Pursuing perfect miters
Methods and equipment for achieving the highest quality. September 20, 2003
How are you professionals cutting perfect miters for the libraries, entertainment centers and other beautiful work that has been displayed on this forum? I have a DeWalt 708 and it is a nice saw, but the damn blade flexes as I cut into a piece of moulding, therefore creating a non-perfect miter, which as you know leads to a hassle when trying to attach to a cabinet. I know some of you like DeWalt and some don't, but seriously, are the miter saws you are using cutting excellent miters and are you using special blades that are more rigid? I want to know the secret, because I am sick of fighting and dreading the trim installation on our cabinets.
Something that might help is to make an initial cut a bit big and then take another 1/32" off in the finished cut.
From the original questioner:
I have tried that, but I still get a problem with the blade "bouncing" off the material. Maybe it is the blade I am using and I just need a more rigid blade?
My DeWalt does the same thing, as do many of the other saws I've used. I kiss most of my miters, when practical, on my 20" disk sander with a jig I've made. I guess I've just learned to deal with the fact that a little extra work is required to get a perfect fit. I also use a sanding block or block plane. I know some who swear by miter trimmers, too.
I used to ask the same thing when I first got my chop saw many years back. But the truth is you can't get absolutely perfect miters with just a cut (unless maybe you have one of those Omga heavy industrial machines on a factory line, but I have never used one of these so I can't really comment). I get as close as possible with a contractor miter saw, then usually have to take a minute or two to file, or on an outside miter, I will take the tool I use to re-edge my scraper (can't remember the name, but it's some cylinder very hard tempered steel tool) and use it to bend the fibers on the edges of the outside of the miters. You can make 1/32 or 1/64 gap completely disappear with just a few passes on each side of the miter. Quick sand and you have a perfect miter. Only way I have ever gotten "perfect" miters.
Just remembered, it's called a burnisher. Use that tool to close any gaps on an outside miter. The problem for everyone is we see Norm make one cut on his miter box, then walk over and put together this perfect joint in the New Yankee Workshop. Perfect miters take but 2 minutes. Ever wonder why they only show one joint go together? I am sure if we had the unedited (and uncensored if it's anything like in our shop!) version, we would all feel better and our customers wouldn't ask why a project takes so long and costs so much.
The first thing is try and make sure the saw has developed its top speed before proceeding with the cut. Once at full speed, cut the piece, then while the saw is still spinning at full speed, slide the cut piece away from the blade, then release the trigger to stop the saw.
This is a bit of an “advanced” move (for lack of a better term), but can help a great deal. If you feel confident that you would not cut some part of your body off, give it a try. If you don’t, then don’t!
I too have the same problem and one day I read that thin kerf blades usually made the problem worse. Those that switched back to full kerf blades said it made a big difference.
Of course I have not switched over yet, so I can't tell you first hand if it is true, but if you're using a thin kerf blade, it might be worth a shot. To remedy the problem, I now cut all miters on my table saw with a sled I made. Doesn't work in the field because the saw is too heavy to lug around.
From contributor S:
The disposable miter saws are the problem, not the solution.
First solution is a fixed knife miter chopper. A large Euro cast iron baby that doesn't even plug in. Step on the pedal and a sharp as a scalpel knife head moves down and slices miters that are dead perfect. You won't believe the quality of cut. Used mostly in old picture frame shops. Don't fall for the Lion trimmer of Taiwan copies - go for the real thing or you'll be back where you are now. Festo and Morso are two brands I know of that are good.
If you like the sound of power equipment, then look at CTD saws. They are linked on this site somewhere. We have one and love it. It is solid cast iron, with a regular type Dayton motor, and the whole thing pivots on bearings and swings like a dream. Does repetitive miters like a dream. Ask the CTD folks for the blade they recommend and get two. Do not compromise on the blade. They are the experts and will get you a great cut if you ask them.
Obviously, either solution has its costs, but will get you tight and square. The "consumer" miter saws are just that - to be consumed.
From contributor D:
The best way to achieve a perfect miter joint is to follow contributor S's suggestions.
