Automobile sign start to finish - mdf material

This is my first project after lots of small practice cuts ie: making dwp611 air diverter. ( I made 6. . lol) It is made out of regular 1/2" mdf from Lowes. The first test failed and I finally found my pulleys were slipping on my stepper motors. Got those tightened down and she worked like a charm.

Finishing of the sign was the hardest part for me so I thought I would detail out the steps I used and see if anyone offers any critiques.

Software Used:
Adobe illustrator to create svg from bitmap found online

1/8" straight bit for roughing
1/4" 90* V-Bit for finishing

Here is the first roughing cut with the pulleys slipping:

Final cut success!

Sealed and Primed the mdf with BIN Shellac based primer in a spray can sanding quickly between the 3 coats. The cut areas of the mdf raised grain pretty bad and I used a rag and my finger tip to “polish” it back down. … what a PITA.

I then used some leftover Chrome Spray Paint and coated the whole sign. 3 coats

After dry I rolled on some satin black paint from the paint counter at Lowes. I bought a small sample for about $3 and I used a small foam roller. The black dipped down onto the edges of some of the larger openings but I am 100% happy with the final product! Once completely cured in a day or so I will cover it in lacquer clear.


looks good. ive been experimenting with finishing techniques without much luck. i wonder how you would do that last step without the black dripping into the carved parts? a really dense foam brush and many very light dry coats would be my guess but i dont know

My thoughts exactly and that is what I did. It worked great - but the large spans of recessed areas allowed the brush to compress slightly and just barely dip in. Honestly, I am just finicky about finishing and it really does look pretty good.

My only other complaint was the MDF is a nightmare to keep smooth where it has been milled. Even after working it as much as my fingers would allow it still has a rough texture.

maybe I am too picky?

what were your feed and depth rates? were your bit(s) getting dull?

Well, the mdf was smooth once milled. It was once applying the initial coat of sealer that they lifted fibers.

I will check my Feed and depth once home this evening and update my first post.

oh ok i misunderstood. thought you meant after carving it was rough, thought maybe your speeds were a cause but never mind that. i actually had an issue with spray shellac raising the grain on some mahogany once, i wonder if you use something oil based or poly to seal if it would work better?

I will experiment on my next one for sure! I will report back. I was surprised at how bad it raised. I researched for a week and settled on the Bin Shellac Primer at recommendation of various sources.

When I am working with MDF, after I cut, I seal the entire piece with:

It is a thin clear glue. I do two coats all the way around the carved MDF (front, back and sides).

Then paint over the glue. It does not allow the paint to bleed into the MDF, and a gallon jug goes a long way.

Great! thanks. I will look into this for next piece.

thin coat of bondo works for me then sand smooth

Very cool project. Just spent some time in a commercial laser fabrication shop and saw that they use a technique that would eliminate the problem you had with the black oozing down in to the silver pattern.

Long story short: Paint the black first and let it cure out well. Then cover it within masking film. Carve your pattern into the MDF through the masking film, then paint the silver…or whatever other contrasting color. Then remove the masking tape/film.

Something to try anyway and I am going to later this week as soon as I am allowed to play with my machine again.

Thanks! I actually just ordered some masking film to give this a go. I think my issue is thinking I can make a sign in 1 day. This is a multiday process letting the paint cure and clear etc.