I’ve had a couple people ask me my technique for filling the open grain of wood with a contrasting color, so here it is, with a few pictures.

First, grain filling is usually only necessary when working with a wood with very open grain. Ash and oak are good examples. But sometimes you will want to fill the grain on a wood like mahogany or khaya. It’s the same technique in both cases.

First is to get the wood sanded smooth, and then to thoroughly wipe off the sanding dust. If you’re filling the grain of the wood with a contrasting color, having that grain partially filled with wood dust from the same wood will lessen the effect. That doesn’t mean that’s not an appropriate technique in some cases, it’s just not what I’m describing here.

an ash pen blank, turned and sanded to 400 grit

If you see that some of the pores still have dust in them, or perhaps even if you don’t, brushing (with the grain) can remove even more of the dust from the pores, leading to a better fill. Both a nylon brush and a wire brush will work, though the effect is different. Thanks to @bento@tinnies.club for suggesting using a brush, which I forgot to mention here on the first edit.

Next is to mix up the grain filler. I use either black or white Wunderfil by Rockler, and then add dyes to the white if I’m after a colored fill. I dilute the Wunderfil with water 50-50 so it’s fairly thin and will flow into the pores of the wood. Some wood fillers need to be diluted with oil, which isn’t as easy to use. Today I used blue milk paint mixed with white Wunderfil. I mixed up the milk paint normally, then mixed that with white Wunderfil with about equal parts of each. Then smear the grain-filler on the wood. I generally put on blue gloves and use my hand, but if you’re working on a flat surface, you can use a squeegee. The important thing is to go across the grain so the fill is pushed into the holes and not wiped back out.

first coat of blue grain fill applied to the pen blank

In many cases, after you give the fill a few minutes to dry, you’ll notice that the grain has opened back up, and can take more fill. If that’s the case, apply a second coat over the first. I almost always need a second coat, but it really depends on the wood and what kind of fill you’re using. Safer to apply a coat you don’t need than to leave some pores unfilled, though.

second coat of blue grain fill applied to the pen blank

With the second coat on, you want to wait for it to dry. A half hour is generally enough with Wunderfil, but more time won’t hurt. Once it’s dry, you sand back to bare wood, but be careful not to overdo it and sand away all your fill, too. I generally will sand with 400 grit sandpaper, but finer will work too.

pen blank sanded back to bare wood, leaving blue grain filler in the grain

At this point, you can begin finishing. I’m going to use a homemade friction-finish made from shellac and tung oil on this pen, so I’ll apply my first coat of tung oil and then wait overnight before moving on to the friction finish. This will give the fill and oil a chance to cure a bit, and makes it less likely the finishing process will pull the fill out of the pores.

pen blank with the first coat of oil applied over the grain filler

You can see how the oil brightened up the colors. If there are spots that aren’t filled completely, you might need to apply more fill at this point (and then sand it back again later), but I generally try to do any more filling before putting on the oil. Sanding back will be messier and the fill may not adhere very well to oiled wood.

Once the blank has had time to cure (at least overnight with tung oil), continue with your finishing regimen. For me, that’ll be two or three coats of an oil and shellac mix, applied at the lathe, and buffed with a cloth so the heat speeds the curing of the oil. That finish will get another day or so to cure before I handle the piece too much.

#woodworking #technique


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Originally written May 2, 2018

I couldn't find anyone describing how to cut dovetails for non-square corners, so I decided to write this up. This trick will work for any angle dovetails, but you'll have to change up the workholding jigs.

This is a description of how to cut dovetails for a 135 degree corner. This is the angle used on an octagonal box (if all the angles are equal). They're not perfect, and there's probably a better way to do it, but this is the best I found.

My first try cutting 135 degree dovetails used no special workholding. I just threw the pieces in the vise and started cutting. I cut tails first and I cut them pretty much as normal, except with the end of the board at a 45 degree angle, so they were pretty easy.

Tails cut on a board with the end cut at 135 degrees

The pins were fairly straight too. This is feeling easy!

Pins marked on a board with a 135 degree angled end

But the fit left something to be desired.

First attempt at a 135 degree dovetailed corner, showing a fairly loose fit

So I sat and thought for a bit and decided that maybe I could use a square piece in the corner, all tails, and put pins on the edge pieces that would go into it, and then cut the 45 degree angle afterwards. It couldn't be any worse than the previous attempt, could it?

A corner piece with tails cut into it from two directions at 90 degrees to each other

Cutting long pins into the end of a board

Boards with long pins inserted into the board with two sets of tails cut into it

The assembled corner, with the corner sanded off, leaving the pin boards almost meeting

Well, that worked okay, and I might end up trying that method again, but I'll have to think harder about the grain direction in that corner piece when I do.

So I tried again. Third time's the charm, right?

I cut the tails square this time, just like you would on a normal dovetail. I even gang-cut them two at a time.

Gang-cutting tails on two boards, as I typically do for dovetails

Then I cut the pins on a board with the end angled 45 degrees using a jig I made for the purpose. I made the 45 degree end on the board using a miter jack before cutting.

One corner together with the pin-board fitting into the tails

Two adjacent corners fit together, with a mirror behind so the inside of the joint is visible too

Those came out pretty good I think. They're a little gappy where I went astray with the coping saw while cutting out the waste, but they glued up solid.

Hopefully someone else will learn from this and find it useful. To get the boards to look good in the corner, just make the corner piece (the walnut in the above photo) 0.7 times as thick as the edge piece (the ash). The example I show has the walnut thicker, and the corner looks kinda goofy to my eye.

#technique #woodworking #dovetails

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