View Full Version : Rosette and soundhole cutter

Pete Howlett
02-09-2016, 09:46 AM
No matter how sharp or new a spiral down-cut router bit is it nearly always generates disappointing tear-out. Here is a fast edited video on how we cut sound holes and rosettes in the work shop.


02-16-2016, 11:20 AM
Really helpful, thank you Pete. I figured out the cutter replacement on my own, but the idea of replacing the drill bit with a solid pin brings it all together. Simple always seems to be best, doesn't it?

Beau Hannam Ukuleles
02-16-2016, 01:10 PM
I want to bespoke my components!

But seriously- Pete, what shape have you found is best to grind the tool steel??- flat leading edge, then beveled sharply behind this leading edge- much like a chisel??

Pete Howlett
02-17-2016, 10:07 AM
Beau - the clearance angles are critical. If you don't get them right then you get tear out as you would with a router cutter. I leave about 0.5mm from the cutting face square and then relieve either side by about 5 degrees. The foot of the cutter has a 10 degree angle away from the tip with most of the tool metal behind this relieved at a secondary angle of about 60 degrees. My drill press runs at the middle speed of a 5 speed selection (those 12 speed ones have no torque so this wouldn't work on a 2 belt drive set-up).

02-17-2016, 12:04 PM
On my Island uke project I managed to make a tool that cut the rosette grooves and the sound hole at the same time...when the bottom of the cross beam hit the soundboard then it came to a full stop...and the job was done.
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1828_zps1a9f2ac1.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1828_zps1a9f2ac1.jpg.html)

chuck in ny
02-21-2016, 03:27 AM
i am thinking of making template patterns in the appropriate diameters and cutting the holes with a router. this would eliminate any center guide on a circle cutter setup. the bearing on the router bit would follow the template.
i have different bearing bits in the shop, some spiral, some straight, some angled. a bit of experimentation could be done. the key here and what pete was avoiding is tear out. since it's template work, the hole could be rough cut with a jigsaw, further improved with a rasp dremel sander &c., and then finished with the router. with routers sawblades and the like you get much finer work when you are only cutting a kiss. you eliminate the inertia of larger wood fibers tearing up smaller ones.

Pete Howlett
02-21-2016, 04:59 AM
Oh well Chuck... how many new wheels do you have in your workshop? Spend some time looking at factory videos of this process. Not a router in sight - the fly cutter model is the way industry solved the problem of tearout that inevitably comes with using a router...

02-21-2016, 06:59 AM
Up till now I have used engraving bits to rout out the rosette channel...and about 50 percent of the time I do get minor tear out ..it depends on the texture of the wood.. I tried using shellac and CA glue before cutting but it don't make a lot of difference CA glue just melts on the cutter...this week I'll try and make myself a fly cutter set up for my Martin style Sopranos..and then I can compare the two methods...more info later.

Pete Howlett
02-21-2016, 07:25 AM
I know the answer Ken :)

Kevin Waldron
02-21-2016, 08:12 AM
LuthierTools has designed a nice apparatus for doing these that works on the principle of the fly cutter and Ken's design ...... This is all we used when we were in production........We had lasered templates to match our sound hole patterns which made setup on the fly easy......

Enclosing a link video for Luthiertools..... watch and they will tell you how they recommend sharpening the bits......attaching a photo of some of our tools as well.





Pete Howlett
02-21-2016, 09:13 AM
I suspect ken's is going to cost a fraction of that tol which is specific to guitar making... I lusted after it for all of 10 seconds :) Thanks for the link Kevin.

02-21-2016, 05:48 PM
Just saying, but I use a dremel tool and a down cut spiral bit and I never get tear-out problems. Ever. (Well almost never). I've also heard that the bearings can be a little loose in the dremel too and have not found this to be a problem at all and tolerances are as fine as you would want. Coveates: 1) Super sharp bit 2) Well shellacked top 3) Super high RPM 4) Nibble, nibble 5) Go slow and down-hill. Simple as kiss your hand. However watch out at 4 o'clock and 8 o'clock. I would never use anything else because this works for me. But there are always two ways to skin the cat.

02-23-2016, 05:20 AM
I just completed the Tool ..My mass produced :rolleyes: soprano rosettes are joint less and the channel has to be spot on in diameter and width so I had to take care to make sure the tool was accurate .... I tried it out on a few scrap pieces to get it set up right and I was very pleased with the result no tear out at all on Mahogany or Koa ...Another feature is that it can't cut the rosette channel too deep cos the tool bottoms out at a set depth .....once set up it is a lot faster than my other method of a rotary table and engraving cutter bit...but I'll have to slow down the speed of the pillar drill on my next efforts co's it was burning the wood a little but nothing serious...I have made a small video of it in action and I'll show that later to day

02-23-2016, 05:56 AM
Here is the Video of it in action..and no I don't sell em ;)

02-23-2016, 08:52 AM
Very impressive Ken. As always

Pete Howlett
02-23-2016, 09:08 AM
Superb Ken. Are you using drill bits as your cutters? Could we have some close ups please?

02-23-2016, 09:45 AM
Superb Ken. Are you using drill bits as your cutters? Could we have some close ups please?
Yes Pete ..1/8 dia drill shanks ground down to the centre line, like a D bit with a 10 degree rake on the end...And I have just found some 3 mm worn out carbide end mills and I think they would make even better cutters.

02-24-2016, 01:08 AM
Close ups as requested, *note * The hole cutter protrudes (sticks out);) 1mm more than the rosette cutter
http://i219.photobucket.com/albums/cc143/shiregreenbod/PICT0011_zpszueebuj9.jpg (http://s219.photobucket.com/user/shiregreenbod/media/PICT0011_zpszueebuj9.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/PICT0006_zpss11qaxjn.jpg (http://s219.photobucket.com/user/shiregreenbod/media/PICT0006_zpss11qaxjn.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/PICT0012_zpsecvgwl7l.jpg (http://s219.photobucket.com/user/shiregreenbod/media/PICT0012_zpsecvgwl7l.jpg.html)

Pete Howlett
02-24-2016, 08:45 AM
Great setup Ken. Wish I still had my lathe as a set of these would be far better than my setup - better balance. I raise my hat yet again to the Fred Dibnah of the ukulele building world.