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When you’re making Mil-Spec carbine buffers or machining tungsten balance weights for elite racing machines, you need to be confident that the materials you’re using can achieve close tolerances and hold fine finishes. Our high-density tungsten alloys are extremely strong and durable (typical hardness ranges from 24-32 HRC), yet easy to work with, machining similarly to gray cast iron. 

Tungsten alloy has a low thermal expansion rate and is resistant to breakage and chipping. Coolants are optional, reducing your processing costs and, in most cases, your carbide tools will machine our high-density alloys well.

See the information below for machining and tooling recommendations.

Machining and Finishing

Turning and Boring

Positive rake is recommended for turning (with Seco Tpg432 or Tpg431 Grade 883 carbide turning inserts). No-rake to positive rake is recommended for boring applications (with Seco CPMT grade 883).

  • Roughing

Cutting depth of .030” to .125” and .008” to .015” feed, at 200 to 300 SFM. 

  • Finishing

.010” to .015” cutting depth and .004” to .010” feed, at 250 to 400 SFM.

Tapping

High-speed steel, two-flute plug spiral point taps recommended. OSG Sossner Premium EXOTAP is recommended. A light tapping fluid or vegetable oil mist can be substituted.

Drilling

Carbide tooling is recommended. Increased clearance angles and automatic feeds are often used to prevent binding and seizing. Carbide drills will extend tool life.

Grinding

Aluminum oxide or silicon carbide wheels of medium hardness are recommended.

Milling

Premium uncoated end mills with a regular spiral made from micrograin carbide, such as SGS, are recommended. Square multi-edge or single-edge insert cutters, such as Kennametal grade KC730, and positive rake octagon cutters, such as Seco Grade 883, are acceptable.

  • Roughing

Feeds of .007” to .015” per tooth at speeds of 200 to 400 SFM.

  • Finishing

Feeds of .003” to .010” per tooth at speeds of 300 to 700 SFM.

Sawing or Cutting

A bi-metal blade, with a blade pitch relative to the thickness of the material, is recommended for sawing. Coarse blades can be run at low speeds, and finer blades run at higher speeds. Coolant can be used. High-speed abrasive cutoff wheels can also be used for cutting.

Stiffness, Machinability

Material Stiffness Machinability
Tungsten Carbide 75-90 Difficult
Osmium, Iridium 80 Bad
Tungsten(Pure) 59 Poor
TZM 57 Poor
Molybdenum 53 Fair
HD 17.7, HD 18.5 53 Fair-Good
HD 18, HD 18D 50 Fair-Good
HD 17.5 45 Fair-Good
HD 17, HD 17D, HD 17BB 40 Good
Cobalt, Nickel 36 Fair
Steel 28-30 Good(Must be H.T.)

Joining

Mechanical Joining

Mechanical joining is the best option for joining high-density tungsten alloy material. Standard fasteners such as bolts and pins are often used, as is threading a tungsten alloy to mate to itself.

Shrink-Fitting

Shrink-fitting is another method of joining tungsten alloy to steel. We recommend .005"/.007" interference per side, depending on the size of the part. Chill in dry ice or nitrogen while the steel is heated. Reinforce the joint with a pin or fixture, and allow to cool slowly.

Contact Mi-Tech Tungsten Metals 

Durability, quality, and consistency – that’s what we’re known for. Contact us today to find out how Mi-Tech can help you.

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