How to draw curves on cabinet sides (MS. PacMan cab)

[hurtz]

I'm working on a mini-Ms PacMan style cab and have a couple of questions:

1) Took mspacman plans from Jakobud's site, then used a spreadsheet to scale down the measurements. I multiplied everything by .68, then used a fractional inch calculator to round up or down to the nearest 1/8" inch. Should the semi-circle radius's (R55, R.75, etc) also be 'scaled' this way.

2) How do you draw these curves? I took a 7 inch long string (or whatever the radius called for), attached a screw at one end and a pencil on the other. Drew the circles on another sheet of MDF, then where they intersect, used that line to draw the curve. Looks like it turned out OK, but I would like to know what others are doing.

[DrewKaree]

Get 2 pushpins. (nails would work FAR better, but some folks don't want holes in their material at any cost, yet seem able to handle a pushpin hole

Stick them into the material at each end of the curve.

Using a flexible piece of wood or cardboard, push it up against the two pushpins (again, a nail will work FAR better here).  Push in the middle until you get a curve that's pleasing to you. 

Stick a pushpin into your material in the location your finger is (you had to use your finger to push in the middle, yes?).  This will keep your curve's shape, while you trace it with a pencil.

[somunny]

That's an excellent idea.

You're one fart smeller, Drew! 

Steve

[hurtz]

Thanks,

What wasn't clear to me is that the legnth of the 'thing' you use (string, ruler, etc) is the radius of the circle your trying to make.

What I ended up doing is taking one of those $4 metal rulers and drilling 2 holes in it the legnth of the radius. I then scribed a small arch using the 2 known ponts, then made the arch using the point where the 2 marks intersect. Turned out perfect! For the front of the cab I had to lay out another sheet of MDF to scribe the marks on.

Hope that makes sense to someone reading this years from now...

[holtdoa]

1, Assuming the curve would be part of a normal circle if you drew all of it, make a dot at the two end points of the curve.

2. Make another dot at the mid point of the curve at the highest point.

3. Pencil a line directly between the end points and make a perpendicular line from the center point crossing that line. That's the initial setup.

4. Now draw a line from one endpoint to the center dot, measure the length of that line and put a dot in the center.

5. Use a square to draw a line from that dot to the center line perpendicular to the endpoint to center point line. The intersection will be the pivot point for your compass, string, or whatever. Make it's length the distance from that pivot point to either of the endpoints (or the middle dot) and it should let you trace out the curve/arc perfectly.

That's confusing as heck without some diagrams, but play with it using a protractor, ruler, and some paper and you'll see how it works. This may not be suitable for your current task, but it's a good way to get smooth, duplicatable arcs.

[DrewKaree]

Wow!  Eleventytwelve brazillion measurements and hopefully precise and exact placement of the midpoint "dots" instead of figuring out 2 endpoints and the center to begin with and using that?

* DrewKaree walks away shaking his head at making something so simple far more difficult than it needs to be.

[ChadTower]

I would model the shape in cardboard and then trace it onto the wood, but then again I'm not much of a woodworker.  That would, at least, guarantee a matching curve for the other side without having to use the first one as a template for the second (which is probably the better way to do it).

[Dudeman]

Print it out on paper, use a pencil and trace the line on the back side (heavily), tape the paper down on your wood and use the pencil to "scribble" over the line of the curve. This will make the graphite from the back side transfer to the wood.

P.S.
Make sure you print it out 1:1!

[NiteWalker]

Get 2 pushpins. (nails would work FAR better, but some folks don't want holes in their material at any cost, yet seem able to handle a pushpin hole

Stick them into the material at each end of the curve.

Using a flexible piece of wood or cardboard, push it up against the two pushpins (again, a nail will work FAR better here).  Push in the middle until you get a curve that's pleasing to you. 

Stick a pushpin into your material in the location your finger is (you had to use your finger to push in the middle, yes?).  This will keep your curve's shape, while you trace it with a pencil.

Drew has the best method IMHO.

[javeryh]

Drew's method is definitely the easiest (and best, IMO) but if you are looking for EXACT measurements (scaled for your mini) then you need to:

1.  Get a string and tie it to a pencil
2.  Measure the radius from the pencil point and put a tack in the string or something
3.  Place the tack at each end of the curve and draw a curved line where you would imagine the center point of the large circle your arc is a part of would be
4.  Where the small curves you drew intersect is the exact center of the circle.
5.  Put your tack on the center point and connect the endpoints.

Voila!

This only works if your curve is an arc though.

[ChadTower]

Would it be possible, if you had a scan of a full sized one, to use an image editor to reduce the full size to whatever small scale... print that out, trace onto the smaller one?  That way the PC would have done all of the recalculations for you.

[NiteWalker]

Don't see why not. The challenges there are getting the scan of the original and printing it out full sized after resizing in photoshop or whatever program you'll be using.

[ChadTower]

Yeah, I was definitely thinking bartop as I came up with that.

[etoasty]

Anybody remember the compass way from elementary school?

Set your compass for whatever radius you want. Then make two marks ( A and B ) on the sides making up the corner:



Then set the compass on point A and make a section of a circle. I don't really know how to describe this, so just look at the picture. Do the same thing from point B and they should intersect.



Put the point of the compass on this new point, and draw a quarter circle from A to B:



Should make a corner. If you want, you can make the compass a little wider for this last part to smooth the edges of the circle out. The real beauty of this is that you can use it to make rounded corners for any angle (like the back of an upright cab, not just right-angled corners.

Also, sorry about the blurry pictures.

[ChadTower]

He's not looking for a circular arc, though, I think.  He's looking for something with variation in it like a Ms Pac cab curve. 

That's definitely the way to make a perfectly circular corner curve.  Been a long time since I used a compass.   

[spriggy]

Anybody remember the compass way from elementary school?

or.... the good old glass/jam/peanut butter lid corners.  Find the right diameter jar lid, chuck her up against the corner... and pencil away.  Never fails for lovely 'Mcyver' rounded cabinet corners. 

[MikeQ]

I'm always doing the peanut butter lid trick except I use my wifes salad bowls and stuff.  It usually gets me in trouble when I return them with sawdust on them.

[fjl]

Just tell her sawdust is a good source of fiber

[ChadTower]

Tell her next time she complains about it you'll bring it back with stripper glitter instead.

[NiteWalker]

All conversations with girlfriends/wives should end with:
"Shut up woman! Now go make me a sammich!" 


Unless that earns you an intimate nite with the couch and whatever pillows that may be on it. 

[ChadTower]

Only an idiot would piss off the person about to make their food.