Curves?

[orchidius]

Hi there,

I've been browsing this forum for quite some time now, and I've done most of the research needed to build my own cabinet. I've stumbled across a design that woke my intrest, but it also posed me with some issues. The cab I set my eyes on is quite "curvey". Now i've got the "skills" it takes to saw and build any cabinet with straight lines, but the curves are quite an issue... I don't have a steady hand, so hand cutting/drawing them is not a possibility.

So... How do I draw/saw a curved cabinet out of a rectangular piece of MDF without the use of professional/CNC equipment?

Thanks a bunch!

[gryhnd]

Search for "kerf cut"...here and google.

[drventure]

Yeah, curves are sexy, but there's a reason most houses are built with angles

Kerf cuts, bendable plywood (google it), sandable foam/fiberglass, bondo, and spray body putty, will all be your friends for a project like that. Just depends on what exactly your plans are.

Pics!

[Franco B]

If you search for posts that contain 'Curve' in the woodworking forum only then you will find a few posts that may give you some pointers/ideas.

As the Doctor said, some pictures (and more info) will give us a better idea of what you are trying to achieve so that we can try to help you

[apfelanni]

build a template of 8-10 mm plywood , use birch or beech + wood if u wonna do more than 1-2 copys . small circles and curves can be done by things u ll find in ur kitchen or livingroom, larger ones with a strip of plywood and some nails to fix it. after u draw it to ur template use a jig + circular saw to cut it out and handsand the rest til its smooth, transfer it to ur cabinet sides and prejig it with +5-1o mm.  then clamp it together with with ur template and use the router with copy bit around the edges. if ur not familiar with a router go for some practice on crap wood. its easy as it sounds.

here are some pics of my recent projects.    

[gryhnd]

Ha...I made the ass/u/mption he meant curved facing surfaces that would require a kurf cut, not just cutting a simple curve. Could be either, I suppose...not totally clear.

[orchidius]

Thnx for the quick responses.

The project that gave me the idea for the "curves" is the following:

http://forum.arcadecontrols.com/index.php?topic=96465.0

So that should give you an idea.

Kerf cutting will certainly come in handy to make the top of the cabinet, but I already had that bit figured out 

The template idea also crossed my mind, but won't I be having the same difficulties there? I mean, if I hand cut a template without tricks/tools to guarantee a clean cut I will end up with a scrummy template (which will result in a cabinet with messy cuts on the curves)...

Using bendable plywood to draw a perfect line of the cut I want to make onto my MDF board is actually a very good idea, I'll most definitely use that one, but... even though I will have the pérfect lines on my piece of MDF, I'm STILL stuck with my sawing problem...

Is making a bad cut and sanding, sanding, re-sanding and sanding again the only option here? 

[Epyx]

So... How do I draw/saw a curved cabinet out of a rectangular piece of MDF without the use of professional/CNC equipment?

If you look at my aliens project in my signature you will see what i used. I just bent laminate and held it in place with clamps then traced the curve onto the MDF.  Unless you are doing the caffeine withdrawal jingle you will be fine to cut with a jigsaw and then sand it smooth. Once you have one side done just use that as your template for side 2.

[orchidius]

Okidoki, thnx for the heads up. I guess I was worried for no reason then I'll let you know how it worked out (starting the project first of july)

[apfelanni]

maybe u should get a jigsaw of some quality. i bought a makita for 300 euro and its cuts plywood like butter. zero prob to follow the drawing in mm precision. the next step of evolution would be cnc routed. the advantage of using a template is that a router does a 90 degree cut much better than a crappy jigsaw. if the cuts are not right angled it sucks when using t molding. cutting thick ply with a lowend machine isnt a good idea.

[apfelanni]

yesterday i found another way of drawing curves . i got the idea while bringing stuff to the local garbage dump. i allways check out what can be recycled for arcade purpose ( usually old tv sets or other electronics ) . i used a shutter ( we replaced some windows at home ) and bend it to the curve i needed , like a flexible ruler . its has an iron core and once its shaped its very stable . i needed it to gain a few centimeters on the backside of my micromission project so the tv fits in .  pic 2 shows the oldstyle method. p3 is ready 2 jig out and become a router template .

[orchidius]

Thnx again for the replies. I'm more then confident that i can find something bendable to draw the line with in all the "garbage" my dad collected over the years... (you know, the "i'll be able to use that someday"-excuse... I guess he was right then :p)

I'm gonna try to jigsaw/sand smooth and hope for the best, i'll be making a worklog so you can follow the build.

Thnx again!

[Nacimroc]

I just used a piece of string tied to a weight and a pen on the other end! Makes a giant compass. Move the weight around to suit the size of the curve. Its just a matter of marking the length of string used to make a matching curve on the bottom part aswell.

