I am a hobbyist woodworker currently working on boxes.
Today there was a post about using a Dremel as a general purpose router. It caused me to reflect on my current work in inlays using a Dremel and a particular issue I can’t seem to get a handle on.
I am interested to inlay small ceramic tiles into box lids. I score around the inlay on the box top with a marking knife, remove most of the the material inside the scored lines with a router, then refine the edges and bottom with chisels. The inlay cavity is as good as I can make it I think.
The inlay typically fits flush in the opening and within 0.5 mm of the edges. But the gap between inlay and surrounding wood is open. I used dust saved from the routing mixed with tung oil to fill the gap. The result was an unsightly mess – the raggedy margin was what catches the eye, not the inlay.
I have tried mixing dust with yellow glue, white glue, “translucent” glue, and shellac to make a pate that I pack into the gap. I have placed a narrow bead of glue, including CA, in the gap and tamped dusted onto the glue, then sanded. Nothing seems to work well in my hands.
I know that filling gaps for cosmetic effect is a fundamental woodworking skill, and I know that I am missing something. There is probably a book somewhere on this topic. Whatever advice you can provide will be greatly appreciated.
Russ
Replies
It's not much of a stretch to say that I fill little gaps for a living.
My go to method is to take a mix of coarse and fine dust, lay it over the gap and tap the workpiece to settle it in. Then I drip Thin CA glue into the little pile of dust, wait a few minutes, them mist with accelerator, and scrape off with a card scraper.
The glue will pull some fine dust into the gap, so it's important to leave a little pile.
If you use accelerator immediately, it tends to boil and create more gaps.
I think a tile worker who inlays tile inside a wood frame would fill gaps with silicone with a color added to the silicone to match the wood color. Just a thought.
Sanded caulk not silicone in a color that matches is what tile workers use.
What works well on ebony guitar fingerboards with mother of pearl inlay is to fill the gaps with clear epoxy. In your situation, I would consider coloring the sides of the tile with a brown paint or magic marker that matches the color of the surrounding wood. Typically, the color of the underlying wood comes thru the epoxy. It may be that your gap is too deep to do this successfully, but it would be easy to look at a sample and see. I suspect that this works better the darker the wood is; probably not great on holly or maple. I use clear epoxy to fill small amounts of planer tear-out, applying it before I plane/scrape the surface. It works well on cherry, walnut, mahogany, and oak. Remember that you should try what you think might work with the whole finish routine on it, not just by itself.
When I am fitting something in (these days it's butterfly keys that are in fashion), I taper the sides of the piece slightly to compensate for the thickness of the groove that the marking knife makes. I'm not sure that would be easy or possible with ceramic tile. I guess that I should also mention (apologies if this is old hat to you) that your chisel needs to be really sharp, and your final cut with chisel in the knife groove needs to be really thin, to avoid the waste wood's resistance to moving pushing the chisel back into the wood that is to remain.
Thank you. Could you explain how you apply the epoxy in small gaps like this to avoid overflow onto inlay or adjacent wood? I believe that acetone is a solvent for epoxy so maybe this a a wipe off excess kind of process.
Thank you also for the reminder about chiseling the final margins. I have learned this the hard way. I now tape mask inside the scribe marks to create a smaller area. I route to the tape then chisel the remaining 1/8” margin.
I overfill the gap, then pare it down or sand it down (not easy with the tiles, I suspect.) The epoxy soaks into the wood a bit, so if you just fill it level the surface drops and it doesn't look full after it sets up.
Acetone is a solvent for cured epoxy, so you could use it to remove any surface excess.
How about taping off the wood and the tile, and filling the gap with flexible caulk in an appropriate color? Tinted epoxy would be done the same way. My preference would be tinted epoxy.
On chiselling a straight line, first you need a nice sharp chisel and a scribe line deep enough to firmly register the chisel. Chisel to a distance about 1/16-1/32" from the scribe line to avoid the chisel backing into the wood and causing a dent (particularly a problem with soft wood).
