This is an article I wrote about single head wide belt machines. My goal is to help the smaller shops get big results out of their little machines.
The amount of time I see wasted on hand sanding in the smaller shops is appalling. It's very common to see guys following their wide belt sander with a hand held belt sander and then go into sanding with orbital sanders. This is a huge waste.
These little machines can yield very good quality results with very quick hand sanding and great stain penetration.
Many wood workers just use their wide belt with 80 or 100 grit to flatten out their frames or doors, or to knock down glued up panels that won't fit in the planer. They don't know the finish they can achieve in even a small wide belt sander. No one ever taught them how.
My hope is that this article will broaden their perspective a little bit.
If I tell you the actual scratch depth of a particular grit you will automatically think you should remove that entire amount. Correct? Everyone has the same reaction.
Imagine the scratch is a little mountain range. You want to break down the mountains, but don't go lower than the bottom of the valleys.
If you remove the entire depth of that scratch you will remove the entire mountain range and create a new one underneath the valley floor. The grains of the sanding belt are smashing through solid wood instead of merely removing scratch.
This creates a huge amount of heat and pressure and will exceed the capacity of the belts. This destroys the openess created by the first belt.
Unfortunately there is a very poorly written book about sanding that causes more confusion and cost my customers more money than anything else in this industry.
I worked on a single head wide belt sander last Friday and it was beautiful proof of concept. We spent a couple extra minutes on the wide belt sander to level the parts and then break down the scratch correctly. The owner was spending 2 minutes a door with a very aggressive electric sander and then the sanding guy was spending another 6 minutes a door on hand sanding including profiles. We cut the entire door labor to 3 minutes total, sanding with only 150 grit after the wide belt. The parts were dead flat and the scratch was perfect.
He paid me the best compliment I could ever receive as a technician. He said I did exactly what I said I was going to do.
I would love to see a chart that tells how much you have to remove to get down to the 'valley' of the previous grit scratch. I have charts that tell me the scratch depth for each grit. Do you use a percentage of that number?
Also, I tried your 80-120-180 sanding sequence as recommended on my last couple sets of doors, and it worked really well for me. Thanks for the helpful info.
I wish I had a more scientific answer, but trial and error is what lead me to those numbers. I found them to be pretty much universal, even though the hardness of the drums can change them a tiny bit. A softer drum might give a tiny bit less depth of scratch, but not enough to change the numbers more than .001" either way.
My stock removal chart was supposed to be on our website, but I can't find it. I'll try to get them to put it up tomorrow. Shoot me an email and I can send it over to you in a PDF.
For you to do 80/120/180 you want to cut the doors flat on both sides with the 80 grit on the drum. Remove another .008" per side with the 120 grit with just the drum. Then remove another .004" on both sides with the platen and drum.
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