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Question on cutting miters with a table saw

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Forum topic by lumberjoe posted 05-03-2012 07:07 PM 1506 views 0 times favorited 7 replies Add to Favorites Watch
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lumberjoe

2833 posts in 902 days


05-03-2012 07:07 PM

I finally got a nice (to me anyway) table saw and wanted to try some things I have never done on a table saw before due to my old ryobi’s limitations. The way my shop is it’s kind of a pain to set up the mitre saw. I made some test molding out of scrap and needed to make a couple test fits to a piece I am making. I decided to put my new TS and incra miter gauge to good use.
I ran some wide scraps through first. They were 1×6 pine, about a foot long. I wanted to cut 4 just to make sure 45 degrees is really 45 degrees. After I got everything dialed in, I cut the test molding. It is an inch wide and 13/16’s thick. I noticed when passing it through the blade, it cut clean on the front of the blade, but it also cut again when it reached the back of the blade. Is that normal? I did fully adjust the saw and the dial indicator reads 2 thousands from the miter slot. I checked again after the cuts and the alignment had not moved was still true.
I also made sure the blade is 90 degrees, and it is.

If that is not normal, what else should I look for, warped blade, excessive wobble?

-- www.etsy.com/shop/KandJWoodCrafts


7 replies so far

View docholladay's profile

docholladay

1286 posts in 1713 days


#1 posted 05-03-2012 07:27 PM

First of all, when you say that it cuts again on the back of the blade, is it really cutting or just are the carbide teeth just kissing the wood a little bit as you pass the rear of the blade? If the latter, I woudn’t worry too much about it. If it is really cutting (removing wood), then you have a problem. The blade has got to be out of parallel with the miter slot. I’m not sure what you mean by the dial indicator reads .002” from the miter slot. The actual reading is not important, but you should be measuring at the front of the blade and at the rear of the blade (preferably rotating the same exact tooth front to back and measuring on the same tooth). I assume that you mean that there is .002” difference from front to rear. That isn’t much, but ideally those measurements should be exactly the same or as close as you can possibly manage. In my opinion, this is an area where zero tolerance is acceptable. Another question is, does the blade tend to lift the workpiece up when you pass the back of the blade on a cut. If so, that is yet another indicator that something is out of kilter. If it were me, I would double check the blade being parallel to the miter slots. Check it against both slots just for grins. Check to be sure both slots are parallel to one another as well. Choose a miter slot that you will use primarily (for me it is the one to the left of the blade) and then adjust it to as close to exactly parallel as you can. Then try it. Finally, check the blade for runout. It is entirely possible that it could have some warpage. If there is any doubt at all, change the blade. Also, remove the blade and clean the surface where the blade mounts and clean the threads. Any dust can create some runout of the blade. Last of all, if you do make any adjustments that affect the alignment of the blade, be sure to re-adjust your fence before doing any ripping. Even if the fence was in alignment, it will need to be re-adjusted. The only fixed item is the miter slot. Unfortunately, you can’t change that.

Doc

Doc

-- Hey, woodworking ain't brain surgery. Just do something and keep trying till you get it. Doc

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lumberjoe

2833 posts in 902 days


#2 posted 05-03-2012 07:42 PM

Thanks Doc. it’s hard to tell if it is removing a lot of material, or any at all. It is definitely making contact with the blade after passing through the front. It makes a slight “zing” and doesn’t really require much effort to push the piece past.
As far as measurements you described the procedure I used correctly. Sometimes I just assume people know what I am talking about. There is a 2 thousands difference from the front to the back measuring with the same (marked) tooth. This was as good as I could get it unfortunately. It is only a 500.00 saw. I may tinker with it more, but from what I read I am lucky to have that little variation. (Ridgid R4512)
I primarily use the slot to the right of the blade as i am left handed and do not want my body in the path of the of the blade. That is the slot I measured to. I will try both. Is there any sure way to check the blade for warpage? I laid it down flat on the cast iron and it seemed ok, but tough to really tell. This is a forrest WWII (40 tooth).

Also thanks for the tip about the rip fence. If I do make any adjustments to the saw, I will be sure to check that for parallel.

Edit – also of note the blade does not lift the work piece as far as I can tell. I just made straight cross cut with a flat pine board and the guard off for extra visibility to be sure. I didn’t detect any lifting.

-- www.etsy.com/shop/KandJWoodCrafts

View Gene Howe's profile

Gene Howe

5642 posts in 2082 days


#3 posted 05-03-2012 07:59 PM

I check for blade warpage with a good straight edge while the blade is on the unplugged saw. Raise the blade as high as it will go and set the straight edge between the teeth at the gullets. Sometimes, one can over tighten the arbor nut and cause a slight warp.
You didn’t say whether or not your miters were true. If it all fit and the corners were square with no gaps, I’d say you were good.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

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lumberjoe

2833 posts in 902 days


#4 posted 05-03-2012 08:06 PM

Gene, yes after dialing in the new gauge, they were true. I cut 8 miters (4 boards, equal length). they fit perfectly. I checked the inside corners with a known good speed square and they were right on.

-- www.etsy.com/shop/KandJWoodCrafts

View crank49's profile

crank49

3434 posts in 1625 days


#5 posted 05-03-2012 09:10 PM

I’m copying my comments to your review of this saw from a few days ago:

I’m glad you got one without the allignment issue. I, too, liked this saw. Well, technically I have the Craftsman 21833, which is the same saw in red and silver paint.

If my trunnion did not change alignment depending on the blade height it would have been all the saw I need.

Quiet, vibration free, powerfull motor, decent fence.

What’s not to like, if the friggin blade would stay parallel with the miter slot?

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

View Sawkerf's profile

Sawkerf

1730 posts in 1722 days


#6 posted 05-03-2012 11:22 PM

Could your workpiece be sliding slightly as you make the cut? When cutting miters, the workpiece will want to slide slightly due to the pressure of the cutting. You think that you’re holding it tightly, but probably not as tightly as you need.

Try making the first cut a bit strong then make your final cut so you’re removing very little material.

Yesterday, I was cutting miters in 8/4 maple and made a sacrificial fence with a stop on the “downhill” side of the cut. Took about an hour to make and set up the fence, and about five minutes to make my four miters.

-- Adversity doesn't build character...................it reveals it.

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lumberjoe

2833 posts in 902 days


#7 posted 05-03-2012 11:23 PM

Doc/Gene you called it. It was something with the blade. I cannot confirm exactly what because I did a few different things all at once. First, I took the WWII off and put on the Ridgid 40 tooth blade that came with the saw on. I had to REALLY work to crack that arbor nut. I may have over-tightened. I have never even unpackaged the ridgid blade up until now. I made a miter cut, and the back of the blade just BARELY grazed the piece, not even enough to leave a mark in the wood (man this blade sucks by the way). I made a few more cuts with the same result. I then REALLY cleaned the WWII with some blade saver and a toothbrush. It didn’t look that dirty, but the before and after were amazing. I have never used this on a saw blade, I clean router bits with it. I put the blade back on the arbor, and was careful not to hammer the nut down so tight. This had better results than the ridgid blade.

So today I learned:
Dirty saw blades can really affect performance
not all 40 tooth blades are created equal
There is such as thing as too tight

-- www.etsy.com/shop/KandJWoodCrafts

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