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Tapering on the table saw question

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Forum topic by randyc posted 08-07-2008 05:41 PM 1335 views 0 times favorited 12 replies Add to Favorites Watch
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randyc

3 posts in 2235 days


08-07-2008 05:41 PM

I’m relatively new to woodworking and have a question/problem regarding tapering on the table saw. I hope you can help.

I built a tapering jig that I used to taper a 2” square coffee table leg down to 1 1/4”. What I’m finding is that the taper is uneven at the top end ( the thick end). By uneven I mean that the taper on one side of the piece starts 5/16” lower than on the other side.

My analysis of the situation is that since the saw blade is circular, the blade enters the piece at table level before it enters the piece higher up. In my case, the blade enters the piece at table level but doesn’t get to the other edge which is 2” above the table until I’ve traveled 5/16”, and that’s the cause of the uneveness.

Is my analysis right?
Is there any way to prevent this?

Thanks for you help.

-Randy


12 replies so far

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SCOTSMAN

5364 posts in 2241 days


#1 posted 08-07-2008 05:55 PM

remember when you take a first cut you are no longer working with a square piece of wood. Hence when you put that newly cut face against the fence it will be off on the second cut by the ammount removed by the first cut. Watch for this as it throws your work out by quite a bit unless you use wedges to compensate ot reset the jig to compensate you will never remove evenly otherwise regards Alistair

-- excuse my typing as I have a form of parkinsons disease

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randyc

3 posts in 2235 days


#2 posted 08-07-2008 07:25 PM

I guess I wasn’t clear in my description. I’ve only made one cut at this point. In other words, I set the jig to start the taper 5” from the end of the board. I make the cut, and then I rotate the board 90 deg. to take a look at the result. What is see is that the taper starts at 5” from the end on the left edge of the piece (exactly what I want), but as I look across the width of the board the taper starts lower and lower, eventally starting 5 5/16” from the end by the time I get to the right edge of the face.
Thanks,
Randy

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lew

10034 posts in 2411 days


#3 posted 08-07-2008 08:34 PM

When I use my tapering jig, I draw a line around the top end of the leg- where I want the tapers to start. Then I mark the bottom of the leg where I want the tapers to end. After making the first cut, I rotate the leg and check to see if the starting and ending points line up with the blade cutting path. If not, readjust the jig accordingly.

Also, remember, the taper starts at the point where the saw blade and table (saw or jig surface) intersect.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

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Ben Griffith

50 posts in 2335 days


#4 posted 08-07-2008 10:47 PM

I think the problem may be that your saw blade and the face the taper is coming off of are tilted just slightly away from each other(vertically). Maybe your table leg is just slightly out of square, or the blade is just slightly off of 90 degrees.
Imagine what would happen if the blade was tilted, say 20 degrees… the top of the blade wouldn’t hit the wood until long after the bottom does. (I find it’s easier to visualize things like that by exaggerating them.)
-Ben

View Steelmum's profile

Steelmum

355 posts in 2618 days


#5 posted 08-07-2008 10:48 PM

I think that you might want to check your set up. The wood should be square to begin with and your saw blade set square at 90. These are the most common errors that come to my mind. Also, be sure nothing is shifting during the cut. Charles Neil just posted a tapering jig. That might also help. Also try a message to him. He is great. This is the link to his site: http://www.antiquesbuiltdaily.com/tips.htm

-- Berta in NC

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brunob

2275 posts in 2825 days


#6 posted 08-07-2008 10:59 PM

I taper my legs to be oversized by a 1/16” at least. I then joint all surfaces. Brings them down to where I want them and the finish is good.

-- Bruce from Central New York...now, if you'll pardon me, I have some sawdust to make.

View Randy Sharp's profile

Randy Sharp

349 posts in 2328 days


#7 posted 08-07-2008 11:06 PM

Randy, I’ve experienced the same problem. Honestly, all I do is sand the face smooth and “blend” that area. It’s not noticable, unless someone is looking for it. With that said, if our fellow LJ’s have solutions, I’d love to learn.

-- Randy, Tupelo, MS ~ A man who honors his wife will have children who honor their father.

View niki's profile

niki

426 posts in 2735 days


#8 posted 08-07-2008 11:25 PM

Hi Randy

I think that it’s normal because the blade is round.

It would not happen on a band saw…

To visualize it, I took these 3 pictures…..sorry, I could not make a “live show” because it’s 11:20 PM here and I don’t think that my wife nor the neighbors would like it…. :-)

That’s a view from above…as you can see, the teeth that are close to the table will start to cut the lower part of the board but, the upper part will “delay” till the upper teeth will start to bite.
Photobucket

Another view from the side
Photobucket

And, the bigger the angle, the bigger the “delay”
Photobucket

As randy Sharp said…sanding….or planing

Regards
niki

View Ben Griffith's profile

Ben Griffith

50 posts in 2335 days


#9 posted 08-08-2008 06:26 AM

As long as the blade is perfectly vertical, the side of the board is perfectly vertical, and the feed direction is parallel to the blade, the taper should be even. The blade being round does not cause it to be uneven because if it did you’d never be able to cut anything square! A bandsaw would have the same problem if it was tilted just slightly to one side, or if the board was just slightly out of square.
With that said, the recommended sanding or planing probably will make the offset invisible unless someone’s going to be down on their hands and knees checking your tapers with a straight-edge.
-Ben

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Ben Griffith

50 posts in 2335 days


#10 posted 08-08-2008 08:11 AM

I’m afraid I must still respectfully disagree. I understood that he meant the taper started a little lower on one side, but I don’t think the round saw blade is to blame. If you sight down your table saw from front to back, the blade appears as a straight vertical line. This is what the wood “sees” as it is fed into the blade, unless the wood or the blade moves sideways. The blade cuts the bottom part first, but as the cut climbs, it climbs straight up (assuming the blade is at 90 degrees, the board edge is at 90 degrees, and the board is moving in a direction parallel to the blade).
With a taper cut, the tiniest (and I mean really tiny) error is amplified. The smaller the taper angle, the more it will amplify any problems. But really, it’s only visible because of the contrast of the fresh cut. Once you sand it down a bit you’ll have a hard time seeing a 5/16” difference.
-Ben

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bhack

348 posts in 2376 days


#11 posted 08-08-2008 04:08 PM

It seems to me that all componets must be at 90 degrees to the blade. I agree with Ben, if you sight down the table top the blade is veritcal just like the band saw blade.

-- Bill - If I knew GRANDKIDS were so much fun I would have had them first.

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randyc

3 posts in 2235 days


#12 posted 08-08-2008 04:34 PM

Thank you all for the responses. I’m overwhelmed by the attention you’ve given to my little problem. I’m looking forward to my new relationship with all of you lumberjocks. Hopefully the day when I can actually give some advice rather than just be on the receiveing end won’t be too far off.

-Randy

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