Slate

**Goonk** · 01-29-2018, 11:16 AM

Just an FYI here. I was walking through Michael's the other day and spotted some slate plaques. Hmmm, I wondered, could I engrave those? Well, yes, we can. I used an eBay tiny V bit (its the yellow version they sell by the dozen for engraving, circuit boards, etc. - tiny little tip - flat on one side). I used 60ipm, router full blast (Bosch 1617), 0.005" depth per pass. Everything went very well and the look is nice. I went a total of 0.015" deep. The only issue was that the slate, being a natural product, is not flat. I used a dial indicator in the router to get it close. My piece had a hump in the middle, which is where I set Z zero. As a result, I had to go back and re cut some areas. I just set a deeper cut and went over them again. I didn't get a perfectly consistent depth, but it looks pretty good anyway. After I was done, it looks like the back of the plaque might have been flatter. I may have introduced some bow when clamping too, although I released the clamps and tightened them back "just enough." I also used tape on the bottom. I'll try and get a pic this evening.

Anyway, just wanted to share that it worked in case anybody else is interested. Oh, Michael's has 40% off coupons weekly, so a 8x6 or so plaque is a couple of dollars. I might get a couple more to play with.

Tony

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**coherent** · 01-29-2018, 11:39 AM

You can also find cheap slate or other natural stone tiles at your local big box home center. Some work really well.

**micknm** · 01-29-2018, 02:10 PM

Any pics of the finished part?

**awerby** · 01-29-2018, 06:18 PM

You might think about using a spring-loaded tool holder for this, which will help with the uneven surface: Engraving Tools and Cutters, Spring Loaded Engraving Tools, Vacuum Chucks, Engraving Software

**rcheli** · 01-29-2018, 06:30 PM

I've seen videos where they are milling circuit boards and it probes the board in a grid to get the topology and then accounts for the height differences while engraving. I don't know what software it was but it sounds like it would help in this process.

John

**Goonk** · 01-30-2018, 08:49 AM

Neat, but I can't afford that!

- - - Updated - - -

Working on it.I forgot to grab a pic last night.

**Goonk** · 02-01-2018, 09:06 AM

This is the piece of slate I engraved. I is around 8x6 I think. Michael's has several shapes and sizes. You can see that some of the engraving is deeper. I recut several areas in 0.005" steps until I got to this. Anyway, I was pleased with the result. I'd prefer the depths to be more consistent, but it is a natural material, so.... I'm just thrilled that nothing exploded across the shop! And the tool and the slate cost me $3 maybe? Converting the bitmaps to vectors had the usual issues and I didn't do a good job cleaning things up, so it took forever. Plus, I had the tool moving pretty slow to be safe. Anyway, fun stuff. Learned something. Might go check out the Home Depot offerings as mentioned above.
Tony