Ive been experimenting lately with my MiniMill and trying to engrave as small as possible. I'm trying to determine the best cutting tools for this small stuff, and would like to see what other people are doing, what accuracies they achieve, and what they are using for machine and tooling.

I am waiting for info on this subject, one of my suppliers does very smalll letterig and swears by D-bit geometry. He has recently bought a D-bit grinder just for this type of work. I have searched for info on sharpening D-bits but so far zilch.

Bfiles

Do you mean drill bits? I have heard about using old drill bits and re grinding them, but in a different shape than a drill bit. Ive used drill bits in place of end mills in plastic and MDF, with mixed results.

Try this site for engraving tools:
http://www.antaresinc.net/

OK, so " D bits " refers to the cross profile of the cutter. Basically a piece of round tool steel or carbide with a little less than half ground away, and one side sharpened. Here is directions for making one from majosoft, a great DIY engraving site.

http://www.majosoft.com/engraving/

look for "making a cutter from an old drill bit".

A machinist I know just uses a center drill. Works well.

A machinist I know just uses a center drill. Works well.

Do they use a center drill or a spot drill? Center drills that have the small diameter pilot followed by a 60 degree taper out to a larger diameter are not suitable for engraving because the web is too thick and the end is ground to something like a 118 degree included angle. Small, 1/4" and 1/8", 90 degree carbide spot drills will do very nice engraving down to a letter height of around 0.10".

Just a plain ol center drill. Goes in .010 or so and it comes out beautifully. Very smooth.

I use these for engraving.

http://www.micro100.com/inch/rtc_two_end.html

Check with a dental supply, they can set you up with all different shapes and sizes of carbide and diamond burrs. They have a 1/16" shank and are inexpensive. I use them in my Dremel tool.

I have a bunch of 1/8" drill bits I use, they're OK, but I'd like to try some of those engravers points from micro100. Its really small text that gets interesting, having a small enough tip and sharp point without digging in.

we use broken cutters. we grind them down on a small bench grinder, sharpening the bit at 15 degrees, rotating the bit untill all sides have been ground. We put 1 flute on the cutter and clear the back edge.. works pretty well. I can take a photo of a cutter if u like...

Do they use a center drill or a spot drill? Center drills that have the small diameter pilot followed by a 60 degree taper out to a larger diameter are not suitable for engraving because the web is too thick and the end is ground to something like a 118 degree included angle. Small, 1/4" and 1/8", 90 degree carbide spot drills will do very nice engraving down to a letter height of around 0.10".


1/8 centerdrill works really well for engraving , if the parts vary in hieght the centerdrill will only make a deeper engraving , where as a 90 deg spotdrill can make the engraving conciderably larger as well as deeper

1/8 centerdrill works really well for engraving , if the parts vary in hieght the centerdrill will only make a deeper engraving , where as a 90 deg spotdrill can make the engraving conciderably larger as well as deeper

What are you engraving in and what rpm and ipm. I did try small center drills and just broke the end off.

i ve used them mostly on aluminum , its been a while since i ve used them so i can t really give any excact speeds and feeds , 8000 rpm @30-50 ipm should be fine ,

1/32 ball nose works well on the steel stuff like 4140 and such

I engrave many parts. I use a #1(1/8 dia) HSS center drill. material is 6061 AL. rpm=7500, ipm=40. Z depth is -.006 Here's a link:
http://www.1dropdesign.com/media/images/gallery/conterojr2.jpg
the letters in the word "contero" are about .08 high.

What are you engraving in and what rpm and ipm. I did try small center drills and just broke the end off.

How deep are you goign!? usually you don't got deeper than a few thousands .001-.02 at most I would say You want about as high RPM as your machine can go

On brass try using a engraving diamond drop cutter. Check the engraving sites

I havent paid much attention to the mini mill lately, Ive been obsessed with buying servo drives and motors. I started out with the intention of putting together a simple three axis controller, and last night, after buying the eleventh Yaskawa AC Servo drive, I started scratching my head and other places wondering what I was doing.

Oh well, I'm obsessed, I geusse. Thats what motors and metal do to a man. The Yaskawa drives on eBay are just about given away for shipping cost's, its pretty unbelievable. Last night I got 3 200 watt drives and a brand new 100 watt pulse and direction drive for 40 bucks each.

This all happened right around the same time I worked all of the kinks out of my two stepper systems, so I've got 3 servo systems and nothing to put them on.

I put tape on the end of the motor shafts and make these long songs of farting sounds while cutting air with them and making imaginary parts.

I think I still have enough credit left to buy a few more drives and motors.

Maybe I should be looking at a gun instead....

This has nothing to do with the thread. The question, "how small is small" made me think of it. My Father (aerospace engineer) told me the story - hopefull it's not urban legend, I doubt it. An inventive sort of guy thought he had solved all the problems and made the smallest drill bit in the world. He sent it to a German company that dealt in such things, looking to sell the patent and stuff. Nothing happened until one day he got a box, which was simply his drill bit, returned to him, no comments, no letters. He pondered that for awhile, and then he examined his bit, and realized that it had been drilled through, down the center. Just a story - a good story, I think, true or not.

