Fried my TS motor.

[Canoath]

The difference between a dull blade and a fresh one is certainly noticeable - the wood suddenly falls through the saw!

Cheers,

That's so true. Very little pressure needed for the full depth cut on the Irwin blade straight out of the packet I was surprised. There was a fast noticeable decline with the first two blades as they were damaged by embedded ballast in sleepers. Whereas the third blade, which was the second blue mak, has pretty much just dealt with clean redgum plus vic ash and one nail, yet its progression to whatever state it's in now was so slow I really didn't think there was an issue. I had a better look at the teeth and I'm still none the wiser.

With two to three months of total TS experience, three blades, one burnt out motor and one kickback in the gut, (despite the presence of a riving knife plus hours of reading and youtubeing to avoid it), I've still got a lot to learn.

[malb]

Whereas the third blade, which was the second blue mak, has pretty much just dealt with clean redgum plus vic ash and one nail, yet its progression to whatever state it's in now was so slow I really didn't think there was an issue.

When saw blade meets ferrous metal, the carbide will always loose the battle. A typical sharpening grind typically removes less than 0.05mm from the carbide provided that the teeth are not chipped. One damaged tooth and they have to grind every tooth equally until the damaged one is serviceable, or else replace the damaged tooth and grind it to match the rest of the teeth and then do a complete sharpen to ensure all teeth carry their apportioned share of the work, or sell you a new blade. A good saw doc is a blessing, as is a decent metal detector if you are using reclaimed timber.

Going back to the shroud pic, I would have expected the shroud to be a moulded thermoset placcy rather than a something like recycled ice cream container that melts with heat. The way that shroud melted and deformed would have further impeded airflow through the motor leaving it more susceptible to overheating. It was a long time ago when I was taught the theory, but I believe that the laminations on the motor stator have one side insulated to prevent eddy currents developing, so the stack of laminations goes SISISISISI etc where S is a steel lamination and I is layer of insulation. I would not place the thermal switch in direct contact with the laminations for fear of upsetting the insulation between layers and generating eddy currents if the switches you bought have a metal sensing surface. If it is plastic it should not be as much of an issue, but some of the 0.5 mm thick thermal conduction/electrical insulation film used between microprocessor chips and their heatsink/cooling systems would be a worthwhile addition. Should be available at Jaycar if you can access one, or send me a pm with your address and I will post you a piece about 20mm square that you can trim to match the base of the switch.

[Canoath]

malb, sorry it's taken a while to respond but thanks so much for your input. You're absolutely right. And thanks for the offer for some film. I may take you up on that offer if I can't find something at home. I've got a few junked computers, power packs and other electricals that I will go through during my upcoming days off and should be able to find some suitable material to fit as an electrical insulating film.

I was curious about the metal pad of the switch crossing the laminations and checked for continuity across the stack and at the edge of a single lamination and concluded there was a coating of some sort not only between the laminates but also on the edges as if a they've been dipped or sprayed before being stacked. However, I wasn't fully aware of eddy currents until your post and I'm guessing that with vibrations and heat I can't imagine the thin coat will provide adequate insulation forever so I will place a film underneath the switch ASAP. The good thing at the moment is that due to work I haven't used the saw again since the initial rebuild.

Regarding the shroud, to me it feels and looks like the same kind of plastic in the winding, presumably with some kind of heat resistance. I'd love to know how hot it got in there for the shroud and the winding plastic to not only melt but the charring suggests some flame too. I've replayed the incident over and over in my head and I simply can't remember the saw bogging down before. Only that it bogged down and seized plus smoked and tripped the RCD on the wall all within a second during the meltdown. If I've mentioned bogging down whilst cutting before it was in reference to the cutting rate slowing down due to a blunt blade but not the speed of the saw as such. I can't remember the motor slowing down at all during the previous abuse I inflicted on the saw. I dunno, my memory's starting to fade how it all went down.

[ian]

just a comment

32 teeth on a ripping blade seems far too many, especially when ripping thick / hard wood

From http://www.rockler.com/how-to/blades-101/

A 10" blade designed for ripping lumber, for example, usually has as few as 24 teeth and is designed to quickly remove material along the length of the grain.

[Canoath]

I agree Ian and thanks for the link. I simply haven't found anyone locally with anything less than 32T. Even the current Irwin blade has 40t. They at least have 20deg hook angles and do seem to rip well when they're sharp. I've found a few places online that sell 10" 24t and have yet to put an order in but eventually will.