Cutting Spirals without a spiral blade - Router Forums
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post #1 of 24 (permalink) Old 09-22-2014, 10:53 AM Thread Starter
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Default Cutting Spirals without a spiral blade

I have made a separate pair of heavy oak gates, (each weigh about 85 lbs), for our Village Hall in Northumberland. I made the top half of the hinges out of oak, (which I plugged with lignum vitae to drill for the vertical pin of the bottom of the hinges, already in the stone wall).
I want to make 'gravity-fed' return devices to fit on the hinge pins, below the top half of the hinges.
This may be incomprehensible, but the long and the short of it is that I want advice please on how to scroll a spiral in 3" diameter wood to try and make these devices.
I have an 16" Grizzly scroll saw on loan from a friend, without blades. It only takes pin-end blades and I can not buy a 5" spiral blade with a pin-end. So my question is this:

Can you advise me of a pin-end scroll saw blade, with which I can cut a spiral please?
Regards, Ian
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post #2 of 24 (permalink) Old 09-22-2014, 06:56 PM
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Ian while I can't help with your query I'm sure one of the forum members with experience in this area will be along to help.

Ross,
Rockhampton, Queensland, Australia


Enjoy the knowledge of others that can be found within.

‘Members are requested to add a first name in their profile as we are a very friendly bunch here'.
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post #3 of 24 (permalink) Old 09-23-2014, 11:03 AM
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How thick is the stock that you are planning on cutting? The scroll saw that you have will only cut wood about 1" thick or less. You will probably need to use a band saw with a small blade to make this piece.

I once made a self closing gate by making a cylinder of maple wood with a 20 degree diagonal cut through the center. The lower half of this cylinder was attached to the hinge so that it couldn't turn and the upper half of the cylinder was attached to the gate. Opening the gate made it rise up on the hinge pins due to the ramp cuts of the cylinder. When the gate was released, gravity returned the gate to it's closed position. This was an indoor gate and not subject to the wear and tear of the elements, and my self closing feature only survived about 6 months.

How about using the early colonial method to close the gate. They used a post located behind the fence at the hinge end of the gate by about the width of the gate. They attached a chain between this post and the non hinged end of the gate long enough to allow the gate to be opened to about 90 deg. At the center of this chain they attached a weight (usually a small 3-4" 2-3 pound cannonball When the gate was opened the tightening of the chain would raise this weight and when the gate was let go, the weight on the chain would fall and pull the gate closed. The beauty of this is that it is nearly weather proof.

Charley

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post #4 of 24 (permalink) Old 09-24-2014, 05:12 PM Thread Starter
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Charley, thank you for your encouraging and informative posting. Today I spent too long making a Coping Saw Spiral; blade it into the Grizzly scroll saw I have borrowed. As ever I was called for the evening meal just when I was about to begin testing! I did present a small section of timber to the blade and it seemed to gnaw it. No chance of cutting the wood. Unless the blade is in upside down, if that would make a difference. I have super-glued some 'ends' on to hair-like spiral 5" blades but I think they are now too short to fit the Grizzly.
I have a medium sized bandsaw and I have found a 1/8th inch blade (new) - so perhaps this may produce a spiral. I read that you need a spiral bandsaw blade, but this would cut-up the rubber 'tyres' on the wheels of the saw..more attempts tomorrow.
(I am hoping to make this 3" dia spiral about 20 degrees like yourself and when I have cleaned the two parts up, I want to use them as patterns and cast them in pewter, which should last a bit longer than oak).
I did think of using lignum vitae bowling green bowls on the end of a chain to close the gates, as we are fresh out of cannon balls - but I would rather use them on the grass (if I could get my hands on some).
I hope to keep in touch.
Regards, Ian
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post #5 of 24 (permalink) Old 09-24-2014, 11:55 PM
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Ian, a spiral scroll saw blade just has tips all around it to make it easier when changing direction. It isn't the best for very fine work. A spiral blade doesn't actually cut spirals. In this case I would make normal hinges and use a pulley system with weights to close the gates.

