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Precise angles - What's the best way to cut them?

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Blog entry by nobuckle posted 1021 days ago 7617 reads 1 time favorited 11 comments Add to Favorites Watch

I’m in the process of making this years Christmas gifts and one project in particular is turning out to be a real challenge. The goal is to create a mirror frame that consists of eight pieces with each piece having a 22.5 degree miter on both ends. For many this would be no problem, it’s just a simple cut on the ol’ power mitre saw. Not so for me. My power miter saw is anything but precise. “Why not use the TS?”, you might ask. I probably will, IF I can come up with a set up that is to my satisfaction. I have also considered using a shooting board and hand plane set up. While this may be more time consuming it may be the best way to obtain the precision I’m looking for. Below is a graphic of the frame I intend to make.

Ideally, I would like to make a deicated set up that would allow me to consistently make precise 22.5 and 45 degree miters.

I ask you, what methods have you used to create highly accurate miter joints? Your insight is greatly appreciated.

Thank you for your time.

-- Doug - Make an effort to live by the slogan "We try harder"



11 comments so far

View dbhost's profile

dbhost

5378 posts in 1863 days


#1 posted 1021 days ago

Don’t know about your “mitre” saw, but my Chicago Electric (see ultra cheapie from Harbor Freight) Miter saw cuts nice, accurate miters…

For cutting miters longer than the miter saw has the capacity for, I have no issues setting up my sliding miter table / fence for this function. On a standard table saw that would be a miter gauge with an extended fence…

If your equipment is too sloppy, fix it, tune it, or replace it with equipment that works. I have seen guys with some truly awful Craftsman direct drive bench top table saws cutting dead accurate cuts every time. They know their equipment and know how to tune it to their satisfaction…

You might be able to rig up some sort of miter / crosscutting sled for the table saw, but I won’t even try to go into how to set one up. Never needed one, so I don’t bother giving them much thought…

I just went and took a gander at your shop posting… It’s not like your miter saw is all that thrashed, or even all that poorly made. So I have to ask.. Did you spend much time setting it up when you got it? Your owners manual should have come with a set of instructions on how to adjust so all your stops are right at the angles you want. The big ones to check are 90, 45, and 22.5 degrees in both miter, and bevel. Once those are dialed in, everything else should more or less snap into place… Prep some good clean cheap boards for doing test cuts while you go through the setup procedure…

Or are you having trouble not related to setup such as slop in the knuckle, or arbor?

-- My workshop blog can be found at http://daves-workshop.blogspot.com

View romc101's profile

romc101

5 posts in 2137 days


#2 posted 1021 days ago

you can use a precise protractor and lay out your angle and using a straight edge as a guide use a flush trim router bit to flush trim it to the desired angle

-- Rob

View Roper's profile

Roper

1359 posts in 2344 days


#3 posted 1021 days ago

Just like in segmented turning you cut close to the angle you want and then take them to the disk sander with a guide and get the exact angle you want.

-- Roper - Master of sawdust- www.roperwoodturning.com

View chrisstef's profile (online now)

chrisstef

10692 posts in 1637 days


#4 posted 1021 days ago

Or you could use a shooting board and a hand plane

-- "there aren’t many hand tools as awe-inspiring as the #8 jointer. I mean, it just reeks of cast iron heft and hubris" - Smitty

View GSwoodworker's profile

GSwoodworker

74 posts in 1922 days


#5 posted 1021 days ago

I would not cut those angles on my miter saw. Not because of an accuracy problem but because they are to short. 5” at the longest leg and 2.515 on the shortest leg of that part. That is to small of a part for me to hold onto while cuuting on my miter saw. I would use my table saw with a home made sliding jig. Use a piece of plywood with a runner on the bottom that fits into your miter gage slot (just have it on one side of the blade no need to mess with a big sled). Lay your part on top of the plywood hanging over the edge where you want to cut off and use a clamp or 2 coming over the top to hold in place. You could come up with some easy stops screwed to the plywood. I have made one for cutting an od shaped picture frame holder like this. I used those brass threaded inserts into the plywood for clamping purposes. hope this helps.

