# Finishing MDF for laser measuring



## AxlMyk (Jun 13, 2006)

My neighbor has asked me to help with a project. He needs 5"x5" pieces of 3/4" MDF with several profiles routed into them. These will be used as a demonstration for a laser measuring instrument for the automotive sector.
After cutting the dados, V grooves, offset surfaces, etc. the MDF will need to be sealed and painted black. The surfaces need to be smooth,

What is a good process to seal and paint machined MDF, leaving a smooth surface?


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## Mike (Nov 22, 2004)

Mike, just prime and paint it with a automotive spray enamel.

PS: Isn't it about "Sawdust Saturday" time?


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## AxlMyk (Jun 13, 2006)

The problem I've had with MDF is swelling after painting. Especially on machined surfaces. I want to keep the sanding to a minimum.


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## Phil P (Jul 25, 2010)

Hi Mike

I'd suggest looking for MR-MDF (moisture resistant MDF, generally green core or green all the way through), deep-route (sold for CNC machining) or HDF (high density fibreboard) instead of standard MDF. All of these products are more dense, machine more cleanly and suffer less from grain rising of "fluffiness" when machined. They should make your task of finishing a lot easier. 

I'd also avoid conventional water-based MDF sealers and try instead to go for oil-based varieties which minimise the problem, assuming that you are using a sealer. If clear finishing a heavily thinned first coat acts as a sealant. Because MDF can tale on moisture overnight it is best to machine it and seal it on the same day.

Just a few thoughts based on some MDF manufacturing experiences

Regards

Phil


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