0.375-in Diameter (+/- 0.007-in.) x 2-in Length
99.95% pure molybdenum pressed, sintered and swaged material
Made in USA! Molybdenum from Maine!
(Moly Stick™ only, holder shown not included. You can make one, or hold the Moly Stick™ in a grinding vise.)
“A little Moly goes a long way!”
Molybdenum is used in the truing of resin-bond and metal-bond diamond wheels. To use this technique, you MUST be able to slow your wheel down from typical grinding speeds, such as 3600 RPM and 5-6000 SFM, to 200-500 RPM and 600-700 SFM (see tables below). This is best accomplished with a VFD on the spindle motor. (Robin Renzetti teaches a method of using the coast-down of the wheel after turning off power, in the event you do not have speed control, in this excellent video. You really should watch the whole video!)
For more information, see the 1975 Kish Patent:
“… improved results in the form of particularly accurate finishes and minimum wear of the molybdenum tool have been achieved with the grinding wheel operating at slower speeds within a range of from 600 to 700 surface feet per minute. …”
Recommended initial speeds and feeds:
Center the wheel on the hub using an indicator to save time, moly, and diamonds.
True your wheel at a surface speed of 600-700 surface feet per minute (7-inch wheel would be 380 RPM, though 700 RPM has been proven to be satisfactory). If you use it at full grinding speed, you won’t be truing, you’ll just be grinding Molybdenum. (See tables below.)
Downfeed 0.002” for a 150 grit diamond wheel as a starting point
Infeed 20 inches per minute as a starting point
You may use graphite to mark the wheel at the start of the truing process to make progress more visible.
Dress your wheel with a Dressing Stick after truing (Such as McMaster 4563A16). See This NORTON Video to learn how to use a dressing stick. (The Moly Stick™ replaces the truing device shown in the video.)
Balance your trued and dressed wheel. You can use the B-200 Balancing Ring if it fits your hub.
And, yes, Moly Sticks™ have been used for years in the manufacturing process for PFG Stones® to keep our diamond wheels true! One of these Moly Sticks™ lasts about a year in this process. Your mileage may vary.
Why does this work?
Imagine a little kid running across a mud puddle while wearing galloshes (boots). They run across fast and get muddy. They run across slowly, at just the right speed, and then lose a boot as it gets stuck in the mud. Well, the boot is a diamond, and the mud is the molybdenum.
Another example…
You are holding a bat (baseball or cricket, your choice), and I toss you a 0.45-inch diameter, 0.6-inch length of lead toward you. You swing the bat and send it 100 feet away. Now, I take that same piece of metal, which happens to be a bullet, and fire it at 1000 feet per second at your bat. It goes right through. The bullet is the diamond, the bat is the molybdenum.
These gedanken experiments show what is happening during moly truing. Molybdenum is really efficient at pulling the errant diamonds out at just the right speeds. Too fast, and you are just making really expensive metal dust.
Happy Truing!
Molybdenum Facts
Symbol: Mo
Category: Transition Metal, Group VI
Atomic Number: 42
Density: 10.28 g / cm3
Discovered: 1778
High melting temperature, 2620 °C
Low vapor pressure at high temperature
Low coefficient of thermal expansion (CTE)
Good corrosion and creep resistance
Load bearing capabilities at temperatures up to 2000 °C,
Excellent thermal and electrical conductivity
Recommended surface speed for molybdenum truing of diamond wheels is 600-700 SFM.
(NOTE: 600 SFM = 3 M/S and 700 SFM = 3.6 M/S)
updated 12 JUN 2024
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The KP logo is a trademark of Kinetic Precision. “PFG Stones®” is a Registered Trademark of Kinetic Precision. Two precision ground stones in a red dual-tray is a trademark of Kinetic Precision. “NOZ” and “Perfect Fluid Guide” is a trademark of Kinetic Precision. “Moly Stick” and “Moly Sticks” is a trademark of Kinetic Precision.