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Does anyone have any comparison of end mills vs downcut spiral bits? I’m looking at some sources such as precise bits and drill bit city.

I plan to use these either in a foredom or laminate trimmer.

Thanks, Jon

I use end mills regardless USE SHARP ones for rosettes I get mine from BQtool.com
down cuts can work but once dull they will overcut the width.

Best advice is use shellac on the top let dry then rout helps for a cleaner cut and removes easy in the sanding process
DO NOT USE CA on spruce tops

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Not an answer to your question, but…it’s OK to use CA on spruce tops if you seal the rosette channel with shellac first. I do it all the time. The point is that you need to seal the channel or else CA will wick into the endgrain via capilliary action and show under finish. This applies Tom binding channels as well…

Like Ed said, I do it all the time too although he builds way more guitars than I do. And when you seal the rosette channel with shellac - I do it twice, just to be sure. Same thing for binding channels.

_________________
Steve Smith
"Music is what feelings sound like"

I have to ask why do a step not needed when duco cement works just fine??
CA if not sealed will stain the top yellowish

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

No argument John, I'm just used to using CA on my inlays so I can position things and then flood the inlay. I do the same with rosettes for convenience although different glues will certainly work. Sealing with shellac is no problem for me but I always have a squeeze bottle of shellac and some t-shirt scraps on my bench.

_________________
Steve Smith
"Music is what feelings sound like"

+1 to John.

Another way to improve channel quality is to leave a couple thousandths of material for a finish pass. Back in the day I'd just route a 1/16" channel with a 1/16" bit and shove some purfling in there. I never do round rosettes these days, but if I did, I'd use a 1.5mm upcut followed by 1/16" downcut. This also allows you to get much more life out of your bits, because super sharpness only matters on the finish pass.

For larger bits, Shars has the best quality and low prices (although shipping is high if you only need a couple things). But their small bits are expensive so I usually buy those from ebay user jtg1969 https://www.ebay.com/usr/jtg1969/ because he sells multi-packs for good prices.

With CA you can get everything in place perfectly and zap it right in place.

I have had the nightmarish CA stain though and it was because I either forgot to shellac it or didn't get it in there good enouhg, never could figure that out. So I am very careful about it.

With duco you have to go piece by peace and inch by inch right? Or can you set everything in place then glue it with Duco?

For cutting rosette channels a straight two flute sharp high speed steel bit will work as good as any and better than many. Spiral bits are generally used to extract the chips either up or down, but the shallow depth of a rosette channel doesn't require that. Carbide bits last much longer in tough materials but usually aren't as sharp as a well sharpened HHS bit. For really narrow channels (1/8") solid carbide is probably better.

Thanks Clay (and all other responders)

I thought the spiral down feature wasn’t so much for material movement, in this case, as for getting the sharpest top edge?

Yes, spiral down prevents the problem of stringy fibers left dangling from the edge. Most woods you can knock them off with a fingernail, but spruce has particularly strong fibers that usually have to be shaved off with a sharp chisel. I haven't tried straight flute bits, but that would probably work just as well. And shellac prevents it for the most part even with upward spiral, by gluing the surface fibers together more strongly.

duco works so well
the more I do this the less I use CA
Duco sticks fast as well and is finish friendly

its just another technique and if CA works for you keep it up.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I use CA for the speed. Straight from putting in the rosette to thickness sanding…

As John mentioned, I've had bad luck with some CA glues. I used some cheap Chinese CA glue from Walmart and had the Glue stain the wood a bright yellow. It didn't do it immediately but took on the color after about a week. Since it had soaked into the end grain there was no sanding it out. I hid it under a burst finish.
I use Loctite CA to glue on bindings and have not experienced any problems with it so far.

Good point. The only CA products I use on guitars are from GluBoost or StewMac.


Steve

_________________
Steve Smith
"Music is what feelings sound like"

+1