grinder. Happy (except for the die).

Thanks...anyone and all.

 

[joe d]

Zee

Your o.157 dia sounds ok as Machinery's Handbook gives 0.164" as the basic major dia for an 8-32, so that should work. Have you tried putting a bit of a chamfer on the end of the stock to let the die ease it's way on? you might give it a little drop of some sort of oil as well. As to the hex/round die question, some are round, some are hex, I've no idea why. Somebody will enlighten us both on that! It should only affect which diestock you're going to use.

Joe

 

[ksouers]

zee,
The 2B, I believe, is the fit of the thread. There are a few grades for the fit, whether it'll be somewhat loose or tight with very close tolerance. Normally you would use the same fit tap and die together when making matching parts. For example, if you know you are making something designed to operate at extremely cold temperatures you'd want things to fit differently than if it were operating at warm temperatures, to compensate for dimensional changes between manufacturing temps and operating temps. Normally for us it's not an issue, but if you were building a jet engine or a satellite it would be.

Dies are made with a taper in the thread, just like a tap, for starting the thread. So, yes, there is a proper side of the die to start from. Did the die slip completely over the stock? Did you possibly slip into one of the reliefs?

You might also want put a slight chamfer or short taper on the start of the stock to help get the die started.

As for the round and hex, round are generally the better quality, made for use in manufacturing in a die holder. The hex nut types are generally lower quality, but still serviceable. The nut shape is for holding with a wrench and chasing existing threads for a quick repair.

Hope that helps.

 

[stevehuckss396]

I had the same problem. I bought a cheap set of taps and dies. Could never get a good thread on anything. Always had trouble starting them.

Started buying high quality HSS dies as i needed them. What a difference. They go right on and the threads are very clean.

Try a good quality die made in the USA or Poland. Them pollocks make some good stuff. You will be amazed at the difference.

 

[steamer]

Steve and Joe D make good point here.

Dave

 

[Davyboy]

Good points mentioned above. My experience with smaller dies is somewhat limited, but here's my take:

1 Backup the die in a holder using the flat face of the tailstock or the large solid face of a drill chuck. This will help getting the die to start true and straight.

2 Start the lathe SLOWLY. Apply pressure with tailstock until die starts to cut. It will take a little bit of pressure to start. It sounds like a 3-handed job, left hand on start button, right hand on TS handle, die stock handle on the compound surface to keep it from turning. Can also turn chuck by hand, forward and reverse to remove the die.

Good luck, and keep trying, it will work out. DB

 

[zeeprogrammer]

All...thanks very much for the replies.

I had tried oil.
And yes, it slipped over the stock but not in a relief.
I had a previous issue with this tap/die set...and was warned then that it was cheap.
Tried the chamfer...your comments made me wonder if it was enough. So I gave it a 'good' chamfer. Still no go.

Right. Time to go shopping (again). Fortunately I'm into this enough now to know it's worth it. Any suggestions who a quality maker might be?

Thanks again. And I'm sure other newbies appreciate the quality information you all give.

DB: Got your post while writing my reply. I wanted to go that way but didn't have the right die shape (round) or holder. I think I'll buy that while I'm at it. Then I'll be a pro - right? ;D

 

[steamer]

Zee,

Most dies are a standard OD and the cheap ones are hex.

13/16 , 1.00" and 1.5" are standard OD sizes

A good tailstock mounted die holder is worth the investment in either time or money

Buy only High speed steel dies and greenfield makes nice ones.

Dave

 

[speakerme]

Hello,

For short runs Hanson dies seem to work well, cut well without much muss or fuss, although they typically are hex style.

Good luck with your item


Chuck M

 

[websterz]

All...thanks very much for the replies.

I had tried oil.
And yes, it slipped over the stock but not in a relief.
I had a previous issue with this tap/die set...and was warned then that it was cheap.
Tried the chamfer...your comments made me wonder if it was enough. So I gave it a 'good' chamfer. Still no go.

Right. Time to go shopping (again). Fortunately I'm into this enough now to know it's worth it. Any suggestions who a quality maker might be?

