I’m betting that some of you guys have already solved this sort of problem and can share your experience.
I’m tasked with assembling 28 tapered Craftsman-style hollow columns around the structural 4×4 posts on four porches of a H4H project. Actually they are upper-half columns where the bottom half is faux stone with an Azek cap that our upper column will sit on.
Site super has dictated using 3/4″ exterior grade MDF with mitered corners. The four pieces are 42″ high, 15″ at the base and tapered 2 1/2° from top to bottom on each side, making them 7 1/4″ at the top. They were cut on a 45° miter using a shooter board and a worm-drive saw. All of which means that I don’t expect both the outer edges and heels of the miter cuts to match up. [Even if the miter angle were accurately cut, would 45° be correct for a box with tapered sides?]
So how to assemble ill-fitted tapered miters?
Gorilla glue and shoot with 15ga finish nails – let the foaming action fill the gaps?
Adhesive caulk and 15ga finish nails – let caulk fill gaps?
Should I use counter-sunk screws instead of shooting finish nails? Sounds like lots of labor and stripped out MDF by volunteers over-driving the screws.
Thanks in advance,
Replies
I'm scarred for you.
;)
But simple solution would be PL Premium then tape with fibre re-inforced tape, then shoot with the 15ga finish galvies.
were I starting from scratch, I'd calc the exact angle, use a lock corner router bit to detail it, and use TBIII glue, but the PL premium construction adhesive will fill gaps like a weld bead
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What, no Piffin screws? Is there a calculation table for miter angles between tapered sides? I think the angle must be something less than 45°, but how much less? Of course that still leaves the problem of cutting something like 44.3° with a worm drive saw. To get them just right, I'd have to try re-cutting them all on a contractor's table saw or take all 56 cut pieces home and re-run them on my table saw.BruceT
Edited 5/5/2008 4:07 pm by brucet9
I'm sure there is a formula, but since I do that sort of thing seldom enough, I just do trial and error with scraps faster than figuring the math cause that way I can have it done before I could find the book.
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even though u r tapering them u still have 4 sides so why do u think the miter would change? all miters must equal 360 degrees right?
Maybe I am wrong, but because it is 45° to a vertical plane and not to each other. As these mve away from being vertical that changes the angle relative to each others planar surface.
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don"t want to argue but they are still square at the top with 4 sides and must still equal 360 degrees no matter what
Sure they do, but the plane that saw foot is riding on is not the planar side of what you are envisioning. It is off by the amout the column tapers.
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Wrong, the miter is still 45°
Doug
Gonna make me prove it eh?I know it isn't, because I built some planters a couple years ago with the sides about a 12° slope. I don't remember what the cut angle was, but it damn sure wasn't 45°
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The angle is exactly 45* if you measure it perpendicular to the axis of the long edge. But since it's not cut that way with the saw, yiou have to take into consideration the taper."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
That is what I keep saying. It is 45 relative to each other in a flat plane, but not relative to the planar surface the saw shoe rides on, so the CUT itself is not being made at 45
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It is 45 relative to each other in a flat plane, but not relative to the planar surface the saw shoe rides on, so the CUT itself is not being made at 45
Ok, this could be where we are having some problems. the miter cut is a 45° right? and the way the saw(in this case I will assume a circular saw) is traveling at an angle that is yet to be determained? Am I correct in assuming this is what your saying? Or am I still missing something?
The question as I remember is what miter will the pieces be cut at? that would be 45°, the travel of the saw has to be figured and I can do that but I'm not sure thats what the question is asking.
Doug
Edited 5/5/2008 10:28 pm ET by DougU
Piffin
Yes, why dont you prove it.
I just came in from outside at the table saw, had to prove it to myself cause you guys were confusing me.
I cut 4 pieces, tapered from 3" at the base to 1" at the top, approx 16" tall, mitered all four pieces at 45° and they make a square! A tappered square going from 3" square at the bottom to 1" square at the top.
Am I doing something wrong? I've made tappered round columns going from 11" round at the bottom to 9" round at the top, 9' long. I used 12 pieces to make up these columns and they were mitered at 15° they came out right on, a 12 sided column.
What am I doing wrong.
Doug
Tomorrow
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How do you refute what I just did then? Is my table saw doing something that cant be explained. I know it's past your bed time but I need answers NOW!
Guess I'll have to wait until tomarrow!
