What are the material sizes to use with small dies?

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Shopgeezer

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So If I want to make a 1/4-24 thread on a part in the lathe I know that I turn it down to 1/4" and stick the 1/4-24 die in the tailstock holder. But what size do I turn for a 2-56, 4-40 or 10-32 thread? I have all the tap drill sizes for taps on my handy wall chart and the densely packed info sheet in my tap and die set but nothing for dies. Putting a 2-56 bolt in the caliper gives around .086 and a 4-40 is sorta about .112. Tap drill sizes for each numbered machine screw size don't help much since a tap drill is smaller than the nominal screw size. Must be a table of sizes for dies somewhere.
 

Shopgeezer

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Thanks for the chart. I assume that the nominal size shown in the second column is the size you would shoot for if turning a piece down to thread with a die. Column D shows a max and min size. With taps there are drill sizes listed to produce percentages of thread depths but I have never seen this with dies. I am curious as to why machine screw sizes jump to numbers below 1/4 inch. They do not correspond to numbered drills. What is the origin and reason for this? An old tapping drill chart I have does not change to numbers below 1/4 inch. It keeps going to smaller inch fractions.
 

stevehuckss396

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Take a 10-32 for example

For a 2a fit considered a medium you would want to be .189 - .183

For a 3a fit considered snug .190- .184

The pitch diameter also changes. You can adjust some dies to adjust the pd and get a 2a or 3a fit. To check that you would need to measure using the 3 wire method or a thread micrometer.

So I'm told.

When I make my sparkplugs I mic the diameter and check the pd using go-nogo gauges.
 

goldstar31

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I have a 'Zeus' notebook but it is only in Metric dimensions. OK, I work in both Imperial and Metric sizes.
Again I have quite amusing 1941 Machinery Handbook. My other book is in the Argus Books called Screwcutting in the Lathe by Martin Cleeve and George Thomas's Model Engineers Workshop Manual.
Eventually, one gets the need for decent tackle to hold taps and dies and I made up Thomas's Universal Pillar Tool which reduces the number of small taps breaking.

I confess to having two lathes- one imperial but with the metric quadrant on the gearbox and the metric one which was ridiculously cheap secondhand but with the 127 tooth transposing gear to go imperial.
Mention must be made of the Model Engineer taps and dies with 32TPI and 40TPI. The latter is ideal for things like making workshop tools tools capable of measuring in thous.

Something to think about too?

Norman
 

HennieL

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Oops... looks like I pasted the wrong chart - these are for taps and not dies... Anyway, I'm sure you will find the right chart on that site...
 

tornitore45

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For Number screw the nominal Screw Diameter is 60 + 13 x N

N=10 60 + 13 x 10 = 190 thousands

One can thread a rod OD = 0.164" with a #8 die
A few thousand smaller make life easier
Pitch = 1000/TPI in thousands
To start the die easy and square turn down the length of 3 or pitches to
Nominal - Pitch == for 8-32 turn down to 0.132" for a length of 1/8" then if that stub can not be accepted remove it but if it can be left it provides an easy cantering in the threaded hole to start the screws.

All my hard to reach bolts and studs on fixtures or even models have that feature, make life easier.
 

accelo

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Just to be sure this is understood;
1/4-24 thread on a part in the lathe I know that I turn it down to 1/4"
This assumption isn't exactly correct.
According to the chart posted the part could be between 1/4 and .243.
In the chart below it's between .249 & .242 for a class 2A thread.
If you measure production screws you will not likely find any at the .250 MAJOR DIAMETER size.
After I began to use the chart(s) for screw threads my success rate greatly improved.
I would use the diameter half way between the tolerances .245.

1590065942459.png

Rick
 

L98fiero

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what size do I turn for a 2-56, 4-40 or 10-32 thread?
There's a thread calculator online, UN imperial screw thread calculator it will give all the dimensions needed including the tolerance on the OD of the blank. The blank diameter tolerances are dependent on the class of thread, class 1 threads and tolerances are looser, class 3 are tighter, coarse threads are looser and fine threads are tighter as well. The good part about the calculator is that you can put in any nominal diameter and any thread and it will calculate what you need. It only legitimately works for UTS threads but probably would give workable results for metric too, you have to convert the pitch to TPI but it will take 16.9333 tpi for an M10 screw.
 

