What Is Thread Whirling?
Thread Whirling is a type of thread milling in which the cutters are positioned on the inside of a Cutting Ring or Cutter Holder rather than the exterior of a milling tool.
Although thread whirling had been popular in Europe for more than a half-century, it was largely employed in North America in the fabrication of massive worm gears and similar parts for the automobile and related sectors. The operations were carried out on big, dedicated machinery that needed a significant initial expenditure.
Thread Whirling Parts such as bone screws and related devices, as well as customized fasteners for complex defense, aerospace, and electronics applications, have resulted in a renewed appreciation for the many benefits thread whirling can provide, particularly when machining hard materials such as Inconel, titanium, and the new stainless steel alloys.
Advantages Of Thread Whirling
Thread whirling has various advantages to single point threading, including:
- Deep Threads – Bone Screws often include deep thread formations, such as Acme forms and other larger pitch threads, that may be manufactured in less time by spinning.
- Long Length to Diameter Threads – When utilized on a Swiss Type machine, the Thread Whirling Spindle works close to the Guide Bushing to provide additional support and stiffness on long length to diameter screws. The operation is typically carried out in a single pass from stock diameter, ensuring consistent material support.
- Faster Setup – Thread Whirling reduces the requirement for specialized support devices, lowering early research and development expenses.
It removes the need for specialized support devices as well as high beginning development expenditures. - Increased Productivity – Greater productivity results from cycle reduction and increased up time. Thread whirling is typically done in a single pass from the stock diameter. This removes the need for numerous passes for single point threading. A single cycle can be lowered by minutes by removing unneeded support devices and several thread passes.
- Longer Tool Life – Because cutter side clearance is obtained by spinning the whirling spindle rather than releasing material under the cutting edge, whirling inserts have a stronger cutting edge than single point tools.
- Cutter Clearance – The enhanced relief of a single point threaded insert weakens the side strength of the cutting edges. If the thread helix angle is 7°, the cutter clearance must be more than 7°.
- Support for big helix angles – By changing the whirling unit, large helix angles may be accounted for.
Thread Whirling Inserts
Thread whirling inserts are tools with carbide inserts that are used in the thread whirling process. Each insert generally has 2-3 cutting blades that are fixtured within a holder or cartridge and then dynamically rotated around the workpiece to generate the completed thread. The cutting edges are intended to produce precise and accurate threads in a variety of materials, including stainless steel, titanium, and Inconel.
Thread whirling setup
Follow these steps for a successful setup:
- Determine which spinning unit will be utilized.
- Select a whirling ring that is appropriate for the whirling unit.
- Examine the thread profile to be machined. Is there a standard insert? If not, a full profile and diameter drawing will be required.
- Calculate the cutting point offset from the swivel axis:
- Remove the whirling unit from the machine;
- measure the diameter of the drive shaft;
- install the whirling ring in the drive unit;
- place the whirling unit body on a flat surface, zeroing the clock at the drive shaft’s outer diameter.
- Determine the height difference between the outer diameter of the driving shaft and the insert seat in the whirling ring (H)
- Determine the insert cutting point location from the insert drawing
- Determine the offset: O = D/2 – H + I
- Speak with an expert for help with setup and reducing data recommendations. Make use of a thread spinning calculator.
- Tilt the whirling unit to the required screw helix angle, and keep the tool centered on the component.
- To obtain the right screw diameter, program the ring off-center.
- For maximum tool life, rotate the whirling ring and component in the same direction (climb milling).
- Slowly rotate the workpiece at a slower pace specified by its diameter and thread lead.
Compared Precision Of Threading Methods
Thread Whirling has a number of advantages, including precise outcomes equivalent to other high-quality threading processes such as Thread Grinding and Thread Rolling.
Grinding | Rolling | Whirling | |
---|---|---|---|
Lead accuracy | Very good | Medium; controlled by subsequent heat treatment | Medium; depends on machine accuracy and stress relief |
Diameter control | Very good; direst through steadies and infeed axis | Medium; indirect through bar diameter | Poor; direct, but depends on centering of bar under machining load |
Lead wobble | Very good | Not controlled | Good |
Thread roundness | Very good | Good | Poor; whirling cannot produce round threads |
Surface finish | Good; depends on wheel used | Depends on polishing process | Good; depends on cutter quality |
Thread Whirling FAQs
What is the difference between thread whirling and thread milling?
The distinction between thread whirling and thread milling is that the inserts are located on the inside of a cutting ring rather than the exterior of a milling tool. To cut the thread in one pass, the thread whirling ring spins around a cylindrical component.
What is the whirling process in machining?
A whirling operation is one in which “a geometrically oriented cut removes material.” Whirling removes material similarly to milling, except the cutter in whirling employs carbide inserts distributed along the inside circumference of a ring.
What are the disadvantages of thread milling?
The major disadvantage of thread milling in various applications is that it is slower than tapping. Thread milling will simply take longer to finish if the hole can be threaded easily and consistently with a tap. Thread milling requires more advanced technology than tapping.
What is the speed of thread whirling and feeds?
The main spindle speed will be 8 to 30 RPM, while the whirling cutter will be 1,000 to 4,000 RPM. The feed rate will be the same as the thread lead.