lettering with ball nose bit

Computer Numerical Control

lettering with ball nose bit

Postby loyd » Sat Sep 29, 2018 6:55 pm

I've been trying to figure out how to do lettering with a ball nose bit. Lettering is usually done with Vcarve calculations but V bits don't give me the distinctive bottom [of the letters] that I want. I've considered just designing a Vcarve tool path and substituting a ball nose bit for the V bit expected but the depth would still be calculated assuming the V shape and won't go to the depth I want. Typically, I like to use 0.5 to 0.75 inch high letters. Any advice?
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Re: lettering with ball nose bit

Postby loyd » Sun Sep 30, 2018 11:05 am

Sometimes asking just asking gets you to thinking differently. I decided a scientific approach would answer my question, so here's what I did. I selected the text I wanted to carve and used the "Pocket" program instead of Vcarve or Profile. Specifying the 1/16" ball nose tool didn't work so I specified a 1/16" end mill. The pocket program did what I wanted, so I went on to run the program but cheated -- I hope I don't get a bad reputation as a cheater -- and used the ball nose bit for the actual run. It worked just like I wanted it to. The pocket is 0.100" deep which should give me some wiggle room for the finishing process; at least I hope it does.
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Re: lettering with ball nose bit

Postby sid_matheny » Sun Sep 30, 2018 2:57 pm

Sounds like a plan coming together! Look forward to seeing the finished project.
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Re: lettering with ball nose bit

Postby loyd » Mon Oct 01, 2018 12:26 pm

IMG_20180930_120921_496 (Copy).jpg

IMG_20180930_162245_744 (Copy).jpg

IMG_20181001_103331_461 (Copy).jpg


Well, it worked! Sorta. The depth of the cut is just about right. I ran it through the planer using extremely small cuts to remove the black. The scheme worked well except that I didn't add enough clear finish under the black to keep it from leaching through to the wood underneath so there was a little black that found its way into the wood grain lines. I only sprayed one coat of sanding sealer on the bare wood and sanded that to kill the raised grain. I think that layer was too thin to handle the fact that lacquer on lacquer will dissolve and fuse the first and second coat. If I had used another coat of lacquer on top of the sanding sealer it likely wouldn't have made it all the way to the wood. At least that's the theory I'm going on. Next try will be to add a second coat of lacquer over the sanding sealer after sanding.

It was just an experiment using the back of another lettering job, so nothing lost so far.

:roll:
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Re: lettering with ball nose bit

Postby sid_matheny » Mon Oct 01, 2018 1:09 pm

That sure looks great from here so you must have it all down pat now!
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Re: lettering with ball nose bit

Postby loyd » Mon Oct 01, 2018 3:30 pm

I may do it again sometime Sid just to have something to show off. Right now this plaque is hung up in my shop out of the public's eye but where it can remind me to "be nice!" :lol:
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Re: lettering with ball nose bit

Postby rgulley » Tue Oct 02, 2018 10:29 am

I like using a ball nose bit for text that doesn't have sharp corners or really thin lines. Either of those conditions can adversely affect the results. But large bulky letters work great, especially with the painting technique you used. The rounded bottoms of the pockets paint easier and you just cut deeper to allow for what's going to be planed off after painting. BTW, by using a little creative masking, you can even use multiple colors when painting.
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Re: lettering with ball nose bit

Postby loyd » Tue Oct 02, 2018 11:39 am

So far I've only used black because that's what I have left over from another project, but I have great-grand-babies so colors may be the thing.
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