Macor Machining Guide

[separator headline=”h2″ title=”Macor Machining Guide – How to Machine Macor”] Macor is one of the few ceramics that can be machined using regular metal working tools. While there is a learning curve to machining Macor, it is certainly achievable with the correct skill and patience. The machining characteristics are very different from metals and plastics so we recommend you take some time to practice drilling, turning, and milling the Macor before you try to make your own component to understand how it behaves. Unlike plastics and metals, ceramics never plastically deform; this means that when machining Macor you must be very conscious of chipping.

On a micro level, Macor is formed by tiny interlocking crystals of Mica suspended in a glassy matrix. When Macor is machined, the tool tip is actually creating highly localized micro fractures in the crystal structure. Due to the unique structure of Macor, the fractures are stopped from spreading throughout the material, keeping the physical properties intact. The crystals that compose Macor are very small, meaning that a very good surface finish can be achieved even without additional polishing or lapping.

In this Macor Machining Guide we will go over the basics of how to machine Macor and cover some more advanced operations.

[mwm-aal-display] [separator headline=”h2″ title=”General Setup information for Machining Macor”] The most important factors when machining Macor are using proper machine speeds/feeds and coolant amounts. Because Macor is a brittle material, we recommend using soft jaws to help distribute the load. When first machining Macor, try using lower machine speeds and smaller cut depths as this will help keep the piece cool, reduce the potential of chipping, and lead to overall the better results. Like with any glass or ceramic material, always avoid physical shock.   [separator headline=”h2″ title=”Recommended Tooling for Macor”] While it is possible for Macor to be machined with conventional high-speed steel tools, it is highly recommended to use carbide tools as they allow for longer wear and better finishes. A dull tool will lead to more chipping. Drilling/milling/turning

  • Carbide C2

Sawing

  • Carbide grit blades
  • Toothed blades will work but have short life
  • Diamond wheels work well but require coolant

Grinding

  • Aluminum oxide and silicon carbide wheel grades 36 or finer with open grain
  • Diamond wheels 100 to 220 grit work very well

Polishing

  • Start with loose 400-grit silicon carbide on a steel wheel
  • For the final polish, use cerium oxide or alumina on a polishing pad for glass ceramics.

  [separator headline=”h2″ title=”Machining Macor with Coolant”] Even though Macor can withstand high temperatures, the best results are always achieved when the Macor and tooling are kept cool. We recommend using a coolant that is specially formulated for grinding glass or ceramics because this will improve the cutting action wash away the abrasive particulates, prolonging the life of your tools.   [separator headline=”h2″ title=”Things to watch for while machining Macor”]

  • Squeaking tools
  • Surface turning grey due to tool abrasion
  • Large amounts of force required

If you notice any of these issues it is highly recommended that you stop and either sharpen your existing tools or obtain new ones.   [separator headline=”h2″ title=”How to Drill Macor”] For drill holes up to 5mm a spindle speed between 1000 & 1500 and a feed rate of 20 to 30 mm/min has shown the best results. It is recommended that you slow the feed rate down (1/2 speed) at the start and finish of each hole to help reduce chipping. Additionally, breakout can be prevented by chamfering the hole entrance and exit or by using a backing plate.   [separator headline=”h2″ title=”How to Grind Macor”] Diamond grinding wheels (100 to 220 grit) always give the best results when grinding Macor. Silicon Carbide and Alumina grinding wheels (grade 36 or finer) can be used. It is very important that the wheels are sharp otherwise the Macor can crack. Always use water cooling when grinding Macor.   [separator headline=”h2″ title=”How to Mill Macor”] Typical head speeds are 1000–1500 rpm with a chip load of 0.05mm per tooth. Depths of cut are as for turning. Climb milling prevents material being pulled off the edge of the MACOR®. Milling Macor Speeds and Feeds

  • Cutting Speed: 23 to 35 sfpm (1 to 1.4 meters per minute)
  • Feed rate: .002”/tooth (.05mm/tooth)
  • Depth of cut: .15” to .2” (4 to 5 mm)

Milling Tool Suggestions

  • Carbide or equivalent
  • Two or four flute and helix milling cutters work well
  • Do not use roughing or chipbreaker mills

  [separator headline=”h2″ title=”How to Saw Macor”] Use a carbide grit blade with a 30 m/min band speed, or a diamond or silicon carbide cut-off wheel   [separator headline=”h2″ title=”How to Tap Macor”] Make the clearance hole one size larger than that recommended for metal (typically 0.1–0.2mm larger). Chamfer both ends of the hole to prevent chipping. A 4 flute tap is preferable to a 2 flute tap. Run the tap slowly in the same direction (turning the tap back and forth can cause chipping) and flush with water or coolant to remove dust. Wire thread inserts can be used with MACOR®.   [separator headline=”h2″ title=”How to Turn Macor”] Using carbide tooling: Cutting speed = 9-15 m/min (30-50 sfm). Feed Rate = 0.005-0.013 cm/rev (.002-.005 ipr)Depth of cut = 0.38-0.65 cm(.150-.200 in).   [separator headline=”h2″ title=”How to Polish Macor”] Start polishing with a 400 grit silicon carbide. For the last polish, use alumina or cerium oxide powders on a polishing pad.   [separator headline=”h2″ title=”Macor Composition”] Macor is a porcelain-like material that is approximately 45% borosilicate glass and 55% fluorophlogopite mica. A breakdown of the composition of Macor is as follows:

  • Silicon – SiO2  46%
  • Magnesium – MgO  17%
  • Alumina – Al2O3  16%
  • Potassium – K2O  10%
  • Boron – B2O3  7%
  • Fluorine  4%

[separator headline=”h2″ title=”Custom Macor Machining”] Precision Ceramics is your Macor machinable glass specialist for your technical ceramic prototyping & manufacturing needs; we are always happy to use our many years of advanced ceramics experience to provide advice on materials, design, and application. If you would like to buy Macor plates, rods, bars, tubes, or custom machined Macor components please contact us and one of our experts will be happy to assist you.