Miter measurement question - Frustration

[pilvr83]

I am attempting to make a mitered frame around my window air conditioner with the ShopSmith and MiterSet. I could use my portable miter saw but I am determined to figure the ShopSmith/MiterSet combo out.

My measurements from corner to corner on the airconditioner are 24.75" across and 17.25" depth.

I measured the 24.75" to the small corner of the miter angle but when I cut the wood it came to 23.75".

My question, how much longer should I be cutting the initial board to make a miter cut? Should the board length starting out at say 28" long, then I cut to 24.75" each corner?

I am getting frustrated that I cannot figure out how to cut a proper miter!!

[GoNavy]

Cases where I am actually framing something, I tend too not use measurements, but cut one side of the mitered piece then mark the other end on the object I am framing. I work my way around the frame with each piece as I go, block plain works wonders to adjust for slightly out of square objects for each piece. Takes time.. yes, lots of back and forth.. yes, but perfection takes time. Right way to do it, don't know, but it is way I have always done it, and the best way I have found. Make cuts on the waste side of mark and block plain down to exact fit. Shooting board comes in very handy for these duties

[Hobbyman2]

LOL You cut it off three times and its still too short ?



I use knife marks on the piece so I know I am cutting it where is is supposed to be cut.

I use the disc sander instead of the block plane to get those crisp edges ..

If you cut smaller miters by hand you can avoid chipping out .

Not sure why you are having trouble if you mark the piece .

[pilvr83]

The problem I have besides "mental"...I can measure the starting point say 24" but how do I figure out how much wood I should be starting with. this is what I did. I looked at a miter then measured 1.5" from the inside corner (my case 24.75") to the outside corner or point of the miter. So I added 3" to my initial board. Meaning my starting board was cut to 28" total length. When I cut both ends to my 24.75" I was short.

I had not thought of GONavy's idea. I guess I was trying to make my two 1x2x8 foot boards last for the whole project outside and inside my workshop. I may have to rethink...

am I measuring backwards? Should I guess where I want the frame to end...no then how do I get my 24.75? Sorry, thinking out loud.

[Hobbyman2]

Keep it simple ,,,If you take a scrap piece and lay it across the other at 90 deg ,,you can mark your 45 and measure it,,,, then you will find the answer to the way you want to do it. I usually measure from the short end of the cut edge first ,

[everettdavis]

I agree to keep it simple is my approach as well. I would cut one 45 on a piece of stock, lay it on top of the air conditioner, and mark the inside of the next miter cut plus add 1/8 inch to cut the opposite 45.

I then take another piece and do the same thing on one of the sides. I then replicate the next two pieces from the first two and have my frame...

Why the 1/8 one might ask. I would allow some space on either side of the frame of the AC for a paintable caulk. I would not want something that would heat and cool, and condense water against the wood frame as it would rot.

If I am painting it anyway, a small finger wipe over any gap in the miter would disappear under paint anyway.

Taking it further... to learn the process with the guide;

To perfect your technique with miters on the Shopsmith I would practice on some base 1 x 2 stock to build a flat picture frame. I might then play with the compound miter lesson in the Shopsmith manual to get a solid feel for how to do that. It will help with frames, especially the multi segmented ones using your MiterSet. I can almost hear my late uncle telling me to practice until my weakness becomes a strength.

Next lesson would be where I might take some stock through the saw or across the jointer angling the guide to cut a slight bevel to simulate what angles on crown molding might resemble and perfect my crown molding cut (if I didn't have a miter saw).

I normally use my miter saw for this type of cut.... Now that the guard on it blew apart when the laser guide exploded last week which I mentioned in another thread, I may need to bone up on that if I need to do that, at least until my new guard (-laser) comes in for my 20 year old miter saw.

Everett

[reible]

Hi, since you mentioned a possible mental block on the subject I thought this might be useful.

When cutting things that have 45 degree angles it helps to remember some basic geometry. A triangle that is formed in your case will have two sides of equal length, and for this case it will be the width of the material you are cutting.

So if you have say a 2" wide piece of stock and what to cut a frame that is 12" on the outside you can see it like this:

ScreenHunter 03.jpg (31.8 KiB) Viewed 11786 times

The dashed lines show up where you will want to make the cuts. Remember the waste side is to the outside here.

Like wise if you wanted a frame with a 12" inside it could look like this:

ScreenHunter 04.jpg (27.87 KiB) Viewed 11786 times

I'm not sure if this answers your questions but I hope it gets you back on the right track.

Ed

[pilvr83]

WOW! Thank you Thank you. I sure needed this.

I printed this all out.

Thanks again.

[dusty]

WOW! Thank you Thank you. I sure needed this.

I printed this all out.

Thanks again.

I read this thread and I believe that you are framing and opening (the air conditioner) that measures 24.75", 17.25". You did not define the measurements of the framing material but Ed prepared a diagram that shows the dimensions using 2" material.

I did the same but created a slightly different drawing. Hope this helps more than confuse.

Framework.png (25.01 KiB) Viewed 11775 times

Remember, if you are using other than 2" framing material the outside perimeter measurements are wrong.

[ARCretired]

As Ed showed in his excellent picture, it is vital to visualize how the geometry works & make sure when you put wood in a miter saw (or SS) that you know which edge is the outside - so you don't cut the 45 deg the wrong way. if the object that you are framing around has long side A, short side B, and the width of your framing material is C, then:

Long side of frame: Outside is A + 2 times C. Inside length is A
Short side of frame: outside is B + 2 times C. Inside length is B

I attached a chart with various widths of framing material as an example.

In general I cut things slightly long & use the disc sander to sneak up on a good fit. Also, as was mentioned, a good suggestion is to cut a practice frame out of scrap. (make sure the scrap pieces are straight).
if your SS or miter saw is in good alignment, the corners will fit snugly. Other problems than alignment are not cleaning wood chips out of the way (a small chip on the fence or miter will really mess up the angles), wood that is not straight, flex of the framing material when it is being cut, etc.