# DEALING WITH 4-40



## riversidedan (Jan 13, 2022)

wanting to make some small threaded rods with a 4-40  die and wanting to know whos had experience  threading that small of rod.
will put the die in the chuck and rod in the TS chuck and have to force the rod in, the die is octagon so needs to go in the chuck.
anyway the setup is good just wondering whos messed with small rod threading////////



gentleman....................drill size for a 4-40 is .0890 or #43  the short steel rod to be cut  is .0935    sound like its too big  for the die???    and yes the rod is chamferd


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## MrWhoopee (Jan 13, 2022)

First, make sure that the die is a thread cutting die and not a thread repair die. Hex dies can be either. Keep the stock as short as possible and chamfer the end "for ease of insertion". Since your are holding the die in the chuck you will have very little feel. It takes very little force to cut a 4-40 thread, but not much more to twist the stock off.


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## extropic (Jan 13, 2022)

What is the length to be threaded?

What is the diameter of the length to be threaded?

What is the material of the rod?

How do you plan to advance the rod, into the die, at precisely the thread pitch? 1/40=.025" per revolution.

Based on what information you've provided in the OP, it not clear to me that your plan is the best way.


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## T Bredehoft (Jan 13, 2022)

Today I was cutting 4-40 threads in brass, turned the 5/16 brass down to .110 for .250, (have the round die stock in a holder,) . I put an Aloris type boring bar  on the tool post, put the die ups against the boring bar holder (to keep it square) and on the stub of brass, with the compound I put pressure on the die and turned the chuck by hand. Easy Peasy, When the die was half way onto the stub, I could turn it by hand, and spin it off. Did this a  couple of dozen times, making thumb screws. 

You'll want to get the proper diameter, (don't bet on .110, I just guessed, and be sure to start the thread true square. You don't want it wandering off to the side. In steel you'll want to use Tap Magic, and be sure your chips clear the die, don't jam up inside.


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## Boswell (Jan 13, 2022)

just curious why you are choosing to put the die in the headstock? is it because of the length of the threads?  To advance the tailstock and thus the material,  you could potentially use bungy cord as a weak spring to put forward pressure on the material as it is threading.


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## WobblyHand (Jan 13, 2022)

Little Machine Shop has a couple of calculators on their site.  die threading  They recommend the rod be turned to 0.1095" before using a 4-40 die. They also recommend a 30 degree lead in (chamfer) to make it easier to start the die.  Getting the die to start square is the key.  A good HSS die should cut well.  Once started straight just make sure you clean out the die occasionally.  I've followed their recommendations for other threads and it has worked out well.  Their rule of thumb is rod size should be about 90% of the major diameter.


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## silence dogood (Jan 13, 2022)

It is more fun to make your own. However, if it very long and a lot, you could get brass, stainless, or steel up to six feet long on the net. Look up Macmaster-Carr, Grainger, etc. on the net.


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## riversidedan (Jan 13, 2022)

MrWhoopee said:


> First, make sure that the die is a thread cutting die and not a thread repair die. Hex dies can be either. Keep the stock as short as possible and chamfer the end "for ease of insertion". Since your are holding the die in the chuck you will have very little feel. It takes very little force to cut a 4-40 thread, but not much more to twist the stock off.


whoopee  the die pkg sez plumbling   maint. and repairs...............thinking I got the wrong die>???   also when I look at the ID cutting surfaces inside looks like 1/2 arent thier and 1/2 are.......in other words the cutters are 1/2 gone


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## riversidedan (Jan 13, 2022)

Boswell said:


> just curious why you are choosing to put the die in the headstock? is it because of the length of the threads?  To advance the tailstock and thus the material,  you could potentially use bungy cord as a weak spring to put forward pressure on the material as it is threading.


I put the die in the chuck to keep the everything straight


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## WobblyHand (Jan 13, 2022)

You could put the die in a die holder (if you have one) and place it against your tailstock to keep it straight.  Then the rod goes in the chuck.


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## riversidedan (Jan 13, 2022)

riversidedan said:


> I put the die in the chuck to keep the everything straight





WobblyHand said:


> You could put the die in a die holder (if you have one) and place it against your tailstock to keep it straight.  Then the rod goes in the chuck.


Ive seen that done but somehow cant picture it...........yes I have a die holder


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## WobblyHand (Jan 13, 2022)

Maybe not the best way to do this, but it works.  You push the face of the drill chuck (with the jaws retracted) against the die holder.  This keeps the die perpendicular to the rod.  If you chamfer the rod, and the rod is the correct diameter (not too big, or too small) the die will start.  As you turn the die, make sure you feed in the tailstock.  That way the die continues to be straight.