Good luck Jeff
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post #6 of 24 (permalink) Old 09-25-2014, 07:16 AM Thread Starter
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Thank you Jeff for yourGood Luck and posting. I understand your point, but so far, I have only found examples of spirals being cut with a spiral scroll saw blade. Although I have made all sorts of furniture and woodturned professionally too, I have never had occasion to use a scroll saw - so I am very pleased to have advice. My experience of scrolling is watching "U Tube"!! Still prepared to learn (84).
I 'rearranged' the holding the blade bits on the Grizzly this morning and inserted a normal Coping Saw blade, - but now I know scroll saws don't like such heavy duty blades. It wanted to bounce the wood up and down!
This afternoon I think I will insert an 1/8" bandsaw blade (in the bandsaw!!) and attempt a spiral, but I think it will 'jam' or snap the blade. (Watch this space!)
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post #7 of 24 (permalink) Old 09-25-2014, 10:39 AM
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An 1/8" bandsaw blade will allow you to cut curves as tight as about 1/4" diameter without binding and breaking the blade. For the size of your gate I can't comprehend that the tightest curve of your spiral would need to be that small.

When you put the coping blade in the scroll saw, did you put it in with the teeth pointing down? If it was installed with the teeth pointing up you would certainly have problems with the board jumping as you tried to cut it, but a blade installed teeth down will also on occasion have the board jump slightly if you are making a very tight curve and the sides of the blade are binding in the cut.

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post #8 of 24 (permalink) Old 09-25-2014, 04:58 PM Thread Starter
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Yes, as I feared, the 1/8" band saw blade snapped on me starting to try to cut a spiral in a2.5" diameter cylinder of elm. I suspect there are hidden and included angles in the development off a 3D spiral which I do not understand and that must be why a guy on U Tube successfully uses a spiral scroll saw blade, (which my borrowed 16" Grizzly does not accept).
I hardly dare disclose what my last throw to produce a spiral will be later tomorrow, but I will! I have superglued the ends of four flat ended spiral scroll saw blades, in a bundle, all facing the same direction. I glued them together at each end and for a quarter of an inch. I then made two short pieces of 3/16" aluminium rod, (ex knitting needles), about 1/4" long and drilled a 2 mm hole through each. I countersunk one side of the through hole and then stuffed each end of the 'bunch of blades' into the hole, counterunk on the outside and suitably prepared with a 5 minute epoxy resin, (beginning with A). My pins!
I have tried to make a tough spiral-type saw WITH pins. I imagine the pins will not be able to stand the pulling pressure and come off as soon as some wood is presented to the saw blade. I will put the teeth facing downwards, as I did with the coping saw blade which gave trouble! I think I will end up having to commission someone to make small spirals for my project!
Thank you continuing to help me..
Ian
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post #9 of 24 (permalink) Old 09-25-2014, 11:50 PM
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But, from designes I've seen of antiquity pieces that would do that are basically... you create a piece that will be the pin socket and the guide as one tublar piece... then cut diagonally across it at an angle.

You use half of it as your socket, which is locked to the mounted structure. The other half is locked to the pin of the hinge. So when the door swings open, it raises on the diagonal. When let go, the weight pushes it along the diagonal to where it fits together (in it's original setting, which is it's lowest position).

Did that description make sense to you? That is old-school antiquity engineering, using just gravity to self-close. Fairly simple design and will work for years on end. I don't remember exactly where I saw those fittings... but I'm thinking it was on old-west styled (mid-1800's) swinging Saloon Doors... And on Victorian period swinging kitchen doors.

"Don't worry, I saw this work in a cartoon once."
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post #10 of 24 (permalink) Old 09-26-2014, 06:45 AM
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They still make Saloon door hinges, but they are a bit small for a gate. Here is an example. Notice the ramps, much like my suggestion about a cylinder with a diagonal cut. They aren't spirals, just ramps.

Charley

http://www.amazon.com/Stanley-Hardwa...afe+door+hinge

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