Multi-cutter blade blunt in 1 day. Bad blade? Bad Technique?

Question

I recently bought Dewalt's Oscillating Multitool. (DSC355) It came with (amongst others) a wood blade and a "wood with nails" blade

Today I was using it to replace wooden brick in a parquet floor. It involved slicing down between bricks to cut the dowels that hold each brick into its neighbour, then cutting an angled slot into the brick so that I can get a flat chisel in to get the brick up.

There was a little bitumen on the undersides of the bricks, but I was trying to avoid getting into that with the cutting blade.

After about 2 hours of intermittent cutting, I realised that I was no longer actually cutting with the teeth of the blade, but was in fact burning a slot into the wood - there was smoke coming out of the slots, not wood dust! On closer inspection I found that the blade was almost completely blunt. I switched blades and the other one was gone after a further hour of (non-continuous) cutting.

Wood in question is old (and moderately wood-wormed) columbian pine parquet. Approx 20 mm deep.

Question:

• Are these naff blades (and if so, whose blades should I buy?)
• Was I DoingItWrong(TM) (and if so, what should I change?)
• Is this just the norm? (and if so, how have the managed to convince us that this is acceptable?)

Any other thoughts welcome too!

Answer 1

All of the above. I'm convinced, because using up two $10 blades to get a $100 chore done is a no-brainer IMO.

Your foremost problem here however, was that you work-hardened your work. You fire hardened it, making it "form a hardened glaze consisting of pitch, wood particles and carbon".

As soon as you see smoke, you're work hardening it. Most likely you have deposits on the blade and you should scrape it clean before resuming. Pull it out every thirty seconds or so; dogging on it for two minuets straight will kill any blade, no matter how expensive it is.

Once your work is hardened, try to bite it at an angle to get back underneath the glaze. Also, check your blade often for buildup and allow it ample time to cool in between cuts and while you're cutting.

Answer 2

2 hours of intermittent cutting on one blade is pretty good.

If those blades are naff, then all of the ones I've used in the past (Bosch, Porter Cable, Dewalt, Imperial, off-brand no-name) are also naff.

The only thing I could suggest is keeping the blade clear of bitumen/ wood/ etc. Vacuuming up sawdust while you're cutting can help.

They've managed to convince us this is acceptable because these tools are so incredibly useful.

Answer 3

Use semi circular multi tool blades for longer jobs. You can then alternate the sides so that the blade will not overheat locally. It also helps if you have a second blade available. With my multitool from Bosh I can quickly change blades and let the blade cool off while using the other one.