LumberJocks

Fixing table saw binding and kickback

  • Advertise with us

« back to Safety in the Woodworking Shop forum

Forum topic by MagicalMichael posted 04-28-2017 09:11 PM 849 views 0 times favorited 12 replies Add to Favorites Watch
View MagicalMichael's profile

MagicalMichael

71 posts in 355 days


04-28-2017 09:11 PM

I searched through and found a number of older threads but none that addressed my concern directly. Three days ago, while trying to rip a bunch of 3/4 x /3/4 pieces of cherry from wider stock I experienced some binding on the back side of the saw, assumed that my push stick must be twisting the wood, and concentrated on pushing straight. The saw is a 3HP General 350 with a Paralox rip guide, which runs on cables. I had experienced a kick back a couple of weeks ago, which was only the second one in the 26 years I have had this set up. The saw has no splitter or pawls. The next piece shot past me, over my head and through both sides of a thermal pain window

After cleaning up the mess, covering the opening and taking the widow to a repair shop I turned to the saw, which now frightened me. I found that the rip guide was dead on parallel. I decided to move the rear end out 1-2 mm. I found the front adjustment frozen and with great difficulty got the rear end moved out about 2 mm.

Testing the saw this morning it seemed to be fine ripping wider pieces but when I returned to ripping the narrow pieces I again experienced some binding and the wood moving away from the fence and toward the blade on the back side.

I am baffled about what to try next. Help needed.

Michael

-- michael


12 replies so far

View crank49's profile

crank49

4026 posts in 2810 days


#1 posted 04-28-2017 09:37 PM

Wood must have some internal stress making it twist or bow when cut.
Very common problem.
Can’t believe you never had this happen in 26 years without a splitter.
You really need a splitter, or at least poke a wedge into the kerf behind the blade.

Did you intend the play on words referring to the “window pain” instead of window pane? LOL

View Loren's profile

Loren

9633 posts in 3487 days


#2 posted 04-28-2017 09:42 PM

View knotscott's profile (online now)

knotscott

7789 posts in 3215 days


#3 posted 04-28-2017 10:17 PM

Many times kickback is caused by the wood, not the saw. A splitter of some sort can help. They can be easy to inst can be very inexpensive.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View Rick_M's profile

Rick_M

10640 posts in 2219 days


#4 posted 04-28-2017 10:35 PM

What they said.

I’ve rarely ever encountered kickback but I tend to buy my wood weeks or months ahead of time and allow to equalize in my shop. Kickback is caused when the kerf closes up on the back of the blade. Several things can cause the kerf to close, usually it’s improper or insufficient drying. Chris Schwartz has a good article about improper drying. I’ve also ran into it cutting limb wood (as in tree limbs, not the trunk). Supposedly it’s because the limb structure is under tension to resist gravity horizontally. When you cut into the wood, the tension releases. I suppose it could happen in a leaning tree or in other situations. But I think most of the time it’s moisture or drying related.

-- http://thewoodknack.blogspot.com/

View pintodeluxe's profile

pintodeluxe

5466 posts in 2652 days


#5 posted 04-28-2017 10:46 PM

1+ improper drying, and internal stresses are potential problems.

Even more common than those are ripping a board with an uneven or bowed edge.
Always joint the reference edge before ripping.
If a board has been kicking around the shop for awhile, I will re-joint an edge to make sure it is true before ripping to final width.

If you’ve been at it for 26 years, I haven’t told you anything you didn’t already know, but it may help someone reading along.

Ultimately a riving knife will help a great deal, but that may not be an option on your saw.
I have found more frustrations than solutions with simple splitters, but true riving knives are great.

Good luck.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View builtinbkyn's profile

builtinbkyn

1924 posts in 780 days


#6 posted 04-28-2017 10:53 PM

Is the off-cut the 3/4” piece?

Edit: “Push stick”? Hmmm? Doesn’t seem like the right application for “wider stock”.

-- Bill, Yo!......in Brooklyn & Steel City :)

View MagicalMichael's profile

MagicalMichael

71 posts in 355 days


#7 posted 04-28-2017 11:56 PM

The wood I was cutting from was well seasoned and jointed. I am making a set of 15 smallish drawer fronts which are birdseye maple with a cherry strip at the top & bottom. I was ripping salvaged pieces between 40 & 50 MM into 20 mm, with the good piece against the fence.

I watched some youtube today with various approaches to making splitters. Looking at my set up, I see that the saw actually has a fixed bolt-on spot behind the blade. I am thinking about trying to mill a piece down to the 3.25 mm of the blade and bolting it in. It looks like the right hand side will naturally line up with the blade. How much forgiveness will I have on the outside? I assume a little bit would be good, but a little more could block the cut off.

Unfortunately I just sold my band saw and then discovered the Rikon I wanted to buy is backordered into late June so making new inserts with a splitter would be a hand tool job.

Michael

-- michael

View Loren's profile

Loren

9633 posts in 3487 days


#8 posted 04-29-2017 12:15 AM

I think about 15/1000s less than the blade
thickness is a good place to start. It doesn’t
have to be very tall.

View Carloz's profile (online now)

Carloz

985 posts in 431 days


#9 posted 04-29-2017 12:30 AM

Op clearly says the wood moves from the fence. I bet he needs to realign the blade.

View builtinbkyn's profile

builtinbkyn

1924 posts in 780 days


#10 posted 04-29-2017 02:12 AM

The OP stated he was ripping narrow pieces from wide stock. When I’m ripping narrow pieces from wide stock, I take them from the off-cut side – meaning the thin strip is what’s to the outside of the blade and not against the fence. I also don’t use a push stick to do so. A push stick is only useful when both pieces are of the same relative size and weight and generally narrow and on the shorter side. Using a push stick with a wide board is just asking for trouble. A push stick doesn’t provide a way to influence the direction the wood will travel after it passes the blade. The OP stated he “concentrated on pushing straight”. That isn’t how this works. Sawing on a table saw doesn’t require aiming at a target.

-- Bill, Yo!......in Brooklyn & Steel City :)

View MagicalMichael's profile

MagicalMichael

71 posts in 355 days


#11 posted 04-30-2017 12:50 AM

I was ripping 3/4” strips from 2” wide pieces, so not so wide. I seem to have the guide realigned, no more than .5mm offset from square and have ripped a few pieces successfully, with no sense of binding. Still, with neither a splitter nor pawls, if I had it to do otherwise I would use a banndsaw. On to glue up.

Michael

-- michael

View clin's profile

clin

751 posts in 835 days


#12 posted 04-30-2017 02:52 AM

Since push sticks were brought up, I think it’s worth bringing up the Grr-ripper. It’s perfect for this type thing. You can hold both sides of the cut down as you move it through the blade. Better still if you have two of them. Then you can walk the boards all the way through the cut.

This won’t prevent binding, but it will ensure the stock, on either side of the blade, doesn’t start to rise up and get grabbed by the blade.

And I agree, that the OP’s binding may have nothing to do with the saw setup. Could just be the wood.

Also, Micro-Jig, the same company that makes the GRR-Ripper, also makes a splitter that fits into a ZCI.

http://www.microjig.com/products/mj-splitter/

-- Clin

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com