Dremel Routing Fret Slots

[Thomas James]

I have always done the old pick, saw, and/or knife cleaning. I am considering checking out the dremel method with the 1/32" bit. I have dremels, a foredom, and a router base. From what I gather reading stuff on the web it seems rather straight forward. Looking for finer points on using this method or any helpful info is much appreciated. My Les Paul needs frets and seems like the perfect candidate.

Thanks. Tom.

[Mark A. Kane]

Mark,

I'm a firm believer in the idea expressed by the phrase "your mileage may vary" and this applies to my experience with the oscillating saw. I composed a write-up for a luthiers group 10+ years ago on this very method after much practice with it and have included excerpts from the write-up in my response below. Some may find it useful in determining if the use of the oscillating saw is a good path for them to go down.

"I tried this method with great anticipation but my mechanical sensibilities were overwhelmed at the potential of disaster at every step. The problems I experienced after many tries are thus:

1. There is no way to control the depth of the cut, other than by feel alone. This tool will go deep so fast you could find the truss rod in an instant! It's astonishing how fast this thing with a good sharp blade will go deep. You can prove it to yourself very quickly by experimenting on scraps. 

2. The positioning of the tool and one's body is precarious and unwieldy. It requires positioning one's body over the guitar in such a way (hunched over the guitar with forearms held close to the chest) as to crank the spine, neck and arms into an uncomfortable and rigid working position that I wouldn't want to hold for more than about ten seconds, at most. Ergonomically speaking, it's a nightmare that any ergonomics engineer would nix as a practical, shift-long, safe working position. Further, it relies heavily on wrist and forearm strength, and a deathly grip on the tool to keep it perfectly aligned with the slot. This brings me to the next point.

3. There are side-loading forces at work that are unpredictable. The slightest twisting of the blade can and often will cause it to grab the slot, thereby propelling the tool out of the side of the neck straight through the binding, if present, or cutting a nice deep slot through the side of the neck.  One must be extremely careful to not let the tool grab the slot and run out the side of the neck. Extra repairs caused by this are not something I'm interested in taking on.

4. It is ineffective at best at cleaning the sides of the slot. It will no doubt cut into the bottom but it takes a lot of manipulation to get the teeth to contact the sides, and as mentioned earlier, doing so causes the teeth to occasionally and unpredictably engage the sides and propel the tool in one direction or another.  That the blades are available in different thicknesses doesn't address this critical shortcoming.  The tool only really cuts depth, and again there is no sure-fire predictable way of controlling that aspect other than by feel alone and guesswork. I like to be more precise than that with respect to depth. I'm not concerned with removing what's in the bottom of the slot as long as I have uniform clearance for the tang. I'm primarily interested in a slot of uniform depth and width".

Just my two cents. As with any technique, practice makes perfect. In this instance, after many tries, I identified another path for myself. But, as stated before, "your mileage may vary." :)

Cheers!

[Mark McLean]

Hi Mark

I think you have raised some really good points.  It sounds like you have trialed this more extensively than I have done and have anticipated the real world issues.  I tried it out on a single old board that was unglued from the neck, so I was able to clamp it down securely to the bench.  I was able to control the angle of attack of the blade to keep the blunt side of the hook blade (the outside curve) in contact with the floor of the slot - to minimize any risk of running out or too deep.  And my tool has speed control.  

I can certainly appreciate that if I was trying to do it on a board attached to a neck it might be much more difficult to control.  There is no doubt that the Dremel tool plus the S-M base and very fine bits would give more precise control, especially over depth.  In a professional setting doing refrets and repairs regularly I can see that the Dremel would be a preferable setup.  I am not a professional repairer and I only build as a hobby, so the oscillating tool will probably get this job done on the odd occasion when I need it.  

[Frank SIlano]

So I got the .020" end mills in today and did my first fret job with them right way. Straight up this is going to work for me and save me a lot of time prepping re-frets so thank you all for that. I can see that you have to watch depth carefully and that the depth of the cutter is very important. I did some test slots and got the cutter just a tad too deep and because of the tapered shape of the cutter it opened up the top of the slot wider than I wanted but it was still workable. Once you get it dialed in it is cake. Also I experienced no wandering of the bit and the slots were super clean and precise. I highly recommend this if you do a lot of refrets like I do. Good stuff! :)

[Walter W Wright]

so i got myself a .022" micro end mill and used it on a late '60s LP custom today and yeah, this method is a winner!

to answer my own question about the bit wandering off into virgin wood, i used it in the little stewmac precision router base with a foredom rather than a dremel (only 18k RPM max but way more torque compared to a dremel) and i found the trick to be that as long as you're pulling the bit along the slot you're golden, it won't wander. it's only if you stop moving the router base but keep the bit running that it wants to eat into the surrounding wood.

@Mark A. Kane's video showed him using the .022" bit to get a .021" slot in a maple board, but i found that in the old ebony of this LP custom the .022" bit got me a .022" slot and a slightly loose .022" at that. might be my newbie technique with the tool but i think i might try a .021" bit next time  

[Frank SIlano]

Congrats Walt! It does take a little practice but it works like a charm. Slow and steady...

Frank

Slamo Custom Guitars