Widia GTD

Widia GTD (formerly Greenfield) Thread Mills

Frequently Asked Questions

What equipment is needed in order to thread mill? A CNC machining center or milling machine that has 3-axis helical interpolation capability.
Will I need sophisticated equipment to program a thread milling operation (such as an NPT thread)? No. In fact Widia GTD provides this service free of charge for any customer who buys their product. Most customers have learned to write their own programs from the information Widia GTD has previously sent them. It only takes a few minutes.
Is thread milling just a new fad?

No. Thread milling has been performed in real production since the mid 60's. The advent of NC or tape-controlled machines made the process possible, but it was a long and arduous task to create a program. Today's CNC controls make the task very simple and extremely accurate.

I have canned cycles for thread milling in my CNC control now, and we have not been able to make any thread mill work very well. Why would your mills work when others haven't? Widia GTD has discovered there are many important steps to consider when preparing a program. Most canned cycles do not take these proven steps into consideration. How you program the tool path is critical to performance. How the tool is made is also key. We freely offer the information we've learned and will help you with difficult applications.
Why is everyone just now talking about thread milling when CNC equipment has been around for such a long time? The reason is simple. Just 10 years ago, most machining centers being sold offered spindle speeds with only 3,000 to 5,000 RPM as standard. These speeds were just too slow to reach economical cutting speeds necessary for small thread milling applications when compared to conventional tapping. Today, CNC mills are delivered with spindle speeds of 10,000 RPM as standard, with options up to 25,000 RPM becoming more common. At these speeds, thread miling is more economical than tapping and can even reduce cycle times, in most cases.
Will I have to stock my tool crib with thread mills for every size hole and pitch as I do with taps? No. If you buy a thread mill to produce a 1/4-24 hole, that same mill will produce any 24 pitch hole size that is larger than 1/4-24. In fact, many of our customers have used our thread mills to complete one-day rush jobs that would have otherwise required several days for a special order tap.
Do I have to order special diameter thread mills to produce different class fits of the same major thread diameter? No. Class fit is determined by simply changing the machine tool offset to mill the hole larger or smaller. Some materials have a tendency to "spring" back after tapping or cut smaller holes. These jobs require special H-limit taps to satisfy fit. Thread mills can produce virtually any fit in increments of .0001" or finer if your machine has higher resolution or repeatability.
What percentage of thread height can I thread mill? All Widia GTD HP thread mill products are designed with 100% thread form as specified for that given thread type. You will need to change your existing tap drill size to a smaller drill in order to take advantage of this feature. It makes no difference if you continue with the existing tap drill you now use; however, the deburring feature of full-form thread mills will not be used if you do.
In blind holes having a counterbore shoulder, how close to the shoulder can I expect to produce threads? You can produce full threads thread milling to within 1/4 to 1 pitch of the shoulder.
For larger thread diameters such as 1 1/4-8UN, will I still need to use secondary tapping equipment, such as a drill press? Thread mills require very little horsepower to produce the desired hole, no matter how coarse the thread. The largest thread diameter you can mill is limited to the shortest X- or Y-limits of the machine bed. In fact, thread milling offers the greatest cost savings by eliminating the need to set up on another machine to complete a job.
If I break a thread mill, will I have to rework the part with tap extractors or EDM operations?

If you break a thread mill in operation, the broken portion of the thread mill will merely fall down the hole. This is because the head of the thread mill is always smaller than the minor thread diameter of the thread. To complete the job, simply remove the broken piece from the hold with tweezers or needle-nose pliers, replace the broken shank in the tool holder and touch off the end of the tool, then rerun the thread mill cycle. The Widia GTD thread mill will repeat to within .0005" from mill to mill.

What industries are best suited for thread milling? In the beginning, we focused on valve industries, automotive, and aerospace products that involve more difficult-to-machine materials. We have since found that thread milling has applications in virtually all metal working classifications. Some of our best customers are job shops and small specialty companies that have limited tool stocks to work from. Because of the flexibility of a single thread mill to produce a wide range of holes, it suites their type of work very well.
Is additional training and support available for thread milling products? Yes. We have technical service personnel available to work with you. Depending on your needs, we can arrange special presentations and training seminars.