Fine miters- miter saw setup and table saw
So I usually do a lot of different things, those that use miters I use my dewalt miter saw but they have to be good not necessarily perfect like a small picture frame. The pieces are also usually of the length that the table saw isn’t an option anyway. The big but here is that I was doing a small corner frame for a gift and found that I had the tiniest of gap on one corner of the inside miter joint. It’s probably a 64th at most but still bugs me. The frame was made of maple and paduak accent glued together then squared up on the jointer and planer and glued using a pair of 90 degree clamp sets.
Now my miter saw is well tuned, with a digital guage the compound adjustment is perfectly 90 to the table checked at 90 degree crosscut and at the 45 degree setting. The surface is flat and the fence is 90 degrees to the table. I only see a slight deviation front to back when the table is turned to 45 degrees but checked front to back though the blade is still 90 degrees to the surface on the angle. I further checked by cutting a miter in a wide board and do see some variation that I can’t seem to figure out.
Now that said, I know that a well tuned miter saw is very good but not necessarily at the level of precision that a multilayered workpiece cut at a 45 for a small frame is beyond having this slight deflection.
So first off should I just bag the super fine work on the miter saw and go to the table saw and invest in a good miter guage? Secondly is there any good way to adjust the rotating part of the miter saw table to make it more accurate. It really doesn’t seem like it’s something that has an easy adjustment and is probably a question of being worn but I am always willing to tune my tools for the best possible performance.
I will have to go back and dumb down the photos I’ve taken to meet the size but basically the only spot I am off is when I turn the table to 45 degrees and then check the level perpendicular to the fence which shows .5 degree dip from back to front. When the table turned back to 90 degrees there is no deflection.
Replies
Getting that level of perfection from any power tool is like a dog chasing its tail. In a picture frame there are 8 cuts. If each cut is off by 1/10 of a degree, when assembled you'll have one corner that's off by almost one degree.
I can't get any machine, much less a miter saw, dialed into 1/10 of a degree on a miter.
You can leave the last piece slightly long and creep up on the final cut to leave no gap. Shim between the workpiece and fence with paper or card stock to get the fit right.
I prefer to use a plane and shooting board to get a perfect fit. It's easier, faster, and more fun than chasing perfectionon a machine.
Well this is a two sided type frame so the combined tolerance issue as we called it when I did qc/product development in truck parts shouldn't be too big a deal but figured since I'm that close it might be something I could get trued up since everything else is dead nuts. I hadn't even thought about a shooting board but I have been neglecting my plane collection of late so maybe time for some love...
John_C2 has got it right no machine is going to give that type of precision, a shooting board is the way to go it only takes a pass or two to really tighten up your miter. You can find many different plans for building them on FW or Veritas makes one you can buy with an adjustable miter gauge and both Veritas and Lie-Nielsen make dedicated shooting planes, but I just use my Model 62 low angle jack plane.
There used to be a tool call a Lyon Miter trimmer that old time framers would use to shave miters to perfection but I don't think they are available anymore.
I know the old miter shavers but not something I'd use enough to justify the expense unless I stumbled across one.
I've always thought I'd like one of those miter trimmers. Every frame shop, ever, seems to use those, and that seems endorsement enough.
I use my miter trimmer that is set to 45. I do not do picture frames but use it for edge banding on chess boards. You have to very careful and walk up to the final fit. Probably a shooting board is a better solution. Frankly, if I was making a picture frame and was off by a tiny bit, I would just clamp it together.
Grizzly still sells miter trimmers. I bought mine for $35 with a set of new blades at an auction. The blades are very sharp. Just saying. . . .
It's more something only I'd notice but still... its only a two sided thing so I didn't expect and issue and it was clamped on a corner clamping jig with one of the old corner clamp blocks where you drill a hole in the middle, cut the wedge from one side and then use it to apply pressure type clamping setups as well. Its miniscule but just bugs me...
If I was doing a lot of miter cuts with a miter saw, I would leave the saw set to 90 deg relative to the standard fence and make an auxiliary fence system to hold the work pieces at 45 deg on both sides of the blade. Then I would cut the 45 deg angle on both work pieces at once. That way, even if the blade angle is slightly off, the error would be + on one side and - on the other and the resulting angle in the work piece would be accurate.
Well I did keep it in the same position and cut them on either side of the blade to cancel out any angle differences but this was more an issue of a kind of off plane- one corner of the miter skewed kind of thing. I know what you mean about making a special fence so that the saw stays at 90 and might be worth trying...
The problem with this is you’ve got lumber hanging out in limbo.
Support it.
Lee Valley still sells a miter trimmer: https://www.leevalley.com/en-us/shop/tools/hand-tools/32922-miter-trimmer?item=03H0101
That link gives me security flags fyi...
I used a Lion-style mitre trimmer for years to make dozens & dozens of picture frames. They are very accurate once set up but weight a ton and it takes time to get all the parts to the exactly correct length without under or over-cutting them.
Some kinds of mitres are beyond them as the workpiece shapes can't be fully cut by the trimmer's blade; or the workpiece can't be got completely on to the trimmer's bed and up to the knife.
So I sold it, eventually.
