Recently I have had quite a time cutting exact angles on my table saw. The saw is tuned up within .002 of an inch and I’m using a new Kreg miter guage. Most of the time I end with less than an exact angle, especially 45s. My son came over, who is a machinist, check my saw and tried to cut also. The same problem. the 45s were off. He tried some red oak again, but push it through very slowly at a 45 degree angle. It came out perfect. While he was feeding it through the first time I could detect the thin kerf blade actually deflecting just a tiny bit. The second time he push the oak through very slowly, no deflection and perfect angles. I think I am going to back to regular blades vs the thin kerf. I can’t imagine how many times I have cut a bad angle and not found the cause, only because the blade was deflecting. Of course after the saw is turned off it all the saw alignments check out fine. Frustrating as it was I am glad that I finally found out how to cut the angles I need accurately. Anyone else have this experience? Your comments appreciated.
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Replies
I have a Rockwell/Delta Unisaw, and was getting an odd vibration when the saw was running. Traced it to the thin-kerf blade that was on the saw. Changed to a full 1/8" kerf blade and no more vibes. There are blade stabilizers out there that may help to solve this problem, but I still like some meat on my blades.
I've had a similar experience with a thin kerf blade. I've since gotten a standard kerf Forrest blade with stabilizers. I still use the thin kerf blade, but only for cuts where I know the board will be remachined later on the jointer or something like that. The thin kerf is still good for cutting to rough dimensions or when lots of rough dimension cuts are called for because the feed rate is faster.
The piece being mitered also tends to creep slightly along the fence due to forces created when making an angled cut. Facing the fence with sandpaper and/or clamping the piece to the fence will help to prevent this movement.
By cutting slowly while you were searching for the cause of the inaccuracy, the side pressure and the resultant creep was reduced, possibly eliminating another common source of error when making miter cuts.
Another trick is to switch to smaller diameter blade if you don't need the additional depth of cut. A smaller blade will be much stiffer and far less prone to distortion.
John W.
Edited 12/18/2007 5:48 pm ET by JohnWW
Another approach is to consider the tablesaw cut as a rough cut and clean up using a shooting board and a low angle plane or one of those mitre cutters that use angled guillotine blades.No matter how careful I've been, I've never been completely happy with mitre gauge mitres - especially with a wide mitre. The vibration of the teeth in the wood "walk" the workpiece along the mitre gauge and change the angle. Sometimes the old ways are the best; sometimes the combination works best like combining the tablesaw with the shooting board.
I had a project in the shop a few years back that required several sets of mitered pieces. Fabricating a dedicated MDF sled for each angle (cheap enough) and equipping each sled with two toggles (hold-downs) eliminated the problem of "creep". Perfect cut, every time.
Miter gauges, regardless of what you spend on them, are rarely useful.
Most thin kerf blade manufacturers make blade stabilizers and recommend them, guess that tells you something. If your work piece is being held against bare metal on the miter head, it can slip, no matter how hard you think you can hold it. If you make skimming cuts, less than 1/8", the blade can deflect toward the unsupported side. Both of the last two can happen with any thickness blade. Folks that use smaller, portable saws, contractor saws and hybrids often use thin kerfs since they take a bit less power. They also waste less lumber but it takes a lot of cuts to add up.
This doesn't mean that thin kerfs are bad. I just finished cutting 64 miters on a project, half vertical, half flat. I used a thin kerf and had excellent results. I wouldn't choose a thin kerf for mitering a 2x6 in hard maple but I might for a 1x3 in poplar. Adding blade stabilizers can throw off jigs, throat plates and auto measuring devices, so they are not always an option. I think a lot has to do with what you are cutting, how you are cutting and the results you are looking for. A blade that seems wonderful when you are mitering door casings may be unacceptable when making picture frames. Different jobs and processes can place a higher performance demand on the outcome than others.
Beat it to fit / Paint it to match
Not sure the thin kerf blade is all the problem. A long time ago I stopped making 45 degree cuts with the miter gage and made a sled that has the head set at exactly 45 degrees to the blade and slides in the miter slot, and a toggle clamp to hold the wood. Thin kerf or not you will get a perfect 45 every time. I found that unless you are a gorilla, the wood will creep when using the miter head to cut 45s. I tried sand paper on the miter, this helped some but you still get some creep if the blade had to work too hard.
My work involves 3 different saws with practice as follows. Portable saw uses the thin kerf, cabinet saw always the 1/8 kerf and the contracters saw mostly 1/8 with the thin blade once in a while.
It's really important to note that not all thin kerfs are created equal, and not all deflection is necessarily "caused" by the thin kerf blade itself. It is true that TK's are more "prone" to flexing or vibration that a full kerf when all other parameters are equal, but may not be the actual cause. Any TK blade is more likely to amplifying or exaggerate a vibration or runout problem with the saw, and if the wood is not flat and stable it's more likely to give a bit from lateral pressure than a comparable full kerf would. But a TK from companies like Forrest, Infinity, Freud Industrial, or Ridge Carbide isn't likely to have a flexing problem...with or without a stabilizer, and is even less likely to be the actual cause if an issue occurs....That's not to say that it can't be the cause, but isn't overly likely either. I've used over 25 thin kerfs with excellent results, though most are pretty high quality, and I don't cut many bevels with them. These were all 10" blades on a TS. A 12" TK is far more likely to flex than a smaller diameter because the span is greater.
