Small letter engraving on plastic buttons

I have an 3 decade old smart lighting system with low voltage keypads instead of normal switches. The company is long out of business, but I can reprogram the software and have bought parts on ebay to not just keep it going, but to modify/expand the system.

My problem is that I need new button labels. Here’s what one of the original buttons looks like:

That’s a decent Shinwa ruler above it, with markings every half mm. So the lettering is about 0.37mm thick and about 2.1mm high.

I secured several blank buttons, which are black through and through. What’s the best way for me to engrave those buttons with lettering that matches fairly closely?

I have a Shapeoko Pro.

What bit and size?
Helvetica font?
Carbide Create?
Masking tape on top and then spray white afterwards, or something else?

The button material is not very thick, so I can’t cut too deeply. Being made from what I assume is an injection molding process, the buttons are naturally shiny so I’d rather not have to sand the tops to such a degree that I re-establish that shine, but I guess that’s possible if it’s the only way to get crisp lettering.

Thanks!

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A 1/64" bit is going to be 0.397mm, just a smidge bigger than your 0.37.
I think I would go with a good downcut Vee bit.

No idea on font. You could use whatthefont.com or any of the multitude of font finder sites if you want to match it exactly. Otherwise just pick a font that looks close.

Carbide Create has more than enough functionality to do this. The trick will be lining up your zero.
You could make a fixture by cutting a blank that the button fits over, then ‘squeezing’ a polymer like Bondo to fit the underside of the button perfectly. Use an index point on the fixture, or Center alignment on the button.

Masking tape, I don’t think will give you a good edge, and the paint won’t look as nice. Oramask should work if you use a downcut vee-bit.
I wonder if a liquid mask might work?? Since the buttons are glossy, a light coat of furniture polish or wax buffed out good would prevent permanent adhesion. You could paint the top of the button before cutting with bondo, 5 minute epoxy, even elmer’s glue & let it dry well before cutting. Then after your paint dries just peel the mask off.

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I’ve got that part covered - I have a CC program that cuts an opening in MDF with a side cut-out to enable a piece of wood to clamp, but I found that the MDF opening is tight enough to hold the plastic button motionless during this light engraving. With the CC program to cut the fixture I already know where zero is.

I’ll order a roll of Oramask and try that out.

I did find this bit 1/64" diameter cutting bit:

I expect to be cutting only 1 to 1.5mm deep.

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I’ve done a similar type of project, engraving name tags for a local church. Maybe not as small but pretty close. I initially used a .015 endmill like you posted but found it way to fragile. I ended up using a 30 degree engraving bit.

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I’m with @brentgrizzle . Even a 1/16" bit is fragile at least once. You’ll need more than one.

I’ve used a 30° Engraving bit just for that purpose. Works fine.

I’m suggesting that you wax coat the top of the button before you engrave it. Then use Rub 'n Buff The Original Wax Metallic Finish silver or whatever to fill the engraving by hand.

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What about a 20º bit?

Looking for a white fill, btw, not silver.

A 20 degree should work. I’ve never used this but I’ve heard of people using these lacquer sticks to do color fills.

https://www.amazon.com/Markal-Lacquer-Stik-Paintstick-White/dp/B002BY8HKS

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All it takes is a breeze to snap a 1/64 bit as shown in a previous post. I would use a V or an up cut spiral tapered angle ball tip.

I couldn’t find a ball tip with a small enough (1/64") tip. Does anyone have a source? I ordered the 20º bit since it was pretty cheap and I’ll see how that goes.

Thanks for all the suggestions on doing the infill. Going to try a couple different ones on some spare buttons I have.

I don’t believe you need 1/64, Amana makes a 1/32. Beware if it’s Prime or not as some companies don’t take returns on 1/32 and smaller because they break.

The lettering strokes are definitely closer to 1/64" thick than 1/32":

I don’t need anything deep - 1.5mm is plenty deep.

Well good luck with that, is the project really worth it?

My other choice is to find an professional shop to do the engraving.

I use a tiny stub endmill like this for pcbs. I’ve never tried it on plastic, but it’s been durable.
https://www.mscdirect.com/product/details/59469155

That said, what about stickers?

Here is a 5-pack of 1/64" - 0.0157" (0.4mm) 2 flute carbide bits for $4.50 ea bit. .

Here is a 5-pack of 1 /64 " - 0.0157" (0.4mm) 2 flute carbide bits for $3.50 ea bit.

I have used these bits and others from drillman1 (Oliver Tool Company) and they work just fine.

Im usually late to the party, hopefully you already got it worked out but i thought id leave this anyway.

I do a lot of cutting like that with my 3XXL and found that using a 6.2 degree ball nose with a 1/32 tip works great. You just have to remeber that the DOC will affect the width of your letters when dealing with such small type. So ive learned to cheat the system a bit if you will.

Amana Tool - 46280-K CNC 2D & 3D Carving 6.2 Deg Tapered Angle Ball Tip x 1/32 Dia x 1/6 Amazon.com

In your example I would use a “NO OFFSET” Contour tool path and start at a pretty conservative with my DOC, something like 0.002 and take my time increasing it by 0.002 or so each time.

A couple other little things ive learned while ruining my fair share of parts while doing small carves in plastic. Make yourself uncomfortable with how low you set your RPM and how fast you have you machine moving. Friction=heat and that = pain in the ass parts clean up.

For that small of a part i wouldnt try to keep oramask on it. It would bring out the cranky in me. I would carve it, spray with a poly, use a fine tip paint brush with a waterbased paint, wipe off the excess paint with a damp rag and spray with poly to protect it for future abuse.

Goid luck Sir

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Thanks for all the suggestions.
So far, I’ve found a few options for in-filling the text with white, and I think at least one of them will work.
I’ve got some of the suggested bits, so now I just need to find the time to try them out and see if any of them will work, as in look like the other buttons.

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