Thanks again. And I'm sure other newbies appreciate the quality information you all give.

DB: Got your post while writing my reply. I wanted to go that way but didn't have the right die shape (round) or holder. I think I'll buy that while I'm at it. Then I'll be a pro - right? ;D

Make yourself a die. Take a piece of drill rod, 3/8 will do nicely, and drill/tap it for 8/32. Chuck up a slitting saw in the mill and split the threaded end into 4 quarters, about half way up the length of the threaded section. Chase the threads with the tap to deburr. Then take your Dremel and use a small stone to grind a chamfer so the die can start on the stock easily. Look at your existing die for an idea of how much chamfer you need. Heat it up cherry red and plunge it into a bucket of water and stir vigorously. This will harden it. If you are just cutting brass you really don't even need to temper it, just use it as-is. You can chuck it up in the tailstock chuck and thread away. ;D

I would make the total length about an inch and drill right thru so the chips don't bunch up.

 

[Maryak]

Zee,

I've got one of those cheap charlie chan carbon steel tap and die sets. On the dies there is no split and no tapered lead in. To get them to cut at all I've reduced the nominal OD by between 0.005" and 0.010". This plus a long tapered lead in and the job well over the required length results in a reasonable thread for ordinary situations.

Hope this helps. ??? ???

Best Regards
Bob

 

[zeeprogrammer]

Davyboy: I misread your post. While I wait for a better die, I'll think I'll give your idea a try...along with some of the suggestions that other members were kind enough to offer.

Steamer and speakerme: Thanks. I'll look for them.

websterz: uh maybe I should have been more specific and said 'pro purchaser' (a hard enough goal competing with my better half). I'm no where near ready to drop hot things into oil...although I suspect I'd better get ready.

Maryak: Thanks. While I search/buy/wait for proper tools I'll give it another go.

Thank you all. Success is around the corner.

 

[tmuir]

The hex dies I've seen have always been for repairing damaged threads not cutting new ones or very cheap nasty ones.
I buy HSS taps and dies individually as I need them and there is a huge difference between them and the cheaps ones in quality and in price.
A good quality tap and die should last you forever for the amount of use we put on them.

 

[websterz]

websterz: uh maybe I should have been more specific and said 'pro purchaser' (a hard enough goal competing with my better half). I'm no where near ready to drop hot things into oil...although I suspect I'd better get ready.

Bah...nothing to it. :big:

 

[mklotz]

SOME hex dies are rethreading dies meant to clean/restore already-machined threads. But only some - I have an older set of Craftsman hex dies that work quite nicely.

The biggest problem with hex dies is that they are generally not adjustable. Most quality circular dies are adjustable.

Buying cheap taps and dies is one of the worst false economy mistakes a novice can make. In model making, threading is often one of the last jobs to be done on a part in which much time is invested. Don't bung it up with bad tools. Don't buy sets; buy quality dies one at a time as you need them.

Forget the handheld die stock for starting a thread on the lathe. A tailstock mounted die holder is definitely the way to go. It's a simple and very useful novice tooling project. Make one end to fit small dies and the other to fit the larger size.

Once you've made the holder, start the thread by hand - not under power. You'll have better control and it's safer.

Don't worry about class of fit at the moment. There are situations where it matters but you're a fair distance from that point right now. Concentrate on getting a male and female piece that will thread together.

 

[Mainer]

Make (or buy) a tailstock die holder. As Marv says, worth the effort. Here's a couple photos of the one I made. It's 2" dia. aluminum, 4" long, lightly knurled, drilled to be a sliding fit on a piece of 1/2" rod. One end is bored out to take 1" dia. dies, the other end bored out to take 13/16" dia. dies. The setscrews to lock the die in place are below the surface, so there is nothing to catch.

To use, I just grab it and hold on, and run the lathe in slowest back gear. While that may sound like a dubious proposition, in practice it works fine. I've done up to 5/16-18 threads, but that's probably a bit much. Anything up to 1/4" though, I have no problem holding.