Hope this helps.


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## riversidedan (Jan 13, 2022)

WobblyHand said:


> Maybe not the best way to do this, but it works.  You push the face of the drill chuck (with the jaws retracted) against the die holder.  This keeps the die perpendicular to the rod.  If you chamfer the rod, and the rod is the correct diameter (not too big, or too small) the die will start.  As you turn the die, make sure you feed in the tailstock.  That way the die continues to be straight.
> View attachment 392125
> 
> Hope this helps.
> View attachment 392128


wish I had some nice collets......... so your saying the die/holder has to be flat against the TS chuck??   just had a thought, what if the round work piece went in the TS chuck thru the die but wasnt tighted down yet spun around in the TS chuck  to really hold things straight  ....... whatdo ya think


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## WobblyHand (Jan 13, 2022)

Yes, it will work with a regular chuck.  (3J, 4J, 6J, ER, 5C or whatever)  It's really no different.  Rod to be threaded held by the lathe chuck and the die holder backed by the drill chuck.


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## WobblyHand (Jan 13, 2022)

riversidedan said:


> wish I had some nice collets......... so your saying the die/holder has to be flat against the TS chuck??   just had a thought, what if the round work piece went in the TS chuck thru the die but wasnt tighted down yet spun around in the TS chuck  to really hold things straight  ....... whatdo ya think


The lathe chuck is really capable of clamping the rod, so why not use it?  It has the advantage of allowing a long rod to continue through the spindle, unlike with the tailstock.  Personally, I would not do what you suggest.  The lathe chuck is designed to hold the rod absolutely straight.  In fact, it is probably better aligned to your ways than the tailstock is.  It's better to allow the diestock to float on the face of the drill chuck and have the rod center the die.  Try it and see how it works.  If you don't like it, try something else.  The method I explained works for me, likely it will work for you!


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## Bi11Hudson (Jan 14, 2022)

Starting a die true to the work is a problem in even the larger sizes, 1" and above. The method I use for smaller screws, Nr 2 and Nr 00 should work for a middlin' size like Nr 4. Start with the proper size, .060 +(4x.013). That yields 0.112". Then extract the few thou for top clearance. A very few thou for Nr 4. Then for the first 1/4 inch, remove down to .113 less .025 (.088") for a slim fit internally. Once the die is slid onto the undersized section, start cutting. For something as large as Nr 4, I would put the stock in a lathe and hold the die by hand or maybe a pair of "Channel-Locks" so it can be released quickly.

The above is for making long threads, like all-thread. For machine screws with 4 or 5 pitches, I just chuck the part and use the face of the tailstock chuck to square the die. There are occasional times when the screw end is exposed. There I trim the end as described above, run the die, and before removing the die clip off the undersized portion and excess length and trim up with a file. It works well enough for the small sizes I deal with. Nr 4 should do well enough.

For long threads I often use oversized stock. Just trueing up a half inch or so for the die to bite. The most common thread I cut is 2-56. The rod is 3/32 brass. At ~.093, a fuzz over size for Nr 2 at .086. Once the die is started, it will shave off that little bit of extra. Be advised, brass is soft enough for that "shenanigan". As is raw aluminium. On the other hand, *steel is tougher* and may not shave so easily.

EDIT: adjusted Screw sizes
.


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## riversidedan (Jan 14, 2022)

am thinking I got the wrong die...........as in thiers teeth in one side of the die and the other 1/2 is no teeth


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## WobblyHand (Jan 14, 2022)

riversidedan said:


> am thinking I got the wrong die...........as in thiers teeth in one side of the die and the other 1/2 is no teeth


Not sure what you mean by that.  A die should look something like this:


The die is usually round, but doesn't have to be, and it has gaps between the threads, for the swarf to be ejected.  Does your die look similar to this?  Some dies have a split, but they don't have to have one.


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## WobblyHand (Jan 14, 2022)

Why don't you take a picture of your die and post it here.  A picture is worth a thousand words!


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## WobblyHand (Jan 15, 2022)

@riversidedan we are trying to help.  If there's something confusing, please ask.  Since we're remote from you, we can't see what you see, or even know what your setup is.  Pictures help us a lot.  Or, if it is hard for you to post pictures, pretend you're on the telephone and you're talking to a friend about it.  On the phone, you would describe the situation, ask a question or two, listen and talk again.  It's the same here, although it's probably slower.

Don't get too frustrated, we've all been there.  It's hard getting started.  My first lathe came home 2 years ago.  I started from zero.  I fumbled a bit, but improved.  Asked many questions on Hobby Machinist.  From some of your pictures, it appears that you are making some good things.  Your skills will continue to improve.  

