[ronm]

Yes, your hole saw is probably dull. I have cut hundreds of cylinder head and prop shaft holes with this method, and never had even the slightest hint of tearing. You have to be gentle while sawing, but if you're careful, you will not even need to sand it after!

Ronm

[nosedive]

Originally Posted by ronm

Greenlee or Ideal of course! Variable pitch cuts the plastic and glass a lot better!

I'm sure you could probably use the CTC model though!

Ronm

Ronm,
Where do you go to buy Greenlee or Ideal hole saws? The CTC units (junk?) are too coarse or do not cut cleanly through fibreglass even when new, in my experience.

[ronm]

I think Home Depot carries the Ideal hole saws. Good ones are not cheap.
Greenlee are available from plumbing or electrical wholesalers, but most sell to the public now. If you know the size of the holes you need, you can buy individual blades. Make sure you get a mandrel that will fit in a 3/8 drill. Also, check the size as they are often labled with pipe clearance sizes, not actual. Best to take it out of the box and measure.

Most importantly, and I know you've probably heard this a thousand times, use GENTLE pressure, let the saw do the work!

Ronm