Doug
It's basic 3-dimensional geometry. The angle you cut on the saw is only 45 if it's a straight column; if there's a taper, the angle changes depending on the degree of the taper. Because the surface the saw is working from is no longer a vertical line, it's the line of the taper, and therefore the angle you're cutting isn't measured off the vertical anymore, it's measured off the angled taper. If the angle stayed at 45 deg, then there's a whole lotta framers here who are doing extra work cutting rafters, because it's the same concept.
Harry
The thing that pizzes me off most about this is I know better! I know the math involved in doing this but I could not get my stupid head off the idea that looking down on a pyramid that I would see nothing but 45° angles! Then when I went out and cut some tapered pieces on the table saw I made myself believe my false assumption even more! If one would look down on mitered crown, 38/52° variety they would see the same 45° but we all know that the cuts are not 45° miters.
Your analogy to the crown is dead on, same damn difference - why didn't piffin say that in the beginning, I'm blaming him - which by the way, where did he go to?
Doug
The key is in exactly what you said = 'looking down on the pyramid'. That's because you're thinking of looking straight down on it....you'd have to look down at an angle, so that the surface of one side appeared as a straight line, then you'd see the angle the way they relate to the flat surface of the side, not to the horizontal or vertical.
I spent several weeks learning that stuff in my drafting class, many years ago, when I thought that being an engineer was a good idea.
There was an FHB article on cutting crown in, I think, '92. Maybe fall of '91. I can't find that issue.
In it, the author had a discussion with a professor of mathematics regarding finding the cut angles for odd corners, non-standard crown molding, etc.
There was a formula that gave you the ability to figure out the bevel and miter settings for any taper.
If anyone can find that article, it would answer a lot of questions.
In it, the author had a discussion with a professor of mathematics regarding finding the cut angles for odd corners, non-standard crown molding, etc.
Dont recall the article but if you have a Bosch angle finder you can find the cut angles/miteres by simply pushing a few buttons.
Doug
Gonna make me prove it eh?
Don't bother, I did it myself!
I was wrong and you are correct. I could not wrap my brain around the concept last night, kept thinking about a pyramid and looking strait down at it from the top and seeing those 45 degree angles. Well yea, they are but they aren't cut at 45 and that was what you were saying and I was not grasping.
I went to work this morn set out to prove I was right on this and after cutting one piece I knew I was wrong. Wish I had a phone # for ya, I'd a called, it was driving me nuts until I finally got the idea strait in my head. FINALLY!
Sometimes stuff is hard to shake!
Thanks
Doug
I've had mental pre-occupations before too to trip over.Glad you figured it out on your own. We had a suicide near here so I forgot all about this thing.
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Even the manufacturer suggests against using exterior MDF for trim since swelling is still an issue. Can't say I'd be excited about this project either.
Beer was created so carpenters wouldn't rule the world.
I have used it for projects just like this that stand up fine.
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The manufacturer's warning was enough to scare me off. :-)
Beer was created so carpenters wouldn't rule the world.
Just imagine an extreme scenario. What if the column tapered from 1000' at the bottom to 1" at the top. Now, it's almost a flat plane. Would the miters still be 45°? No, they would be nearly 90°!
Granted, that's a grossly extreme scenario, but it does make it easier to see how a taper affects the miter.
I really don't know if 45° is "close enough" in this particular case.
Just imagine an extreme scenario. What if the column tapered from 1000' at the bottom to 1" at the top. Now, it's almost a flat plane. Would the miters still be 45°? No, they would be nearly 90°!
Don, as an experiment, and something that I've done quite a few times, I went outside and cut 4 pieces of wood about 16" long. I tappered them from 3" at the bottom to 1" at the top. I then 45'd(mitered) them on both long sides, when I hold them(all 4 pieces) together I get a square that is 3" at the bottom and tappers to a 1" square at the top. This would be the same senario as the OP'er is doing, just different numbers to the pieces.
You could punch in any numbers for those 4 pieces and I would still miter them at 45° and I would get a square column that tappers.
What am I missing from what you and Piffin are saying?
Doug
I think what you're seeing is "close enough" works. I repeated your experiment, but I went from a 12" base to zero at the top on a 12" long piece of wood. It didn't work. I ended up with corners that were much greater than 90°.
Maybe a picture would help:
View Image
The picture helps and I'm going to have to repeat this little experiment at the shop today, gotta clear this up in my head!
Doug
Don
I am WRONG!
I cant get the thought of a pyramid out of my head, all day long! I keep thinking of the pyramid looking down from the top and seeing the miters, those miters look to be a 45 degree, which they are but are not cut at 45 degrees.