But if you are the average Joe, you use what you have or get what you can afford. The DW708 is a 12" sliding compound miter saw. Perfect miters are elusive. First, you must have a perfectly tuned saw with no slop in the slides or runout in the arbor. Part of the operation is manual - the part where you must push the saw straight through the wood. It's awfully easy to push or pull with pressure favored to one side or the other, creating a not so perfect cut. Then there is the matter of the 12" blade. The farther from the arbor the teeth are, the greater the opportunity for flex and vibration to set up when the saw is under power, and a thin kerf blade is even more prone to such flex. You'll have better cuts with a smaller diameter, thicker blade, all else being the same. I use a 12" Dewalt compound miter saw and long ago gave up on thin kerf blades. Unfortunately, 10" blades usually come with 5/8" arbor holes, which won't fit the 1" arbor of my 12" saw. 10" blades can be ordered with a 1" hole but I haven't done so yet. Sharp blades are a must and the saw must reach full speed and maintain as much of this speed as possible when making the cut. As the blade slows while cutting into hard woods, the blade will often move along the intended kerf line and deform the cut, albeit very slightly. Another culprit to a ruined cut is when the wood slips on the saw table or fence. This can be very difficult to feel, but it only has to move a micron or two to ruin a perfect cut. Pay attention to all this stuff and your cuts should improve to at least be acceptable.
By the way, I can't usually tell how precise the joints are on Norm's show since there is usually so much glue squeeze out when he puts his joints together. :-)
My own experience has taught me to buy the absolute best blade that I can afford. For a really good 12 inch blade, you may have to spend a hundred bucks or so. I have a 12 inch DeWalt cms, and it has been a good saw, but the 10 inch Hitachi belt drive seems to produce a better cut. I have been told that the belt drive will help to eliminate a lot of the vibration from the motor. You also have to pay attention to the blade itself. Some blades aren't ground properly for use on a cms, and they will flex, or shift when they hit a hard spot in the grain. This is what the guy at the tool store, not H.D., or a place like that told me. It seems to be true. I personally would stay away from the 12 inch saws, and stick to the 10 inch saws where possible. The blades are less, and all of the cms saws seem to have the same cut capacities when used on a 45 degree miter. Hope this helps, as I too have had this problem.
From contributor V:
I have the DeWalt 12" double compound sliding miter saw. The 12" 60 tooth blade with the 5 degree negative hook that comes with the saw is junk. I use it to cut laminate flooring and other difficult material that I wouldn't want to damage a good blade on. I have a 12" ATB with 30 degree bevel grind, 100 tooth 5 degree negative hook blade on the saw. This is a 1/8" kerf blade. I have used it to cut 3 1/2" thick red oak, 6/4 hard maple, etc., and have gotten excellent cuts from it. This blade goes for $150. It is also important to tune up the saw occasionally. I check my saw with a machinist square to set the blade to the table and the fence, and then make the adjustments to the miter and bevel scales. Other things to check for are arbor run out and play in the guide tubes. You can adjust the allen bolts on the top tube to increase tension and remove some play from the slide mechanism. I like the design and capacities of the saw and the high fence, but the designs of these type saws in general makes it easy for them, if not handled carefully, to get out of adjustment or damaged. If you are the only one that uses the saw and take good care of it, it will cut well. If your saw gets knocked around in the back of the truck or on the job site and it's being used to cut deck lumber and everything else, chances are when you need to do precise work, you won't get the results you are looking for.
I remember reading a column in Wood & Wood Products by Jerry Metz about cutting miters. He recommended cutting the miter a little greater than 45 degrees (in the case of a 90 degree angle) so that the tips of the miter just barely touched before the rest of the joint. This makes for a better looking joint and it won't open up with seasonal moisture changes in the wood.
I use a 14'' radial arm. I tune it up at the 25 inches cross cut, getting it as close as the human eye can see or finger can feel, if it's that close at 25 in. It's even closer when only cutting a board a few inches wide, sharp blade, no flex to mention. On the job I use an old DW705 (11 years old) 12'' thick kerf, keep it sharp, never noticed a problem. It's not a slider, just compound chop… would that matter?
I've had good success with a straight miter saw, not compound, not a slider. Mine is an old but well tuned Makita. I also use a Freud LU 85 10" blade on it and that makes a good enough cut to assemble and finish without having to play around. I've bought a few saws over the last years and all the blades that came with them were not good enough to produce the cut quality you're looking for.