I've heard this story - with the exception that in the version I read the bit came back with a drilled and tapped hole in it! - and with a corresponding screw! I think this story is in one of the "Machinist Bedside Readers" http://www.lautard.com/ - though I could be wrong.

yes it is a good story.

Another marvel was the engraving of the lords prayer in the head of a pin. ?
What micro stepping would one need to do this with a CNC engraver.??
Back in my teaching days I always started a Course by telling my students that To Get The answer One Must First Know The Question and
There are NO STUPID QUESTIONS.. ONLY STUPID ANSWERS

Also not really on subject.... But you can ge real small...

The image was engraved with an AFM (Atomic Force Microscope) and is about 2 micrometers square. Thats 0.000008"!!!

Engrave on the tip of a needle? You Betcha! :D

this small enough for ya?
http://i82.photobucket.com/albums/j253/fixittt/Jewlery%20Designs/sprint1.jpg

Just anthor FYI I use a Number # Center Drill to ingrave part numbers in steel
I only use the HSS/cobalt as the carbide tends to break 8k rpm 40 ipm
.005 inch depth. This works for hundreds of cycle from same tool.

Numbers are 1/8 inch in height and about 10 digits long carved on a curve in a flat plane.

I am happy with the center drill method even in the 6061 alum.

Fixittt you need car numbers, scare stickers and then cutt to coin shape drill a hole a viola, sale as pendents LOL who knows it might just work.

opps, make that a number 2 center drill

The tool used is going to depend alot on the material used. (We all know this)
That being said. here is a GREAT site for small detaild bits.
http://www.bitsbits.com/

My little sprint car was a 3d releif attempts in Artcam from a coloring book page :)

Ohh hey Looking thru my pics, Looky what I found!!! Hows this for small? Same sprint car scaled down just a tad
http://i82.photobucket.com/albums/j253/fixittt/MAXNC/sprintsmall.jpg

I'm in the ranks of those who make their own tools. Take an old tool, and grind a simple conical point. I use a 5C collet for this, in a workhead on a tool grinder. I slip a thin piece of brass shimstock under one side of the collet to decenter the tool. I make a note of which way the eccenticity lies. Then, change the approach of the grinding wheel to bring it in from the side and grind half way across the cone, forming a spade. I position the tool for this in such a manner that the eccenticity of the cone creates a wee bit of relief for the cutting edge. It is a physical impossibility to have a point on center with relief behind the cutting edge at the tip. But a thousandth or so eccentricity seems to help enough for the engraving I have to do.

Defintely try Bits & Bits for small milling and engraving tools - http://www.bitsbits.net (http://www.bitsbits.net/)

I use a lot of the half round and quarter round profile bits from them. I usually use the smaller sizes (.010 to .003 range for day-to-day stuff), but they have larger bits as well up to 1/8" or so. Thier engraving bits and endmills rock. I know folks who swear by their pyramid bits, though I don't like them much myself. They offer resharpening as well.

Grinding your own is definately the way to go, broken 0.125 in. drill bits are perfect for making engravers...

That Bits&Bits is a great site!

Try using a single flute 60 deg countersink, MA fords work really good in stainless steel, they seem to be stronger than say a carbide d-bit.....

Bits & Bits is the way to go for small stuff. I've been using them for years, conical cutters with tips down to .001". I didn't like the spiral cut either, they sent me some to test and mine had runout. The conicals work just fine. They'll make custom ones too as well as resharpen the ones you break.

I have used a .010" dia Robb Jack endill to engrave a serial number a some small parts. They are carbide with a 1/16" dia shank.

I use NS tool, they sent me this document showing them engraving and putting holes in a human hair. pretty cool.

Mike
www.art-cam.com (http://www.art-cam.com)


46771

I use NS tool, they sent me this document showing them engraving and putting holes in a human hair. pretty cool.

Mike
www.art-cam.com (http://www.art-cam.com)


46771


That is wild! Very nice.

DARN! That's amazing. :eek:

We just buy them, you can get them from micro 100 as specified earlier in the post. Also Harvey Tools sales them. Google them... you can buy them in a few different points. I think the last one we tried had a .005 cutting radius on the bottom. We do not do much of it anymore. but if everything is really flat we had great success

How small is small? Well its up to you really. Some people think less than 1cm is small, some think less than 1mm and still yet some even go smaller to the nanometer scale. For the nanometer scale the people that do it use and tungsten rod drawn out to the atom level to make a very sharp very strong cutting tool, but the results you get are 95nm and smaller usually done in silicon. Ie. 45nm Core Duo Intel CPUs and the 55nm clock carved onto a single sliver of silicon and painstakingly brought together. Basically to cut something really small you need something harder than the material you are cutting ground or drawn out to a fine point that can hold the edge without alot of work keeping it sharp. Tungsten and Titanium alloys are the best for aerospace and high tech stuff but if you are doing this at home Id just use a very strong steel and case harden it after you ground the bit you wanted.

Good luck with it, hope this helps a little.

http://www.mmsonline.com/articles/040701.html

This is pretty small stuff

Shannon.