After striking the chisel, do not remove it from the wood, but tilt the chisel slightly and by tapping on the side of the chisel, and keeping it registered, knock it over about 1/2 the width of the chisel. Tilt it back straight, strike, & repeat this across the line.
The wider the chisel, the more accurate you're line will be. Also, take your time and do light strikes on the chisel. I think you'll find this it give a good result.
This is a chiseling lesson for me. I have been chiseling the full 1/8” margins left after routing and probably causing some expansion of the cavity. Reducing the width of the gap should reduce the gap-filling challenge. Thanks.
Is the edge of the ceramic tile square to the back? If the edge is not square, it will either always show a gap around the edge (edge bevels in) or the tile will not be flush (edge bevels out).
You are right about the importance of the tile edge geometry. I should have been clearer.
I am first inlaying a piece of contrasting wood (wenge) into the box lid, then insetting the tile inside the wenge. This provides a “picture frame” for the tile.
The gap I am try to fill now is the one between the wenge edge and the inlay cavity. The edges of the wenge are perpendicular to its top and bottom surfaces so I think the gap is uniform through the thickness.
I am able to sand the tile edges to get the edges perpendicular to the surfaces. So I think if I am able to fill the wenge gap correctly, the tile gap fill should be similar.
Thanks for your input.
One picture is worth a thousand words. I am imagining your box lid and it sounds really cool. I am sure that all of us would like to see it, "warts and all". It is giving me ideas for my own projects.
OK, Dave, Here are some photos.
I would like to say that this was my worst woodworking outcome. But really it is not in the top ten.
The first picture is the wenge inlay as of today. The tile inlay would be inlayed inside the wenge inlay.
Note that the wenge is now a mess because I decided to put it through the planer to see if the gap is uniform through the depth (it is). But the planing put divots in the wenge, so disregard this piece that is going to scrap.
The dark lines in the gap are not shadows (the inlay is flush), but are cured tung oil that I had mixed with dust to create the gap filler (won't do that again).
Photo 2 shows the piece with a conventional tung oil first coat. This was a suggestion from someone earlier in this thread. The left half is finished, the right half original. The finish masks the dark line a little bit but the line is still raggedy as you can see.
The paduak has an open grain so when the grain in cut at the inlay edge, it seems to contribute to a sense of raggedness. My mental standard is the border that you see in well-done dovetail joints in two different woods. I'm definitely not achieving that.
Picture 3 is the box that the lid would have gone on. I wanted the wenge in the splines to be repeated in the top. I may go to a more forgiving inlay material for the next trial but still using a contrasting color.
Feel free to offer comments. They won't be taken as criticism. This is exhibit A in missing the mark. I'm just trying to get better and appreciate the advice I have gotten from this Forum.
Russ
Given this new information, I strongly suggest that you undercut slightly the edges of the wenge and the tile, to compensate for the width of the knife cut. It doesn't take much, tho I suggest that you do a couple trial runs to make sure you get about the right amount. Then, with proper paring (sharp chisel and very light final cut) the piece should be a compression fit. Be aware that if you put it all the way in, you won't be able to get it back out. Also be aware that you don't want a lot of compression (hence the trial pieces.) This will allow you to need no filler on almost all the edges, given that 100% perfection is not easy to achieve over many attempts. However, you should be able to reduce the number of spots that need filler to a small percentage.
Thank you. I think you are right. That will be what I try next.
I have just posted some pictures (#13) that may be helpful.
Your comments on this question have been really helpful.
Thanks.
Russ
One thing I didn't mention is that I didn't taper the whole edge, just the bottom 2/3rds or so. That way if I needed to remove some wood to flush the surfaces, I didn't make the piece smaller, opening a gap.
Lee Valley sells very low viscosity CA glue with hair thin applicator tips. It fills seriously thin cracks with no effort. Once dry sand or plane smooth.
and there are black and brown CA glues available that work well for gaps.
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