O.D. Threading

[TheKid09]

I thread whirl daily..
It is an AMAZING way to get a really good, and constant screw.
Only thing that will get you is the inserts..

I would recommend using the G32 command if you do try it...especially if you have to come back into your thread...using the C-Axis for this is REALLY hard and tricky..

[PixMan]

Before you go off on tooling up for thread whirling or thread rolling, tell us more about the task at hand. The requirements of the job are paramount in the world of sliding headstock machines, as in how many do you have to make, what is the cycle time goal, what machines are available, will the job repeat, and so on.

I find that many times when people go looking for a different way, they've overlooked examining just how inefficient the current process may be. For example, if there is one major, almost ubiquitous deficiency I find in single-point threading it's in selecting the right tooling (often just the right insert) and the number of passes.

I'd guess that perhaps 1 in 20 CNC Swiss-style machine programmers has ever looked up the recommended number of passes for any given thread pitch, selected the best insert for the job, optimized the cutting parameters, pre-turned the correct diameter, and more.

The 1144 stressproof materials is BUTTER to cut, especially in oil. With the right full-form cresting insert, a 1/2-13UNC thread should be done in as few as 5 or 6 passes in that material. With newer machines, the right insert (with today's grades and coatings), you should be able to reliably thread at speeds of over 2000rpm and in some machines, over twice that. Use the tools, they last longer!

Another option I don't see mentioned is Geometric die heads. Those can cut the thread in one pass and be the second-fastest way of making threads. I would think that only rolling in a flat die machine as a secondary operation could be faster.

How many of these threads need to be made, over what period of time? How many spindles are now making them? Has a multispindle machine been considered?

I've done some thread whirling, thread milling and thread rolling (that in both on-machine roll die heads and on flat die 2nd ops.) I find that Geometrics are the quickest. Single point threading (done right) is good for reasonable cycle times in the lower-quantity parts or in the no second op possible situation.

Give more info info about the thread requirements and we can collectively help find the most cost-effective solution.

[CitizenBrian]

I had the Fette rep come out to our shop the other day and he is going to set us up with a thread rolling tool to use for a few weeks for free, all we had to do up front was buy the thread rolls. We are starting with 300 pieces of each of the following threads then we will be doing thousands per month of each one.
3/8-16
1/2-13
5/8-11
M10x1.5
M12x1.75
M16x2.0

[PixMan]

If you're doing thread rolling on a Citizen, you may soon find the limits of spindle torque on those machines. While it should be able to roll the 3/8-16 and perhaps the 1/2-13 and M10, the coarser threads may need more than what the machine has available.

[SirDenisNayland]

Tip: if you must run a specific thread on a specific machine but it doesn't have the torque to push out the whole thread, peck threading is an option. I've done it with taps, don't see why it couldn't work for other phased threading applications.

[gizmo_454]

If you are going to peck thread, of which peck tapping is usually used for clearing chips out of deep holes and not power related issues, you are back to burning more time than it is worth. You might as well be single point threading. As Mr. Scott once said on Star Trek, "The right tool, for the right job!" In this case, if the threads needed to be rolled, and the machine didn't have the torque to do it, then a bigger machine or different approach would need to be taken. Since he has been open to discussion on different approaches to the thread, on the parts that can be rolled, by all means, do so. On the ones the machine cannot do it, by all means, single point it, thread it with a Geometric die, or many others.

Peck rolling would NOT be my choice. Rolling inherently cold works the material, effectively work hardening many materials. Once you try to go back over it, it may destroy the tool.

Mike

[SwissType1]

A full profile true Swiss-style threading insert might do the trick here and certainly is a lot less expensive than a dedicated head or special attachment. Full profile inserts should generate extremely clean threads in that material.

UTILIS makes a 1/2-13 full profile threader in their 3000 series product line.

-Scott@Genswiss

[SirDenisNayland]

@gizmo

You're right about the work hardening aspect, probably would not be the best for all types of material.

I just thought id throw it out there for anyone who hasn't used or thought of it before. Like I said if you're constrained to a specific set of conditions you can't change, it may just be a life saver.

I've used it tapping a rather deep 5/16-18 thread in the sub on an L20 where it kept stalling, tap was fine, chips were evacuating but the machine was at its limits for sure. It was 304 iirc, and an id single point would not have lasted at all. That small a bar as deep as it had to go would have taken a retarded amount of passes, not to mention 304 work hardens if you don't take a deep enough cut. Peck tapping was definitely the best option for me at the time :bigthumb:

[gizmo_454]

I just thought id throw it out there for anyone who hasn't used or thought of it before. Like I said if you're constrained to a specific set of conditions you can't change, it may just be a life saver.

I've used it tapping a rather deep 5/16-18 thread in the sub on an L20 where it kept stalling, tap was fine, chips were evacuating but the machine was at its limits for sure. It was 304 iirc, and an id single point would not have lasted at all. That small a bar as deep as it had to go would have taken a retarded amount of passes, not to mention 304 work hardens if you don't take a deep enough cut. Peck tapping was definitely the best option for me at the time :bigthumb:

I completely agree!

[z369]

A full profile true Swiss-style threading insert might do the trick here and certainly is a lot less expensive than a dedicated head or special attachment. Full profile inserts should generate extremely clean threads in that material.

UTILIS makes a 1/2-13 full profile threader in their 3000 series product line.

-Scott@Genswiss

Swiss type tools for swiss machining, the rest are losing money.

[CitizenBrian]

I started machining the parts last week and I am currently single point threading them. As for the thread rolling test I ordered rollers for the largest thread, if the machine doesn't have the power to do the largest one then there is no sense in spending thousands of dollars on a head that can just do a few threads. Single point is working fine and I am using a full profile insert.

[CitizenBrian]

Update: The thread rolling head we got would not fit in the machine, it was about 1/8 inch too long and would hit the guide bushing when that station was called up. Sad part is we checked that on the spec sheet and it says it's 1/4 inch smaller than it actually is. So we said the hell with it and we are just going to stick with single pointing. Thanks Brian