When I started my wood patternmaking apprenticeship at Caterpillar in the Spring of ’81, it was Wacko World at first. I had completed an apprenticeship in my dad’s mill/cabinet shop in the 70’s (just before the economy tanked) so was very familiar with many of the wood machines and processes. Some were foreign though. The big disc sanders were completely new to me and I soon learned they were the work horses of the pattern shop.
Cat’s pattern shop had 50 journeymen; I was one of 3 apprentices. Some journeymen had served their apprenticeships right there at Cat. Others came from around the globe and all aspects of industry. The shop was air conditioned, well lit, and quiet. Four banks of duplicate machinery was laid out evenly so you never had to go far to find an open machine. The lumber rack area was in one corner of the shop; it was ~100ft long and 2 stories high loaded with 8/4 mahogany, Perfect Plank pine, and plywood up to 2” thick. That area also housed the “rough” processing machines: 24” jointer, 36” planer, 16” ripsaw (all Oliver), and a 18” RAS.
Each steel bench had a 8’ maple top, an Emmert vise, a back frame to affix drawings, and a 3’X4’ granite surface plate to the side. On day one, I was assigned a bench and given a drawing to make. It was a simple core box. Thankfully, all the journeymen around me were friendly and most helpful. After some discussion about what a core box is (ha) and a possible build approach, I went off to prepare the wood. I came back from the lumber area with some mahogany boards face jointed and planed thinking I was ready for the next step… wrong!
Journeyman- “It’s not flat enough.” Me- “But I face jointed it.” Him- “Jointers don’t get things flat enough.” Day 1, lesson 1: flat to a cabinet maker is NOT the same as flat to a wood patternmaker! How do you flatten?... “On the disc sander.” Wacko World! Each machinery bank at Cat had a large disc sander. Three banks had a 30” Master; one bank had an Oliver 34” double disc. These things were 2000 lb behemoths! They ran all day and were dead quiet.
My dad’s shop had a 6X48 Delta combo sander with a 12” disc on the side. The abrasive flew off the disc years back and he never replaced it. The stationary belt was the only thing I had ever run. Who cares right? A belt can do anything a disc can but without the “swirls” I thought. Also running through my head was the lesson from my dad that “sanders don’t sand flat.. they always round over.” Now, this patternmaker is telling me to go flatten on a sander??? Wacko World. I didn’t believe him so I nicely challenged his premise. He smiled. He had me face joint a 4’ plank; he faced the other side on the sander. Testing flatness is done by “hinging” the stock on a surface plate. Yeah, I lost.
You quickly learn that disc sanders CAN sand flat… and straighten stock too! Just like learning to run a jointer or a belt sander… you need to learn the necessary stroke. Starting the “cut” on the downhill side of disc, you smoothly move the stock across the disc to the uphill side and back. Minimal force is required. Contact is maintained across the disc. You’d think the uphill side would lift and throw the stock…. It actually wants to “turn” with the disc but won’t if you apply a light downward force keeping it to the table. The stroke can be practiced moving the stock across the disc with the machine off. A disc should be setup to “cut”: large machines get 40 grit, medium 15”-24” get 50 grit, and 12” discs perform well with 60 grit. Change the abrasive when it wants to burn end grain. This skill was pounded into the young patternmakers. Now I’m old and retired and still do it often.
I’m writing this because it seems this skill has been lost (like many patternmaking techniques). A friend recently retired and started woodworking as a hobby. He made his first end grain cutting board this year and struggled getting it flat. He said he spent hours working away on the random orbit. He reads a lot and watches woodworking videos (which I don’t) and mentioned some WW’s run their end grain boards through the planer (wow)… some use drum sanders… and some build router sleds. All possible solutions but he has a 12” disc… so I mentioned that he should learn to flatten on that. He practiced the stroke; now he’s a pro!
I recently made a cutting board for the Fall raffle at church and made a video to share how I flatten using this process.
https://www.youtube.com/shorts/YehlcEdHj-8
For years I used a 12” Delta disc. The cutting boards were always taller than the disc! No biggy. Using the same stroke, I just make 2-3 passes along one edge turning the board 90 deg (to the next edge) to make additional passes, keeping the cut uniform. This video shows flattening strokes along each edge to complete “once around” the board (50 sec) on a State D16 sander. Most end grain boards are cleaned up and flat in 3 trips around the board…. about 2-3 minutes. Ready for final sanding!
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Originally Posted by Randy Benway
