Blade stoppage during cut: A moment of panic

[Bill in Buena Park]

On Sunday I was switching gears from cross-cutting hardwood boards to ripping some redwood 2x6 for a yard project, and accordingly exchanging the 60T Dewalt blade in my 21829 with a new 24T ripping blade which had never before graced the arbor.

After mounting up the new blade and snugging the arbor nut (remounting TP, lowering blade, etc.), I started to feed my first 2x6 - and after about an inch of kerf, the blade slowed and stopped! (After turning off the saw) I immediately pulled the piece back, and on start-up, the blade resumed motion. I mentally ran through the litany of what I could be doing wrong - feed rate, alignment to fence, etc - and cautiously began to feed the piece again - and this time, the blade slowed and stopped even faster than the first time! Out came the workpiece again.

I began to worry that my 2-year-old saw was already developing motor or belt problems, or perhaps there was a defect in the carbide on the blade, so I shut off the saw, and noticed that the blade kept spinning WAY longer than it ever had in the past - and my panic about motor problems is skyrocketing. After unplugging the saw, I fed a sacrificial piece into the still-spinning blade to stop it, which worked - only to discover the blade was very slightly wobbling! - not as if warped, but as if the arbor bearings were shot. (now groaning in dismay.)

So I removed the TP, and wiggled the blade to see what was going on, and discovered the once-snug arbor nut was now loose, allowing the blade to wobble on the arbor. Boy did I feel sheepish.

What I failed to notice was 1) a little factory paint in the blade's arbor hole had prevented the blade from properly seating against the inboard arbor washer when I originally mounted the blade, and 2) that when the blade stopped during my cut, the motor was actually still running. Apparently, during my first cut, the paint broke free, allowing the blade to seat deeper onto the arbor, releasing the tension on the outboard arbor washer/nut, allowing the blade to spin freely on the arbor.

I re-snugged the nut, ensured a good grasp by both arbor washers, and got back to work - ripped the 2x6 like butter, no problems.

Lesson learned - always check that the blade is properly seating, even if the arbor nut feels snug when tightened.

[radhak]

Been there, done that. All the way to the panic and wild surmises !

Only thing I did different was : each time, I shut the TS off before removing the piece. Thought too dangerous otherwise.

[atgcpaul]

Been there, done that. All the way to the panic and wild surmises !

Only thing I did different was : each time, I shut the TS off before removing the piece. Thought too dangerous otherwise.

Exactly! Turn off the saw and let the blade stop before pulling the piece
out. If you don't, you could inadvertently nudge your piece to the side, and
you're well on your way to a kick back.

I'm glad your sinking feeling only turned out to be a loose nut.

Paul

[kirkroy]

Something probably worth mentioning is that it can be iffy to rip dimensional lumber without first squaring it up (I don't know how straight redwood tends to be as that's not exactly a local species for me). Even with squared fir/pine dimensional lumber that's available to me locally it can be iffy as it tends to move a lot more when cutting than the oak and poplar I usually deal with...

Anyway, glad you've still got all your fingers and that you weren't impaled!

Kirk

[Knottscott]

It's interesting that my experience with the DeWalt PT series also involved some paint in the arbor hole (DW7150PT). It wouldn't mount right until I removed it, so I didn't encounter the same things you did, but did need to remove some paint ....something that should be done at the factory. A minor nuisance for what otherwise proved to be a good blade for the money.

[cgallery]

Another thing I'll mention is that blade nuts need to be sufficiently tightened.

Internet folklore says you don't have to tighten them much because (due to the reverse thread).

But I've twice witnessed people put them on with barely any torque on the wrench. In one cases my friend told me there was something wrong with his new saw cabinet saw because it just didn't have any "umph."

Once we had the new blade cleaned (it was a little oily) and the nut tightened it worked like a champ!

[Alex Franke]

Only thing I did different was : each time, I shut the TS off before removing the piece. Thought too dangerous otherwise.

I would also be sure to turn the saw off before re-tightening the blade. It's hard to get the wrench onto the arbor nut when it's spinning so quickly.

[Russianwolf]

The inside washer on the saw can get moved slightly as you take off a blade and not seat right when putting the next blade on. it will of course adjust itself when the saw is turned on and let the blade spin free.

Happened on several occasions on mine. And I tighten the nut down fairly well when I change them.

[radhak]

I would also be sure to turn the saw off before re-tightening the blade. It's hard to get the wrench onto the arbor nut when it's spinning so quickly.

Oh - I thought that the easier way, not having to rotate the wrench manually ...!



But seriously, with the LOML completely paranoid about any power-tool, the only way I could get her to relax with my hobby was to commit myself to caution almost to the extent of 'wimpy'. The only time my hand gets closer than 2" to any cutting surface is when the power is off, maybe even unplugged. I know this for certain - the day I get injured enough to need ER, she's gonna sell the garage en-bloc before I return home, and I can't take that risk !

[Ed62]

The only time my hand gets closer than 2" to any cutting surface is when the power is off, maybe even unplugged. I know this for certain - the day I get injured enough to need ER, she's gonna sell the garage en-bloc before I return home, and I can't take that risk !

We all have our own motivations. Mine is that I don't like the site of my own blood.

Ed

[Wood_workur]

My motivation is I need my hands for drumming.

But I've only stopped the blade once and I quickly hit the power. I'll have to check my nut and make sure its tight.

And how do you get a wrench in around the blade guard you all are obviously using?

[pelligrini]

I had the nut loosen up on a dado stack once. They really made a bunch of racket until they finally stopped spinning. I doubt the neighbors heard it over my cussing though.

You don't want to tighten up the nut too much, you can introduce blade runout if it's torqued too tight. I learned that one too.

[Bill in Buena Park]

Exactly! Turn off the saw and let the blade stop before pulling the piece
out.

Always good advice. Since my blade was already stopped in the kerf, it was easy to turn off the saw and then remove the workpiece.

It's interesting that my experience with the DeWalt PT series also involved some paint in the arbor hole (DW7150PT). It wouldn't mount right until I removed it, so I didn't encounter the same things you did, but did need to remove some paint ....something that should be done at the factory. A minor nuisance for what otherwise proved to be a good blade for the money.

Surprised me as well. Didn't have this problem with the Dewalt 60T blade, or any others I used on the saw.

And how do you get a wrench in around the blade guard you all are obviously using?

Raise the guard and pawls, tilt the blade 45degrees and raise all the way.

[gsmittle]

But seriously, with the LOML completely paranoid about any power-tool, the only way I could get her to relax with my hobby was to commit myself to caution almost to the extent of 'wimpy'.

IMO, that's not wimpy, that's smart! Physical therapy after a traumatic accident (assuming you still had an appendage or two) would not be fun.

g.