Puzzle size and spirals

[chrispuzzle]

I know that the conventional wisdom on what size of jigsaw puzzle you can cut is that a line drawn from the centre of a long side to an opposite corner - ie a half-diagonal - must be shorter than the throat of the saw, so you can rotate the board enough to cut interlocking knobs. So an 18" throat such as my Axminster can cut a board about 12.5" by 25" at most.

But if you used a spiral blade, presumably you could cut much larger boards. You'd start by cutting off sections that are less than the width of the throat, and then cut those into further sections until you had sections that could be cut with a standard blade. Or you could just go on cutting with the spiral.

Now, I also know puzzle cutters don't usually like spiral blades because they cut more kerf than the equivalent standard blade so you don't get the tightest possible fit. But I wonder if it is worth the sacrifice in order to be able to cut really large puzzles?

So one question is, what is the equivalent of a spiral 2/0 in a standard blade when it comes to the kerf? I see figures for the thickness and the diameter of spiral blades on Mike's Workshop charts but I'm not sure what the relevance is when it comes to the kerf, eg, if the cut is governed by the diameter of the blade, what is the point of knowing the thickness of the teeth?

[Carter-Johnson]

I guess I don't understand the problem. As someone who has cut probably a quarter-million puzzle pieces, primarily with Flying Dutchman Superior Puzzle blades, a narrow kerf 2/0 blade, when I'm confronted with the need to cut a puzzle from a picture that is longer then the throat of the saw, I simply make a cut in a middle of the picture, or I cut off a section. I make sure when I'm doing that that I don't follow a pre-determined line, that I honor color lines within the picture, and that I insert locking tabs at regular intervals.

I can't see using spriral blades for puzzles,. unless you're cutting childrens puzzles with thicker wood. I use 1/4" wood and spriral blades would make the pieces so loose as to be useless. You can pick up any of my puzzles by an edge piece and wave it in the air without it coming apart.

Here's an example of one where I cut down the middle:



I've never had this problem, though I've cut a number of puzzles that were as long as almost twice the saw's depth. I'm not quite sure I understand the question about "equivalent" kerf? Why would that be desireable?

Sorry to sound ignorant.............Carter

[chrispuzzle]

Carter -

I'm the ignorant one when it comes to puzzles, that's why I'm the one asking the questions

I was thinking of puzzles where the board is considerably larger than twice the length of the throat. Sorry if I didn't make that clear.

For example, a 3,000 piece card puzzle I have here is 48" by 32". You would not be able to scroll that on most saws. Even with a 24" saw you wouldn't get it past the throat because of the substantial width.

My question about the cut of a spiral blade, which would otherwise make such huge puzzles easier to cut and manipulate, was just to establish how loose a cut it is, for example, would a 2/0 spiral be like scrolling with a #1 blade or #5 blade or what? Is the diameter of the blade the key dimension? I can appreciate the thing about picking the puzzle up by one corner. But you are not likely to be doing that anyway with a puzzle that's 4 feet wide.

I'm not really planning on cutting such a monster, certainly not any time soon. I'm just ruminating on how one might go about it. They are the sort of puzzles I've enjoyed doing in the past, though.

I love the beach shoes and the way the bare wood looks like sand. I think the centre line cut is very well disguised.

Chris

[PuzzledMoose]

I don't have any spirals here smaller than a #3 but the kerf from a #3 spiral is a lot wider than a #3 SR blade - I can't see even a 2/0 spiral being any use for puzzles.

Thinking about Carter's suggestion of halfing the puzzle first, could you not cut the puzzle into quarters first when you get round to cutting your mega-puzzle?

Ian

(mind boggling at the thought of cutting a 3000 piece puzzle! )

[chrispuzzle]

Thinking about Carter's suggestion of halfing the puzzle first, could you not cut the puzzle into quarters first when you get round to cutting your mega-puzzle?

Well, geometry seems to say no you can't. In order to cut an interlock you have to rotate the board more than 180 degrees, right? Otherwise you just get a semicircle or equivalent which won't lock. That means at least two adjacent corners of the board must pass the throat of the saw.

