Hand sanding in cabinet shops can be a huge bottle neck, or a huge labor drain. One or the other, take your pick. For most companies it is a daily struggle to achieve and maintain consistency. Not only that the sanders miss spots, but also that over sanding and swirls are a constant issue as well. Understanding the factors effecting the hand sanding will help everyone have a more consistent result. Prepsanding is everything.

 

The questions almost every shop owner asks themselves on a regular basis:

How do I achieve consistency?

How do I control swirls?

How do avoid blotchiness?

Why does my hand sanding take so long?

Why does it seem like I can never get rid of all of the cross grain?

Why does my color go light so often?

 

All these questions are related.

 

Almost all of the issues on the hand sanding table start with the wide belt sanding. The first wide belt contact has as much to do with the final color and consistency as everything that happens after. That is a profound statement, but one that is easily proved.

Everyone knows that a part sanded with an 80 grit belt on a hard drum will go very dark when stained. This openness is the basis of the ability of the wood to accept color and good topcoat adhesion. What happens after this step that causes damage?

The goal on a wide belt is to ensure that the subsequent contact points only remove the scratch pattern from the previous head. Never going below the bottom of the valleys  created by the first head. Those valleys represent the openness of the surface.

The finer the belt, or the closer a belt is to it’s maximum capacity, the less open the surface will be after that initial contact. If you start out very open, it is easy to maintain good color. If you start out somewhat closed, it is much harder to open the surface up later.

 

Consistency is achieved by very consistent opening of the sanded surface. Some wood will have curls in the grain structure just waiting to show as a dark blotch in your stain. These curls cannot be simply closed up to avoid blotchiness without further closing the surfaces around them.  The more open the surface around those blotches the more consistent the look of your stains. Once a surface is opened by a coarser belt, very little of the openness created by the curl in the grain will show. If the openness is maintained through the rest of the sanding process, the differences in the grain structure will remain very minimal.

A big part of consistency is in the hand sanding, but not for the reasons you think. If a part goes to the sanding table polished, with the right disks the orbital sander will help to open up the surface for stain. If the operator misses a spot you will have light spots where the surface is still polished.

If the product comes to the hand sanding table open, then the operator only has to remove the scratch pattern to make it look nice. Openness is already achieved. As long as the disk is not polishing it closed then a missed spot is much less noticeable. Only a small amount of wide belt scratch might sneak through.

 

Getting rid of cross grain scratches and the time it takes to hand sand are closely related. The length of the scratch and the depth are closely related. Longer contact surfaces means less depth. If you want quicker hand sanding you want only longer scratch.

Polishing plays a big role in time spent on hand sanding. The more polished the surface the harder it gets. This means that a scratch pattern can be very shallow and still be hard to remove. If there are any shorter scratches mixed in with the hard polished scratch the time it takes to sand will be much longer.

Low sanding pressures in the wide belt mean softer wood comprising the scratch pattern you want to remove. If the scratch is long, the surface is soft, and the scratches are shallow, they will sand away easily.

It is not uncommon to use these concepts to eliminate 80% or more of the time it takes to hand sand the flat surface of a cabinet door.

 

Controlling swirls is a different animal, but completely related to the state of the wood coming to the hand sanding table. If the surface is polished and closed, the surface is basically a very flat plane. When the sanding disk bites in it’s like a plow digging a furrow into a field. It’s really hard to touch a very flat shiny surface without leaving any scratches that show.

When the surface is prepared correctly, the surface will be open, the scratches will be shallow and soft. The wide belt scratch pattern will melt away like butter on a hot skillet. They are very easy to remove. The quicker you stop sanding the less swirls you will see in the final results. As you grind away the little mountain peaks of scratch you will see very little swirl. Once you get to the bottom of those peaks you need to stop sanding.

 

I hope this article will help the reader understand the concepts I have been teaching all over the country for many years. The results have been extraordinary.

 

Adam West