Had to duplicate an arch yesterday, so grabbed a thin piece of oak about 3/4″ wide and did the string thing (making it like a bow). It didn’t bend evenly, though, so wasn’t getting a consistent curve. What type of wood is best to make this gizmo with?
forestgirl — you can take the girl out of the forest, but you can’t take the forest out of the girl 😉
Replies
Jamie,
I would have thought a piece of knot-free ash would be OK, but what about a steel rule?
david
Although using a thin strip of wood is easy for us woodworkers it never results in a smooth balanced curve. There is too much inconsistency in the average strip of wood. So I suggest you use metal. You can get 1/8" flat bar in either steel or aluminum from a local metal supplier. The aluminum will obviously be cleaner and lighter weight. If you go with steel, try to get cold rolled rather than hot rolled. The CR will have very square corners and it will have a very smooth surface. However it will most likely be coated in oil when you get it to keep it from rusting. Use rags and naptha or even 409 to clean it. Then apply a good coat of paste wax. The metal will bend easily and evenly.
Thanks for the tips on what kind of metal, what variety, to pick. The cold-rolled steel will be the choice for the next time (if I don't need to use a formula and all that stuff).forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
I don't know how relevent this, but for what it is worth. I have a rewind spring from a recoil starter on my skidoo that makes a wonderful band for drawing arcs or tangent lines. soft edges, small, long, and consistant bend.
Pedro
Bending something isn't the way to draw an arch. You need a large compass for a half circle, or trammel points. Make your own with a stick with a nail in it and a hole for a pencil.
Jamie
Is the arc a constant radius semi-circle, or are you altering it as you go. If it is constant radius, let me know, and I'll shoot you a formula based on the width and height of the arc to make it perfect with a compass beam. Easy to build, like hammer stated. Long piece of scrap, with a hole drilled in one end to hold your pencil. It's how I make all my arcs.
Also, if you're planning on cutting this arc into solid stock, it's a heckuva lot easier to make a template out of mdf, which is easy-easy to sand or rasp to perfection, and then use it with a flush trim bit on your solid stock. Also, you'll have a template for that radius forever. I've got them hanging all over the walls in my shop.
Jeff
All you need is two straight boards and three nails:
you do not need a formula, nor do you need to determine (or access) a center point nor radius value.
Method A (Pivoting on two end-points only)
1. Mark the center point and end points. Put a nail at each end of an arc.
2. Make a "V" from two stiff pieces of wood. For large legs, you may want a center brace (making an "A" shape).
3. Put one edge of each board at the nail at the end of the arc and join them at the center point. Fasten the boards together securely.
4. Put a pencil at the apex of the V and while keeping contact with both end nails, move the V and trace the shape of the arc.
Note: if the V is 90 degrees, the result will be a semi-circle (half circle).
Method B (pivoting on each end and center)
1. Put a nail at each end of the arc and the center point
2. Make a "V" from two stiff pieces of wood. For large legs, you may want a center brace (making an "A" shape).
3. Put one edge of board one at the nail at the end of the arc and at the center nail
4. Put the other board parallel to the chord (measure up from center line and end point . Fasten the boards together securely.
5. Put a pencil at the apex of the V and while keeping contact with one end nail and the center nail, move the V and trace the arc. Repeat for the other side.
The advantage to either of these methods is lack of math and it may be impossible or unwieldy to run a radius to a center point. Consider a 4" drop in a 10' section of fence -- how much room would you need to do a trammel bar for that? Using method B, you'd need two boards less than 6' long. Likewise if you're doing an 8' high arched doorway with a 20' radius curve, where are you going to put the center?
Edited 1/18/2007 7:09 pm ET by byhammerandhand
Wonderful solution!! I love those methods that don't use numbers!!!
I use this drawing bow from Lee Valley.
http://www.leevalley.com/wood/page.aspx?c=2&p=44631&cat=1,42936,50298&ap=2
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer (1891)
Battens for sails work the best. IIRC, your in Seatle so it shouldn't be to hard to find a source.
