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I feel so stupid. The flower box tapers from 31 inches down to 24 inches or 15 degrees on all sides. Using my table saw I first cut all 4 sides with the 15 degree tapper. To get the 45 bevel joint I then placed all 4 sides on a 45 degree jig while also using a stop block to keep the then at 15 degrees.
As a beginner I thought this would achieve the perfect 90 degree angle joint for my wife’s flower box. I guess what I’m asking is if there is a formula of chart to calculate the beveled angle knowing that a 15 degree tapered flower box is wanted. All I know is that the 45 degrees is too sharp with a 15 degree taper.
Ps I went on and horsed this first box together and (gulp) swallowed my pride and calked the stink out of it, yuk!!. It looks ok but any help would be greatly appreciated.
Replies
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If the side slopes in from the horizontal at 75 deg, which is the complementary angle of the 15 deg. then,
*your dihedral angle is 93.84 degrees, and to mitre the joint you need half this, viz. 46.92 deg. Tilt your sawblade to describe this angle (47-) from the table.
*The correct angle that the edges of the sides describe to the top edge as viewed perpendicular from the face of the side is 93.84 deg.. Set your mitre gauge to this, or 86.16 deg., it's complementary angle, depending on how your gauge is marked.
*Your mitre and bevel gauges are really best if accurate and reliable, for although once you have got the bevel cut right (i.e., the blade tilt) and you won't need to reset it, you will almost certainly need to adjust the mitre gauge angle to suit depending on which side edge of each piece you are cutting because you have to alternate between holding the bottom edge and top edge of each side against the mitre gauge.
*Also, you'll need to make adjustment to your technique for left tilt and right tilt sawblades. Left tilt blades mean you cut the sides with the outside faces down. Right tilt blades mean you cut with the inside face down.
< Obsolete Link > Click once here. Old discussion. Same topic. Useful links there.
Sliante.
*Sgian Dub;The complementary 75 degrees is correct and this answers my question. Thank you. Your solution indicates the blade angle should be set to 47. Please note the following site has a chart. http://www.scrollsaw.com/miter.htmThe chart says for a 15 degree slope a blade angle of 45.99 or 46 degrees is correct for a 4 sided box. If you emphatically state that 47 degrees is correct(after re checking your figures) then I'll go with yours. By the way I'm not using a miter gage. I'm using my own sled big to clamp for the 15 or 75 degrees. Same goes for the blade angle, I'm locking the blade to 90 and using big to quire the needed 46 of 47 degrees. If you say 47 then I'll build the jig at 47 degrees. Standing by.
*in previous message where I spelled big, it is suposed to spell jigsorry.
*in previous message where I spelled big, it is suposed to spell jigsorry.
*I took a look at the chart. I believe you might be reading the wrong line. You should be reading the information on the line for a side that slopes 75 deg from the horizontal, and this gives a blade tilt setting of 43.08 deg., which is the complementary angle to the 47- deg. figure I provided. I'm 99.9% sure my figures are right. It's usually best do a test piece in something like 12 mm or 18 mm MDF or ply to see you've got it right (MDF is cheaper.) There is always a wee bit of a fudge factor in this, but if you follow the figures I gave it should work out. Let me know how you get on. Sliante.
*I guess if you like solving problems your in the right profession. I thank you again for your time. At age 56 I'm no beginner, but this is the first table saw that I've ever owned and the cypress flower box is my first project. My building savy, if I have any, comes from scratch building model airplanes. I presume my angle solution will be based on my being able to take your 47 degrees and prove it by another method. Trial cutting MDF or scrap lumber cutoffs is probably best. I resolved from the beginning and with the help of an Kirby's table saw book that, as a rule, one does better to lock the blade to 90 straight up and don't mess with it except to realign along with the occasional parallel realignment. Completely using and clamping to jigs to aquire proper angles has an extra safety margin in that it keeps your hands away from the blade and holding something other than the work piece which is a lot closer to the BLADE. Just my opinion. Most don't like the added task of making jigs. I feel, after a little experience one will find it worth the extra effort and not as tough after all. Though, For the extra trouble of constructing a jig you can understand that I wish not to have too many hit or misses on that angle. How did you arive at the correct dihedral if I may ask? ( I don't understand trig btw) RegardsBob
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