The jigsaw and sanding method is fine. I used a 40 grit paper to start and this gets rid of all the imperfections from using the jigsaw.

[hyiu]

to draw larger curves, you can use router.

with a homemade compass jig, I have done 21 inch radius circle.

it seems like yours is just an arc, but with even bigger radius...

there are also elipsse jig...

but if you want, you can do what nacimroc suggest, then use a belt sander to smooth things out.

once you get one side, a router can be used easily to make the other side EXACTLY the same...

good luck.

[kronic24601]

My one advise is to not "require" things to be exactly like you "planned".

Symmetrical isn't an issue, but using the jigsaw/sand method can leave things slightly different than a CAD file specifications. So long as you plan for that you should be fine.

For example, when working with my control panel, I just bent a large ruler, traced it, jigsaw sand ... but my artwork wasn't perfectly matched to the curve I cut ...

That's ok though cause I left plenty of black to compensate for any imperfections.

Point is, I'd cut 1 side panel first, route to match, THEN do anything else that might be impacted by the actual shape of the curve.

[ami-man]

Hi Orchidius,

The best way to get those side panels the same is to clamp them together and cut them together.

Draw on the top panel the shape you require, for the curves use any bendable material and hold at each end and push in the middle till you get the curve you desire and get someone else to draw the line for you. I use a yard or metre rule for jobs like this. Any thin material will do that does not kink a wooden strip or hardboard/thin plywood.

The curve can be cut with a jigsaw on both sheets together, you can sand or use a bendable rasp (Surform) I would use a bendable hand plane (for use on inner and outer curves) or my router.

Please let us know how you get on.

Regards
Alan Hood
ami-man

[orchidius]

Thanks for all the interesting and creative responses.

Here's the way I'm gonna go on this:

1) Clamp together
2) Jigsaw while clamped
3) Belt-sand while clamped

I don't have a flush trim bottom bearing router bit, only have some (blunt) regular ones. I'm considering getting one of those cheap 10-bit sets, but I'm not sure It will have a bottom bearing bit and I don't really want to "waste" 30$ on a single router bit (I don't own a good quality router and I don't do enough woodworking to justify the purchase). If anybody knows of any good router bit deals out there...

[kronic24601]

Just make sure your jigsaw is of good quality.

My jig saw has a tendency to "wobble" due to the vibration down at the bottom so you won't get a 90 degree cut if you clamp things together.

[orchidius]

Won't be a problem, thnx for the heads up!

[erictrumpet]

My jigsaw (and/or my possibly flawed manner of using it) makes it very difficult to get a nice square edge to my cuts. In fact I just started a thread on this board about that very thing. As for curves, lots of good advice in this thread. My current project has a very important large-radius curve and I am planning to do what I always do - jigsaw by hand, then cleanup/tweak with sander - but the sanding part would be a lot less involved if I could get a squarer cut in the first place. I find that the blade bends and gives me a beveled cut more often if there is any sideways pressure. So even though you are cutting a curve, try as much as possible to push the saw "straight ahead" as you cut.

Eric.

[patrickl]

Does working with a jigsaw through thick material actually ever work? I haven;t tried it very often, but I noticed that the blade tends to warp if the material gets too thick.

[Nacimroc]

Unfortunately, its almost guaranteed to happen!  No matter how slow I go it always seems to happen.

The easiest thing to do is repeat the exact same curve a half inch inside and do one sheet at a time. Try to get a flush trim bit and router. You will use it constantly.

The other thing to be careful of is the curve! If using the pen and wire way I said, you get a perfect symmetrical curve. If you just use a bendable sheet and pin it in place it might not turn out right. Just something to keep in mind. A mistake I also learned the hard way.

[orchidius]

The other thing to be careful of is the curve! If using the pen and wire way I said, you get a perfect symmetrical curve. If you just use a bendable sheet and pin it in place it might not turn out right. Just something to keep in mind. A mistake I also learned the hard way.

I see how the way you did it is foolproof, but if I understood correctly, you can only make circular curves with it... Not what I'm going for sadly enough

[kronic24601]

There is a formula for doing different sized ellipses as well ...
http://www.wikihow.com/Draw-an-Accurate-Ellipse

[Blanka]

It's very easy to make a compass for a router. It allows you to route perfect circle segments with any radius with ease.

[The Lumberjackass]

curves , regardless of size , should be fairly easy to cut out.
i do all, and any curves by using the old trusted stick and nail method . look at my vid and you will understand
what im talking about.

skip to 6 mins and 6 seconds :



any time i need to cut a curve , i always cut it out as a template first on mdf.
that way, you can refine the curve, or change it, before you cut into your main project.
all you need is a router with a bearing to match the template.
hope this helps