Milling MDF

Jari is making plugs for our latest IOM-project, and he posted two new videos:

Rough milling:


Finish milling:

The 1000 mm long hull plug will be made from a left and a right half, and each half consists of three parts. This is the first part from the bow to around 300mm.

3 thoughts on “Milling MDF”

  1. Hi Anders,

    nice work!
    Lot's of questions come to mind seeing this.
    I did some MDF milling like this but then for a (recumbent) bicycle. Light sanding and a few layers of filler and paint make nice molds. I have also seen negative molds (for parts of a time-trial racing bike) made out of MDF that are finished off with epoxy resin before finish milling and these last (according to the maker) about 20 times.

    MDF consists of different layers, the two outer layers are different (High Density) from the inner layer (Medium Density). I found that glueing MDF together to get the correct thickness may show slight lines where the different layers meet.
    Someone suggested to remove the high density outer layers before gluing the boards together.
    How did you get a thick MDF blank? I currently glue using white waterproof wood-glue and compressing the blank in a vacuum bag.

    Are you using any special MDF mill cutters? I found that standard HSS cutters don't last as long a I would expect in MDF ; they tend to burn up due to the binding agent in the MDF. Since I am going to create some large plugs or molds (up to 1.5 x .6 meters) this is becoming important.
    These molds are for small series or one-off parts so making aluminum or steel molds is way out of budget.



  2. Hello Rob,
    I see you are already familiar with the ways of the MDF-dust!

    We've not had any big problems with the surface being harder than the middle of the board. Could be that the brand we are using doesn't show this effect that much. On old things that have been in storage for 12+ months we do see the seams between boards print through the surface of the plugs.
    Like you we are using water-proof white wood glue to build up the stock material from 20 or 25mm sheets of MDF.

    We are trying the 'poor-mans-tooling-board' you mentioned. That is we first mill the MDF to 1mm under-size, then coat with a thick layer of quickly curing hard tooling gelcoat, and then mill to final shape. Of course there are very good hard tooling-boards available (cibatool, necuron etc.) but they are very expensive.

    Cutters: we use cutters made for cnc-milling of wood. We've used a roughing cutter for both roughing and finish milling, since the finishing is done with the tip of the tool and not the side of the tool there is not much difference between a finish cutter and a rough-cutter.
    Ours looks like this one:
    it's 12mm in diameter and quite long, maybe 80-90mm cutting depth. They are solid carbide and a bit expensive, 80-90 euros per cutter.
    The spindle on our mill only goes to 5000rpm, but if you have a high speed spindle they could probably be run at 10 or 20 krpm.

    If you have any links or pictures of your bicycle moulds/plugs it would be interesting to take a look!


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