Official Luthiers Forum!

Well after 20 some odd years avoiding it, someone suckered me into pearl fb inlays. Simple Martin diamonds so not to bad but...

How tight do you make them? Is it prudent to leave a space for humidity changes?

I've never made any allowance for humidity for pearl inlays. I think most of us like to make the inlay cavity as tight to the inlay as possible.

I'm not an expert, but I was taught by someone who is very good at it. I was taught to make the recess the inlay fits into as tight as you can get it. However, when inlaying into dark wood like ebony, you can get away with a slightly looser fit by gluing the inlay in with black epoxy or CA, or with matching wood dust in CA or epoxy. If you are inlaying into lighter wood like maple, the tighter you can get it the better to avoid having whatever you use as adhesive show as an uneven dark line around the inlay. You can try to color match your adhesive to the lighter colored wood, but it's not easy to get a dead on match that won't show.

If those diamond inlays are going into ebony or another dark wood, I was taught a trick that helps with the sharp points since it's impossible to rout sharp corners. If you rout the corners with a tiny bit (like 1/32") to make a tiny circular pocket that extends just slightly outside the diamond outline right at each tip of the diamond, you can get a nice clean inlay when using black epoxy or CA.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Exactly. I take a 1/32" bit and just nip the ends of sharp corners to give just a tiny amount of additional clearance for the inlay. It disappears if you're inlaying in dark wood.

As for the inlay pocket itself, I like to keep it close but not super tight. In my opinion, the inlay should drop into the pocket without having to push down very hard at all. The way I do it is to glue the inlay to the surface I'm inlaying, scribe around the inlay with a very sharp scribe as close to the inlay as possible. Pop the inlay loose from the board, rub chalk into the scribed line and then when routing, rout until the line JUST disappears. Then, I give any points just a little tiny zap with the small bit. This method allows a tiny bit of a gap for the epoxy (in my case) to squeeze out around the inlay instead of trying to push the inlay back out of the pocket like a piston (which can happen if it's too tight). If you're careful, the gap won't show even in light colored woods.

Dave

This is how I do it as well, but our methods differ from this point. Rather than using a router bit, I switch to an x-acto knife and jab at the corners to make them fully pointy. But you can't really get them pointy to full depth (usually the tip of the knife will bend or break off if you try), so the final trick is to sand the underside of the corners on the inlay piece, so they're only pointy at the surface, and somewhat rounded down inside the pocket.

I have made pieces tight enough that they had to be pressed in with significant force, and never had anything bad happen later on (I have cracked a couple pieces before getting them fully seated though). Ideally they should be tight enough not to fall back out when turned upside down, but loose enough that you don't need a wood block to push them in. Wood inlays should be a little looser than shell, because they immediately expand when glue is applied, and may not go in if the fit was tight when dry.

+1 to both the previous posts. My problem is getting good enough visibility to hit the scribe line with a router bit. I get close and do the final fit with a couple chisels.

I also glue the inlay on but I use a 0.3mm pencil to trace the outline. I use a Blue's Creek Precision Inlay Tool to route the cavity, when it's time to route the edges I use a 1/32" bit up to the pencil line. After the initial route I erase the line, place the inlay over the cavity and mark the areas that still need work with the pencil. I use an Xacto knife along with a selection of small chisels {some of which I've made from Xacto blades) and sharpened dental tools. Good dental scaling tools are made from good steel and will take an edge quite well; they are very useful for working the bottom edges of corners.

Probably the most important tool is my Optivisor

_________________
Steve Smith
"Music is what feelings sound like"

Yes I’m not looking forward to the headache from actually having to see what’s going on, lol...

+1

I use a stereo microscope for engraving--the optivisor isn't strong enough any more...

Dave

Pretty much what Jay said for me too. I would only add that for diamonds, or any inlay, I hold it in position with an awl then scribe a line around it with a pencil. Then I rout out to the inside edge of the pencil line and then fine tune from there. Sometimes you have to erase the line then fit the inlay in place trace again and rout out to the marking.