So keep communicating and posting.  We will be able to work through most of the machining questions.  Lots of good people here that want to help.  Keep plugging away, and it will get done. 

There are no stupid questions.  Just ask.  That's how we all learn.


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## riversidedan (Jan 15, 2022)

WobblyHand said:


> Not sure what you mean by that.  A die should look something like this:
> View attachment 392247
> 
> The die is usually round, but doesn't have to be, and it has gaps between the threads, for the swarf to be ejected.  Does your die look similar to this?  Some dies have a split, but they don't have to have one.


yes I know what a die is and am not stupid as some here seem to think>>>>>>>>>>like I said. thiers teeth on one side but not the other, I just returned it so no pic , sorry..................but no, the teeth didnt go all the way thru the die


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## riversidedan (Jan 15, 2022)

riversidedan said:


> I put the die in the chuck to keep the everything straight


me too


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## riversidedan (Jan 15, 2022)

Bi11Hudson said:


> Starting a die true to the work is a problem in even the larger sizes, 1" and above. The method I use for smaller screws, Nr 2 and Nr 00 should work for a middlin' size like Nr 4. Start with the proper size, .060 +(4x.013). That yields 0.112". Then extract the few thou for top clearance. A very few thou for Nr 4. Then for the first 1/4 inch, remove down to .113 less .025 (.088") for a slim fit internally. Once the die is slid onto the undersized section, start cutting. For something as large as Nr 4, I would put the stock in a lathe and hold the die by hand or maybe a pair of "Channel-Locks" so it can be released quickly.
> 
> The above is for making long threads, like all-thread. For machine screws with 4 or 5 pitches, I just chuck the part and use the face of the tailstock chuck to square the die. There are occasional times when the screw end is exposed. There I trim the end as described above, run the die, and before removing the die clip off the undersized portion and excess length and trim up with a file. It works well enough for the small sizes I deal with. Nr 4 should do well enough.
> 
> ...


>>>>>>>>the rod is steel


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## WobblyHand (Jan 15, 2022)

If the steel is hardened, a cheap die will have trouble with cutting it.  Can you file the rod, and it cuts?  Or does the file sort of glide over the steel without cutting?  If you can file the steel, a good die can cut threads in it.  If you know this already, my apologies.


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## T Bredehoft (Jan 15, 2022)

I believe you'll find the "skip teeth" in your die are to reduce the need for extra tool pressure while cutting the threads. They will certainly cut good threads.


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## riversidedan (Jan 15, 2022)

WobblyHand said:


> If the steel is hardened, a cheap die will have trouble with cutting it.  Can you file the rod, and it cuts?  Or does the file sort of glide over the steel without cutting?  If you can file the steel, a good die can cut threads in it.  If you know this already, my apologies.


the file glides over the rod so I use a dremel drum sander to round the end off


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## WobblyHand (Jan 15, 2022)

riversidedan said:


> the file glides over the rod so I use a dremel drum sander to round the end off


This is a good clue.

A carbon steel die won't cut hardened steel, or won't cut it for long.  If it's hard enough, you can damage the die.  I'm not sure how hard your steel rod is, but I'd go with a HSS die in 4-40.  High Speed Steel will cut better and longer than carbon steel.  It also stays sharper for a longer time.

As an alternative, you might also consider using some different steel rod that isn't hardened.  That way you could use a cheaper carbon steel die for your threading.

Hope this helps.


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## RJSakowski (Jan 15, 2022)

riversidedan said:


> wanting to make some small threaded rods with a 4-40  die and wanting to know whos had experience  threading that small of rod.
> will put the die in the chuck and rod in the TS chuck and have to force the rod in, the die is octagon so needs to go in the chuck.
> anyway the setup is good just wondering whos messed with small rod threading////////
> 
> ...





riversidedan said:


> yes I know what a die is and am not stupid as some here seem to think>>>>>>>>>>like I said. thiers teeth on one side but not the other, I just returned it so no pic , sorry..................but no, the teeth didnt go all the way thru the die


It is difficult for forum members to know how much experience someone requesting help has.  From your original post, it appears that you are new to the craft.  Dies are usually round or hexagon.  A 4-40 thread has a .1120" nominal outside diameter.  The nominal drill size for tapping internal threads for 75% thread engagement is .089".  All this would indicate a lack of familiarity with cutting threads.

For the most part, forum members try their darnedest to help others solve their problems.  This is often done with insufficient information to properly assess the situation.  Nevertheless, we will persist in our effort to help you find a solution.


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