diamond tipped saw blades; when to replace?

I recently completed a partial residing of my home using HardiePlank cement board siding. To make the long story short the folks at the building supply business told me that if I was going to make more than a few cuts with a circular saw (as opposed to nippers) I ought to buy a diamond tipped blade. I did, and the blade performed admirably. But at the very end of my project it seemed the blade was getting tired.

The blade was $19, which I considered inexpensive given the “diamond” aspect. But as I said, it performed admirably.

My question to those SDMB construction folks, is, when do you decide a diamond tipped circular saw blade needs replacing?

My experience has always been that when they start to go, they go quickly. It gets hot and stops cutting.

They start cutting slower and eventually you are just burning through stuff instead of cutting. I’ll get a little more life out of them using a brass brush on them to clean them up. The smaller blades are so cheap these days it’s hard to justify not just replacing them as soon as they slow down.

You could get a backup blade now and compare the two on the same type material. If the original blade performs substantially worse throw it away; if they perform about the same keep using the original blade.

Don’t worry about the low price. There’s a world of difference between industrial diamonds and engagement ring diamonds. We’ll save the artificial price inflation discussion for another thread,

Thanks for the scoop folks. I like PastTense’s idea. I can do that and get some hard data.