If you want to have interlocks facing in different directions - it would be a strange puzzle if all the interlocks in a line bisecting the puzzle faced the same way - then you are at some stage going to have to pass all the corners past the throat. So the best possible starting point is halfway along the longest edge, and the distance from there to the furthest corner (a corner on the opposite edge) is the distance the throat must clear.

Even on a much more modest 24" x 16" puzzle, which is a quarter the size of the 3,000 monster - a 750 piece puzzle if we had similar sized pieces to an ordinary cardboard puzzle - we would need a 20" throat to squeeze two adjacent corners through the throat. (Start in the middle of the 24" side, and the furthest corner is SQR(12x12 + 16x16) away). You could start say, 6" along the longest side. Then you would have SQR(6x6 + 16x16) = 17" to clear one way - you could cut a line of knobs all facing away from that near edge - but if you wanted to add knobs facing the other way you would suddenly need a throat of SQR(18x18 + 16x16) = 24.1" to get the other two corners past.

That's what the math is telling me, but if Carter or any other puzzler knows how to beat the "two adjacent corners" theory and still cut a very large board in half so that it interlocks, I'd love to hear how. I'm sure most of you experienced puzzlers are not so stupid as to try and cut a puzzle too big for your saw in the first place, but it nags at me that there *ought* to be a way.

Chris

[Carter-Johnson]

Chris, you must be an engineer.

I know many of the puzzle makers in the U.S. personally, and I don't know anyone who has or would even try to cut a puzzle of 3000 pieces, except perhaps as a montage of smaller puzzles. It doesn't sound like fun to me. The selling price would have to be at least $3500.

If they had to make a puzzle from one large piece of wood, they would undoubtedly use the smallest spirial blade for the cuts necessary to reduce the overall size so it fit their saw.....or, they just might buy a saw with a huge throat (I've seen one that's almost four feet). I suppose some cuts could even be made by hand. Others could probably be made with very thin blades by stopping, disconnecting the blade and turning it (the blade) around before finishing the cut. All of the above go way, way beyond my threshhold of patience.

The important point is to have phun.....

Carter

[PuzzledMoose]

OK - an idea - but maybe a stupid one ...

Assuming you have multiple copies of the original picture -Make several copies of the original picture - cut it up and attach sections of it to smaller rectangular backing boards but with the sections of the picture slightly offset to allow for overlap -then line up the picture on two of the boards and stack cut the interlocking section - repeat as necessary ...

Does this make sense? I know what I mean but I'm not sure this explanation is clear.. and it could be a pain to do .. but it might work ...

Or you could look for one of these that Carl posted a pic of a while back - the one with the unlimited throat ...

http://www.scrollsawer.com/forum/showthread.php?t=7517

Ian

[workin for wood]

I'm no puzzle master, but I have had to inlay an intarsia into a frame that is 32" wide, when the saw is only 26" deep. I'd do as the puzzlers are saying and cut the puzzle in half or quarters like they say, but here's something you may be forgetting. You can turn the blade around so that it faces the back of the saw, that's what I do....start with the blade in the normal position, when you get halfway around a pin, the wood will hit the back of the saw..so turn off the saw, pull out the blade and reverse it then thread it back up through the wood and now you can finish the pin, then rethread the other direction and so on. It's a pain, trust me, I made about 20 cuts like this and it took me about 6 hours, but it got the job done. Once you have the puzzle in half or quarters, it's sure to be smooth sailing. If you want to make me the inventor of this technique, I'll call it "puzzlefret."

[chrispuzzle]

Thank you guys for some brilliant ideas!

I suppose since it should be possible to cut a line of knobs that all face the same direction, closer to an edge, to section the board, then using the reverse blade technique - thanks Jeff, and Carter too - you could produce enough variety to disguise what you were up to. Of course the width of the board might come into play as well.

