How do I cut this compound miter piece? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 20 Old 02-22-2013, 08:08 AM Thread Starter
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How do I cut this compound miter piece?

Hello and welcome to the noob zone.

Guys, I need some help. OK, I actually need you to hold my hand. There, I said it. I'm building some PA speakers and one of the panels is a compound miter cut. I am having a lot of trouble with this one and really need a walk-through on how to do it. Here's what it looks like...notice the piece is NOT square it tapers at the back from 12 1/8" to 8 inches and has two different angles on the opposing sides:

Name:  compound miter.JPG
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Here is how this piece is used: I put a black mark on it.

Attachment 63750

I have a TS (standard left-tilt blade) a BS and a router, FYI.

I understand how to put a single miter on one side of a workpiece and how to make two 45's meet up (like a picture frame) but that's about the limit of my understanding of miters, never mind compound miters. Like I said, "noob zone."

Practicing on scrap, I discovered that if I cut a 12 1/8" x 4 1/4" piece, I cannot put any angles on any side and still keep the piece the same size. If I cut it over size, and put a 45 on one side (while cutting it to length), then I can't get the opposing angle on the other side and still keep the board the same length. Hope this makes sense. It's driving ME nuts!

Would you please give me a step by step on how to cut this? Literally starting with how big to initally cut the workpiece, which angles to cut first? I'm thinking a 13" x 5" rectangle to start with...now it's your turn b/c that's as far as my meager skills will go. Thank you VERY much!

Last edited by mikeintexas; 02-22-2013 at 08:31 AM.
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post #2 of 20 Old 02-22-2013, 08:15 AM
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I would cut it to size with a circ. saw first.

Then you could use this method.

http://www.woodworkingtalk.com/f5/ho...-joints-48745/

Scott
OH, wait a minute ............Yep!.............That's what he said!

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post #3 of 20 Old 02-22-2013, 08:24 AM
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You didn't say what the panel is, or whether you can use the faces. The easiest way would be to just cut the two parallel cuts with the blade tilted.

Then attach to the face a straight piece of anything...wood or any substrate a strip that overhangs the other side, but is set to the angle of the taper. You can attach this with a couple of brad nails (or hot glue). Tilt the blade to the bevel and run the strip against the fence. The next cut, attach the strip to the other side at the angle, and run it through for the cut. Note: The strip has to be wide enough to be used as an edge against the fence.





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post #4 of 20 Old 02-22-2013, 08:25 AM Thread Starter
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Thank you, Scott. That explains part of it. I never thought to use an aux fence, nevermind moving the fence to the other side of the blade. OK, so I would imagine I cut all 4 mitered sides first, then cut the board down to it's final shape (parallelogram?)
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post #5 of 20 Old 02-22-2013, 08:29 AM Thread Starter
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The panel is 1/2" BB plywood. Sorry about that. I don't understand "can the faces be used?" If it helps, here is how this piece is used. I put a black mark on it.

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Quote:
Originally Posted by cabinetman View Post
You didn't say what the panel is, or whether you can use the faces. The easiest way would be to just cut the two parallel cuts with the blade tilted.

Then attach to the face a straight piece of anything...wood or any substrate a strip that overhangs the other side, but is set to the angle of the taper. You can attach this with a couple of brad nails (or hot glue). Tilt the blade to the bevel and run the strip against the fence. The next cut, attach the strip to the other side at the angle, and run it through for the cut. Note: The strip has to be wide enough to be used as an edge against the fence.










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post #6 of 20 Old 02-22-2013, 08:30 AM
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Cut it to final dimensions with a 90deg. saw setting.

Then you can run the 90's using the fence to get your bevels.

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post #7 of 20 Old 02-22-2013, 08:33 AM Thread Starter
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Quote:
Originally Posted by mdntrdr View Post
Cut it to final dimensions with a 90deg. saw setting.

Then you can run the 90's using the fence to get your bevels.

"Using the fence" as shown in the link you showed above, right? An aux fence clamped to the TS fence on the OTHER side of the blade, right?
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post #8 of 20 Old 02-22-2013, 08:34 AM
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Quote:
Originally Posted by cabinetman View Post
You didn't say what the panel is, or whether you can use the faces. The easiest way would be to just cut the two parallel cuts with the blade tilted.

Then attach to the face a straight piece of anything...wood or any substrate a strip that overhangs the other side, but is set to the angle of the taper. You can attach this with a couple of brad nails (or hot glue). Tilt the blade to the bevel and run the strip against the fence. The next cut, attach the strip to the other side at the angle, and run it through for the cut. Note: The strip has to be wide enough to be used as an edge against the fence.