I went to the shop this morn and cut 12" squares of MDF and took them out to the job site, made a cut from 12" down to 1" at the top, mitered the piece at 45 and stood it up on my saw bed, BAM, it was like someone stuck a 500 watt halogen bulb in my face! The light did actually come on.
I could not wrap my damn brain around it last night and when I saw your pic this morn I was doubting myself and that was pizzing me off!
You mentioned the "close enough" factor and I think that was convincing me. At least if was reaffirming my thoughts.
Someone else mentioned in this thread that if you cut a segment out of the pyramid that you'd see 45 degree angles on the corners, ya you will but they aren't cut at 45, couldn't get that through my head but I think its stuck there now!
Thanks for playing along, parting gifts are at the front door, don't forget to stop and pick one up.
Doug
...parting gifts are at the front door...
LOL! Thanks.
I know that in order to figure out the actual angle would require trigonometry, but I don't know how to do it.
exactly. PL Premium and tape. I'd use backer blocks at top and bottom,but that would probably be more than time will allow."The nearest thing to eternal life we will ever see on this earth is a governmental program" -Ronald Reagan
I cant understand why the miter would change Its still a square. Am I wrong? but it seems 45 whould have to be close enough anyways.
I think I would stay away from gorilla glue for that application, I used some on a table outdoors and It broke down off I figured because of the elements, It lasted a year though
The best extiror glue you got (titebond III suposed to be good) and caulk when done
Tapered, mitered columns cut with a worm gear saw? Is abusing the volunteers part of the H4H philosophy?
Seriously, I thought that H4H was about basic living for needy people. Faux stonework and laborious, geometric details don't sound like they fit that goal.
Sounds like the local leadership needs to review the aims of that fine organization, then get on to the next project.
Edited 5/5/2008 5:05 pm by Hudson Valley Carpenter
Around here the city building depts force their own requirements on us, making our decent housing goal more costly to achieve in both time and materials.Faux stone, fake dormers, etc. - even fire sprinklers in living spaces in Stanton.
BruceT
OK, but why miter those columns?
Assuming paint grade, you'd get a much better joint by cutting 90's and fastening with pocket screws and exterior wood glue. Easy to lay out, cut and fit. Maybe a little sanding. Glue and clamp the fourth side. Done.
"OK, but why miter those columns?"Not my choice. Site super said "Here are your mitered pieces - put 'em together."My choice would have been square cuts [actually slightly off-square due to the taper], lap one side over the edge of the next, glue and screw a little bit proud, plane the joints flush, fill the cracks and sand. BruceT
Agreed.
Good luck, making the miters work. I hope they stay tight until you get out of town, anyway. ;-)
MDF and exterior don't belong in the same sentence.
You haven't used Medex, eh?
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MDO is the material you are referencing, I'm sure. I've used it before and it's the best. Paint well and seal all seams. It will work fine!."The nearest thing to eternal life we will ever see on this earth is a governmental program" -Ronald Reagan
These craftsman architectural elements are all the rage here... Personally I'm kinda of tired of it....
That said, I've done a number of houses within the last several years that got those 1/2 high tapered columns.
What my carps do is make a jig out of 3/4" plywood or similar and use that and a sidewinder circ saw to cut the tapered columns. (actually they have a few jigs that they carry in their van). Obviously the jig has to be pretty accurate. Maybe make it on a table saw? The jig has the column taper but just regular square edges. The jig is about 4.75" narrower than the width of the finished column. 4.75" because the foot on most skill saws protrudes 1.5" out from the side of the blade, 1.5" +1.5" = 3" plus add another ~7/8" on each side for the bevel cut so it's 1.5"+1.5"+7/8"+7/8". The jig is shot to the 3/4" MDO, medex or whatever, with temp finish nails. If you were looking at the jig tacked to the stock, and the jig's long dimension is side to side, the first cut would be left to right and the second cut would br right to left. Kind of hard to explain in text - I wish I had a picture. If you need me to make a drawing I will...
The saw bevel is 45 degrees. If there were a way to set the saw to 45.25 degrees that would be even better. It just can't be even 1/4 degree less than 45.
Personally I'd recommend Tightbond III glue. Gorilla glue is OK, but it always seems that either you don't get enough on, or you get too much and end up with a mess. And that stuff doesn't sand too well. My second choice would be a polyurethane construction adhesive like PL400, but that stuff can get quite messy too, and like gorilla glue takes days to wear off your hands - so gloves are required. If you use medex you have to brush off the cut pieces well as that dust is just nasty and will interfere with the glue bond. A dust mask would be in order too. Columns are assembled with 2" ss 15ga finish nails.
