[Halfnutz]

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.

[wjfiles]

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

[Halfnutz]

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.

[ger21]

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

[Halfnutz]

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".

[sanddrag]

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

[Geof]

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".

[sanddrag]

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

[wholepair]

I use these for engraving.

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

[2muchstuff]

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.

[Halfnutz]

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.

[Bubbles]

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...

[dertsap]

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

[Geof]

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.

[dertsap]

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

[shawncnelson]

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/ima...conterojr2.jpg
the letters in the word "contero" are about .08 high.

[Trapper14]

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

[skip20]

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

[Halfnutz]

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....

[jjdon]

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.