This would be the easier method! I stand corrected...

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post #9 of 20 Old 02-22-2013, 08:59 AM Thread Starter
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Cabinetman: I'm not sure I understand this part:

Quote:
Then attach to the face a straight piece of anything...wood or any substrate a strip that overhangs the other side, but is set to the angle of the taper. You can attach this with a couple of brad nails (or hot glue). Tilt the blade to the bevel and run the strip against the fence. The next cut, attach the strip to the other side at the angle, and run it through for the cut. Note: The strip has to be wide enough to be used as an edge against the fence.
Thanks; I appreciate the help.
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post #10 of 20 Old 02-22-2013, 09:00 AM
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Quote:
Originally Posted by mikeintexas View Post
Sorry about that. I don't understand "can the faces be used?"
The question was directed as to whether you were able to use a fastener or not in a face. Some projects we don't want any holes, even tiny ones.





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post #11 of 20 Old 02-22-2013, 09:07 AM Thread Starter
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Oh, I'll make all the holes that I have to! That's what PL glue is for. The final result has to be airtight, that's all that matters. There will be a grill on the front so it doesn't matter what it looks like. Thank you for the help.
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post #12 of 20 Old 02-22-2013, 11:23 AM
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I'd do it a bit differently

You need to lay out the lines and angles on the board(s)or a practice piece.

Cut the parallel sides with the blade bevel over at 45 degrees.

Using the miter gauge and the paralleled beveled edge against a long miter extension, make practice cuts UNTIL the cut and the layout line is parallel. Note the angle setting on the M/G. Then set the blade over to the 26 degree bevel and make the first cut. Make all your similar cuts using this setting before changing it to make the opposite side bevels.

I have a long extensions(fences) on all my miter gauges for increased accuracy. It show exactly where the kerf is and supports the entire length of the workpiece.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 02-22-2013 at 11:28 AM.
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post #13 of 20 Old 02-22-2013, 12:16 PM Thread Starter
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Many thanks, Woodnthings. I think I'll be using up quite a bit of my scrap bin tonight...it'll probably take me awhile to figure it out, but I'll write down all the relevant numbers/settings once I do. I have to cut 8 of these things and they have to be accurate to about 1/16" or they won't fit.
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post #14 of 20 Old 02-22-2013, 01:37 PM
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Quote:
Originally Posted by mikeintexas View Post
Many thanks, Woodnthings. I think I'll be using up quite a bit of my scrap bin tonight...it'll probably take me awhile to figure it out, but I'll write down all the relevant numbers/settings once I do. I have to cut 8 of these things and they have to be accurate to about 1/16" or they won't fit.
You may not have enough room before the blade to use a miter gauge.

Using an add on edge to the face (we'll call a face the flat side up when laying on the table), just creates an edge to run against the fence. the opposite side gets cut. If the add on is set at an angle (one side of the taper), as you run it through the saw it will cut the taper at the opposite edge.

What it does is create the positioning of the piece as it gets cut.





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post #15 of 20 Old 02-22-2013, 03:07 PM Thread Starter
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Thanks, CM. I don't have my TS in front of me, but being that the long edge of the piece I'm cutting is 12" long, I THINK I should be good to go to use the miter gauge. On my saw, the right miter slot is about 8" from the blade. I'm excited to get to it. Thanks for the help.
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post #16 of 20 Old 02-22-2013, 05:19 PM
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your only cross cutting a width of 4 1/4"

Quote:
Originally Posted by mikeintexas View Post
Thanks, CM. I don't have my TS in front of me, but being that the long edge of the piece I'm cutting is 12" long, I THINK I should be good to go to use the miter gauge. On my saw, the right miter slot is about 8" from the blade. I'm excited to get to it. Thanks for the help.
that's plenty of room in front of the blade, even at a 30 degree angle.

I'm right handed and use the left miter slot so the waste falls to the right side of the blade when pushing with my left hand...yeah I know?
So when it comes to cutting the bevel on the left side of the work, I'd probable switch miter slots and change the setting to the corresponding opposite angle. I'd still make a careful layout and check to see if it works out that way. You may have to fudge the angle a 1/2 degree or so. An Incra or Osborne miter gauge or a good sled would be the way to go.

I suppose there is a way to make a sled that keeps the blade at 90 degrees and just carries the work at an angle , but I'm not up to sorting through that at this point. Maybe someone has done it?

Sometimes placing the work upside down and backwards give an equal but opposite cut/bevel. In this case I donno? Not up to sorting that out either.... Help me out here Hammer 1.