There are some pluses with a TK too...A good TK can make a significant difference in feedrate and perceived cutting power on a saw that's under 3hp. I tend to feel safer using my TK's because they require less pushing on my part, and they definitely put less strain on the motor than my full kerfs....just a matter of physics there. It's worth noting that in more than one recent blade test, the TK's scored on par with the best full kerfs for cut quality. There are definitely some potential downsides to TK's in general, but there are also significant and noticeable benefits. If you're saw is well tuned, has low runout, your lumber is flat, and the blade is sharp, clean and of high quality, the TK isn't likely to be the actual "cause" of a problem. I use them and recommend them regularly where power is a bit lacking....just stick with the good ones and all is likely to go well with them.
Edited 12/18/2007 8:16 pm ET by Knotscott
Thanks for your detailed analysis of the TK blades. I agree that they are great for smooth cuts and always seem to work well when cutting 90 degrees. As some of the others have mentioned, the pushing force must be parallel to the blade (not always easy to do) and the use of a stop guage on the fence really seems to help. I probably will switch to a 1/8 inch standard blade for my angles and reserve the TK for regular ripping or 90 degree cuts. Again thanks to all for your comments.
regular blades vs the thin kerf. I posted something on this awhile back. I was having a similar problem cutting angles. Rips seemed OK.
The blade was a Freud Industrial thin kerf combination 50 tooth.
NOTE: I am not knocking Freud blades. I like their blades.
I finally noticed that the blade 'flexed?' to the right as it came up to speed. Maybe just this one blade? I have no idea. I use the blade but NOT for cutting miters!
In my quest to run through my children's inheritance as quickly as possible, I have recently taken up the turning of segmented bowls. Segmented bowls consist of hundreds, if not thousands of mitered pieces all glued into circles, then stacked, then turned , a ridiculous excersise in frustration if the miters aren't perfect. In one of the (many) books I have on the subject there is mention of avoiding the use of thin kerf blades for precisely the reason you mentioned in your post. Of course I had forgotten said mention until I read your post, so thanks! Coincidentally, the blade I had been using was the exact same TK blade mentioned in WillGoerge's post. This forum is great.
Theoretically, the thickness of your blade won't matter if your pushing force is perfectly parallel to the blade - but who can really do that by hand.
When you're cutting miters, some of the forces being imparted by the blade teeth are trying to travel down the length of the workpiece - and it will try to move away from the force of the teeth. If you're holding the stock by hand, you're trying to resist that force as well as keep the stock firmly against the miter gauge bar.
Using a stop block on all miter cuts will probably eliminate most (if not all) of the problem. The stop block will resist the forces trying to push the stock along the miter gauge and your hand only has to keep the stock tight against the miter gauge bar.
Using a stop block on all miter cuts will probably eliminate most (if not all) of the problem. Not knocking your reply at all. I agree with your statement. However, I was using my JessEm sliding cross-cut table with a stop. I also tried clamping the sticks to the fence. Still the same. Going to a non thin kerf blade solved the problem.
Will -
Having spent (mis-spent?) my student days delving rather deeply into the subtleties of physics and mechanics, I have a tendency to want to "overexplain" things like this. (Just ask my kids, if you don't believe me. - lol)
What I didn't get into (and probably should have) is that stresses always relieve. In this case, if the workpiece can't move away from the blade (because of the stop), then the blade will want to deflect away from the stock. Therefore, a thicker (stiffer) blade is better because it has more resistance to the lateral force.
FWIW, I've never quite understood the fascination with thin kerf blades. I have one that I got to cut some special kerfs, but haven't used it since I finished that job. It's certainly a nice blade (and was pretty spendy), but other than the fact that it makes less sawdust, I don't see any advantage to using it on a regular basis. My "standard" blades give me great cuts with less flex and I don't loose any sleep over "wasting" a bit more wood with each cut. - lol
"FWIW, I've never quite understood the fascination with thin kerf blades. "
That one's easy Dave! The primary advantages I get from TK's are increased feedrate, less drag, less strain on the motor, etc., which equates to the equivalent of increased power. Cutting 2" maple with a full kerf blade on a 1-1/2hp saw poses quite a load. A good TK will feed faster in that situation. For me, it isn't so much about gaining speed as it is better control from having lower resistance and increased flexibility in feedrate that it offers....it's much like the difference between waxing your table and not...it just glides better. For a larger saw a TK would have less appeal.
Wood savings are miniscule for me, but they do add up for some folks.
Ditto John on the smaller blade. I have a Freud full kerf 8" HiATB, 40tooth Premiere series that I only use for fine and exacting work. It does cut down on harmonics and vibration.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
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