I can cut mitres very accurately on my table saw using it's sliding carriage with the crosscut fence set to 45 degrees. The fence can be very accurately set for that (or any other) angle; and it'll accurately shave o.1mm per cut off the workpiece end courtesy of the micro-adjust stop on the cross cut fence. But ... even the finest 80 tooth blade may leave enough saw-mark to prevent those hairline fits between the mitred parts. And in use, things can drift-off just a tad, especially the angle.
So eventually I made a chuting board and even a plane to use on it. This has a Veritas adjustable fence at it's heart but is otherwise made of scrap bits of various kinds. The trick is to use inert stuff where it matters, such as the heavy-duty impregnated (waterproof) chipboard used for flooring, which is dead flat and won't easily warp.
The chuting board also has a donkey's ear for shooting longer edges such as those of mitred corner little boxes (or even mid-sized ones).
The plane is a wooden item I made myself with a low bed angle, in the style of the Veritas mitre plane rather than their shooting plane. It has a Veritas fine adjuster and one of their blades as the metal parts. The blade is kept in the plane very accurately by use of four grub screws through the body that press on the blade edge. They can be set to keep the blade at exactly 90 degrees to the sole. That can be hard to do with just a Norris adjuster.
The chuting board and plane make glass-surface mitres that are very accurate indeed, so that the mitre-joins are those hairlines that can only be detected because of the change in the grain direction. Whilst the table saw can cut off 0.1mm, the chuting board enables the user to take just 0.025mm (1 thou of an inch) per pass if necessary.
A chuting board is the way to go for ultimate accuracy, as others have said - even if you have a machine that can cut mitres well. And most can't as they lack either the inherent precision or a means to accurately adjust them even if they are precisely made. Even their vibration can cause issues with mitres.
Lataxe
I see plenty of people making miter sleds that seems to work.
Minor trims can be done by padding with tape.
I agree. Once you get a good miter sled dialed in, you're good to go.
As RobertE referenced, I’ve used the same miter sled I built decades ago, plywood, maple fence, and cold-rolled steel miter bar. Still exactly 45 degrees, not a fraction out.
A tablesaw sled is the way to go. Every time you shoot a miter on a 4-sided frame you change its relationship with the other parts in an endless cycle. I might shoot a miter on door trim, but that's about it.
I have been down this rabbit hole and the thing that convinced me to leave the miter saw behind for this was an article (which I will never find again, sorry) pointing out that you can’t really set up a tool reliably to a level of precision tolerance that it was not designed for. Although some of them have pretty advanced features that make them increasingly useful for fine woodwork, a miter saw is fundamentally a job site construction tool. I have used the 5 cut method for squaring, and I have reached a point where the result is not repeatable from one test to the next, which tells me I am past the working tolerance of the tool.
I now use the tablesaw and am happy with the results I am getting for frames as well as box sides.
I use a miter saw for rough length and not final length. If you work logs to make boards, a miter saw helps get you to rough length after you have sawed off a plank. If I use it for miters, I always follow up with a shooting board until I am satisfied with the fit. It is like other tools in that it helps to make it zero clearance with a fence and a bottom hardboard under it so you can see where the blade is cutting. That's what I have learned by using one.
One possible cause is the workpiece moving during the cut. Mitre saws have a tendency to pull hard back towards the fence and with an angled cut this can move the piece. It needs only be a very small amount to put it off - it sounds very much like this is your problem. Firm workholding can help, but for accurate machine-cut mitres, the Table Saw is better as the blades are different and the applied force is perpendicular to the cut, rather than in line with it.
You can also use the William Ng method to check your mitre saw cut accuracy.
Miter saws just not accurate enough for fine woodworking - lots of movement and flex going on. And hard to clamp workpieces. I cut it rough on the miter saw, then use a miter trimmer too. I'm working on a jig for the table saw, and a shooting board, but for small frames and such, I use a (hand-powered) Nobex miter saw.
I haven't read all of the replies so far, apologies in advance.
My experience comes from years in the trades, having lugged a miter saw onto the jobsite and hanging miles and miles of crown, a bazillion miles of base and shoe, stairs, wainscoting, etc. Now, I've moved off the jobsite, into a shop and originally used my miter saw for a lot of rough cutting... and tried using it for the super accurate stuff... And, was never quite happy.
I've owned an Incra Miter 1000SE for years, but until I committed to being in the shop all the time, I didn't really make good use of it. Recently, however, I have begun using it and had excellent results!
But, I also have a couple of sleds for my table saw with known, commonly used, angles. I have a 45 sled I use for picture frames, door trims, small parts, etc.
Box building, and some of thew furniture building I do? That requires a shooting board, like others have said.
As stated in a previous post I use the miter trimmer where I have a very good base to attach the trim pieces. My 90 degree table saw sleds are set using the five cut method.
I use my miter saw for trim work and am amused, maybe even envious, by folks who have a high precision miter saw for trim work.. Nothing in my house is level or square, I am always fudging the cuts to accommodate for actual conditions.
For me the miter saw is for breakdown, the TS sled and trimmer are for precision work.
My version of the ultimate miter saw, 1958 DeWalt GE, 3hp, 24 inches stroke, 110t, 14 inches Royce blade.
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