Don't let the work slide at all on the miter gauge. Face it with sandpaper to increase the grab or your angles will be off.

A sliding compound miter saw would work also.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 02-22-2013 at 05:24 PM.
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post #17 of 20 Old 02-22-2013, 07:39 PM
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Mike, since you are making 8 of these, you might consider making a template of just the shape without worrying about the bevels on the side. Once you have a template of the shape you can make a jig for the table saw that is similar to a band saw jig and use it with the blade set to the correct bevel. This is a technique I've used several times for making end caps and dividers in pentagon shapes for toy cabinets that look like old fashioned vegetable bins. The jig is simple and, most importantly, safe.

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post #18 of 20 Old 02-24-2013, 12:29 AM Thread Starter
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Success!

Hi all,

I'm back and most importantly, still have all my fingers.

I wish I'd read the tip to face the miter gauge with sandpaper before this evening; it really would've helped! The workpiece wanted to slide around on the miter gauge something fierce. By the way, the magic number was 64. As in the miter gauge needed to be at a 64-degree angle left/right to make the "reduction cut" from 12 1/8" to 8.0".

This was a brain-busting, nerve-wracking exercise for SURE, but I learned so much. Next time I have to do this, I will just say "Oh, this....I know how to that!" I do not like my fingers anywhere near the blade. I use push sticks for everything and the guard is always on the blade, but for this there was no way to go but "bareback" for this operation. I did have the riving knife installed though. Stupid, I'm not.

Not the best pics, but at least there's pics. I don't know where the burns came from. Some of the pieces were binding as I slide them through the blade. I did all 8 the exact same way. Is that from the workpiece moving? Yeah, the sandpaper trick would've helped. Not sure if the workpiece moved as all the cuts look straight to me. Long sides are at 45, short at 26.




I'd be very interested in seeing what a jig for these types of parts looks like. While I'm aware of the useful, time-saving benefits of jigs, I'm not real smart on them. I'm a visual learner...helps if I see the object in question.

I'm pretty impressed with the miter gauge that came with my Grizzly 0690 TS. It only has snap detents at 45, 30 and 90 degrees, but the twist knob locks down securely at any angle in between and the markings on the gauge are easy to see. That said, an Incra with a positive detent at every degree b/t 0 and 90 is definitely in my future.

I can't thank all of you enough; I would not have been able to do this without all of your help. I learn from each and every one of you. Thanks, guys.

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post #19 of 20 Old 02-24-2013, 07:14 AM
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Quote:
Originally Posted by mikeintexas View Post
Hi all,

I'm back and most importantly, still have all my fingers.

I wish I'd read the tip to face the miter gauge with sandpaper before this evening; it really would've helped! The workpiece wanted to slide around on the miter gauge something fierce. lp. I learn from each and every one of you.
Sandpaper might have helped, but there is still the ability of the piece to move using a miter gauge. The burning is evidence of that. That slight bit of movement allows for kickback. It's not the safest or most efficient method for this project. Not all suggestions are well thought out to consider the possibilities of the hazards. I've done that type of procedure with a miter gauge and am aware of the problems.

Using a sled has it's drawbacks as some pieces may be too long to fit before the blade...as with using a miter gauge. At least with a sled you could get better support. An angle piece as I described in posts #3 and #14 would still have to be mounted with a sled to create the taper cut.

I'm not sure if you understood the method, but if you do this again, you could make an overlay template that is the length of the distance between the two parallel cuts, and the angle is cut on one edge. To set it up, once the two parallel cuts are made using the fence, attach the template to line up with the two parallel edges and fasten to the face. Running the angled edge against the fence will cut the taper on the opposite side. You can set the blade to the bevel and make the bevel and angle cut at the same time. Another advantage is the taper angle will be the same for both sides, as no changes have to be made.

It's a much safer method, and a more secure method, as you are guiding the cut against the fence. It should be a faster cleaner cut.





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post #20 of 20 Old 02-24-2013, 11:57 AM Thread Starter
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Thanks, CM. The next time I do something like this, I definitely want a safer way of doing it. I'm a bit of a safety nut with the TS b/c big things can go wrong very quickly. Making these pieces I violated 99 out of the 100 TS Safety Rules. I'm just happy that nothing went remotely wrong. When I was sliding the pieces through the blade I had a death-grip on the workpiece and miter gauge. I didn't realize that when making these compound cuts, the workpiece would want to "climb" out the of blade. It was very unnervving! Keep in mind the end of the workpiece I was clamping down on was cut a 45. Made nice, deep grooves in my fingers. I'm a little bit sore today. But that won't keep me out of the shop!
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