table saw rip kickback

rjj45

Yikes Batman!
I got some sawmill 15/16 x 6 inch white oak, and crosscut it into 15 inch long pieces for baffle.
Wood has sat in my basement for several weeks, so it should be moisture stabilized, and
certainly does not appear to be wet in any way.
I want to make face glued butcher block baffles, so I'm cutting 1 1/2 inch strips that I will face glue later.
I built a jig that fits against the fence, and holds the wood so that the cutoff piece is between the blade / jig and fence,
and the off cut piece is free.
The first couple of pieces went pretty well, then I had a piece where half way through the cut 
the TS started struggling and the blade overheating.
Looked at the piece closely, and it looked like the kerf was narrowing after the cut.
Although the grain appears to be straight, there is obviously something in there that's twisted.
At this point, I have to assume that the rest of the wood will have this problem, and try to complete
this safely.

I've still got a lot of cuts to finish this stage. 
Here's what I've come up with.
1  Use the riving knife, anti-kickback pawls and continue with the current jig.
2  Use gripper blocks without the jig to cut 1 1/2 inch strips directly against the rip fence. (can't use riving knife/pawls for this)
3  alternate gripper use, cut 1/2 the thickness with a gripper, then turn the piece over and make the through cut on the other face.

R-Carpenter

You need a ripping blade. Something like this

https://www.amazon.com/Tenryu-RS-25524CBN-Carbide-Tipped-Blade/dp/B000G1IHJE/ref=sr_1_13?s=power-hand-tools&ie=UTF8&qid=1540384046&sr=1-13&keywords=tenryu+blade&refinements=p_n_feature_seventeen_browse-bin:8557106011

Appearance of the wood to be dry means very little. Moisture meter is what's needed to determine if the board suitable for machining. If you got the wood from any sort of lumberyard, it is most likely kiln dried and minor moisture content variations are irrelevant.

Oak will often try to kickback even if the grain is straight.

Address your blade situation first. Overheating can mean a few things.

Too many teeth.

Blade is dull (overheating helps to dull inexpensive or even pricey carbide so it's a snowball)

You pushing the wood through too slow. (Comes naturally for under-powered table saws.)

Also, the edge of the board that's guided against the fence looks pretty straight. However, was it straightened on the jointer or hand plained?

rjj45

Thanks Roman - I"ll get that rip blade and give it a go.
The reviews are promising "cuts oak like butter" 
Good tips - experience always counts!
The edge of the board against the fence is very straight and smooth. In general, the lumber yard delivers the boards with 1 edge ripped. That's what I try to use against the fence. As far as I know, not jointed.

R-Carpenter

Tenruy does make nice blades. And they do cut oak like butter.

Ripping blade of many other brands will work miles better than general blade you have on the saw now.

GL!

jhollander

You got a board with some internal stress.  Other than changing the blade, you may want to oversize the piece and then final cut.  These pieces will have some twist or bow that will need to be corrected.

rjj45

Thanks John - yeah, that was my feeling, since several strips were cut with no problem. But now I know that oak can be a problem. For this application, I _am_ cutting oversize, then will plane and sand to the final thickness after the baffle cutting-board glueup. Realistically, I knew there was/is some stress in the board, because I stopped the saw in the middle of the cut and found that I couldn't even back the board out, it was now binding in the same kerf that it had just cut!  So I knew then that I needed some knowledgeable input,and above all, I want to work safely!

BobBarkto

What you are encountering is often referred to as "reaction" wood. Something caused internal stress to develop. Two most common causes are growing conditions and improper drying/storage.

Since some cuts are ok and the problem seems to be in the cuts nearest the center I would think it was drying/storage related. This is better than growth induced stress as you can often salvage the boards by cutting oversize strips and letting them rest a good long time. Then you can plane an edge and rip again to final width.

No guarantee, but it usually works. You might still see some movement after planing,ripping but it can be so minor that clamping up will take care of it.

Stress from poor growing conditions normally shows up in every cut since the whole tree is affected. Very poor drying can cause this level of defect, too, but is less common ime.