The person I learned from liked to use a very fine lead mechanical pencil to mark around the inlay as has been mentioned a couple people above. He then routed away the line and that gave a nice fit. I had too hard a time seeing the line though especially on certain woods so I switched to using a scribe. I rout up to or very close to the scribe line and then finish off with micro chisels from StewMac. https://www.stewmac.com/luthier-tools-and-supplies/types-of-tools/chisels-and-knives/micro-chisels-set-of-4.html A potential downside of using a scribe is that it sometimes wants to follow the grain of the wood away from the inlay so you have to watch out carefully for that to avoid it.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Good point (no pun intended). Having a super sharp scribe is absolutely necessary, and I sort of automatically find myself scribing in the same direction relative to the grain as I would rout binding channels--always trying to go downhill. Habit, and I hadn't really even thought about it until you mentioned it.

I've started using a white pottery marker (like a grease pencil) instead of chalk a lot of the time, since it stays in the scribed line better when routing. Keeping the line visible, no matter what, is the important part IMO.

Also, Steve mentioned the Blues Creek pneumatic router setup. I use that too, and it is such an improvement over any kind of Dremel or Foredom type tool I've ever used. Runs fast enough that it doesn't really care which way the grain runs, and it's much lighter and easier to control.

Dave

I have one of those - I never thought of using it for engraving.

A friend showed me a trick - lay a piece of dental floss in the recess when you push in the inlay, then you can easily get it back out again

Ed M

Good trick!

Dave

Great thread, thanks all.
To this day I havn't found a scribe method of work that is satisfactory for me.
Exactos, pins needles, sewing machine needles chucked up in pin vise, dental picks and scribes. That rosewood is just hard to scribe! I have 3mm pencil, can't see it unless the light is just right. I may try working from the lighting end and put a ring light on my inlay router.

meddlingfool, when your inlay pockets are tight, its very important to check fit with the inlay "perfectly" parallel with your pocket. Tilt it even a little and it wont drop in causing you to chase your pocket and make it too large. I use a little masking tape handle to lower my inlay into the pocket when I check the fit. You'll get tighter pockets that way.

_________________
Measure Twice,

Karl Borum

Admittedly the pencil lines are hard to see. I find a glancing light (low angle) works best for me.

_________________
Steve Smith
"Music is what feelings sound like"

X-acto is no good because the double beveled blade results in the line being offset away from the inlay piece by half the blade thickness. Needles are too flexible and not sharp enough out of the box, and would likely dull very quickly if you did sharpen them. I use a StewMac scribe, but it would be easy to make one yourself out of any tool steel wire 2mm or thicker (preferably 5-6mm just because it's more comfortable to hold).

And don't forget to rub chalk in the scribe line to make it visible.

I agree pencil is too hard to see.

Even though an Exacto #11 blade (or many other blades) has a double bevel, just tip the handle away from the piece to the same angle as the bevel. When you work close to the tip and change the #11 often, the line is just right

Low angle light is helpful in a lot of areas. Inlay outlines, finding faint scratches on surfaces after sanding, finding lines that just aren't quite straight. Low angle light just has a way of bringing out contrasts that you can't see otherwise.

Dave

After trying outlining the inlay with a very fine mechanical pencil and marking scribe lines with chalk and having trouble with both approaches, this is what turned out to give the best visibility for me when routing out the recess. I use a StewMac scribe and after removing the inlay, I shade in the wood outside the scribe line right up to the line with a yellow lead in a mechanical pencil on dark to medium-dark woods or with standard black lead on light wood like maple. It makes it pretty easy for me to rout up to the scribe line but not beyond it.

Here's what that looked like on a headstock logo inlay I did a couple weeks ago into walnut. I think it came out nicely considering that lighter colored woods like walnut are not as forgiving as dark woods like ebony or Indian rosewood.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Nice one Jay!

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Sometimes lines and scribe lines can be hard to see because of dust.
If you’ll take a little piece of tape and wrap around the bit shank leaving a little flag it will act like a fan and keep the work area nice and clear for you:)


Sent from my iPhone using Tapatalk

That's a good approach. Roger Siminoff recommended using your finger and rubbing a thin layer of white water based paint to the surface to be inlaid first. Then , attach the inlay, trace around it, etc. It really can make the lines a lot easier to see.

Dave

I bought the Larry Robinson tape (it's DVD now) many years ago. He covers design, cutting the inlay and inlaying it. His methods have worked well for me. Regarding the dust problem while routing, I use the StewMac dremel attachment with the airport and attach a fish tank blower with plastic tubing and no more dust.

_________________
Joe Beaver
Maker of Sawdust