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Mitered table joints do not fit

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Forum topic by Henry82 posted 05-22-2018 08:53 PM 862 views 0 times favorited 22 replies Add to Favorites Watch
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Henry82

3 posts in 124 days


05-22-2018 08:53 PM

Topic tags/keywords: oak joining modern

Good day everyone!

I am creating a small TV table with mitered corners. The material is purchased Oak glued panels.
After cutting at 45 degrees, it turns out the corners do not want to fit. The saw i used was electronically controlled and is used in furniture factory. I am suspecting that the panels are warped or something. Any advise is welcome.

Thank you for the time.
Henry


22 replies so far

View Mario's profile

Mario

181 posts in 3515 days


#1 posted 05-22-2018 09:30 PM

The saw is not cutting at exactly 45 degrees….......and make sure you have a square assembly when gluing

View fivecodys's profile

fivecodys

1128 posts in 1755 days


#2 posted 05-22-2018 09:37 PM

My guess is warped panels. Is it a panel saw you are using?

-- There' are two theories to arguin' with a woman. Neither one works.

View sras's profile

sras

4874 posts in 3248 days


#3 posted 05-22-2018 09:47 PM

One or more of:

Incorrect angles (saw set slightly off, piece was positioned slightly off during cut)
Warped wood
Inconsistent length of pieces
Misaligned at assembly

It seems to me that if it was just warped wood, the joint should be tight in at least one spot along the joint. I guess that would depend on how it warped. A straightedge might help show any warp.

-- Steve - Impatience is Expensive

View Loren's profile (online now)

Loren

10477 posts in 3767 days


#4 posted 05-22-2018 09:48 PM

Case miters can be tricky to get right if the
panels are warped at all, which is likely.
The warping results in curved miters, miters
which are off 45 by a little, or a combination.
The 45 degree stop on the saw could have
been off but if the panel isn’t dead flat when
sawed (can be clamped flat sometimes) the
miter will not be perfect.

It takes some discernment and patience, but
the miters can be fitted by attaching a piece
of coarse sandpaper (a cut piece of sanding
belt is ideal) to a flat surface like melamine
or mdf and rubbing the parts back and forth
apply pressure to remove material where you
want.

This sort of device can be used to flatten boards
for mitering. (image from Home Depot)

View Aj2's profile

Aj2

1661 posts in 1917 days


#5 posted 05-22-2018 09:55 PM

Here’s my diagnosis from a thousand miles away.
If they were cut 1 hour ago then the saw was off.
If they were cut 1 week ago you waited too long and the wood warped.
Miters are very tricky

-- Aj

View Woodknack's profile

Woodknack

12336 posts in 2499 days


#6 posted 05-23-2018 12:52 AM

Get a protractor and measure the angles.

-- Rick M, http://thewoodknack.blogspot.com/

View Charlie H.'s profile

Charlie H.

260 posts in 769 days


#7 posted 05-23-2018 02:43 AM

I think mitered joints this long are very hard to cut even with careful setup.
The slightest wiggle during the cut and it’s hosed.

If you did not machine the panels to all be flat, square, and the same thickness it turns a difficult build into an impossible build.

I don’t know what kind of furniture factory saw you have access to, but the store bought furniture I have taken apart and examined / repaired has not had precision cut joints.

-- Regards, Charlie in Rowlett, TX --------I talk to myself, because sometimes I need expert advice.---------

View recon49's profile

recon49

7 posts in 124 days


#8 posted 05-24-2018 03:57 AM

It looks like not perfect 45-degree angles to me.

View enazle's profile

enazle

66 posts in 127 days


#9 posted 05-24-2018 05:46 AM

You need to make yourself some miter joint assembly jigs out of 3/4 shop plywood. Use C-clamps or wood clamps to draw your miters up tight. Let me know if it isn’t clear what to do?

View Henry82's profile

Henry82

3 posts in 124 days


#10 posted 05-24-2018 07:25 AM

Thank you all for your quick response.

The workshop i used had computer controlled saws therefore i assumed everything is accurate and square. I try to get myself a protractor and measure the angles.
Unfortunately i did not indeed machine the panels flat, before cutting. Does that mean i should discard the plan of TV table and make some floating shelves from the material (another project i want to make and seems more easier)?
I forgot to mention, the panel width is 40 cm (15 3/4 inch)
Enazle, i will try out your jig. and see, if i can press them together.
What kind of glue you guys recommend? I read from other topic that 2 compound epoxy is most suitable (strongest) for mitered joints like this, or can is stick to regular PVA?

Regards Henry

View Loren's profile (online now)

Loren

10477 posts in 3767 days


#11 posted 05-24-2018 07:58 AM

PVA fills gaps adequately but isn’t very strong
when it’s tasked to do that. Polyurethane
glue foams up and expands, filling gaps very
well and with good strength, but it’s messy
and spoils in the bottle.

Epoxy would probably work well because it
can fill gaps with integrity.

As I mentioned above, the joints can be sanded
with some elbow grease.

View Henry82's profile

Henry82

3 posts in 124 days


#12 posted 05-24-2018 08:03 AM

Thank you Loren for the encouragement, I sill try to sand the angles right and see what happens.

View bonesbr549's profile

bonesbr549

1576 posts in 3186 days


#13 posted 05-24-2018 12:39 PM

I think all gave some guidance, but I’d also check to make sure your sides/ends are all the exact same length. I don’t mean you had a pencil mark to cut your pieces, but a stop of some kind. I had that problem and it masked itself as a miter issue. I’d also ask when you cut that 45 is that final cut just shaving off a hair. Depending on blade, you could be having some deflection there. I cut them close then the final pass is a shaving and that will fix it some times.

Finally, get a precision angle 45, and check it. Run several through it and are there any differences. If so, your arbor lock could be slipping a hair.

Good luck !

-- Sooner or later Liberals run out of other people's money.

View tomsteve's profile

tomsteve

808 posts in 1338 days


#14 posted 05-24-2018 01:34 PM

there are corners open on the inside and corners open on the outside- are the lengths of opposite sides equal? is the box square?

View Rich's profile

Rich

3544 posts in 708 days


#15 posted 05-24-2018 03:14 PM

It’s unfortunate to see so many inaccuracies being promulgated regarding the characteristics and performance of various glues. Fine Woodworking did thorough testing for their July/August 2007 issue that should clear the air. Patrick, of Old Brown Glue, has a PDF of it on his web site:

http://www.oldbrownglue.com/images/articles/HowStrongisYourGlue_FWW.pdf

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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