THREADING: TAPPING TITANIUM:

Titanium and titanium alloys are most often found in aerospace applications due to its lightweight and high strength.

However, other industries are discovering the benefits of titanium as well. One of the more common alloys is Ti 6AL-4V. It is generally machined at a hardness ranging from approx. 28 to 37 Rc.

One the characteristics that makes titanium difficult to tap is its tremendous elastic memory. When tapping, the material closes tightly around the cutting tool, generating friction and heat, resulting in increased wear of the cutting edges. This material also easily work hardens.

To successfully tap titanium, a tap specifically designed with additional clearance to overcome the extreme elastic memory of the material is recommended.

Tap clearances would include extra back taper of the threads from the front to the back of the thread section, full radial clearance in the threads across the tap lands, and additional relief in the tap chamfer area.

All of these features are used to reduce friction and heat. In some cases, larger H limits might be required to overcome the shrinkage.

Premium grade materials are also used for heat and wear resistance. Obviously we offer these in our standard product lines.

Lubrication and proper pre-tapped hole size are vital to success. A compatible tapping fluid should be used that provides plenty of lubrication to reduce friction.

The drill should be selected to produce the largest hole size that is allowed by the thread class callout (2B or 3B).

Due to the additional clearances required on these tools, positive feeding of the tap is highly recommended.

Machining Titanium Tips

Inserts for Machining Titanium

Machining Aluminum

V8 Engine Block Machining From Solid Aluminum

Aluminum is Inexpensive, Lightweight and is Formable at Cold Temperatures

Aluminum is one of the most common materials used in manufacturing strong, lightweight parts. PMF manufactures parts made purely of Aluminum alloys as well as parts made from two or more materials such as Stainless Steel and Aluminum.

Common Forms of Aluminum (in various tempers)
6000's, 5000's, 1000's, 2000's, 3000's, 7000's

Benefits of Aluminum

• Inexpensive
• Lightweight
• Formable at cold temperatures

Considerations of Aluminum

• Softness can lead to tearing
• Low tensile strength (approx. 1/3 that of steel)

Applications of Aluminum

• Military munitions
• Aerospace
• Microelectronics
• Automobile parts
• Many others

Looking for inserts for machining aluminum? Find them at pgsTools.com. Your choice

PCD Inserts for Aluminum

Carbide Inserts for Aluminum

What is Induction Hardening

Definition: A widely used process for the surface hardening of steel. The components are heated by means of an alternating magnetic field to a temperature within or above the transformation range followed by immediate quenching. The core of the component remains unaffected by the treatment and its physical properties are those of the bar from which it was machined, whilst the hardness of the case can be within the range 37/58 Rc. Carbon and alloy steels with a carbon content in the range 0.40/0.45% are most suitable for this process.

What to do about Poor Thread Quality

Often taps get the blame for poor thread quality or rejected threads and it is natural to look to the tap itself as the culprit. Actually, the tap is often the victim of a badly drilled hole. You can't produce a great thread out of a bad hole! Following are some issues and possible resolutions.

1. A dull drill will create a very rough torn hole. Expect poor or incomplete threads.

2. A reground drill must be perfectly concentric. The cutting lips must be of equal length and be ground to the same angles. Failure to create a concentric point will cause the drill to cut on one side more than the other and a crooked, bent hole will result making an attempt to tap that hole very difficult. This can also produce an oval egg shaped hole.

3. Castings sometimes have a tapered hole so the part will release easily. Threading requires straight walls and tapered walls are impossible to thread correctly.

4. Undersized holes are difficult or impossible to thread.

5. Holes that have had the surface work hardened by too high a temperature in the drilling process can become too hard to thread effectively.

6. Materials that shrink or close-in after drilling are undersized for tapping.

7. Holes too near welding or flame cut areas can become hardened and difficult to thread.
Bottom line, consider good hole quality as essential in producing quality holes and if you are having difficulty, dont forget to investigate the drilling process in addition to the tap.

Selecting Thread Mill Diameters

Tips for Selecting Thread Mill Diameters

When producing internal threads, selecting the right thread mill diameter insures it will operate efficiently.

Thread mills are usually offered in several cutting diameters for a given threads per inch. Smaller diameters are used for small thread sizes, such as 3/8-16 NC.

A larger tool diameter could be used for producing a 3/4-16 NF. However, the smaller thread mill could be used to produce the larger 3/4-16 as well.

Generally, for coarser pitches (coarser than 14 TPI), selecting a cutting diameter no larger than 70% of the nominal thread size to be produced is recommended.

For finer pitches, the thread mill can be as large as 75% of the nominal diameter. Although the tool has radial clearances similar to end mills, if the tool diameter is too close to the thread diameter, the tool may rub, producing more heat that could result in excessive wear.

This rubbing may also distort the thread form affecting the thread angle.

The question is, should the largest thread mill that will fit the hole be used? The answer is, not necessarily!

For the greatest efficiency, smaller mills will remove more cubic inch of metal than a larger one, resulting in greater productivity.

There will be more clearance for the tool and more space for coolant and chips.

However, to optimize the tool, it will be rotating much faster, which may exceed the capability of the machine.

Also, the thread length on the tool may be too short for the thread depth required.

On the other hand, the larger diameter thread mill will minimize deflection, particularly on coarse thread series, but is more prone to rubbing and chip congestion.