Whenever possible I use my 10" miter saw for crown until it gets too wide, then I use the 12" Dewalt. I have found the cut contributor V uses where you go a bit stronger than 45 works well.
I also have the Dewalt dw708. I recently purchased one of Dewalt's newest blades. I think it is an 80 tooth blade and can't remember the model number. What a difference in the cut! And it was only $50. When mitering/cross cutting the end grain feels like it spent much time on the sander and the saw cuts like the hickory is butter. What a deal. I also purchased one of their new ripping blades for the cabinet saw. Very nice cut again and this blade was even cheaper than the miter blade. I would have expected to pay twice as much or more for the blades considering the quality of the cut.
I use an 80 tooth blade also, ground to 55 degrees. Very pointy. I've been working this angle on my blades for the last two months and am happy with the results. This was after consultation with the sharpening service. Good clean cuts. I also hold the stock down real tight so it cannot move at all. And I try and keep it as steady as possible with just enough pressure to push it down so it's not springing back at me. Now I don't know how that sounds when it's got full speed and vibrating. The bottom line is, precision cuts are just that. You have to work like a doctor. Wouldn't it be nice to charge like one.
From contributor H:
12" triple chip should do the job each time. Good clean cut but you should know that there is not much need for a perfect miter in the field. In the shop it's a different story and most of us have a jig or sled made up for this application.
Just an afterthought... My cuts got much better after I went and bought the thing-a-ma-bobs that attach to the table on the saw to hold the moulding in just the right angle. Now I can push down really tight on the moulding without worrying about it flipping down on me. A long infeed/outfeed table on both sides set to just the right height makes a world of difference also.
From contributor P:
Perfect? Miter saws won't get you there. The trimmers as per contributor S will, as will a good heavy table saw with a sled jig. Miter saws cannot give the blade support (heavy arbor supported by large, closely spaced ball or needle bearings) and vibration damping that a good heavy cast iron table saw can. Drawbacks? It's s-l-o-w, baby! Are you getting paid for perfect?
From contributor D:
Very well said, contributor P. It took me many years (and constant reminders from other businessmen) to recognize your point about "perfection".
Contributor H, how can you recommend a triple chip in order to achieve a perfect miter cut? Triple chip saw blades are designed for composite materials like melamine boards. Take a look at the A-shaped tooth within a triple chip saw blade. That's where your problem starts because that tooth generates so much cutting pressure that your molding or trim will be forced away from the saw blade. In order to achieve a good miter cut, you need the right machine, needle bearings and so on, as well as a saw blade with a 0 degree or a negative hook, because a miter saw works the same way a scoring blade works. Tooth combination needs to be ATB. And at last, a little trick of trades - take some stain with you when you install trim at the site and stain your miter cut - that covers up a lot of crap and saves you a lot problems.
From contributor H:
I have had a lot of good cutting with the triple chip - that's the only reason why I am suggesting it. Most guys just jam through the cut and with a triple chip it just seems to do better and last longer. I do not do a lot of hardwood cutting, though. 75% would be pine with the balance being oak.
A 12" saw for cutting trim is overkill, unless you're cutting 4x4's. My Hitachi 8 1/4" saw has given me outstanding cuts for years, with no extra tune-up needed, and I even cut framing lumber on it when working on my house (different blade, of course). When I go back to crown mold, with a Forest Chopmaster blade or equivalent, it's as perfect as I can see - if only the walls were perfect, crown molding would be a breeze!
I have a DW708, and I have made table and desk tops, with a mitered frame around the top, 5 and 6" wide. I never got one of those to come out right until I got a better blade. 96 and more teeth and sharp are required. Any flex at all, and you lose. I have not tried a triple chip, but use high angle ATB's. Feed it slow, and flip the board, not the saw. One 90° detent can be made perfect, and the other one will then not be. I can make four miters around a desk top that look like nice uniformly fine pencil lines.
I have used too many different saws to mention, however the one thing that remains consistent is the effect of the even or uneven pressure on either side of the cut due to amount of wood being removed. When I'm looking for the best cut I sacrifice enough wood so there is equal pressure from both sides of the blade. For sliding saws I raise the material on the bed of the saw so the bade is cut more tangent to the blade. Anyone else had similar experiences?
