Best material for an abrading stone???

[Sleep Junkie]

Seeing as how money is in short supply at the moment, I am trying to put together or make my knapping tools out of stuff that I have around the house.  I have most of the stuff, but I am missing the abrading stone.  I have two items that I think I could use but I am not sure exactly how rough the stone needs to be.  The first is a puck style axe whetstone that has a rough and smooth side.  It was a cheapy that I bought in my younger days, so it is no big loss if it can never be used to sharpen things again.  The second thing I have is an old emery wheel off a grinder.  I figured I could break it in half to make it more manageable but it is really course.  Which would be the better choice? 

[DanaM]

Both should work Try em and see what ya like best, I use a chunk of old grinding wheel myself.

[aaron]

either would work... I use a fairly coarse grinding wheel for percussion work and a finer one for pressure. If it's too coarse, it'll break off chips, if it's too fine it'll just take longer to grind.

[mullet]

 Both, you'll wear them out pretty quick.