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Dave_c

45 mitres

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Hi All,  Now at my limit of frustration with 45 mitres!! i have cut them on my dewalt compound mitre and tilting the blade over on my tecnica panel saw. Referencing off the bed then on the blade with my wixey gauge. The two surfaces meet up fine but when pushed together all looks ok, BUT at 45 there a slight gap aarrhh! On the panel saw i think this is because there's low values of 45 and high values of 45!!! the gauge says 45.0 but i can still advance the tilt until 45.1 appears so obviously 45.0 isnt 45.0. As for the dewalt its just not up to the job to be that accurate. 

Is that the difference between 45 on an building site and 45 for furniture? How do people overcome the inadequacies in their saws to cope with this? i have a friend who has a bit of paper folded 3 times he places between the stock and fence 300 to the left of the blade on his saw (new makita)........another suggested a 45 shooting board. How do you get an acceptable degree of accuracy to start with?

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Larger, heavier, more expensive machines have a better chance of maintaining accurate setpoints. A sliding miter saw is designed for carpenters, not furniture builders, and generally will be difficult to set and lock to a perfect angle.

I find that when such precision is needed, a carefully built jig for my table saw gives me good results. The shooting board and hand olane is another good option.

Understanding the movements of your machine, where and how it might shift or flex under stress, is key to using it effectively. And sometimes, the machine is just not up to the job.

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I never trust the built-in angle gauges or stops on tools. Using the wixey gauge is better, but still may need some test cuts and tweaking. If you do a lot of miters, it would serve you well to make a shooting board or dedicated 45* sled for the table saw.

I have the Incra 1000HD miter gauge and have been very pleased with its accuracy out of the box.

I took a picture frame making class and they had a Festool Kapex to cut the miters. One student asked how to verify that the miter saw was set to exactly 45*. The instructor said something along the lines of, "It's Festool, you just know it's right. You have to use a square to check other brands, but not this one." Guess what? Everyone ended up with gaps in their miters.

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A panel saw and a miter saw are fine tools for the tasks they are designed for.  Trimming out a kitchen and building a furniture-quality sideboard are different tasks.  A lot of folks turn to miter sleds on their tablesaws for this task.  There are even versions where the angle doesn't need to be perfect as long as the two mating faces are cut on opposite sides of the jig.  What works for you is what works.  I just run a basic Incra V-27 miter gauge on the tablesaw.

694181321_5X5Frame(16).jpg.3cd71bb4141f9b091353bc86462fa0aa.jpg

This is not necessarily super helpful.  Someone showing me the air-tight dovetails they can cut by hand does not make my fussy attempts at them any better :).  I needed to work at it till I found the method that worked best for me (and I'm still not very good at them).  If you Google 'miter sled for table saw' you will get a selection of methods to try.  One of them will become your favored way of doing this.

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The blade matters too.  A lot of them will pull ever so slightly one way, or the other.  Often not so much the blade, but the sharpening, or lack of it is the cause.  I can get perfect miters off several saws, with a good blade, or none of them with a blade that's not perfect.

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Are we talking casework miter or picture frame miter? They are different worlds that require a different approach. Both an accurate 45 degree square is a must.

The other option is to remove the 45 degree angle from the equation. If the blade is set to 43 degrees for example one side cuts 43 the other side cuts 47. I cut my miters at a table saw with a jog that holds the parts at 90 degrees and cuts the miter on opposite sides of the blade. Can't mess it up that way.

Reference for picture frame miter

 

Reference for casework miter (bevel)

 

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I always cut my miters at the table saw with the aid of a Wixley and have had good results.  The blade in the table saw is more stable as is the bed to reference from.  Most of my miters have been for boxes of one sort or another and if there's gaps they're too fine for my eye.

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So much great advice given above!  

IMO, people try too hard (and often fail) to get perfect 45s.  The only thing that really matters is perfect 90s.  If you have 44 on one side, if the other side is 46, the eye will never notice that one degree difference.  I built and use a sled at the table saw to get great results.

In the end, find a method that works for you and stick with it.

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One thing you didn't mention, but I assumed - are the miters you cut part of a rectangular frame? If so, one important item is often overlooked. The opposing sides of the rectangle must be EXACTLY the same length, or you will have gaps, no matter how perfect the angles were cut. Cut the parts together if you can, use stop blocks if you can't, and if that can't happen, cut piece #1, both ends, then one end of piece #2. Then, stack the parts and use your fingertips to feel for when the ends are aligned, they should feel like one piece. Now mark the opposite end of piece #2, using piece #1 as a gauge.

Transferring measurements with a ruler is almost impossible to get perfect.

Especially with a metric ruler! /*ducks and runs*/

:D

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3 hours ago, ..Kev said:

So much great advice given above!  

IMO, people try too hard (and often fail) to get perfect 45s.  The only thing that really matters is perfect 90s.  If you have 44 on one side, if the other side is 46, the eye will never notice that one degree difference.  I built and use a sled at the table saw to get great results.

In the end, find a method that works for you and stick with it.

Kev, can you post a link to your picture frame miter sled? 

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Thanks for the comments getting some good ideas.  Have include pic of saw and the frame i'm making, the end product is going to be a coffee table, clear epoxy up the holes.  A couple of projects to try i might try a mitre sled on the saw or even build a 45 shooting board which would allow finer adjusting of the joint.

IMG_2600.jpg

IMG_2601.jpg

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The margin of error for a design like that doesn't approach zero.  It is absolute 0.  Also, even built perfectly, the odds of it staying perfect are about the same.

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9 hours ago, K Cooper said:

@gee-dub, how did you darken the groove in your frame? 

It is a frame within a frame. The outer frame has a strip of leopard wood laid in prior to machining.

1891190987_5X5Frame(14).jpg.d9c1c7c19f861da7f1275ec69ac1885f.jpg

The angle of the other picture made the inner edge of the outer frame look like a strip but, it is actually a Peruvian walnut outer frame with an inlay.

1173598518_5X5Frame(15).jpg.fb3d07b474d1ac425334af9e3d26481a.jpg

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11 hours ago, Tom King said:

The margin of error for a design like that doesn't approach zero.  It is absolute 0.  Also, even built perfectly, the odds of it staying perfect are about the same.

a

yes! thats my point of frustration and  puzzlement how on earth can this be achieved with the saws that just dont appear to be up to the job of fine joinery? between 45.0 to 45.1  adds up to gaps when the joint at 90. Do people just accept the fact close enough is ok and clamp the hell out of it?

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The saw pictured looks like it should be capable. Is the panel you are wrapping sized correctly to 'float' within the frame? Perhaps the panel itself is a hair too large, and not allowing the miters to close?

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1 hour ago, wtnhighlander said:

Is the panel you are wrapping sized correctly to 'float' within the frame?

Critical,  Your panel must float or the table top will tear itself apart as humidity changes.  (I speak from experience - yes it was a coffee table.)

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