Inlay Tool Tip - Luthier Tips du Jour Mailbag
In this episode, Robbie O’Brien shares valuable insight on preserving the integrity of small inlay components during inlay work, offering practical guidance to prevent breakage.
Video Transcription
[on-screen text reads: Luthier Tips du Jour Mailbag]
Mailbag question: I break a lot of downcut spiral router bits, what can I do to prevent this from happening?
Robert O'Brien: Today's Tips du Jour Mailbag question comes to us from Florida. "Robert, I'm using a 1/32nd spiral down cut bit for inlay work, and I'm breaking a lot of bits. These things are not cheap, so is there something I can do to keep from breaking them? Thanks for the advice, Michael in Florida."
General safety rule
First of all, Michael, let's talk about the general safety rule for the depth of cut with a router bit. The general rule is you never want to go deeper than half the diameter. For example, if you're using a router bit that's a half inch diameter, you never want to go more than about a quarter inch deep in one pass.
Now for inlay work, we use very small bits. For example, as low as 1/32nd like you said. So if we were to follow this rule, we couldn't go more than 1/64th deep at a time, and that creates a problem for inlay work. Most of those things we're going to inlay into the surface are thicker than 1/64th, so you would have to route the channel twice. That could create extra work and problems.
Recently I visited David Nichols from Custom Pearl Inlay at his shop in upstate New York, and I learned a thing or two about how not to break bits. Let's go over to the bench and I'll show you.
Dremel tool limitations
So Michael, even though you didn't mention the equipment that you're using for the inlay, I imagine this is probably it. This is what most people use for the inlay work, a Dremel tool with the router bit, usually a spiral down cut bit, and this one just happens to be 1/32nd. The problem with the Dremel is that you have an adjustable speed control here and it goes from 5,000 to 30,000 RPMs. In my opinion, a little bit slow.
Using a micro die grinder
Let me show you what I got from David Nichols. So this is what's known as a micro die grinder. This particular model goes up to about 60,000 RPMs. However, you can get more expensive models that go even higher, and I think that's a great advantage. The faster you can turn that tool, the cleaner it's going to cut. I'm also using a clear, transparent base that David designed to hold the tool. Using this, you can clearly see what you're doing.
I've got this tool set up, so that's the complete depth of the piece of pearl that I'm going to inlay so I can make the cut in one pass. I'm going to plug this into my airline and I'll show you how easy it is to work with something like this spinning at a faster RPM. So here's the tool. I'm going to turn it on full blast and I'm just going to have my way with this piece of ebony.
So you notice I just free-handed it through the piece of ebony. I went the full depth, or full thickness of the pearl, which is about a little less than a whole 16th of an inch, which is pretty deep. You'll notice I had no problem, the bit didn't even think about breaking, and I think that's due to the high RPMs from the micro die grinder.
So thank you David Nichols at Custom Pearl Inlay for turning me on to this fantastic little tool. Also, thank you very much Michael in Florida for your question. And I think that if you use the higher RPM tool, the micro die grinder, you'll find that you'll break far fewer bits and happy inlaying.
