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KICKING BACK -- not in a good way

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Forum topic by Mary Anne posted 08-24-2010 10:09 PM 1639 views 0 times favorited 43 replies Add to Favorites Watch
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Mary Anne

1057 posts in 1927 days


08-24-2010 10:09 PM

Topic tags/keywords: kick back safety

The incident happened a little more than a month ago. The bruising has cleared up and I only have one small scab left. It is a little embarrassing that it happened in the first place, but more upsetting that I still can’t figure out how it happened. It is my practice to always stop to consider “Is this safe?” before I go near any of my tools, and this seemed okay to me. Obviously, something went wrong.

I was working on a box/cover for tissues, a simple project to give my Incra Positioner for the router table a go. The wood was hickory, thicknessed down to about 1/4”. I had four side pieces cut to 5”x6” with box joints cut into the long sides. I wanted to put in a 1/8” deep groove on each one to accept a top piece. I know there are several ways to go about this; I chose to put the piece on my table saw sled with a stop block to cut the shallow dado I needed. I figured on a couple of passes with my normal combo blade. I did 3 or 4 test cuts with scrap that was the same thickness and about the same size as my project pieces. The piece was snug against sled fence, firmly against the stop, and held flat with my fingers slightly to the side of the blade. There wasn’t even a hint of a problem or danger on my test cuts.

But when I put the first side piece for my box on the sled and barely touched it the saw blade, all hell broke loose… and so did my piece of wood. There was a loud BANG!! like a gun shot, followed so closely that it might as well have been simultaneous, a sickening impact to my gut and a stinging sensation in my fingers from the force of the wood kicking back off the blade. The wood exploded! When everything settled, there was one piece behind me, and another piece and several large splinters left on table saw. There were TWO sets of perfectly cut box joint marks on my belly, and several of them were bleeding. I am glad I was wearing a heavy canvas apron. I hate to think of the damage that would have been done if it was a larger, heavier piece of wood or if my fingers had been over the blade. Whew! I will, from now on, always, ALWAYS stand to the side no matter how small the piece or how safe I think the procedure might be.

Anyway, like I said, I know there are several other ways I could have accomplished this task, but was there something inherently wrong with putting my small piece of wood on a miter sled to cut the dado?


43 replies so far

View michelletwo's profile

michelletwo

2281 posts in 1734 days


#1 posted 08-24-2010 10:16 PM

were you cutting with the grain or against? Why use a sled? why not directly on table top? I’m not sure I understand your process..I think your piece might have tipped on the sled, the blade grabbed it and whammo…a thought..I don’t understand the sled & incra positioner in combo…

-- We call the destruction of replaceable human made items vandalism, while the destruction of irreplaceable natural resources is called development.

View Kent Shepherd's profile

Kent Shepherd

2698 posts in 2005 days


#2 posted 08-24-2010 10:18 PM

Mary Anne, From your description, I really don’t see anything wrong with your method.
I am scrathing my head wondering what might have happened. Maybe if you could post pictures of the process someone might offer some help.

Sometimes on smaller pieces, clamping to the sled is a wise choice. I do this all the time.

-- She thought I hung the moon--now she just thinks I did it wrong

View michelletwo's profile

michelletwo

2281 posts in 1734 days


#3 posted 08-24-2010 10:18 PM

Another thought for the future..
I would have chosen a router in a table..and the piece directly on the table…

-- We call the destruction of replaceable human made items vandalism, while the destruction of irreplaceable natural resources is called development.

View rance's profile

rance

4145 posts in 1879 days


#4 posted 08-24-2010 10:20 PM

Mary, I’m glad it wasn’t any worse than it was. Hope you heal quickly. I can’t quite picture what you were doing. I would be interested in a picture of your setup if you have the chance.

It almost sounds like you were ripping the pieces using your TS sled. Unless you have proper blocks set in place that sounds like a problem. Unfortunately, I’m not sure I understood your description. I’m sure I have it wrong.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Dustin Dishner's profile

Dustin Dishner

11 posts in 1564 days


#5 posted 08-24-2010 11:06 PM

One thing that might have caused the blowing apart you described is the wood itself. Hickory is a very hard wood and with hardness you usually get brittleness. Since the side pieces were so thin, you likely got a lot of vibration in the wood (like when cutting a thin piece of plywood).

If that is what caused the problem, you might try clamping a support block made of some softer wood on top of the hickory side piece on your sled. This would allow the vibration to dissipate.

I hope you get to feeling better soon.

View Domer's profile

Domer

248 posts in 2085 days


#6 posted 08-24-2010 11:19 PM

I would second the thought of putting in directly on the saw table instead of a sled. You can put pressure over a larger area and the wood would be supported more over the whole piece. I would think it would be hard to put enough pressure over the whole piece on a sled.

The Gripper Ripper would be a good tool to use in an operation like this.

Domer

View Dennisgrosen's profile

Dennisgrosen

10850 posts in 1834 days


#7 posted 08-24-2010 11:22 PM

AAuuch !!
hope you recover fast Mary Anne

take care
Dennis

View Mary Anne's profile

Mary Anne

1057 posts in 1927 days


#8 posted 08-24-2010 11:38 PM

Thanks for your responses and concerns. I appreciate it! I am fine now but for the last little scab.

