Is wet sanding a wooden handle a bad idea? expansion, shrinkage and dust mitigation.

[sogflash]

The handle is very close to the shape I want. It mostly needs small adjustments and of course a finer finish. This will all be done by hand with sand paper.
I'd like to do this inside if I can, but the dust stops me. Is it a bad idea to use water to mitigate all the dust?
I wonder if the wood will expand too much from the water and then shrink when it has dried giving high and low spots or even cracks.

The handle consist of multiple pieces of wood mixed with brass. it's a hidden tang knife. The brass itself is going to be a challenge to keep flat with the wood especially if the wood shrinks after I'm done.

Bonus question! How can I sand the brass and wood equally flat? Just hard backing for the sandpaper? At this point the brass sticks out a little bit.

 

[Taz]

Wrap the sandpaper around a file to help keep the wood and brass level. Sharp sandpaper helps too so you can use less pressure to make it cut. Let the abrasive do the cutting. Some people do a "museum fit" when assembling the handle where the corners of the pieces are rounded a bit so if there is any expansion/contraction, the sharp corners don't get exposed.

Depending on the grit, you may be able to use Tung Oil when sanding at the final grits? Tung Oil will gum up sandpaper though!

I usually wipe down the handles with Denatured Alcohol; it removes the sanding dust and dries quickly. Another thing is to dip the sandpaper in water or use a damp rag to wipe down the handle as you are sanding versus dunking the entire handle into the water. You may be able to use a down draft table. Take a box fan and flip it so it is pulling the air downwards and put a filter of some sort on top of it and sand over that. The dust will fall onto the fan and should be pulled into the filter.

 

[Hengelo_77]

If there is metal between pieces of wood, use a hard backing for your sandpaper. I've never had good results with using a file for that. Smooth metal or micarta works better for me.

There are two kinds of wet sanding:
1) with wood oil to fill the pores. It mixes the dust with oil to form a paste that fills the pores.
2) raising the grain, have fibers stand up on the surface and sand them off.

nr 1 should work for you

 

[Stacy E. Apelt - Bladesmith]

Wet sanding is not a great idea in most cases on a knife. Wiping with denatured alcohol helps, but isn't a cure-all.

There are several setups for hand sanding that vacuum up the dust as it is created. They are called "downdraft collectors". You can buy them from woodworking suppliers or make your own. It is basically a shallow box with a port for a vacuum. The top has holes or slits all over it. Set it in your lap , turn on the vacuum, and sand away. There are kits with only te topplate and you build your own box. Thise are pretty cheap.
It does not need a huge shop vac, so a smaller and quieter unit will work fine. I found a HEPA vac at a thrift store that as used to clean out copy machines. It is very quiet and does not emit any dust out the exhaust. There are other quite vacs that filter out to around 1 micron.

Here are what they look like

 

[sogflash]

The down draft setup looks interesting.

I'll see if I can find a straight and sturdy piece of metal or something for the brass.

If you use oil while sanding do you have to make sure it's compatible with whatever finish you'll end up applying in the end?

 

[Stacy E. Apelt - Bladesmith]

The oil used in hand sanding is in the final grit. You are sanding the oil and fine dust into the wood surface to seal the grain and penetrate the wood. Sand, wipe off, apply a little more oil, repeat. When about five sanding coats are applied, done, wipe the surface clean and let the oil cure at least overnight. Do five more coats the next day for a even better shine. Lightly sand again without oil and buff by hand with a soft cloth. This is where many folks stop.

If applying a final finish, after the sanding coats are dry, apply another coat of the same oil or a compatible product. Most folks don't do that, as the desired final product has the finish IN the wood, not ON it, I don't like the look of a varnished handle. I like my wood to glow with the finish in it.

 

[sogflash]

What type of oil do you use? Are all types suitable for that technique?

 

[Stacy E. Apelt - Bladesmith]

Tung oil, most of the time. Sometimes I use BLO.

NOTE:
the paper towels with oils in/on them need to be put in a bucket of water, then disposed of properly. Just tossing them in a pile or the trash may cause a fire by spontaneous combustion.

 

[C_Claycomb]

What kind of wood, and what style of handle?

I sand stabilized wood handles on my bushcraft knives with water to keep dust down and stop the paper clogging. Sanding with 220, 400, 600, 800 grits. Have to do final sanding dry at 800 or 1200 otherwise the finish looks matt.

I wet sand natural wood with Danish oil, starting at 400 grit for walnut but 600 for tighter grained material, and going to 1200.

For the folk saying wet sanding with water is a bad idea, the way I look at it is that the handle is wet for less time with me sanding it that it would be on a successful rainy day with a hunter. A lot less. I would not do it for unstabilised softer, absorbent woods like walnut, maple or birch, which rely on a finish to help with managing moisture in the field, but have done it on bocote and cocobolo with no ill effects.