Engraving Bit

[ctwo]

I'm looking for some info on how to make an engraving bit for use in Aluminum with an RPM around 3500, and what IPM to use.

I tried a two flute 90° V end mill and it worked OK, but is a bit large.

I took a broken 1/8" end mill, chucked it in my drill and put it to my grinding wheel to make an approximate 30° (included) point, then I created 4 flats and honed them on a diamond plate. It worked OK too, but I was getting a bur.

I've seen engraving bits that are about as the one above, but instead have half the diameter ground off. I also have a few 60° countersinks or spotting drills I could try.

[GlennW]

I did OK with a .010" engraving tool .005" DOC at 2 IPM with flood coolant to wash away the swarf. 3800 rpm.

That was before I did this:

http://www.chaski.org/homemachinist/vie ... ng#p217470

[f350ca]

I've had good success making cutters like this from broken carbide drill bits.

Grind to a point as you did then grind away half the thickness.

Greg

[ctwo]

I'll give the tradition looking bits a try. It may be a challenge for me to keep it at half thickness at the point since I just have a sloppy bench grinder and will be free handing it.

Glenn, I found your post earlier, and those grinders are expensive! You've seem to have done just about, everything...

[ctwo]

Here is my 4-sided bit, two passes to a depth of about 10 thou. Second is the half cone about 5 thou deep. The second looks very much better in person...

About 3500 rpm and 6 ipm... The f is 1/8" high.

[f350ca]

These graduations were done with a cutter I ground, should have twisted the spindle to show the cutter profile.
https://lh3.googleusercontent.com/-pvOH ... G_0325.jpg

Greg

[ctwo]

Hey Guys. Thanks for the insights. One thing I am considering when looking at the half conical bit - there is no relief! It worked great for one job, but today it just frosted up the aluminum. I confess, I did touch a stone to it while it was mounted in the spindle, just a few strokes on the flat and the back side. I thought I'd freshen the edge...so much for thinking...

I removed it and did some more hand work on the diamond lap. I tried to sharpen the cutting edge first by taking a few swipes on the flat, then a few on the trailing radius. I then worked to give more relief on the conical back side. I do not understand why these bits would work without relief.?

Then I put a flat on it, but at a compound angle, so there would be just a point doing the cutting. I tilted the bit to the side away from the leading edge, then back away from the flat. See what I mean?

It worked great! Better in fact. It probably works more like a micro fly cutter... It revealed that I need to work on my cnc program.

Also, there is this pesky aluminum sludge to deal with.

[Magicniner]

Then I put a flat on it, but at a compound angle, so there would be just a point doing the cutting. I tilted the bit to the side away from the leading edge, then back away from the flat. See what I mean?

Yes,
You've almost re-invented the industry standard for engraving cutter sharpening;-)