I guess the really cool way to do this is to buy a Diamond and rotate the blade without removing it from the clamps, which I hear you can do on a Diamond scrollsaw.

If one could sell Monster Puzzle for $3500+ that would be some incentive to patience. At a reasonably sedate two minutes per piece, a 3,000 piece puzzle would take 100 hours to cut, after the boards were sectioned to something manageable. Spread over two months that could be done without too much hardship? Less than a couple of hours a day?

Of course, if I did such a foolish thing, I had better remember to rebuild the puzzle as each piece is cut, or I'd take another two months just to assemble it again for sanding...

Chris

PS I am not an engineer. But I do hang out with engineers more than is good for me.

[Gill]

I guess the really cool way to do this is to buy a Diamond and rotate the blade without removing it from the clamps, which I hear you can do on a Diamond scrollsaw.

Indeed you can.

It might also be worth figuring out how you could stack cut a monster puzzle like that. Just imagine, four (or more) for the price of one !

Gill

[PuzzledMoose]

!

Gill

I love that smiley, Gill ...

[workin for wood]

Here is another puzzler for you then. Lets say you have a diamond saw, and then you can reverse it without unclamping the blade. what is the size of the blade from front to back as compared to side to side? if the blade is twice as deep as it is wide, can the blade be spun around ? I think you might still have to unclamp it and manually re feed it, or else do some damage to your puzzle.

[chrispuzzle]

Here is another puzzler for you then. Lets say you have a diamond saw, and then you can reverse it without unclamping the blade. what is the size of the blade from front to back as compared to side to side? if the blade is twice as deep as it is wide, can the blade be spun around ? I think you might still have to unclamp it and manually re feed it, or else do some damage to your puzzle.

Good point, Jeff.

However, if you can cut a curve at all, there must be enough play to rotate the board a certain amount while cutting, or we could only cut in straight lines.

The geometry of the curved cut must be capable of being broken down into a series of small rotations and straight cuts, since the saw teeth themselves are straight. It follows that you can rotate the board *a certain amount* without damaging it. If you can do that, then you can also rotate the blade *a certain amount* without damaging the board. You may not be able to rotate it 180 degrees, but surely you can rotate it a certain amount at a time and get your cut done that way.

Gill may be able to tell us how far she can rotate the blade of a Diamond while it is in the middle of a cut?

Chris

[Gill]

Gill may be able to tell us how far she can rotate the blade of a Diamond while it is in the middle of a cut?

I've certainly managed to rotate the blade holders through more than 45 degrees whilst in the middle of a cut using a #3 blade which was under slightly less tension than normal. After a couple of millimetres I was able to rotate it through a further 45 degrees and continue cutting. I felt it would have been possible to make more radical rotations than that but the project didn't demand them.

The biggest problem I had making these cuts was in actually seeing where the blade penetrated the board; it's much harder to judge this accurately at a distance. Manipulating the board was also a major task simply because of its mass - there's a lot of difference between the 11" pieces which are my usual maximum and that piece which, if memory serves, was approximately 36" along one side. A further complication was the need for a lot of clear floorspace around the saw, not just for the board as it was turning but for me so that I could run round and support the board. If you're cutting a board with a large diagonal, don't forget to make sure that you've got enough space to run around the outside of the board as you're spinning it or be prepared to duck under it and possibly control the cut blind from underneath.

Oh, I did switch the machine off each time I adjusted the blade holders, of course. Just in case anyone was wondering...


Gill

[chrispuzzle]

Thanks, Gill.

Looking at the Flying Dutchman charts at Mike's Workshop, I see that an FD #3 blade is always more than twice as wide as it is thick, sometimes quite a lot more than twice as wide.

The special puzzle blades, on the other hand, are less than twice as wide as they are thick. So they ought to be able to turn further than the putative 45 degrees - perhaps about 60 degrees (after jotting down some quick calculations based on an FD Polar #3 vs an FD Puzzle Blade).

As you say, the manipulation of Monster Puzzle starts to become the most serious obstacle...

Chris