The Changing of the Knives

Posted May 11, 2015 by Brady Banks

It’s no surprise that it takes much longer to change 240 knives on the top head of a planer than it does to change the guards at Buckingham Palace. At first glance, performing planer maintenance may not seem as grand either, but after a closer look, I disagree. Working alongside Steve Brantner and Chad Klatt, maintenance gurus at our Menomonie, WI division, I have been exposed to the intricacies involved in taking care of one of the most important machines at Banks Hardwoods – The Newman S-382 Planer.

According to the manufacturer the 382 “is designed to take random width rough sawn lumber and calibrate it to target thickness.” In 2014, we ran approximately 70.5 million feet of lumber through our planers (including Quantum). Keeping sharp knives and as-good-as-it-gets alignment is extremely important to producing a Quality Everything product for our customers.

The helical carbide cutterheads, or “heads” for short, are an industry standard. Carbide steel is much harder and more durable than average steel, particularly when exposed to the increased temperatures inherent in high speed cutting. The replaceable knives fit precisely into the eight helical rows to form the most advanced cutting edge available. Other benefits include lower operating costs and better performance.

Performing planer maintenance is a time consuming process that normally occurs before or after production hours. Because changing the knives is more involved than simply honing (sharpening) or jointing, only one head is done at a time. In general, the bottom lasts longer than the top, but the timetable varies due to which species are being planed, production hours worked, and the occasional “oops…”

These knives were last replaced in July of 2012. The entire process took us five hours.
Let’s get started.

  1. Follow Lock Out Tag Out protocol.
  2. Remove old knives with an impact wrench and discard.
  3. Use a wire brush to scrape away residue.
  4. Wipe down the head thoroughly with a clean rag and WD40.
  5. Insert new knives by hand near the middle of the head and work outwards while tightening. This prevents uneven matches between neighboring knives. Use the impact wrench to tighten each bolt.
  6. Check each knife with a torque wrench. (That’s a fun little workout.)
  7. Attach and lower the grinding wheel onto one end of the blade until sparks fly, and crank the wheel across the row. It is important to follow a consistent pattern while sharpening all eight rows (for instance, 1-3-5-7-4-6-8-2). This keeps the entire processas even and circular as possible. It often takes many attempts, lowering the wheel in small increments each time. Relying on sound, sight and feel, continue until there is a steady grind/spark across each knife.
  8. Switch to the jointing attachment and crank through each row, except this time with the cutterhead running at full speed! This brings each knife to the same height, creating a thin relief on the leading edges across the blade.
  9. Due to the difference between the new and old knives, everything needs to be re-aligned. This process is complex and finicky. I usually take a step back and watch Steve move straightedges and a wood setting block around, checking his work with feeler gauges.
  10. Lastly, run some lumber through the planer to see how you did. Check the thickness at various locations on as many boards as it takes to get the finish to near perfection. And you’re ready for production!

There you have it, a little bit of planer knowledge for your back pocket. Of course, there is so much more to it and many years of experience that allow Banks Hardwoods to run smooth and efficient production every day. We certainly owe our maintenance crew a round of applause and a big, “Thank you!”