Ignoramus30138 wrote:

On 2010-12-17, Snag wrote:
Get a piece of 3/4" MDF - medium density fibercore - looks like brown paper
bags pressed together because that's basically what it is . But it's cheap ,
it's rigid , and it won't hurt your cutters . And you can buy less than a
full sheet at ho-de-po or Blowes .

I thought that it actually is abrasive and also clogs the coolant
pump.

i

It's not a good idea to use coolant when using a wood / wood product
backer. This is one of the many times that it's best to machine aluminum
dry and just vacuum up the chips and backer dust when it's done.