How to cut slots for Dulcimer frets?

I’m building a dulcimer (similar to guitar) and need to cut slots in the fret board to install the frets . The grooves that hold the frets are about 1mm deep and suggested cut with a 0.5mm cutter. I have what is labeled PCB Titanium Milling Cutters 0.5mm. Not sure if this is the best tool?

Does anyone have recommendation for setting up the tool parameters for something this small?

Any other suggestions would be helpful?

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I haven’t used any really tiny cutters yet, but I gotta believe RPMs should be as fast as you can go (24000 for my spindle), DOC 0.1mm, and a pretty gentle feedrate (500mmpm or less??)

Is the fretboard flat? or arched?

I would look for shorter tools (after you break this one :smiley: ) 1mm - 2mm length.

And consider marking the slots with the CNC, and then using a kerf/jewelers/luthiers saw to finish them. You could mark them with a 30° vee bit, or even a 15°


Is that tool Titanium or Titanium coated? Makes a difference because if its carbide with a titanium coating, carbide is very brittle so you’ll have a tough time with that tool against hardwood. The smallest end mill I’ve run is 1/16" and that was just for a shallow raster cut surface finish. With that tool I used around 10 IPM (254 mmpm) feedrate.

There are other options e.g tapered or V-groove bits. Those depend on the profile of the groove (shape when looking side-on). Here’s an example of a tapered bit with 1/32" tip with a 1/64" radius.

or just a deep angle V-groove bit.

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Usual preface, I’m with PreciseBits so while I try to only post general information take everything I say with the understanding that I have a bias.

A lot of this will come down to the material you are cutting and runout. Runout will add to your chipload, so it becomes vastly more important when dealing with cutters this small where you have very little room to absorb more chipload. The material will also make a huge difference here as woods like rosewood and ebony are vastly harder to cut and act more like composites than wood. I went through this related to fret cutting in decent amount of detail a while back so I’ll leave this here instead of repeating myself. Best practice for tiny endmills

I can’t really see the flutes of that cutter in the picture but from the description it is most likely a chip-breaker or diamond-cut router with a titanium variant coating. Those are grinding not cutting geometry tooling and typically rely on very high RPM and low feeds (e.g. 60KRPM at 20IPM/508mm/m). They are designed to cut FR4 and other composites so they may or may not work depending on your material, they will not be ideal regardless.

If you are using rosewood or ebony be aware that any with light colored stripes/striation in it will be much harder to cut. Those are basically glass where the tree integrated silica into the wood.

One other thing I would check before doing any cutting is actually measuring the fret wire. We ended up having to create a range of diameters for fret slots going by 0.001"/0.025mm due to how much extra pressure it took to press in the wire if the slot was too small in rosewood and ebony. As long as you have a smaller cutter though you could pocket it, it would just take more time (and potentially dealing with chip thinning).

Let me know if there’s something I can expand on or help with.


+1 to everything that has been said already, all great information.

I’ll just reiterate that knowing your runout on tooling this small makes a world of difference. I usually cut metals with sub 1mm endmills, the precise bits page on measuring runout was fantastic for getting me up and running.

Another strong recommendation to reiterate is to get a tool with as little stickout as possible. If you only have to go 1mm deep, a shorter tool will save you a ton of headache. In my experience, stickout matters much more as your tooling gets smaller.

Lastly, I’m not a precise bits shill and I’ve got no affiliation with them: That said, I know if I were cutting frets I’d look at fret slot cutters from precise bits “specialty bits” section first… #notsponsored :slightly_smiling_face:

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I have a post here with what I use and I have done many fretboards in Rosewood and ebony


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