View oluf's profile

oluf

256 posts in 1670 days


#6 posted 1021 days ago

Your project will require exact angles and exact legnth of all the pieces. If eather of these things is off . It won’t go togather right. If uou use a shooting board or sander to true up the angles, be sure to do them in pairs.

-- Nils, So. Central MI. Wood is honest.Take the effort to understand what it has to tell you before you try to change it.

View GregD's profile

GregD

612 posts in 1767 days


#7 posted 1021 days ago

If money is no object, get yourself an Incra Miter 5000. They also have a somewhat smaller and less expensive option.

If it is, I recommend a cross cut sled using a 30” commercial runner like this one from Kreg on the bottom of a piece of melamine or MDF. You’ll probably need a pair of T tracks in it for hold-downs, and you can use them also for holding fences at the appropriate angles.

For truing the fences the slickest method I’ve seen requires a dial indicator and a reference square. Drafting triangles would work. This method works for sleds that are only on 1 side of the blade. Clamp the square to the sled with one edge firmly against your fence and the other edge a bit proud of the cut edge of the sled. Attach the dial indicator to the table approximately where the saw blade is so that the indicator rides on the edge of the triangle. Adjust the fence & square so that the dial indicator measures no offset between the two ends of the square when you slide the sled along the miter gauge slot. There is a video of this somewhere here on LJ. Drafting triangles for 90 and 45 degrees are easy to find and accurate. Not sure what to use for a reference for 22.5 degrees though.

-- Greg D.

View William's profile

William

8976 posts in 1473 days


#8 posted 1021 days ago

I have an Osborne miter guage for my table saw. It is the best I have ever found for making repeatable angle and length cuts. It has possitive stops for every five degrees of angles, and also for common angles such as 22.5. It has a stop for up to four feet of length that can be flipped up out of the way and then back down to make another identical length cut with amazing accuracy. Since buying it, I haven’t used any of the several dedicated sleds I used to use. I no longer have a need for them.
The only problem I see doing what you are with the Osborne is the short length. When I have to do anything shorter than about four inches long, I use a spacer block between the stop and the material I’m cutting. This provides enough stability to do lengths as short as two inches. At least that’s as short as I’ve cut. Anything shorter than that and I, personally, am too nervous about how close it puts my fingers to the blade when doing sharp angles.

-- http://wddsrfinewoodworks.blogspot.com/

View KenBee's profile

KenBee

108 posts in 1266 days


#9 posted 1015 days ago

I lay my miter joints out by hand then rough cut them on my BladeRunner. Once I get them rough cut I set my Incra router table miter gauge to the desired angle and using a 1/2” spiral bit trim them to the line. I don’t have room to put a table or band saw in my work area so the BladeRunner was the next best solution. It cuts any kind of material you throw at it with ease using the proper blade of course. I am in the process of building a mirror out of Red Cedar and the 45 degree angles came out perfect using the above process. I put glue on each facing, band clamped it together then let it sit overnight. I checked it for squareness and it was off 1/64th across the bottom otherwise it was right on the money. Now if I can get my planned inlays to come out that well I will be satisfied.

-- If it won't fit get a BIGGER hammer.

View Randolph Torres's profile

Randolph Torres

295 posts in 2159 days


#10 posted 1014 days ago

many tools could make miter cuts. But the best for frame work like that is the Miter Saw. Just be sure to confirm on occasion its true on 90 degrees vertically and horizontally, when you true it to 90 it sets the whole miter guage and all the pre-set angles. Remember the other part of being accurate is the exact lengths. On a octagon like that I would recommend as a last resort cut and glue 7 pieces then cut to fit after the glue has cured the last or 8th piece.

-- another tip from cooperedpatterns

View Bertha's profile

Bertha

12951 posts in 1324 days


#11 posted 1014 days ago

My RAS actually outperforms both my mitersaw and table saw for this. Strange, but true.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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