Hi FG ,
Well you have been given some wonderful methods how to draw an arch , and as almost always there are certainly many ways of doing the same thing . And here is how I typically draw arches , I make a half template , then flip it to complete the arch , a steel rule can work well and a piece of 1/4" mdf with veneer skins or not can mark a nice smooth arc .
example : if you want to make an arch 88" wide with a rise of 7 " , make your template 44" plus any flat or straight part before the arch starts X at least an inch or so taller than the rise , and mark the 1/2 arch on the 1/2 template , cut and sand to the line then transfer to the work piece .There are many ways to cut or template rout , shape or sand the work piece .
good luck dusty
Morning FG...
I'm with Hammer1 on making a compass from a narrow board.. with a nail in one end and a hole for pencil in the other. Then I do as Jeff Heath suggested and make a template from MDF. Once you get the true line established and scribed on the template, I cut it proud about 1-2 mm with a jig-saw or band-saw if small enough. It can be taken down to true at that point with files, rasps and sanding as noted by Jeff.
Once trued, the template gets clamped on top of the true stock and the true stock scribed. Remove the template and again.. cut the true stock about 1-2 mm proud. Replace and re-clamp the trued template back on top of the stock. The router with an over-head bearing bit gets the call to true the stock with a smooth edge as the trued template you shaped by hand.
The aluminum bar mentioned would seem OK to me for small arcs.. but if you ever have to build semi-round table tops or black-jack tables for instance, the compass can't be beat IMO. The home-made compass can be made long (just move the nail position) and used for large projects where you might nail it on as assembly table with the stock laid on another (work-bench, etc.) to get that big of an arc.
Regards...
SARGE.. jt
I'll bet a pint of your favorite that Forestgirl wants to draw a free arc. That is one that's judged by eye and not necessarily one that's derived from a circle, spiral, elipse or any readily derived mathematical formula. Thus all your compasses, tramels, and what-nots will simply cost her time and money but be useless for THIS project.I've nothing to go on but my hunch and assumptions from her original question.
BINGO! The responses in this thread are fantastic, and will cover all present and future arc-drawing tasks. The current one was making the top and bottom "orange slices" for a miter-saw dust collection hood or cove-sorta-thing, so simplicity was paramount (over precision). forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Sarge
NO NO NO! You can't use a beam compass to make a circle! Didn't you know that's wrong? You need 2 nails and a string!! That's the proper way!
Smiling and laughing all the way, :>)
Jeff
How often do we need a 20 foot radius arc on a piece of furniture?! In 20 years, I never have. I've yet to be commissioned to build a arch top bed for the Titans. Ha ha.
Morning Jeff...
How often do we need a 20 foot radius arc on a piece of furniture?! In 20 years, I never have. I've yet to be commissioned to build a arch top bed for the Titans. Ha ha. .... Jeff
You're just hanging out in the wrong circles and I suggest you make a point to get invited to a few Titan dinner parties to get acquainted! :>)
Interesting that you have never done any large arcs (just assuming from the comment?) especially doing this for a living. As an amateur I was asked and built a 100' showroom counter for my company as the lowest bid from a cabinet-maker was $40 K the way my company wanted it done. One end was a semi-circle with a 14' radius an a challenge for the size of my shop. But the little amateur shop got it done with the use of dollies anchored together.
On another occasion I did 2 full-size black-jack tables for a Catholic church to use for "casino night" fund-raisers for charity. They paid for the materials and I donated the time.
So.. I believe in not ruling out any possibility. Even thought I don't keep a permanent one on hand, there's always a compass as close as the scrap pile and nail bin in my shop. Life is simple! ha.. ha...
Gotta run.. I got the Titans holding on the other line...
Regards...
SARGE.. jt
Sarge
Good post! I've done large radius' before, I was just joshing. I've built 2 pretty large commercial bars. For those, I used a 100' nylon tape measure. It actually came with a pencil holder for this very thing from Stanley. I always just made templates out of mdf, as described before. Took the templates to the jobsite, and laid them out on the floor for one, and on the other, I had to actually build a plywood mockup. Good thing, as I had to change it twice (finnicky wife of the owner!). They were both very good jobs, though. Wish I had one like that now!
BTW, I enjoyed all your info on the Steel City bandsaw. Well done!
Jeff
Thanks, Jeff. Now I have an inkling why the contractor who's shop is across the street has a huge, HUGE circle-type jig hanging on his wall.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Evening Jeff..
