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Cutting an irregular shape at 90 degrees
Posted: Thu Aug 27, 2009 2:08 am
by rdewinter
I need to cut an irregular shape at 90 degrees, or at a right angle so I have a flat bottom. The attached file shows the shapes that I need to cut. Can someone offer a jig or a method or secret procedure to cut these shapes down and make the resulting bottom of the shape square? I know the best way is to square the bottom before creating the shape but in this case I'm trying to salvage the piece.
Bob
San Diego
Posted: Thu Aug 27, 2009 8:10 am
by JPG
rdewinter wrote:I need to cut an irregular shape at 90 degrees, or at a right angle so I have a flat bottom. The attached file shows the shapes that I need to cut. Can someone offer a jig or a method or secret procedure to cut these shapes down and make the resulting bottom of the shape square? I know the best way is to square the bottom before creating the shape but in this case I'm trying to salvage the piece.
Bob
San Diego
The conical shaped piece is the most difficult to do. This task is best done with a band saw or jig/scroll saw(they are safer since you will be holding the workpiece by hand very close to the blade). The cylindrically shaped pieces can be set on a scrap piece with the smallest diameter resting on the scrap piece. this allows the larger diameters to 'hang over' the edge of the scrap piece. A second scrap similarly positioned between the smallest diameter and a miter gauge will assure cutting square in both dimensions. Due to the small size of the workpieces, this is easier said than done.
If doing several at a time(or often) a small jig could be make to provide the two surfaces the workpiece rests on between the table and the miter gauge. The offset needs to be cut into the 'jig' before assembling it tnto a 'corner' shape.
The conical shaped piece can be cut by turning(internal) a square shaped jig with a matching taper(inside). The jig is then cut off so that the workpiece will extend through it to allow access by the blade.
That is the limit of my creativity this A.M.!
Posted: Thu Aug 27, 2009 8:48 am
by discordanian
rdewinter wrote:I need to cut an irregular shape at 90 degrees, or at a right angle so I have a flat bottom. The attached file shows the shapes that I need to cut. Can someone offer a jig or a method or secret procedure to cut these shapes down and make the resulting bottom of the shape square? I know the best way is to square the bottom before creating the shape but in this case I'm trying to salvage the piece.
Bob
San Diego
I'm not entirely sure I understand the question, so I'll try and explain what I'm getting from this.
You want to be able to cut out the project of those shapes onto a flat surface.
Is that right? So you could photocopy these shapes and past that onto a board and take it to the bandsaw or scrollsaw, right?
Or am I way off base?
Posted: Thu Aug 27, 2009 10:19 am
by rdewinter
Discordanan,
No, I want to cut a square bottom (i.e. 90 degrees) on these pieces. Because they are not square, they do not lay or fit square on the flat surface of a table or chop saw. I need to figure out how to hold them perpendicular to a saw blade.
Bob
San Diego
Posted: Thu Aug 27, 2009 10:26 am
by beeg
I'd use a belt sander, instead of the saw.
Cutting an irregular shape at 90 degrees
Posted: Thu Aug 27, 2009 10:27 am
by flashbacpt
Use a set up similar to squaring the ends of a pen blank with your disc sander.
I suggest making a "V" shaped jig, that would hold your piece square to the disc sander, and with a light touch, you just might be able to square the end.
Good Luck!
John
Posted: Thu Aug 27, 2009 2:29 pm
by rdewinter
Beeg
A belt sander, flat disc sander or saw to make the cut or sand is fine, but I'm still faced with how to secure the piece so it's square to sand or cut.
Bob
San Diego
Posted: Thu Aug 27, 2009 2:33 pm
by rdewinter
John
A "V" shaped jig is fine, but just laying the piece in the V doesn't necessarily make it lay perpendicular to the saw blade.
Bob
San Diego
Posted: Thu Aug 27, 2009 2:50 pm
by tom_k/mo
If you're trying to salvage these pieces, I think I'd be tempted to try chucking them in a Talon, Oneway or Barracuda chuck, and using a parting tool to cut the bottom square. You could then use a jacobs chuck on the tail stock and drill the centered hole in the bottom of the stopper centered automatically.
Posted: Thu Aug 27, 2009 3:20 pm
by hobbydad
Are the tops of any of these pieces already flat and square? If so, can you hold the top against the fence of a bandsaw?