From contributor D:
Absolutely. It's very difficult to get a good cut with only one side of the blade cutting wood. Unless the wood is extremely soft, the blade will most often wander away from the cut line, producing a cut that is not perpendicular to the saw blade, through and through. Those times that have required me to remove only a partial kerf, it must be done very, very slow and making a full cut with a slow movement can (itself) lead to an inaccurate cut or burned edge.
I haven't done enough work with a sliding CS but what you say makes perfect sense.
When I had a portable saw set up for miters, I used a 10" full kerf Chopmaster blade in a 12" DeWalt (non-sliding) saw. The DeWalt arbor was 5/8" and used a bushing to get to 1". This worked much better than a 12" Chopmaster blade. I also built an auxiliary platform and fence system using DeStaco clamps for holding. It just wasn't possible for me to hold the work rigidly in place by hand. Now I used a CTD D45 that I got used from a frame shop. Perfect for the repetitive work that I do.
I am a contractor slowly moving full time into cabinetry and casework. Over the last 15 years I've owned several of the compound miterboxes. The Delta 10" sidekick and 10" Hitachi have cut many a "perfect joint". I wouldn't recommend the 12" Dewalt even for door casings. I like 60-80 tooth Freud blades for trim work. In the shop I find myself using the table saw and miter gauge for precise cuts.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor A:
I too have had problems cutting "perfect" mitres on the chopsaw. With 5 years picture framing and 12 years as a professional furniture/cabinetmaker I would like to add my perspective. It is simply not possible on a cms or cs to make this kind of cut on anything larger than 2" wide and more than 3/4" thick.
I was asked to make newel caps from 2"x6" (net size) eastern maple. These caps are just 4 "perfect" mitres coming together in a perfect center point. Not only that but they had to be perfect all the way through and on the bottom as well, and I mean perfect, as nothing less would be acceptable to the owner. So I puzzled over this problem for many weeks until I came up with the answer. I cut the miters on the bandsaw! Then I cut them perfect on the shaper. It's a simple jig and with a sharp square cutter I had them done in no time.
I made an extra cap and I show it to visiting woodworkers and watch as their jaws drop when they realize just how difficult it is to do this. Not only are the mitres hard to cut, but the assembly is not very easy either. Things get very slippery when the glue is on. Anyway, if you want truly perfect mitres and are willing to spend the time, this is the only way. No other piece of equipment will do this kind of job. No matter how smooth they cut, a rotating saw blade will not leave a perfectly smooth or square surface. A shaper will. Guillotine style cutters are good but cannot handle material this size or shape.
Comment from contributor B:
I have cut 5-6" wide miters with the DW708, and never got one to come out right until I got a really good blade. There are several out there. Thin is not good; lots of teeth and high bevel angle are. I also made a 90° fixture to set my planks in and then usually cut both at the same time with a miter cut. As long as the miter joint looks like a pencil line, I am happy with it. If the edge of one stands a bit proud of the other, I will take that off with a plane, and no one will know except some machinist with a micrometer, and he will begin to doubt his mic. I also use those little beadlock tenons and poly glue in my wide miter joints, instead of biscuits. It seems to work better; I don't know why, but it does.
Comment from contributor C:
For panel mouldings and similar trim pieces that make up a nice wainscoat job or ent center I like to cut my material first with the mitre saw just a bit oversize. Then I use a hand me down tool that came from my grandfather. It is a mitre knife and it will slice a perfectly true and clean mitre every time. It is an extra step but it makes a huge diffference, especially on eye level focus areas. I think these are also used in the picture frame industry.
Comment from contributor E:
I hear all of your pain... I have found the sled approach is best for machine cutting. However, unless you clamp all parts down, you still get shift - and the machine marks still require a quick clean up that risks loosing the perfect plan for a flat surface.
Frustrated, I reverted to an old-style over-head frame guided large miter hand saw for all miter cuts. Dead-on, baby's bottom smooth cuts and matches, every time. But you gain an appreciation for the strength it took in the old days, with eight cuts per frame.
