Table Saw Bevel Cut Dangers

[Jenny Steel]

As a newbie I have read with interest the various posts on the dangers of bevel saw cuts and have concluded that the possiblity of kick back occurs when, for example, a right tilt arbor is used from the right side (i.e the larger piece of wood and the fence/mitre are all on the right) so that the small waste piece falls to the left and jams in the blade. Is this a correct interpretation ?

I have a right-tilt Delta cabinet saw with a unisaw fence and extension table on the right, I work always on the right side of the blade.

Now here's my question. I want to build some cabinets that will a

45% bevel through 1" thick MDF -- I will therefore need to run the short end of a 17" by 48" through the saw. I can't do this cut from the left as I don't have any extension table on that side and it's too close to the wall of my workshop. I am hesitant, however, to run it through from the right on a right-tilt arbor. Given that that the danger only appears to be when small bits fall into the blade, would I be OK to work from the right side provided I allowed for a reasonable amount of waste on the left ? (say three or four inches).

Or, is there some other inherent danger that I missed.

Thanks for any information

Jenny

[Paul Hays]

On Mon, 2 Feb 2004 22:16:19 -0800, Jenny Steel wrote (in message ):

I don't think so. My interpretation is that the danger lies in the piece to the right of the blade, ie. the piece *beneath* the blade, will become jammed between the blade and the fence if the work twists at all.

[Bridger]

flip the stock over and make the bevel cut from the safe side of the saw.

[Upscale]

That's ok if the piece is not too wide, but for sheets of wood of any size, you run into support problems for what hangs over the left edge of the saw table top. Extensions and wings are there for a purpose.

[J Pagona aka Y.B.]

You could make a large cut off sled, specifically for beveling at a 45° angle. The sled, which should extend to both sides of the blade and have a runner in each miter slot, would make the cut safer by:

-not having a fence, so the board couldn't get pinched between the fence and the blade.

-support the off cut.

-allow you to clamp the board to the sled if you feel you need the extra precaution.

Cross cutting a 17" x 48" piece by running the 17" side against the fence is asking for a kickback, even if the blade is vertical. A sled, sliding table or an extended miter gauge is pretty much a necessity.

David

remove the key to email me.

[Stephen M]

To cut the SHORT side of that pannel, you do NOT want the fence anywhere in that operation. Even without a bevel, that is an invitation to kickback. This is why people build sleds (a.k.a. pannel cutting jigs).

When using a rip fence, the *long* edge of your stock should ride against the fence, otherwise there is not enough support to counter any possible twist in the orientation of the workpiece. Twist, brings the workpiece into contact with the trailing edge of the blade; contact with the trailing edge of the blade is what will fling wood at you. Kickback!

Be safe,

Steve

[Joel Jacobson]

possiblity of kick back occurs ....

Kelly Mehler, the table saw maven, describes "kickback" as the situation when the blade grabs the work and pulls it back through an arc leaving a gouge and possibly injuring the operator's hand. The situation where a piece of cut off stock which is trapped between the blade and the fence and shoots back as "ejection". This was called a "trapped arrow", and is really grim to be hit by one.

thick MDF -- I will therefore need to run the short end of a 17" by 48" through the saw.

I was taught an excellent beveling technique for a right-tilting blade:

1) Attach a sacrificial fence to the regular fence. 2) Set the fence distance from the blade to the thickness of the stock 3) Tilt the blade to 45 degrees 4) Turn on the saw and raise the blade into the sacrificial fence. 5) Pass a sample along the fence 6) If you have a sharp bevel, it's okay. If not, stop the saw -- retract the blade --- adjust the fence- to-blade distance properly --- raise the blade and make a test cuts until the bevel is okay.

IMPORTANT:To avoid getting a prism shaped trapped arrow, I make small chamfer with a router along the edges that I'll bevel. This leaves a thin piece under the blade that presents no danger.

This may sound laborious, But it isn't, and I get perfect beveled edges safely.

Joel

[GeeDubb]

That's what I did recently. I can post pictures if anybody wants.

Gary

[Bob Davis]

Joel, what did you mean in statement #6 by "okay"? I didn't follow.

[Joel Jacobson]

6) If you have a sharp bevel, it's okay. If not, stop the saw -- retract the blade --- adjust the fence- to-blade distance properly --- raise the blade and make a test cuts until the bevel is okay.

I mean that your bevel's edge should come to a sharp, crisp line. If you set the fence at the improper distance, you'll have a flat rather than a shard edge.

