Wood tolerance?

[lagfish]

Hi there,
I am trying to make a mold on a lathe for a fiber composite bicycle wheel, and I think MDF would be the cheapest material. My question is, what tolerance will MDF hold? I will be running at reasonable speeds as to not overheat it, nor using any coolant.
The way I am planning to turn it is to machine the wheel profile (about 1.5" wide) onto a steel plate. Then feed the tool slowly into a flat disk of MDF until the desired wheel diameter. (see picture) I was planning on using regular alloy steel, unhardened, since I will only be using this once, is this acceptable?

Also, any tips on rake and relief angle of the tool? What about cutting speed and feed rate?

Thanks

[ger21]

MDF will change size with changes in humidity. In the humid summer it'll tend to grow a little.

[Geof]

MDF is quite abrasive so an unhardened tool may have a very short life; even a hardened tool will dull after several minutes of cutting.

Also it is likely you will find that the MDF tends to chip out when you plunge the tool in.

An approach you could consider is to make a router cutter with the profile your need from an oil hardening alloy then rig up a router so that the router is doing the cutting while the lathe turns the disc of DF slowly.

[lagfish]

Thanks for the input,

making a router bit out of steel for the geometry I want requires a CNC lathe, which I don't have access to.

If not MDF, then any other suggestions for material? Oak? I need a 16"x16"x2" piece, and my max budget is $100.

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