Since the blade is very fine toothed, it must be sharp. Make sure it is shiny clean and apply a few drops of camillia oil with your finger. Cover the teeth and depth of cut on the blade. The camillia oil is expensive, but lasts forever and is amazing. It reduces friction and speeds the cut without staining the wood or gumming up over time. Really great on sharp chisels, too.
With that setup, I can get first-time perfect miter-matches with extremely dense/figured woods or pine, it doesn't matter. (Except for the workout!) And it's portable with no electricity requirements.
Comment from contributor F:
I install mouldings on a daily basis. For the most part I'll do crown, cove, and light valance with little enhancements from time to time with rope moulding or dental. Everything I install is pre-finished and no patching is possible, so a perfect miter is expected.
The materials are mostly birch, cherry, oak and maple, then of course the thermal foil on mdf and that annoying film. For a nice miter in the solid wood mouldings, the stiffness of the blade has never bothered me. I use a 12" blade often with 72 teeth and acheive great cuts. The 12" tends to wobble, but the cut is very nice. I do what some others have mentioned here and make the initial cut close to the point, then simply glide the blade through the last 16th or 32nd to get a clean line. I also find that when you cut of that 16th at a decent speed, the bare wood accepts the glue very well and gives a stronger joint. When I used to use 100 teeth on a 10" blade I would run the blade through a lot slower and found the heat can polish the wood and leave it less pourous.
One last point for getting a seamless miter joint. If you cut piece (A) at a 45 degree, then cut piece (B) at the connecting 45 degree, you will want to leave enough for a retrim before the final cut. You will want to be sure the 45 degree cut on each piece is exactly the same.
If either piece is off by 1 tenth of a degree, they won't join evenly in lengh, even if it's a perfect cut.
Whenever possible, try to make your joining pieces from the same strip of moulding. If profiled like crown moulding, two separate 8' lengths can deviate a bit in profile.
Comment from contributor J:
I noticed that my Dewalt 12" slide miter saw's 45 degree notches were not stamped correctly. If you adjusted the right, the left would be off and vise versa. When a buddy called Dewalt, he was told the saw was not a trim saw. I think you need to cut the plate in two so you can adjust the right and left independently.
Comment from contributor O:
I make picture frames, and I use the original Lion miter trimmer. I have found it to be the perfect tool for this type of miter. For mouldings I use a trick my dad showed me - it takes a little longer but turns out really nice. I cut the piece I want slightly proud of finished and then I back-cut and cope the miter. When assembled the pieces fold over into each other and it is the tightest crown or trim miter you will ever see.
For large pieces I use a cabinet grade table saw and a sled that is dead square to the runners in the table, which most often produces a very fine cut. I use a custom made Forrest blade to make my miters for frames and then trim them on the Lion trimmer. Changing the blade is worth the extra effort, and often I can glue them together without using a biscuit.
Comment from contributor K:
I've had excellent results with the Delta Industrial 36-412 12" Dual Bevel Miter Saw for cutting pre-finished hardwood crown. This is not a sliding saw, but out of the box it cuts very accurate glassy smooth miters. It has built-in crown stops which are easily tweaked so the bottom edge of the crown fits flat against the vertical fence. I was concerned when I bought it that the gear drive would cause chatter in the blade, but it runs very smoothly. With an upgraded blade it's a dream, within its size limitations.
Comment from contributor G:
This is what I do. First off I use glue on all my miter joints. On a job site I keep it with me as well as a piece of 180 grit sand paper. I cut my pieces a little long, and trim them back to fit as tightly as possible. I think it's important to dry fit everything especially if working with stain grade material. Once I'm happy with the fit, I apply the glue and nail it. You want to apply enough glue that it squishes out. With a damp rag, wipe the excess and use the sand paper on the corner. Remember to sand lightly as to not distort the sharpness of the corner too much.
What happens is the dust from the sanding sticks to the glue and closes the gap. The glue dries, and dusts does too. Once it’s stained or painted you can’t tell there was ever a gap in your joint. Doing this as you go along does two things - it saves you the time of going back and inspecting all your joints and trying to fill the gaps. Also, if you're on a job site where foremen are constantly walking around looking for things to pick apart, you look like a champ because to the eye, your miters look great. 1/16 of an inch is about as big a gap as you want to fill this way. Any bigger and it looks ugly.