Fix a nearly perfect miter?

[Arlin Eastman]

Actually they are all imperfect and the result shows at the final joint.

A Lion Miter Trimmer will address this.  There are lots of knockoffs lately (so many that LION went out of business).
http://www.rockler.com/miter-trimmer?sid...gKvIPD_BwE


But a more precise adjustment of the miter gage will also address this.  A sled works better however.

I'd say your angles are not exactly 45°, they are just a little less, and the other corners aren't really 90°.  This is where a shooting board is your best friend.

John

Brad

What both of the guys said.  Did you use scrap first to make sure it would come out square?

You can always use a plane to shoot the edges square or a sander, but again try it out first on scrap.

Biggest thing is bad cuts compound themselves over cuts and yours might have been only 1/64 off  but after three or four cuts it gets worse.

Here is some Youtube I found helpful and some tools

https://www.youtube.com/watch?v=AgVthkUE4AU


https://www.youtube.com/watch?v=bSSnNOuDc74


http://www.leevalley.com/us/wood/page.as...at=1,42884


http://www.leevalley.com/us/wood/page.as...3553,49716


or hand tools

https://www.ebay.com/itm/Digital-Protrac...SwiqFahcbs

https://www.ebay.com/itm/Folding-Goniome...SwlbtalZhp

https://www.ebay.com/itm/0-200MM-360-Deg...0505.m3226


These will get you in the ball park of where you can angle the saw blade to the right angle.

Hope it helps

[mike4244]

I'm using an Incra 1000SE.  Upon clamping, *one* 90* miter doesn't close all the way.  The others do.  

Before I attack this and mess it up, can you guys advise me on what to do?  Yes, I know the miter gauge is off, but I don't know which way to go.

To fix it, do as Derek said. Use a fine tooth saw and cut thru the joint. 
To prevent this, try this method that always works for me.
I use a miter saw not a table saw but the method is similar.
Set the angle to 45- 1/2° instead of 45°. The result on all 4 corners will be a tight miter. Theoretically the joint will be open but in reality the joint looks perfect. This is an old carpenters trick used on outside miters of door, window and base trim. Works with picture frames too.
mike

[®smpr_fi_mac®]

Thanks for the advice, gents. Like I said, I'll tackle this problem properly when I can get to building a proper sled for table saw use, and then again when I build a hand tool bench for a shooting board.

[Cooler]

An easy way to get a perfect miter sled is to mount an aluminum framing square on the sled as accurately as you can.



Then slice right through the blade with your first cut.  A carbide blade will have no problems with aluminum.  

Then cut the left side of the miter on the left side of the framing square using the rabbet for the reference.  Then cut the right side on the right side of the square.  

If your framing square was 90 degrees to start then the result will be perfect even if you misalign the framing squae a bit.  If the right side ends up at 45½ degrees, then the left side will end up at 44½ degrees and the total will be 90 degrees.  

You can get similar results on your chop saw if you make a similar table top and leave the saw at the 90 degree setting, cuttint in either side of the blade.  Chop saw indexes are not accurate enough for picture frame work, but a table with a 90 degree  angle set in advance will work if you leave the blade at the one setting.

Here is a photo of a picture framer's sliding table miter saw.  The cuts are made on opposite sides of the saw.  The miters are always perfect.

The extrusions support the framing material.

[Derek Cohen]

I'm using an Incra 1000SE.  Upon clamping, *one* 90* miter doesn't close all the way.  The others do.  

Before I attack this and mess it up, can you guys advise me on what to do?  Yes, I know the miter gauge is off, but I don't know which way to go.

Earlier I suggested that the fix for this was a thin Japanese dozuki through the centre of the kerf. That is the one-time fix.

The reason for the joint being off, however, does not look to me to be a result of inaccurate set up, but user error. The kerf on the joint is not straight but rounded. This is why it is tight at the outside and open on the inside. It does not taper, which is what you would get with a straight cut. In other words, the workpiece moved when the cut was made. One rule, when sawing mitres, is that the work piece must be held steady. This can either from a clamp or a stop.

If using a shooting board, ensure that opposing ends are exactly the same lengths. Place them back-to-back and examine for this.

I built a mitre jig for my Hammer K3 sliding table saw. The critical component was that the ends had to be exactly ... and I mean EXACTLY ... 90 degrees. It does not matter then if the saw cut is a smidgeon off 45 degrees ... as long as the sawcuts are sequential.





This is based on one sold by Felder for $!!!! 

Regards from Perth

Derek

[Wild Turkey]

Use a Japanese dozuki saw (thin blade dovetail saw) to saw through the mitred kerf. The mitre will then close up perfectly.

Regards from Perth

Derek

Do the opposite corner too for best results.

Good luck!