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micro mills for wood engraving recommendation anyone?

mark thomas

Titanium
Joined
Dec 15, 2004
Location
SF Bay Area
I'm doing some shallow engraving in hard maple, 1/32" - 1/16" diameter, flat bottom. I'm using misc end mills I have inherited at various points, but I need to get some new ones. There are some end mill options , mostly: HSS vs. carbide vs. diamond coated, 2-4 flutes, various helix rates. The stuff I inherited and have used include 2 and 4 flute HSS and carbide, and I've got mixed performance, but I cannot tell how much is due to the mil and how much to the original condition (some were obviously new, others unclear if new or lightly used)

So, I'm looking for recommendations for type of end mill and also possibly suppliers.

Btw, with respect to performance, the main issue is getting a clean, burr-free cut, especially where the cut is parallel to grain. Second main concern is life. Clean cuts seems to suggest ultra sharpness, which may favor HSS? Life favors carbide. But are high-quality carbide sharper than lower-quality HSS? Probably no value in diamond here? Does the helix angle have much influence on cut quality?
 
I use micrograin carbide single lip engraving bits on my gorton pantomill you can call quality 1 engravers down in rancho cucamongo and tell them the specs of what you are doing and they can custom grind engraver bits for your application. I tried to use .125 shank endmills but they had a tendancy to break if you looked at them crosseyed.

Justin Bowerman
JB Enterprise
Gunsmith in Central Ca.
 
Had similar results long ago using endmills in cuts parallel to the grain. The helix angle makes a lifting force at the edge of the cut, wood has very low shear strength at the corner of the slot and the surface normal to the cutter axis when moving in that direction. Corner fuzz for sure.

Take a look at the geometry of wood router bits, they have little to no helix angle to minimize upward tearing force. Best results (life and finish) came with micrograin carbide by duplicating router bit geometry. HSS didn't last long.

For diameters as small as yours one lip will work well, JB's source could be worth looking into. We made our own to get positive rake, zero helix angle, SHARP and good back clearance.
 
Thanks for suggestions. I briefly tried single lip cutter, but did not experiment very much. It was OK but tended to burn a little. I speculated the slower feedrate required by just one flute created burning risk. But cutter may just not have been sharp enough.

I had wondered if there was a zero-helix "end mill", and I googled around for things like "miniature router bits" and other things that might yield router bit (wood) geometry cutters, but didn't have any luck. Woodwhacking suppliers seem to consider 1/8" to be miniature.

I should probably also try reverse helix bits. Seems like if the shearing is downward there should be a lot less tendency for the fuzz.

I also am not expert is evaluating sharpness of such small cutters. I should stick some under the microscope and get a feel for how to evaluate sharpness.

The regular end mills cut beautifully in end grain by the way (not surprisingly)
 
LH helix will get instant burn, they pack the swarf down and make a good imitation of friction ignition. Getting the swarf out is helpful, an air blast aimed into the cutter path with a vacuum behind it to keep the mess down was helpful.

Single lip cutters meant for metal (mostly used for engraving) don't have enough rake or back clearance to do well in wood.

Agree with you, hardwood endgrain is a piece of cake.
 
Hey mark what is your spindle speed my panto mill and my new hermes engravers both run at about 30,000 rpm at that speed with wood feed rate shouldn't be a problem a little blast of air doesen't hurt either.

Justin Bowerman
JB Enterprise
Gunsmith in Central CA.
 
I have some interest here as my partially rebuilt Gorton Pantomill is intended in part for some use in wood engraving.

Just a thought- are you getting fuss or burning?
It may be that a light touch with a sand blaster may clean up the work without cutting into the wood surface or altering the engraving.

Another- have you tried pre finishing the work?

It could be that finishing will sufficiently stabilize the surface so as to diminish the tendency to leave fuss on cuts.
 
Onsrud doesn't make micro stuff (very few bits under 1/8", none under 1/16")

My max spindle speed is 22,000 rpm.

With regular end mills, I do not get burning, just a little fuzz at edge.

The Amana thing is interesting, though just a single lip cutter, designed for homogenous materials (MDF, plastics, etc) it would appear.
 
Try these guys: www.kodiakcuttingtools.com. they have micrograin carbide endmills, 2or 4 flute down to.005 inches! I use their .023 cutters to mill fretslots in ukulele fingerboards with great success, and .031 to cut inlays from shell and corresponding pockets in wood. Very reasonably priced IMHO.

Barron
 
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I would go with Robb Jack Corp, made in Lincoln, CA. Not far at all from San Fran. They make solid carbide end mills down to 0.005" in diameter and ball end mills down to 0.010" in diameter. They also have tools with specific geometries for wood. RobbJack: Manufacturers of Premium Rotary Cutting Tools - Carbide End Mills, Saws, and Router Bits

Thanks. Looks like a great source for micro mills and others. However, the things they advertise specifically for wood (incl with downshear helix) only go down to 1/8".
 








 
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