The die – Everything you need for cutting external threads

In this blog post you will learn all about the most important features of the cutting tool. The following questions are answered: How is a die made? Where are the holes for retaining screws, the through holes or chip holes, the thread teeth and the gate? What is the purpose of the peel cut in a die? Which tools do you need for the die?

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Description of the die

When it comes to dies, the name says it all: it is in fact a shaped piece of iron that can be used to cut threads into metal.

The cylinder of the die has four holes for holding screws and a slot (V-groove) on its shell side. Inside it there are three or more through holes that serve as chip holes. In the centre there is the threaded part with the corresponding thread ridges in the profile of the desired thread size. At the end of the webs there is a flattening on both sides. This is the so-called lead-in of the die.

Most important features of the die

In the following overview screen you can see all the important characteristics of a die:

• Peel cut ensures a simplified first cut and good chip removal
• Tail hole
• thread part with studs
• Hole for retaining screws
• Form B = pre-slit with V-groove

Production type of the cutting die

A round bar with a corresponding outer diameter of steel is the starting material. With a hacksaw, corresponding cylinders are sawn off at the desired height. In the soft state, the outer holes, the inner holes and the V-groove are made and the contour of the cutting tool is chamfered. First, however, the core hole is drilled and the internal thread cut, then the chip holes are made. The product is then hardened. In the hard state, the first cut is ground, the surfaces are flattened and the insides of the chip holes are lapped. The inscriptions are then “lasered on”.

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Dies – Types

There are different types of dies that are used in DIN/EN are named. Usually the die is round and pre-slit (form B). There are also slotted dies with and without horizontal or vertical adjustment screw. However, these versions are available in German market is hardly significant.

Dies are made of different materials: HSS dies for cutting steel up to 800 N/mm2 or HSSE dies for cutting stainless and acid-resistant steels. Their performance can be optimized by nitriding and vaporizing. However, there can also be square dies or hexagonal dies (so-called hexagonal die nuts for recutting threads or for cutting threads in hard-to-reach places).

Another distinguishing feature is the lead-in: dies can have a straight lead-in on both sides or a peeling lead, which improves chip removal.

Tools for die cutting

To insert a die, you need a die holder. There are die holders for manual operation or holders for dies that are clamped on a lathe in the tailstock or in the chuck of a drill / cordless screwdriver. In order to guarantee a straight cut, guides are used in the dimension of the pre-machining diameter. More information about the bolt diameter can be found here!

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By the way you will find die holders in our shop:

• Die holder in all sizes

Dies in all sizes and shapes are available here:

I have a project where the client needs to tap their own solid material to form a nut and then thread their own rods to go into these tapped nuts. The material we are using is A304 stainless steel. I am wondering how one would go about making sure these items are capable of resisting the design loads imposed by them? ie, if the thread on the rod will be long enough/strong enough/not eat into the rod to reduce the tensile capacity of the member with the same questions for the tapped material. To preserve 100% of the tension capacity, I'd think that you'd need upset threads or tapered threads similar to some rebar splicing products. The folks at Portland Bolt may be a good resource.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it. The bar is 1" dia ASTM A304. The length varies but is 10'-14' in length (it's part of a bracing system for a tower).

I'm thinking that maybe we should just increase the size of the rods by 1/4" across the board and not have to worry about it. Then again, I was a bit nervous about the project so these bracing members are only 40% stressed.... but I wouldn't be too enthused with cutting into my design FOS. SteelPE:
You really should give some more detail, maybe some sketches, to explain what you are trying to do. You say you have a 1" dia., A304 stainless steel bar, which is part of a bracing system, but it is only stressed at about .4Fy. You should have no problem putting an adequate threading on a rod with a load of .4Fy, although SS can sometimes be tough to thread. Also, there can be galling problems with SS threaded parts. Then, the question becomes, what does the rod thread into, is this pl. A304 also, or mild steel? You may have to adjust the thickness of this plate to get enough female thread. Do you need a turnbuckle in the system to make up the final connection? As mentioned above various Machine Design texts and Machinery’s Handbook should show you how to do the analysis. This will not really be covered by one of our normal bldg. codes, the design is a matter of some engineering experience and judgement.
dhengr,

This project is a 100' tall tower in a coastal area. The owner originally wanted to build it out of mild steel (or carbon steel, I don't know the correct term) and after the bids came in they decided they wanted to switch it to stainless steel. The tower has 4 legs with bracing that runs in-between the legs. The SS fabricator switched every detail we gave them on the drawing in favor of details that were easy for them to construct. They also seem more focused on the aesthetics of the tower with the structural stability playing second fiddle. Some of the questions you asked are the same questions I sent back during their first submittal It has been a fight over the past 1.5 months that I did not anticipate when I put my proposal together.

Attached you will find a partial elevation of the tower. The X rods you can see are the bracing members I am talking about. In the specific elevation shown, the rods are 1/2" diameter. Also, my stresses are not 0.4Fy my unity equation is 0.4..... or I guess you could say 0.4Fy/omega.  http://files.engineering.com/getfile.aspx?folder=9f177f2c-9d4f---a04c29f2b717&file=Partial_Tower_Elevation.pdf
Carbon steel - rusts until failure, Alloy Steel - doesn't rust, Weathering Steel - forms coating of rust for protection. Mild steel refers to steel that hasn't been worked (OK, a little working) and treated to increase it's structural properties.

Structural stability never plays second fiddle and no one in their right mind would promote that. Take this as meaning the client has full faith in the structural engineer in making sure the final structure is stable.

How are you going to adjust the length of the threaded rod so that it fits the field conditions? If you have tapered threads on both ends of the rod, then you will have no adjustment = super bad idea. You also need to account for offsetting the rods (can't tell if you have or not). Just cut standard threads into both ends and design for the reduced section - KISS.

The simplest approach, in my mind, will be to provide clevises (with just a hole and no threads) at both ends (offset the holes for geometry) provide a jamb nut on the outside of the clevis and double nut the inside so the rods are tight. If they really want pretty, then they should get those gussets normal to the angle of the rods and line the rods up with the panel points, but alas, I am not an architect.

You might look at rigging used for sail boats. Also I would check the connections for fatigue. Once had a 60 foot tower with a detail similar to yours but not as sophisticated where one of the tie rods failed and stabbed the deck of a bridge that the tower was cantilevered off the floor beam outriggers. Your tower is surely going to be resisting a lot of windage with the canvas infills. I imagine there will be a lot of shaking from the turbulence. Might be noisy as well. What if I had them fabricate a connection and had them send it out for testing. I assume that would be acceptable? This fabricator is just plain useless when it comes to answering my questions in regards to this item (which is quite important).

My other option is to look at similar items (carbon bolts) and mimic what I see in terms of material sizes and thread lengths (and just be conservative) as stated above. Hi SteelPE

I think stainless threads on stainless threads is not a good idea, mainly because of galling as others have mentioned.

Regarding analysing the joint you need to check that your external force does not cause the screw threads to strip internally before the bolt physically breaks in tension, this condition shows you have enough thread engagement. If you have a fatigue situation then clearly the bolt needs to be checked for failure in fatigue as well as the joint.

One point about thread engagement, following the formula for thread engagement either on the Roy mech site and/or machinery's handbook will lead you to believe that the shear stress can be reduced indefinitely by increasing thread engagement which is not so, there is no benefit increasing thread engagement beyond a length of 1 to 2 times bolt diameter.


“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein