Workshop safety #1: Workshop fire -- averted . . . and a "whuf" question

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In the process of making a jig, I routed a dado for T-track in recycled plywood. Since my trim router was already set up with a ¾” straight bit, I used it – making four shallow passes 9” long and a total depth of 3/8”.

After each pass I stopped and vacuumed the sawdust. After the final pass when I started to vacuum, I saw burning embers and immediately stopped vacuuming. (You can see the burn remaining in the dado in the photo above.) I knocked the sawdust out of the dado and onto the concrete floor, removed the filter from the shop vac, and dumped the contents of the vac on the compost pile. Then out of an abundance of caution, I sprayed the pile with the garden hose even though I saw no embers.

This started me thinking and I couldn’t get to sleep last night. As a child, I liked to play a game with friends. I called it “whuf.” “What if this happened? . . . What if that happened?”

Well, my adult “whuf” question is: What if I had my shop vac/DC connected to the router/project? Could I have started a fire in the vac/DC?

What caused the fire? We’ve all had burn marks from uneven movement – pausing too long or moving too slowly – especially when routing hardwoods like maple and cherry. But in all the miles of routing I’ve done, never has the sawdust caught fire.

Could it be the glue in the plywood? Or simply the build-up of sawdust in the dado overheating from the bit? Each pass was smooth and quick (and only 9” long) and I took plenty of time vacuuming up between passes. Does anyone have any ideas? I certainly don’t want this to happen again.

Thanks for any insight you can give me.

-- “Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.” Benjamin Franklin

  • Part 1: Workshop fire -- averted . . . and a "whuf" question

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