If you make one, aim for "rattling good" fits. I made the clearances a bit too snug, and sometimes a slightly expanded die won't fit easily in the counterbore, or the holder binds on the rod because of a chip.

 

[mklotz]

Mine has threaded holes into which I can insert threaded handles to give me more torque when threading the larger sizes (note: I don't thread under power).

Also, if you have hex dies, you can make the counterbore large enough to accept them and then prevent them from rotating with a couple of axial set screws. There's no need to broach or otherwise construct a hex-shaped hole.

We haven't explained split dies to Zee yet so perhaps a preemptory explanation is in order.

Split dies, as the name suggests, are split and fitted with a small screw that can be used to slightly pry the die apart thus increasing its bore and consequently diminishing the depth to which the threads are cut. This is useful in tough materials or if one wants to purposely make a tight-fitting thread.

Once these shallower threads are cut, the die can be closed down by backing off the small die screw and using the set screws in the die holder to close the die down again to cut deeper threads.

Try to always buy split dies. The flexibility they afford can be very useful and you'll appreciate having same as your work becomes more complex.

 

[arnoldb]

Zee, just to add my 2 cents FWIW

I agree with all who recommended getting quality dies. I've made a habit of buying a whole "kit" when I need a certain type and size of thread - my "kit" consists of a die, taps, and appropriate drill size for the taps. These I keep together - makes life a lot easier

The reason that the original specifications say that you must thread, and then reverse the die to thread the last bit, is because - usually - a die has a correct side to start with. If you look at the die, it will have a visibly larger opening on one side with a deeper chamfer than on the other side - that is the one to start from. If you finish the thread with the die reversed, you can cut the actual usable thread closer to a shoulder on your workpiece. A chamfer of _just_ more than the inner diameter at the start of the piece to be threaded helps a lot.

I specifically stated the "usually" above - most of my dies are good German-made HSS ones, with the difference that they don't have a right and wrong side that I can establish - they easily cut both ways. While easy to use, this has the disadvantage that I cannot use them to get close to a shoulder, which, it appears, is what you need. Don't throw away the "cheapies" if you get quality dies - you can use them to finish closer to a shoulder if needed by reversing them(you could even grind their faces down on your bench grinder to make this more effective )

Also, I agree with Marv - don't do the tapping under power, unless you are _very_ confident that you can stop the machine _VERY quickly_ if something goes wrong. If you find turning the chuck manually hard work, try to set your lathe for highest turning speed, or if possible, completely disengage/slacken drive belts - this will ease the turning effort you have to put in to manually turn the chuck, and give you a better "feel" for the threading. On my Myford, I set the bull-wheel lock for back-gear, and then leave the back-gear selector for high speed. When like this, the mandrel, and thus chuck, is completely free-spinning without any drive back through to the fan-belts to the motor.

Regards, Arnold

PS: HMMM... today 1 US$ was worth 8.26 N$, so my "2 cents N$" is just worth somewhere around US$ 0.00242 :big: !!!

 

[zeeprogrammer]

Marv: You've admonished me before regarding cheap kits. And, while I understood it then, I just haven't gotten around to it. So tried (and failed) again.

Mainer: As it turns out...I do have a die holder. 13/16" and 1". I just don't have the appropriate 1" die. Your pics helped me realize what I had (to my chagrin).

Marv: Thanks very much for the explanation of how to use split dies. Very very helpful. I thought the idea of using the holder's screws to squeeze in interesting too.

Arnold: Yes. I'll be purchasing the bits this weekend. (grumble - I'm running out of things to do while I wait for tools ) The 2 cents might be worthless..the info - priceless

Marv & Arnold: I won't be using power.

Thank you all. Very excellent help.

 

[Foozer]

Just a itty bitty miffed...

It's not cutting. Nothing. It's like the diameter is too big. It's 0.157 as called for.
Tried reversing the die on a lark. What? The die simply slipped over. (Dead lark?)


hanks...anyone and all.

Did a clutch job the other day, ordered the parts, came in a box, right part number, but no way was an 11 clutch going to fit that 9 inch flywheel.

Right numbers, right markings but wrong part. Mis-marked die perhaps?

Robert