Myian

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I can recommend Tubal Cain's book 'Drills, Taps and Dies' from the Workshop Practice Series Number 12. What is good about this book is that it is aimed at model engineers and the practicalities of working in a home workshop. It also provides the information mentioned in the many references above for charts etc but also provides tapping hole sizes for a range of thread engagement which is important for home machinists who want to avoid many breakages of taps particularly for small taps.
 

Shopgeezer

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One of my many head scratching issues involves the pushrods for my model RC airplanes. These are the wires that move the control surfaces. For little miniature indoor flyers .032 music wire is standard. The next step up is .047 wire for larger models. Even larger is .072, which is fairly heavy. Pushrods are often threaded at one end to allow a clevis to screw on. The clevis clamps to the control horns of a control surface like a rudder or elevator. It is important to have adjustment at one end of the pushrod so you can centre the control surface.

So I want to use .047 wire for the pushrods in my new 3D printed model. I have two factory rods with threaded ends. I need two more. I have unthreaded .047 music wire, a bunch of dies, and a steely determination to make my own threads and save 0.003 cents per rod. Just for fun I tried my smallest die, a 2-56, on the factory push rod and it sorta screwed on ok. The UN calculator suggested above says a 2-56 thread requires a major diameter of from .0854 to .0813. The only die size that comes close to .047 is 0-80 at .0595 to .0562. So I am curious to know what thread my .047 factory rods have. I am going to try my 2-56 die on the .047 music wire to see if I can make enough thread for the clevis to grab. Maybe between the threads and some CA glue it will work well enough for me to limp around the flying field once before crashing (also known as landing).
 

tornitore45

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0.047" is a #00 screw size a #2 die will just slip through.
#0 is 0.060" same rule apply going negative subtract 0.013" and add one 0 to the # #000 would be 0.034"
 

L98fiero

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So I want to use .047 wire for the pushrods in my new 3D printed model. I have two factory rods with threaded ends. I need two more. I have unthreaded .047 music wire, a bunch of dies, and a steely determination to make my own threads and save 0.003 cents per rod. Just for fun I tried my smallest die, a 2-56, on the factory push rod and it sorta screwed on ok. The UN calculator suggested above says a 2-56 thread requires a major diameter of from .0854 to .0813. The only die size that comes close to .047 is 0-80 at .0595 to .0562. So I am curious to know what thread my .047 factory rods have. I am going to try my 2-56 die on the .047 music wire to see if I can make enough thread for the clevis to grab. Maybe between the threads and some CA glue it will work well enough for me to limp around the flying field once before crashing (also known as landing).
I have no experience with and haven't seen the push rods but the major diameter of a 0-80 is .060 and the pitch diameter is .0496/.0574 so the thread could be a rolled 0-80. It won't help you unless you have the tooling but according to CJ Winter who make thread rolling equipment, Blank Diameter = MAX thread pitch diameter - .002 inches [or .051 MM].
 

Shopgeezer

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My steely determination is rusting a bit. I found micro-miniature dies at Newmans. The 00-90 is $463.88. Probably that again for a holder for those tiny little things. Maybe I will just buy a bunch more factory push rods. I don't think the lathe threading tables go down quite that far.
 

Shopgeezer

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Thinking about this again I am coming at it from the other direction. Rather than consulting a chart for the numerous variations on one particular size, I would like to know what my die in hand is designed for. It would seem that a die would dictate the size of blank it is designed to use, especially my collection of small dies that are not split and adjustable. Even the split dies would have some diameter that they are designed for. This is not stamped on the die, but I would think this info should be available from the manufacturer.
 

L98fiero

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My steely determination is rusting a bit. I found micro-miniature dies at Newmans. The 00-90 is $463.88. Probably that again for a holder for those tiny little things. Maybe I will just buy a bunch more factory push rods. I don't think the lathe threading tables go down quite that far.
Newmans is probably a good die and made to order but I found this online too, no idea of the quality but just $17 to try it out DIE0090 - 00-90 - Dies - Carbon Steel - Micro Fasteners
 
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