V-carving with engraving bits: Bottom flat, bottom radius

[Chuck Keysor]

Hello Shopbot friends:

Background: I have done a lot of V-carving in "Vinyl Composite Tile", your run of the mill 12" x 12" x 1/8" kitchen floor tiling.

While everything else is great, the engraved grooves always get plugged up with gunk, not quite re-melted, but gunk which I can only remove by manually scraping with an X-acto knife. This is really tedious work,,,,, (I use a CMT 60 degree "Laser" bit with a very sharp tip. It works great, EXCEPT for the gunk. And re-running the entire toolpath a second time does not help for cleaning out the Vinyl gunk....)

Questions:

1) Would using a bit with a flat or a radius tip do a better job of clearing out the grooves then a super sharp tip that is just a point?

2) With the complex motions of V-carving, would a flat or radius tip mess up the V-carving? (I don't care about the BOTTOM of the grooves not being flat, because those just get filled with paint anyway.)

3) Any thoughts on the .005", .010" and .015" flat widths? (Which would work best to clear grooves, but not POSSIBLY mess up V-carving?)

My first thought was to just buy a bunch of these bits 30, 60, 90 and 120 degrees, with flats of .005, .010 and .015, and experiment. But the list I compiled from Harvey's catalog was around $200. So I thought it may be cheaper to get some feedback before buying any bits.

Thank you for your comments and suggestions, Chuck

PS: I was not able to get a good photo of the gunk, my focus that close is no good.

[bobmoore]

I am curious what you make with kitchen tiles. Before you mess with bit geometry I would try sandwiching the tile between 2 acrylic tiles to get it flat, then freeze it and run it before it thaws. I have done this with soft polyethylene in the past with good results. Good luck and show some pics if you can.
Bob

[Burkhardt]

No personal experience with such tiles but keep in mind that the sharper the tip of the Vee, the slower the surface speed. That means at such a real sharp tip there is actually no cutting action and the rotating tip just drags through the material. An additional problem is that the manufacturer has to stop the flute edge shortly before the tip since they can not cut a flute into a diameter that approaches zero.

I believe a specified flat tip like the Amana in-groove blades might do the job. Or you can try to blunt an old engraving bit a little with a diamond hone.

You will have to adjust the zero point to follow the calculated v-carve path on the surface, depending on the V angle and the width of the flat end. If the v-angle is "a" and the flat width is "w" the zero has to be "d" higher than touch-down: d=w/(2*Tan(a/2))
Example for a 60 degree bit with 20/1000" flat tip: d=0.02/(2*Tan(30deg)) or d=0.017".

Tss. And now they want to eliminate trigonometry from the math curriculum because nobody needs it in daily life.

[scottp55]

Chuck,
Just a thought, but perhaps buy this combo?
The one 30degree has a .06" flat, but unless mentioned all the rest have a .012" flat (which I can barely see, and nearsighted as heck)
My go-to's for small VCarving hardwoods (Maple/Bloodwood/Walnut), but plastic is mentioned and may just have to muck with feeds/speeds and need a .125" collet. Just thinking.
http://www.ebay.com/itm/SET-OF-10-MICRO-ENGRAVING-TOOLS-30-through-120-degrees-Kyocera-Tycom-/381480846723?hash=item58d207c583:m:mT_Y1Y-4I7gJ0iPQPUDHvEg
I have no use for his 30 degree sharp(Tip breakage), but the 30 standard tip is used a Lot.
Might give you something to use and then buy Onsrud with the correct tip/angle based on the .012"flat?
scott
Triga whatsit G?
Was that before or after Calc? :)

[Chuck Keysor]

Thanks for the quick replies. Bob, here is the typical thing I carve with these tiles. I back them with MDF when completed. That keeps the tile stable, as it would wilt in the heat, or crack in the cold without the backing.


Thanks for the mathematical calculations,,,,,,, My math skills have fallen far off.... Considering that I have bachelor's and master's degree Electrical Engineering, I USED to be pretty good in math, as required to get through such programs. Today, well, I can barely add and subtract ........... Rather embarrassing, but true.:( I am glad you haven't let your brain rot like I have........


As to the Amana In-Groove bits, I bought the packaged set from Tools Today, SPECIFICALLY for engraving these tiles, and every one of them had the tip break off after just cutting a few minutes. I was doing my testing in MDF when these bits broke, so I never even got to try them in my tile material! I broke every sharp bit in the set. I am still steamed, as these bits were NOT cheap! :mad: http://www.talkshopbot.com/forum/attachment.php?attachmentid=27562&stc=1

Thanks, Chuck

[Burkhardt]

....As to the Amana In-Groove bits, I bought the packaged set from Tools Today, SPECIFICALLY for engraving these tiles, and every one of them had the tip break off after just cutting a few minutes. I was doing my testing in MDF when these bits broke, so I never even got to try them in my tile material!

Ha, same happened to me with the really sharp Amana inserts. :) Nowadays I use the same Drillman1 Kyocera bits that Scott recommends. But I think e.g. a 60-deg Amana bit with 20/1000 flat tip should hopefully not be too delicate.