To clarify: The Incra Positioner had nothing to do with cutting the dado; I only used it to cut the box joints on the router table. Sorry for the confusing extraneous info.

I was, however, using an Incra Miter Express sled with a Miter1000SE which is a rock solid, zero clearance setup that rides tight in the saw’s (Grizzly G0690) miter slots, no room for wiggle, tipping, or drop off. This setup, at the time, seemed like a good idea for putting a shallow dado in small, thin stock.

Kent, I think you are on track that I should have also clamped the piece to the sled. As secure as I thought everything was, something must have moved. The strange things was that it happened the instant I touched the workpiece to the blade; it just grabbed and blew up.

Dustin, the vibration of the thin wood and the brittleness of hickory also sound like major contributors to what happened. That is something I had not thought of in the last month of second guessing myself.

As for the “coulda, shoulda, why not this way or that?”... as I said, I know there are other ways. When I re-did the project, I dadoed the whole board up against the TS fence before cutting it down into the individual sides. That is my normal practice, but the dado was a design change. I probably would have used the router table for its easier, quicker setup, but I do not have an 1/8” bit. Yep, using the Grrripper would have been another excellent alternative that I could have used with less likelihood of kickback.

What I am asking is if there is something inherently inappropriate or dangerous in using a sled in this way?

View michelletwo's profile

michelletwo

2281 posts in 1734 days


#9 posted 08-24-2010 11:56 PM

I’m sure this could be safe, but I still wonder why you used a sled..direct on table..you are not cutting up thru the piece of wood, so it’s safe to use a pusher of some sort, directly over the piece. One of my rules in the shop is use the smallest blade/bit presentation I can..a 1/4 or 1/8 th bit leaves very little metal above the table top..a dado blade is lots more surface area to catch anything.(was the dado dull? any bad teeth?) Was there a knot? Is your sled on both sides of the blade? no dropping onto the table after cutting? I believe you had a vibration/slippage problem and you had an accident..glad you are ok…If you insist on using a sled for these operations you need to get your clamp right up close to the cut line..as close as you can..keep the vibration down when the dado hits the wood. Or 2 clamps..

-- We call the destruction of replaceable human made items vandalism, while the destruction of irreplaceable natural resources is called development.

View Mary Anne's profile

Mary Anne

1057 posts in 1927 days


#10 posted 08-25-2010 12:27 AM

michelle
I don’t insist on using the sled for these operations—it is just what I chose to use at that time, and I want to learn from the experience. While I consider myself a rookie at “fine” woodworking, I have owned and operated table saws and every other kind of power tools for nearly 40 years (eek) without incident. When something does happen, I go over it in my head until I ‘get’ what happened. When I understand, it is from there I may or may not use the same method in the future.

No dado blade; it was a sharp, nearly new high end Freud combo blade… can’t remember the exact model. No knots, no drop off. Yes, the sled covers both sides—zero clearance. I believe Dustin got it with the vibration and brittleness issues. And clamps might/probably would have prevented it.

View Kate's profile

Kate

397 posts in 2593 days


#11 posted 08-25-2010 12:37 AM

With small stock I personally think it’s dangerous not to use a push block that covers the cut (or holds both sides in the case of a through cut – with a Gripper for instance). I think you could have had the same sort of “explosion” happen on a router or with the table alone. I know a lot of people don’t use them, but they make me feel better.

As to the cause, I’m with Kent. I had a thin piece splinter like that on me once. It was LOUD!! Scared the out of me, but fortunately no injury except to the workpiece.

That’s my two cents.
Sorry you had the accident, but glad to hear you’re okay.

-- Kate, http://www.wooden-box-maker.com

View patron's profile

patron

13142 posts in 2060 days


#12 posted 08-25-2010 12:37 AM

MA .
even with your new explanation
i too have trouble understanding what you were doing .

i am how ever glad that you made it thru this without to much injury .

as i know nothing of the incra tools you used ,
i can’t imagine what you are talking about .
please show us pictures of a mock up as it was happening .
we can understand what happened better
you will be safer ,

and maybe someone else will be too in the future .

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

View Mary Anne's profile

Mary Anne

1057 posts in 1927 days


#13 posted 08-25-2010 12:50 AM

Thanks, Kate. The annoying thing is that I had a Grrripper hanging on the wall right next to my saw and it is what I usually grab when I am doing the same thing on longer pieces, but for some reason, the sled made sense at the time for the smaller stock. Oops. :/

patron,
It’s dinner time now, David, but I’ll go down and take a photo after… if I don’t fall asleep first.

The whole thing is worthwhile if it prevents someone else from having the same thing, or worse, happen.

View Dale 's profile

Dale

412 posts in 1899 days


#14 posted 08-25-2010 12:52 AM

The important thing is that you’re ok.

-- Dale West Central Pa. Do it all, before last call.

View BroDave's profile

BroDave

107 posts in 2533 days


#15 posted 08-25-2010 01:11 AM

Mary Anne, sometimes it isn’t what you did. Wood will “explode” sitting on your bench. I may be as simple as that piece of wood was “ripe” and you simply couldn’t have known or done anything to prevent it.

-- .

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