Thanks on the SC review and BTW.. you got some serious space to work with from the pics you posted in the other thread. Two things caught my eye especially. That jointer which you would have to chain a team of Clydesdales to move.. and what appeared to be kerosene heaters.
I had a large kerosene heater that did a nice job of heating my shop here in Atlanta. BTU wasn't a problem and the slight cracks in the shop (garage) doors provided natural venting. But... the fumes still penetrated to the house upstairs and my wife couldn't handle them.
While sitting in the shop with a cup of coffee, I glanced up and remembered that I had a 1/2" natural gas pipe going down one side feeding the gas fireplace starter located up=stairs about dead center of my shop on one wall. That lead me to Lowe's in Feb. which had all heating on sale. A tap in to that line got rid of the fumes.. cheaper fuel and I can raise the temp to 80* degrees (don't of course) on nights below freezing.
Sorry for rambling. I've been working with finish fumes from chairs and a kitchen table base for 2 days and any excuse not to go back and breather them anymore today is warranted. ha.. ha...
Regards...
SARGE.. jt
Edited 1/19/2007 7:00 pm ET by SARGEgrinder47
Edited 1/19/2007 7:02 pm ET by SARGEgrinder47
Sarge
Oh, yeah!!!! I hated those dang kerosene fumes. They gave me a headache. Those two heaters in the photo were just temporary heat sources while I was waiting for the delivery of my radiant tube heating system, which is also in the photo's. I haven't had those 2 guys lit in 2 1/2 years, thank goodness. No more advil!
My shop is 440 feet from my house, so no such luck with the natural gas line. In fact, it was so darn expensive to run a line that far, that I just had a big ole' propane tank parked on the side of the shop. My heater is liquid propane fueled. Expensive, but not as expensive as the 500 foot gas line, changing the gas meter to the house (added pressure to pump NG that far), and all the regulator's to the gas appliance in the house. I checked into all that, and quickly settled on propane. Where I live, the gas company wouldn't give me a seperate meter for the shop because of it being on the same property, blah blah blah.
Jeff
Two years ago I was comissioned to build the clading for will smiths new house in malibu canyon it had a 20' radius arch i had to cut out of spanish cedar. Pretty long router jig.
On second reading, Sarge, Forestgirl is probably looking to draw an ellipse, or part of one.http://www.benchnotes.com/Laying%20out%20an%20oval/laving_out_an_oval.htmBeat it to fit / Paint it to match
Thanks to all of you for the wide variety of answers! These will all be printed out (and Hammer's BenchNotes page bookmarked) for future, more sophisticated needs. The task at hand was making a frame for a miter-saw-DC hood.
View Image
View Imageforestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
The wood I use for drawing large arcs is from the rare, tubular PVC tree.
Freud America, Inc.
Masonite (tempered hardboard) works. If absolute symmetry is desired, one of the mechanical means (including flipping the template) would probably work better.
FG -
I just made three arches with radii of 36", 57" & 82". To lay them out, I ripped strips of 1/4" ply and used them for my "beams. I drilled a small hole at the pivot point (for a finish nail) and slightly larger holes the arc dimensions (for a pencil). Lay the whole thing out on the bench, drive a finish nail thru the pivot point and draw the arcs.
If I had known that you would ask this question, I would have taken some pictures as I did it. - lol If you want, I can post some pictures of my "beams".
FG
Easy formula is; take rise squared plus 1/2 the chord squared, then divide by 2 times the rise and you have the radius.
If h=rise (height) and c=chord and r=radius
(h² + c²) / 2*h = r
Easy math that can even be done with a graphite calculater.
Rich
The Professional Termite
What kind of arch? roman? 3/5's?, segmented?, shallow?, pointy?, There are all different formulas, although Ive never heard of beng ing a stick before
"Ive never heard of beng ing a stick before" Seen in many articles and books. Take a thin, flat, narrow piece of wood (oak, ash, other bendable wood), notch it or drill holes in each end, thread thin rope/string through and bent it so it looks like a bow (as in arrow) to replicate a given arch or ad lib one. Not a formula-type thing.
Arch may have been a misleading word to use in my OP. It was a gentle curve, as seen in the pictures I posted not too far back in this thread.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Not good for obvious reasons.
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