[screensnot]

I used to have a boss like that. One of the reasons I quit working for them.
The cheap b********s would not buy threading inserts with standard radiuses for UNJ threads :argue: . We used to hand grind the radiuses on the ends of sharp threading tools with a diamond hone. Got perty good at it too..

I used to have tons of dumb boss stories, but my hypnotist erased them from my memory for me. It was the only way to cure my ulcers.

[tex]

Why is it not an option?

Well, I am not sure...but the guys who are actually trying to do this job approached me with a question about machining this with triangular or diamond-shaped inserts...with small tip radius, of course (0.4mm or similar).

[tex]

How about some parameters of the job?

What material? Dimensions? Tolerances? What are the end conditions like? (Don't tell me -- both ends have to have sharp shoulders.)

How many pieces do you have to make?

Ken

Actually, I have no idea......this is not a job that I should do, but just make a suggestion how to write a program for it and whether the machine like a plain CNC lathe (we were talking about HAAS SL-30 or similar) is able to do.

The screenshot that I've attached is there just for you guys to get an idea how the d**n thing should look like, it is NOT a screenshot of the actual model...I've made the model just to take that screenshot.

As far as I could understand, this thread is used in some kind of drilling heads for drilling through hard rock, very likely in oil industry, which could mean that the thing is HUGE. I guess that there is an original part available, but is either too expensive so they are trying to save funds or want to start a production of a reverse-engineered part for the market.

I apologize if I made you think that this is something that I should machine in my own shop or at work, it was not intentional. I am not going to make a penny out of this, but just saw this as an opportunity to learn something new.

[tex]

Taking ghyman's approach one step further, use the sine function to calculate the increments in X/Z. This way you can get equal sized scallops along the entire form.

Notice how his equal increments in Z will cause relatively small scallops at the bottom of the inside radius (and top of the outside radius). But the scallops will be relatively large near the point where you transition from one radius to the other.

To help you understand what I mean, see this post for my approach to get even sized scallops when creating an outside radius, using a Z-level toolpath.

I get your point, it is enough for one to just take a look at the pictures ghyman has attached...it becomes obvious.

Now I have, hopefully, understood at least the idea ghyman has suggested. However, what I thought at the beginning was to make a program that would guide the tool along the X and Z axes SIMULTANEOUSLY, with a feedrate calculated in a way so, at the end, a proper thread profile with an exact pitch would be obtained and the scallops would be avoided. If you take a look at the thread cycle (G76) there is no way to make a tool move along the X-axis while making multiple passes. That's why this task seemed like the one that can't be done.

[tex]

<snip>
I am curious now to see the actual dimensions. I forgot to do an offset for the tool radius in my sketches, and now I sort of HAVE to know what it is!!!

Please take a look two posts up...I've explained that I have no idea about the actual dimensions.

[ghyman]

Sorry... must've posted b4 I saw your reply.

[tex]

Sorry... must've posted b4 I saw your reply.

Yes you have, but just because I have not replied yet. Then I just did not want to write the same thing twice, so I asked you to see the reply I've written to lerman.

[oldjohn]

G'day
Why don't you EDM wire cut a full form tool. It's only an idea
John

[ghyman]

G'day
Why don't you EDM wire cut a full form tool. It's only an idea
John

Nobody likes a showoff, oldjohn!

Actually, I'd done that on a daily basis several years ago when I was making a "magic thread form" for bone screws for a spinal implant company... it never dawned on me to do the same thing in this case!

I guess I've gotten so used to "creative" programming, that I forget the easy answers!

[Call Maker]

Here's an idea...send it to a thread grinder and let him worry about it.

[froya]

If you will get the full profile, it's easy with the tools you have. Just cut the threads with the standard 55` or 60`, then use a formed cuttingtool to take care of the upper radius.