Hope this helps.

rjj45

Thanks @BobBarkto - appreciate your expertise! I just bought a Freud LU87R010 rip blade from Amazon, I felt that the .094 narrow kerf would work better on my Dewalt 745 TS, and several reviews mentioned good rips on oak. If the wood still gives me problems, I'll probably try cutting 1/2 thickness and flipping the board over to complete the cut. Absolute precision is not needed for this because I will plane it down later.  

dynamo

Your title me of a story of when I was in high school shop class. I was ripping some mdf panels about a foot square on a 14” powermatic table saw and I pushed them through but had to walk around due to the size of the table and one of the panels was close to the blade; It vibrated over a little (because I foolishly left the saw running because I was young and stupid) and it caught the blade. It flew back about 15-20 feet where it hit the overhead door, about two feet to the left of the shop teacher’s knee. I thought I was done for, he was a high strung guy anyways. He asked if I was ok and gave me a “did you learn your lesson” look and never mentioned it again. That could have been worse on many levels.

anyway, I digress, I agree with the above suggestions to overcut to relieve twist and stress, then cut to size from there. I work with naturally dried locally cut lumber a fair amount and this works well for me.

rjj45

Thanks Dynamo - I am always concerned about safety, and strongly prefer to stand off line of the blade in case of kickback. And I have learned to always just back off the cut and turn off the power if there is any question of completing a successful cut
.

rjj45

Thanks for the help guys - last night I made a new strip cutting setup and tried cutting 1/2 thickness, then flipping the piece over and completing the cut. This meant that I could use my DIY gripper blocks, and the cut was really very safe. Unfortunately, the old blade was pretty dull at that time, and only managed a few cuts before I got a lot of burn. 

Today I got a nice thin kerf Freud blade, flat profile teeth.
https://www.amazon.com/gp/product/B0000225UH/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

same setup, cut like butter - clean, smooth cuts. 
In about 20 minutes, I was done with enough pieces for a baffle. No hassle.

Thanks again.  don

6thplanet

That'll make a set of sweet looking baffles.

rjj45

Thanks - made up a new router sled, and in a few minutes, they routed flush and beautiful. Dropped a thin slice of Sapele in the mix for a little visual interest. Now I just have to not muck them up while cutting holes and routing the edges.  ;-)

dynamo

I love that accent stripe. Looking good!

Tom_S

Love it! And that was a great idea for a router sled. I noticed the plastic pieces on the legs for easy repositioning. Clever!

6thplanet

When you routed, did you go with the grain, diagonal, or cross the grain?

PWRRYD

I'm feeling very slow today...  did you use the router and sled as a sort of planar?

rjj45

6thplanet said:

When you routed, did you go with the grain, diagonal, or cross the grain?

I basically routed with the grain, from left to right. Mostly because that was convenient - the shape of my support board and the router sled was setup for that direction. That said, I don't think it made that much difference - it was quick and smooth with little effort. I learned from the 1st baffle that it was not necessary to make multiple thin passes, and to never pause the router with the bit lowered on the work piece - it left a little "divot". Easily sanded out, though.

rjj45

PWRRYD said:

I'm feeling very slow today...  did you use the router and sled as a sort of planar?

Yes - no budget or space for a planer or sanding machine. This worked great, very easy. good results.
Very similar to this: https://www.youtube.com/watch?v=TpU5dZlW2pg
or this: 

PWRRYD

Awesome!  Thanks!

6thplanet

6thplanet

I used a similar method to taper the bases to my Kamayuri speakers

6thplanet

Another bonus to this method of "planing" is zero snipe. 

MartyH

Go easy on the bushings on your Craftsman because you can't get them these days.  

jhollander

Missed you Marty at Iowa.  

6thplanet

Routers are a dime a dozen at pawn shops. I found a Ryobi for free, it had a $30 Bosch spiral bit in it, they wanted $30 for the router, SCORE!!

rjj45

6thplanet said:

Routers are a dime a dozen at pawn shops. I found a Ryobi for free, it had a $30 Bosch spiral bit in it, they wanted $30 for the router, SCORE!!

Luck!

MartyH

I ordered two new bushings for my Craftsman router and they came in at about $11.00, but shipping and handling took it over $21.00.  Now they're backordered.  Wonderful.  

Ron_E

I've bought a number of tools at pawn shops.  I once picked up a like new 3hp Bosch router and Dewalt jig saw for $168.

Ron

MartyH

jhollander said:

Missed you Marty at Iowa.  

Thanks John, I missed being there too.  On a cheerier note the CD player is terrific!  Much better midrange clarity than the Panasonic that it replaced.