Grit Sequence for a Wide-Belt Sander

Thoughts on the coarse, medium, and fine grit selections for sanding solid wood on a widebelt. March 26, 2013

What is the finest grit, practically speaking, to use on solid hardwood doors in a widebelt sander? Application is 5 piece cabinet doors in walnut, cherry, oak and alder, and probably 1-3/4 passage doors in the same wood. We will glue them up and when the glue is dry and scraped, we will run it through the widebelt. We have a two head 1.3m wide widebelt sander and the second head has a platen.

We want to do one pass through the sander with two belt grits. We want to do minimal orbital sanding after it comes off the wide-belt. We don't want sanding lines, and we don't want belts that clog up all the time.

Recommendations on what belts to use? 100 first head 180 second? 150 - 220? 120 - 220? Is 220 too fine for hardwood? Will it clog? Is 150 too fine for the first leveling pass after glue-up?

Forum Responses
(Solid Wood Machining Forum)
From contributor D:
We run 80-120-180 grit. Scratch patterns are shorter not using the platen. This is good enough that paint grade doors intended to be primed don't need any random orbital work, and large entry doors out of most woods need only a 5 minute dusting to remove crossgrain scratch. Typically the 80 grit head is only used for dimensioning parts before machining, the last two heads for assembled doors and final passes on stuff. We keep old belts just for pine because of clogging, and never run pine through on the good belts. Using any finer than 180 for us has been problematic, most especially with cherry as it burns easily with anything but brand new belts and taking off no more than a few thousandths a pass. Using 220 on cherry takes patience.

From contributor J:
We are able to go to 240 for a final pass, removing just 0.05mm beyond 180. It is a subtle difference, but my customers definitely prefer it over a 180 final pass. The sander has air jets on the fine head for cleaning the belt. Have not had any burning issues, the key being to remove the least amount of material while still creating a new scratch pattern. The sander needs to be set up carefully and it helps (I think) to have a steel drum for calibrating.

From contributor J:

Forgot to mention, grit sequence depends some on how level and glue-gooped your surfaces are. We do not skip more than one grit, running 120 - 180 - 240. Hope that helps. We also run paper belts for all grits and have never had one break. Uniformity is very good from belt-to-belt.

From contributor A:
Many people find sanding beyond 150 grit (Euro) is a waste of time. Many product manufacturers recommend sealer/primer coats should not be sanded beyond 180 grit. At 240 grit there may be adhesion problems. That said many people spraying CV find it necessary to start at 240 grit in order to get a smooth finish with 2 coats.

As mentioned sanding cherry/maple or some mahoganies will potentially cause burning at 240. You can always wide belt to 180 and random orbit to 240.