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Need help with miter joints for boxes

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Forum topic by doncutlip posted 03-10-2012 05:49 PM 4647 views 3 times favorited 41 replies Add to Favorites Watch
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doncutlip

2832 posts in 3017 days


03-10-2012 05:49 PM

Topic tags/keywords: joining tablesaw question

First, let me say I did a search on LJ first but got tired of looking. I’m making medium sized boxes and I want miters on the corners. My latest box was 12 long by 7 tall by 5 wide. I did a test cut on scrap wood and the angle looked good against a precision square. I had two problems after I made all the cuts. First, the cut bowed in inwards down the line of the cut. I put a Pinnacle straightedge on the fench to check it, looks good. So I guess I moved the wood as I cut? Second problem was the age old problem in that the joints just don’t line up. Guess I didn’t set the saw angle as well as I thought. I bet many of you have answered these questions before, but I’d certainly appreciate any help iI can get.

-- Don, Royersford, PA


41 replies so far

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HorizontalMike

7143 posts in 2375 days


#1 posted 03-10-2012 06:05 PM

While I am still cutting mostly 90 degree cuts, I built a TS sled and find that helps making exacting cuts, a lot!
http://lumberjocks.com/projects/57667

-- HorizontalMike -- "Woodpeckers understand..."

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Joseph Jossem

492 posts in 1730 days


#2 posted 03-10-2012 06:22 PM

I have found it depends on the thickness and type of wood and blades used
if everything is square then the blade is flexing through the cut or you are moving it or the jig or what ever is being used is moving in the track make sure the rip is also straight on the wood being used
I you ususally run scraps of the same wood being cut and adjust to the flex of the blade if need be to get the 45 degree I use a thin kerf carbide blade and incra slide hope any of that helps mahalo Joe

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Jim Finn

2409 posts in 2383 days


#3 posted 03-11-2012 01:40 AM

I make a lot of small oak and cedar boxes. (Hundreds of them) I cut them all in my DeWalt miter saw. One thing about making simple boxes: if they are not perfectly square it is not a big deal.

-- "You may have your PHD but I have my GED and my DD 214"

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gfadvm

14940 posts in 2151 days


#4 posted 03-11-2012 02:05 AM

I bought a digital angle gauge on sale at Woodcraft recently and it has REALLY helped with my mitered boxes. The other important factor is to be sure your miter gauge is square to the blade on the tablesaw. I never had any luck cutting these on my compound mitersaw. Third suggestion is sandpaper on the face of your miter gauge fence to minimize movement.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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handi

128 posts in 3901 days


#5 posted 03-11-2012 03:06 AM

Cutting a clean straight 45 with the saw blade beveled is a difficult proposition. Keeping the part dead flat and the blade from flexing is tough.

If I must make the cut on the saw, I’ll pre cut it just shy of the line, then make a second cut to the line. This second cut is less stressful and will be more accurate.

In most cases I prefer to pre cut the angle on the saw and then clean up the cut on the router table using a 45 degree bit. Using the bit also guarantees the angle will be exact.

Ralph

-- www.consultingwoodworker.com

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a1Jim

115202 posts in 3039 days


#6 posted 03-11-2012 03:21 AM

A good jig like Mikes can help a lot. Another way to go is when cutting your angles clamp your wood to your miter sled to prevent creep(movement) then after every cut put a “L” or a “R” on it with out adjusting your miter gauge to designate which side of the blade you cut the angle on, If parallel sides are the exact same size and you have one “L” and one “R” at each corner you should have a nice flush cut at 90 degrees. This way if one side is 44 degrees and the other 46 degrees you will still have a clean cut and a 90degree corner.

-- http://artisticwoodstudio.com Custom furniture

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devann

2200 posts in 2154 days


#7 posted 03-11-2012 06:01 AM

Here are the three things that I’ve learned to get accurate miter cuts for making boxes.

1. It doesn’t matter what type saw you prefer to use. It’s important to have a method of indexing the true angle required for the number of sides of the box.

2. Making certain that there will be NO movement of stock after you begin your cut until you finish the cut.

3. Using a “stop block” along the fence that will allow you to make accurate, repeatable pieces of stock of the same size.

-- Darrell, making more sawdust than I know what to do with

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TCCcabinetmaker

930 posts in 1816 days


#8 posted 03-11-2012 06:04 AM

IF the wood is not flat, it will do odd things.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

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wooded

362 posts in 1733 days


#9 posted 03-11-2012 06:25 AM

I use s smallish crosscut sled dedicated for 45s and also use a digital guage zeroing from the sled bed near the cutline. Always use stopblocks and maintain an even speed to prevent blade flex. I FIND A COMBIATION BLADE TO BE THE BEST. J

-- Joe in Pueblo West, Colo.

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doncutlip

2832 posts in 3017 days


#10 posted 03-11-2012 04:50 PM

Thanks all for the tips. Hopefully things will go better next time. I went ahead and glued up my box anyway, and as expected there are some gaps but I think it will hold together.

-- Don, Royersford, PA

View woodrookieII's profile

woodrookieII

243 posts in 2125 days


#11 posted 03-11-2012 05:01 PM

These are all good points: precise equipment setup and no stock movement being critical. And I use 2 straps when I do the glue up, checking for square with…well…a square of course. :)

....rookieII

View TCCcabinetmaker's profile

TCCcabinetmaker

930 posts in 1816 days


#12 posted 03-11-2012 05:41 PM

well if you are using a sled….

make sure you don’t have too much side to side movement in your mitre guage slot when using the sled. If there is, it can start in one spot and finish in another when the blade pushes it to the other side. Which is a pretty good reason not to use a mitre sled.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

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Sawkerf

1730 posts in 2530 days


#13 posted 03-11-2012 05:49 PM

Another possible problem could be the length of your pieces. If the opposing sides aren’t EXACTLY the same length, you’ll get three nice joints and the fourth will be off.

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

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woodrookieII

243 posts in 2125 days


#14 posted 03-12-2012 12:50 AM

Sawkerf: good point!!

.....rookieII

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CharlieM1958

16241 posts in 3680 days


#15 posted 03-12-2012 01:09 AM

I was just getting ready to post an answer, but I see Sawkerf took the words right out of my mouth!

-- Charlie M. "Woodworking - patience = firewood"

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