I hope this is clear.

By the way, I've used this technique to make several display stands for sculpture and folk art. The display folks at the National Gallery of Art told me about this.

Make an outer box the proper size from MDO by beveling the vertical edges and the top edges and the top. Leave the bottom flat. They staple the bevels together and fill and paint the box. Then make a box that will fit snugly inside the display box, and place weights in that. They use elevator weights --- I use lead ingots. Slip the outer box over that and place the object on that pedestal.

I'm considering creating a web page to show this technique, is it worth the effort?

Joel

[Bob Davis]

Thanks for patient reply. I get it now.

Bob

[Jenny Steel]

Thankyou all for your interesting comments.

Firstly I'd like to clarify that I had not intended to use a fence for this operation (thankyou Mr M for your words of wisdom) ... although a newbie I do realize that to cut the short end of a 17" by 48" using the fence presents all kinds of dangers.

I have a heavy-duty extending mitre gauge (with a clampdown attached) that I had assumed would give sufficient support for the considerable weight of the MDF -- would a cut-off sled be better ?

Unfortunately Mr Bridger, flipping the stock over and cutting from the "safe" side is an option only if I completely reverse my table saw set-up. As Mr Upscale notes all my support is on the right side and I'd prefer to leave my current set-up intact if I can.

I've never seen a "cut-off sled" as suggested by Mr Pagona so yes Mr Geedubb I would really like to see your pictures and receive any words of wisdom on its construction techniques.

While I think I understand Mr Jacobson's technique to avoid "trapped arrows" I'm not sure that I understand why this technique would in fact prevent a trapped arrow or how I could apply this technique to my particular problem -- the technique seems applicable for small pieces or when working from the left side. Certainly a further explanation of the technique and why it presents more safety would be useful.

So to return to my particular problem of how to cut a bevel thorouh a

17" by 48" piece of 1" MDF using a right tilt arbor on a right cut-off table set-up....will the following, in all your opinions, be safe ?

1) I use my miter guage(or a sled) and not the fence to prevent the blade/fence twist problem and, 2) I allow for three to four inches on the waste side to prevent the "ejection" or "trapped arrow" problem.

respectfully

Jenny Steel (newbie)

[bob]

This is correct. I speak from experience. I did this very cut a couple months ago on a piece of 5/4 stock. The piece between the blade and fence (on a right tilt) came FLYING out, hit me square in the left hip, ripped a 4 inch slash in my jeans (heavy denim), and left a nasty bruise and scrape on my hip. It actually didn't hurt much, but it scared the poop out of me.

I won't do that again. Fortunately, I have 66" rails on my Incra fence. All I should have done (but will in the future) is flip the fence over to the left side of the blade and then do the cut.

Bob

[GeeDubb]

Three pictures posted on abpw.

Gary

Jenny Steel wrote:

[charlie b]

Got a router table with a good fence? With a 45 degree chamfer bit you can savely bevel edges if you've got the bit and the fence set up correctly. You will need feather boards to keep the stock firmly against the fence if you want nice clean edges.

If you want to get tricky you can go with a lock miter bit (see thread in a.b.p.w.)

Not as fast as on the table saw but a hell of a lot safer.

BTW - MDF will dull saw blade teeth AND router bits a lot faster than most woods will.

charlie b

[GeeDubb]

snip

Correct of course. I think this should be in a FAQ somewhere.

Gary

[Jerry]

Get a set of small ball bering casters and put them in the miter slot along with the runners. This would lift the sled and make pushing it much easier.

[Jenny Steel]

Charlie,

Yes I do have a router table but unfortunately not one with a big enough cut-off table to handle my 17" by 48" piece of MDF, nor am I sure that I can acquire a chamfer bit that would cut a 45% mitre in a

1" piece of MDF. I'll look into this technique more.... perhaps I could rig something up with the router table. Thanks for the suggestion

[Stephen M]

IMHO, yes. With a sled, all of the friction is between the sled and the table, with a miter gauge, there is more "contact" between the work-piece and the table than the workpiece and the fence. This drag can cause the workpiece to shift in relation to the fence. This won't happen with a sled.

Also The fence on a sled is generally longer. It is also more stable because its squareness to the miter slot is triangulated by the base of the sled.

GEEDUBB's posting on ABPW is a fine example.

All you need is a 1/4" more than your waste piece.... but just move the rip fence out of there.

-s