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Tips/Techniques Threading Basics from April 6 Toronto Meet

Tips/Techniques
Here is a PDF of my notes from the little tutorial I presented at our April 6 meet-up. Hopefully it's not too convoluted.

If anyone has any questions, I will try to answer them as best that I can.

There is more information that I need to post regarding this in the next couple days.
 

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Thanks for posting your Tips/Techniques for threading it definitely was a lot to take in so it will great to be able to go back to this reference to fill any of the gaps. I got down to the shop for a bit and cut a practice 1/2 13 thread and it was improvement from past results by doing a few things in the document and what we had discussed, so looking forward to doing some more experimenting with the techniques and improve that skill.
 
Lets assume that the section of the bolt in the picture below is a perfect ASME B1.1-2019 Unified Inch Screw Standard, 60° external thread. And let's just say it's a 1/2"-13tpi bolt.

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According to that ASME standard, it states that the Root width = .250 ÷ TPI. And in our case, using 13tpi, gives us the Root width of 0.019". The Crest width = 0.125 ÷ TPI, therefore, in our example, it should be 0.009".

The depth of a 13tpi UN thread is 0.042".

Some of the other basic dimensions for 1/2"-13 UNC are shown below.



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So now that we have the basic dimensions for our 1/2"-13UNC thread we need to cut, we can start. Well, not quite yet.

Let take our hss tool and grind it to a sharp point. Lets have a look.

From our specs or calculations we determined that the depth of this thread is 0.042". If we advance this hss cutter to that depth, we still have not reached the thread width that we need to achieve the correct pitch diameter and thread form.
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We need the threading bit to fill that whole area.

Ok, we can go deeper with our tool.
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This will give us the proper fit.

But we have gone 0.017" deeper than required for the UN standard, and haven't taken into consideration of the root width.

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Attached is a quick reference for some of the Unified Thread dimensions.

In the column, Root Width, that should be the width of the flat that you would grind the tip of your hss threading tool for a corresponding thread per inch.

The last column in the chart will give you a basic pitch diameter for any given thread pitch and diameter. For instance, if you wanted to make a custom bolt of 1.5"x32tpi, the pitch diameter would be:
1.5" - 0.020" = 1.480"
 

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Now that we know the basic dimensions of our thread we want to cut, and the form required, let's choose a tool to cut the thread.

There are basically 3 types of tools utilized to cut a single point thread on the lathe.
1. HSS tool bit
2. Partial profile/non-topping carbide insert
3. Full profile/topping insert

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The HSS tool will be very similar to the V-profile non-topping insert.
 

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Here is an example of a full profile/topping insert (bottom),
and a partial profile/non-topping insert (top).

The full profile insert will only make an 8tpi UN 60° thread, while the partial profile can make threads from 8tpi-16tpi.

The tip of the inserts will form the root of the external thread.
 

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Here is a couple of my inserts I have the numbers are mmt16IR AG60 UE6020 and mmt11IR AG60 UE6020 would the first one be considered a full profile the not much of a radius on it but does have a form type bump looking similar. The smaller one doesn't have any bump so I guess its just a v type which should be ok for finer threads.
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Those threading inserts are partial profile.
16IR AG60 UE6020
16=length of the insert
IR=internal right
AG=pitch range it will cut (A=48-16tpi)
(G=14-8tpi)
(AG=48-8tpi)
60=angle of thread
UE6020= I believe is the coating on the insert
 
Ok thanks, I wondered how they identified the pitches that it could cut, ag 8-48tpi sure seems a lot to ask out of a little insert but I did cut an 8tpi internal with it which was challenging but I was able to get it on about half way at the end of shift last night so a little investigation into that will happen next time I get back to it. The joy of that is I can chuck either side back in there for more passes with the 8tpi leadscrew. I have been happy with my external threads, internal and especially internal blind bit more challenging, I have to experiment more with doc and maybe more spring passes but armed with more information and ideas I can experiment that will be half the fun.
 
You know, Accusize sells internal and external threading inserts in a variety pitches of Full Profile and Partial Profile in kits. I just recently saw this in there catalogue which I think is a great idea. They also have replacement kits, (inserts only), if you already have the tools.
 

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thestelster said:
You know, Accusize sells internal and external threading inserts in a variety pitches of Full Profile and Partial Profile in kits. I just recently saw this in there catalogue which I think is a great idea. They also have replacement kits, (inserts only), if you already have the tools.
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Its doesn't look like they are online yet or its just kbc search engine quirks but its a good idea, I thought about that for acme inserts buy 10 packs of a group of sizes and then make up packs to resell them amongst the group 2 inserts per size would probably last most guys a lifetime.
 
combustable herbage said:
Its doesn't look like they are online yet or its just kbc search engine quirks but its a good idea, I thought about that for acme inserts buy 10 packs of a group of sizes and then make up packs to resell them amongst the group 2 inserts per size would probably last most guys a lifetime.
Click to expand...

That's an excellent idea. Count me in if it works out.

How would you make sure they fit all the different tool holders out there?
 
Thanks for posting this here Stell, It was a great presentation, and I learned a few things I didn't know about threading. Even though it appeared I was talking to Stuart the whole time about press break tooling, and different copper metal finishes, I WAS Listening :D. You gave me a couple things to try and look out for the next time I single point something, which isn't very often.
 
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