Walnut kicking back on miter saw

[Peter Hawser]

I had an unpleasant first yesterday. Kickback on my miter saw (Makita 7 1/4 slider with a nice Kreg fence). The wood is 3/4" thick walnut and about 7 inches wide. As I got about 2/3rd through it would suddenly get much harder to cut and I could feel the handle being pushed back to me. I made scoring cuts and went very slow, but it kept happening, though some cuts on the board went fine. The wood seemed nice, but could this be due to inconsistency in the wood or, for lack of a better term, "hard spots" that are not quite knots, but like a knot?

The wood has me spooked and I am feeling a bit chicken to cut in on the table saw (even though I have a riving knife and Grrripper).

[Bob Carreiro]

Change your blade?

[Tom Willoughby]

Maybe change the blade to a negative rake angle blade if it isn't already.

[John TenEyck]

I would guess the wood has tension in it. Could be from non-uniform moisture, could be from poor drying, could be just the tree it came from. Any could cause the kerf to start closing as you cut it, which would cause the saw to want to kick back towards you. If this is true there's not much cure for it. You could alleviate the problem by rough cutting it on the bandsaw first, leaving only slightly more than a full kerf for the miter saw to cut off.

[Darrin Vanden Bosch]

Souds like it may have just a little bit of a bow in it and is not actually flat against the fence all the way across. When you get about 2/3 though it the outer edge starts to pince in. Make sure the piece is flat all across the fence.

[David Kumm]

Peter, I have had similar experiences with my hitachi slider although usually with thicker or wider wood. I have come to believe that sliding miter saws are more prone to that problem. Wood under tension causes the saw to stess and - in my opinion- causes enough stress on the motor to rails attachment to make the situation worse. Any stress on the rails causes the blade to shift slightly in an all ready tight kerf. Absent a sliding table saw, I take shallow scoring cuts before plunging all the way. going slow also. Dave

[glenn bradley]

I'll toss out my guess; is the edge against the fence jointed flat? If you can't joint your edges at least make sure to put the convex side against the fence. Second guess; blade sharpness or appropriateness.

[Harvey Melvin Richards]

On my Hitachi slide I prefer to bring the saw forward and push it backwards, instead of letting the saw climb cut. It doesn't always work in all situations, but I feel that it's a safer way to cut.

[Trevor Walsh]

In situations like this with a sliding miter saw I make 2 or 3 plunge cuts rather than sliding. I process rough lumber to length before jointing or planing this way. Never had a problem.

[Larry Edgerton]

Nothing wrong with the saw, its the wood. Do as Trevor above suggested, but just a bit long so you can clean up the cut in the next pass.

[Mark Engel]

Probably is tension in the wood. Sometimes when I feel the kick starting, I stop the cut, flip the work over and go at it from the other side.

[Peter Quinn]

The wood is pinching the blade causing the blade to climb out of the cut and back at you. I assume you are starting with the slider forward and pushing it back toward the fence? This is the proper way to use a SCMS. If not, then definitely start there. Either the wood is not flat, or the wood is not straight, or both. You might get away with this with a soft wood or very thin trim, but walnut is hard enough to to give you a problem. I always sight boards before cutting with the SCMS, because mine kicks like a mule if it doesn't like what I'm trying to cut. If its not flat, I put the crown down so as it cuts the wood drops away from the blade, not into it thus pinching. And if the edge is not straight I either straighten it or put the crown to the fence so that the material directly behind the blade is supported as the cut is made, thus mostly avoiding a pinching situation. If its thick finished trim and it has too much bow, and you can't change orientation to make your cut, a clamp may be in order to keep the stock flat and tight to the fence. It doesn't take much bow to cause a problem.

I have read so many "SCMS versus RAS" threads where lots of wood workers seem to think the SCMS is a complete replacement for the RAS, but not so IMO for just the reasons you experienced today. The SCMS HATES rough stock, my RAS doesn't much care, rough or not, though I still sight and orient my stock the same as on a SCMS (crown to the fence, crown down to the table) for added safety.

As a last resort I have on occasion made several 'light' passes pushing forward to basically weaken the wood in stages I can control rather than let it drop on the blade all at once causing one big kick back, but I'm never too comfortable with this dance because. And if the blade is at all dull, remedy that ASAP. Dull blades are dangerous.

[Dave Cav]

Souds like it may have just a little bit of a bow in it and is not actually flat against the fence all the way across. When you get about 2/3 though it the outer edge starts to pince in. Make sure the piece is flat all across the fence.

This is exactly what ishappening. Chop saws and SMCS are construction tools and are designed to cut lumber with straight edges, not rough S2S lumber. We have this problem all the time at school when the students try to cut unjointed boards and they put the concave side against the fence. This leaves a gap between the fence and the board. When the blade has cut part way through the board the board tries to pinch the blade causing a kickback. Ways to cure the problem are (1) cut only jointed or ripped lumber with a straight edge against the fence; (2) put the CONVEX side against the fence so there is no gap between the board and the fence at the blade; (3) put a spacer between one side of the board and the fence which will keep the section of the board on the other side of the blade from contacting the fence and then pinching or (4) get a RAS.

[Peter Hawser]

Sorry, should have added the wood was jointed and planed. It wasn't rough. The edge against the fence was as straight as Billy Grahm.

[Peter Quinn]

Sorry, should have added the wood was jointed and planed. It wasn't rough. The edge against the fence was as straight as Billy Grahm.

Huh? Did you sight it to make sure it was flat? I can tell you that not every jointed piece of stock that leaves my planer after several passes comes out flat. But assuming it was as straight as Billy Grahm, my next check would be the miter station tables. check to see that the tables are flat and not lifting the stock. After that, I'm going with wood tension being released. I'v certainly seen it on both the SCMS and a sliding panel saw, enough to slow the blade and burn the stock. I make a habit of never cutting wider boards right to length, I always go about 1/4" over, then take that last 1/4" of in a second pass just to avoid any burning that may come along with the pinching that's caused by the release of tension. Doesn't make that kick back any less scary though.

[Peter Hawser]

Huh? Did you sight it to make sure it was flat? I can tell you that not every jointed piece of stock that leaves my planer after several passes comes out flat. But assuming it was as straight as Billy Grahm, my next check would be the miter station tables. check to see that the tables are flat and not lifting the stock. After that, I'm going with wood tension being released. I'v certainly seen it on both the SCMS and a sliding panel saw, enough to slow the blade and burn the stock. I make a habit of never cutting wider boards right to length, I always go about 1/4" over, then take that last 1/4" of in a second pass just to avoid any burning that may come along with the pinching that's caused by the release of tension. Doesn't make that kick back any less scary though.

Thanks Peter. I have checked everything and the saw, platform, fence are very straight and flat, as is the board. As a test I have cut, the same day, other boards with no problem - maple, sapele and cherry... It was perfect and smooth going. I also tried your idea of cutting two cuts. In some cases the saw bogged even when cutting that little 1/2" cut. So, I really think it is a quirk of this wood. It has spots that seem to be super dense. I've heard that walnut can be difficult in this way and should have been clearer in my questions. I wondered if others had similar issues with walnut. I even read on the Bad Axe saw site a user saying he has difficulty cutting walnut with kickback on a miter saw and uses his fancy new handsaw instead. I bought some new walnut from a different place that seems lighter and more consistent.