My guys make very good looking columns using this method.
BTW - I volunteered for HfH for roughly 10 years but no more. I got sick and tired of the circus atmosphere. That, and them never having what was required to do a job... The last time I volunteered they had me install 356 casing prehung doors and 445 casing on the cased openings of the same house. The rest of the day I spent fixing other people's mistakes - stuff like back exterior wall of house 2" out of plumb and I was supposed to install an exterior door in that....
One final thought - you said something about 4x4 posts sitting on top of the Azek caps - I think.... 4x4s must not bear on the Azek.
Thanks for your thorough answer."One final thought - you said something about 4x4 posts sitting on top of the Azek caps - I think.... 4x4s must not bear on the Azek."4x4 is full height. Bottom columns and caps surround posts, hollow upper column sits on Azek cap.
BruceT
Ok.
The answer is tapered pieces are cut first to dimension, then beveled at 45*. Done.
Using MDF, or MDX,outside is an unwise practice. Both will swell like the dickens and collapse in short order. MDX does NOT mean exterior- it means it is made without formaldehyde in the glue. Use an appropriate product.
Expert since 10 am.
Medex is made specifically for exterior applications, I've used it for panel work ( bay windows and whatnot ) for 15 years, and it has held up very well.
Bing
I have to disagree. I spoke with a company rep awhile ago and they said Medex is moisture resistant NOT water proof. And is not warantied for exterior use.http://www.sierrapine.com/Media/MedexSpec041508FINAL.pdf
"...Medex is moisture resistant NOT water proof. And is not warantied for exterior use."Medex is not the same as Extira brand exterior grade MDF. Extira is made expressly for exterior trim and carved sign boards.See comparison between Extira, Medex and NorBord here:
http://www.extira.com/pageBuild.asp?PageID=B_extiravmdf_e
BruceT
I( remember this discussion once before. The Medex did used to be sold as exterior. I think at some point they may have adjusted the formula to use less good stuff or they just decided to cover their liabilties by issuing a disclaimer.I would not use it where water puddles or right under the drip[ line of a roof, but once painted, it handles occasional wetting just fine.
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"The answer is tapered pieces are cut first to dimension, then beveled at 45*. Done."45° bevel will not make a tight miter joint on tapered pieces. It's like mitering crown except the spring angle is only 2 1/2°, so the bevel angle is something like 44 1/4°.
BruceT
With the angle, you are correct, I was slightly off. The miter is not 45*, but very close- more like 44.6*
I built a four sided pyramid once and remembered that it was just under 45*. Expert since 10 am.
"The miter is not 45*, but very close- more like 44.6*" If it's that close, then the error factor of cutting with a shooter board and a worm drive set to "45°" will certainly exceed the theoretical bevel angle on our panels. Your way with the router would at least have made the deviation the same on every piece.I'll probably have to use a lot of caulk. BruceT
Edited 5/7/2008 12:42 pm by brucet9
There are all kinds of calculators for figuring this.http://www.delorie.com/wood/compound-cuts.html
http://www.scarletta.net/WoodJoy/compound_miter.htmlJoe ???? has one on his website.But since I can't remember his name I don't know his website..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Joe ???? has one on his website.
But since I can't remember his name I don't know his website
Thanks for the links. You're thinking of Joe Fusco here:
http://www.josephfusco.org/Calculators/Box_cutter.html
Exactly..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
You should post that on this threadhttp://forums.taunton.com/tp-breaktime/messages?msg=104125.1
"I'll probably have to use a lot of caulk."Why I said to use PL Premium construction adhesive. It has body and fills gaps, like a weld bead
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Thanks for the PL suggestion. We bought a case of the stuff today.
BruceT
I did square, mitered columns, 8' tall for a porch addition. I cut slots for biscuits and used gorilla glue. What a freakin nightmare! Took a week for the black stains on my hands from the glue to wear off. That was the first one.
On the rest of the columns I mitered and used exterior yellow glue, taped the corners together, and shot with 15ga. Paslode.
Since then, any column I build is done with a locking miter. I have a sample thats been laying in the back of my truck since June 2007 with one coat of primer, and one half-assed coat of laytex exterior paint on it. While the sides are cupped, the miters are as tight as the day I glued them, and I used REGULAR yellow glue to boot.
I can't say if the lock miter will work for the tapered columns but give it a try on some scrap.
just my 2 cents
Thanks.We put them together with PL premium-sticky-as-the-devil construction adhesive and 1" #6 trim-head screws. BruceT