Thread Rolling - Need A Suggestion What To Do

[The Last Mouse]

Hello
In our manufactury we produce bolts and screws. We are new manufactury so don't have much experiences with problem solving. I would like to ask a question because I need some help. While doing my quality check, I have noticed several times that threads often have wrong angle. Either too big or too low. Bolts have been created with cold heading process and material of wire/bolts is alloy steel. What should I do so the threads created on bolts in thread rolling process won't have wrong (either too big or too low) angle? Actually I am interested about preventive and not coorective solution. I already know the possibility of changing the die or whichever other tool (wheel etc) or adjust the settings on machines and so on. But this is coorective solution. Could anyone suggest what to do? Dies are flat and not cylindrical. Also tried to change the material of die (or at least hardness) and other tools but once again those solutions are not useful because they are coorective. I want to know what to do so wrong angle won't occur again which is preventive control / solution.

Along wrong angle, I sometimes noticed another ''disaster''. Diameter of external thread, already created on bolt, is often wrong, either too big or too low. Whats up with that? Im not asking about the cause but what to do so this won't happen again?

Note that I named two different subjects so please reply with clearly definition on which of those two are you referring. Thank you.

p.s.: here are many subsections of forum and hopefully I chose correct location where to post my question(s).

[The Last Mouse]

hello? anyone?

[djr76]

Not really sure and taking a wild stab here, after they are rolled, if they are to big, the thread is getting extruded to much and if to small, something must be knocking the crowns down to much. As for the angle, the blanks must not be tracking right. Ive only seen this done on "how its made" on cable tv. But to me the way they roll through the die like that, it sounds like a setup issue. Its just like anything when you run new, run some samples, make adjustments to you get it right.

[The Last Mouse]

djr I think we misunderstood each other what I was trying to say. I was asking about the preventive solution (and not coorective - adjusting something is coorective) - what to do so this won't happen again but you were mentoining the causes.

[djr76]

Im well aware of what preventative and corrective is. You have many variables in the process to have that "set it and forget it" ideal. Tool wear, machine wear, temperature, material, feeds, speeds all affect the outcome. Machinist are constantly adjusting settings to keep parts in tolerance. I suggest doing some extensive testing to see when problems start to occur, then see if they occur at the same intervals, then you know when the machine is gonna need to be tweaked to keep it making good parts.

[fizzissist]

Pay the money, hire someone who knows thread rolling, or contract a consultant to come in and set up the system for you. No substitute for experience!!!!!

And this is predicated on your having machinery capable of outputting the quality you're asking. Thread rolling is a precise process.

If you're trying to get by cheap....you haven't learned the first rule....

Good. Fast. Cheap.
Pick 2.