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Canadian Scroller
Starting Member
Canada
12 Posts |
 Posted - 12 February 2006 : 10:25:31
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I cannot attest to the Diamond saw but I do sing its praises.
I was looking at the blade clamps in the two photos and aslo in the Scroll Saw Bench guide.
I really like the countersunk blade holders that will self center the blades. That has to be a huge improvement on what is out there. I thought of a blade guide of a similar nature, with a collet, like that in an Xacto knife. Once the blade was slipped into a self centering hole either a knurled ring could clamp it or some kind aof a lever cam could clamp it.
I had another thought for a saw I would like to share too.
My idea for a scroll saw is having two fixed arms, any length since they will not move. Inside the arms will be drive shafts run by gears. A motor drives both gears in opposite directions. The drive shafts will mount to Scotch Yokes in the end of the arms. The Scotch yokes will convert the rotary motion into vertical motion. Since both drive shafts run in opposite directions to drive the yokes, the vibration will "hopefully" cancel each other out. The Scotch Yokes will also make the blade travel vertically.... absolutely no lateral motion. This would be one of the few saw designs that would do that.
I know I will never build the saw, but it is just an idea worth some discussion. Perhaps when I eventually get a Diamond, the idea will flit away.
If this isn't appropriate for the forum, please erase it.
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Gill
New Member
United Kingdom
60 Posts |
Posted - 12 February 2006 : 13:34:28
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Hi Carl
Not being an engineer, I don't know if your idea could be realised. However it sounds good to me  .
I particularly like the idea of a collet-type blade holder. Perhaps the lever or cam that would be used to clamp the blade could also tension it? That would make blade changes and subsequent tensioning incredibly fast.
Gill |
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The Woodman
New Member
United Kingdom
98 Posts |
Posted - 12 February 2006 : 16:44:17
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| Who said Gill is a busybody ? |
Edited by - The Woodman on 28 July 2008 20:51:33 |
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Canadian Scroller
Starting Member
Canada
12 Posts |
Posted - 12 February 2006 : 20:56:19
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The Dewalt is pivoted from the back. Two rods move back and forth driving triangular blade holders up and down. The movement is exaggerated in this picture but it shows there is some linear front to back play.
In a Scotch yoke, the rotary movement from a drive shaft creates a linear motion in a pin mounted in a barrel.
Here is a link http://grove.ufl.edu/~wgsawyer/Laboratory/Wear/Applet/ScotchYoke.HTML to a Java applet of a Scotch Yoke, unfortunately this animation is used to indicate wear :(
If the drive shafts were mounted in bearings within the upper and lower arms of the saw the only mass vibrating would be that of the yoke and the blade clamps.
I believe this kind of mechanism is used in "sabre" saws. It was also use many years ago in the oil bath saws produced by Delta Milwaukee.
Those saws had a spring on the top of the saw to hold the tension on the blade. They were awkward to set up. |
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Gill
New Member
United Kingdom
60 Posts |
Posted - 13 February 2006 : 06:08:01
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Carl, I learn something new each time you post . So that device is called a Scotch Yoke, huh? Well I never...
So what you're saying is that with a drive like that mounted directly underneath the blade, you wouldn't need moving arms on a fretsaw at all? Okay, you'd need a fixed arm to hold the top of the blade, but that arm could be incredibly long because it would be stationary. I'd love to hear Doug's views on the feasibility of your suggestion.
Gill |
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Canadian Scroller
Starting Member
Canada
12 Posts |
Posted - 13 February 2006 : 08:09:27
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There would be a yoke on both arms.
The drive axels fit inside each arm.
My original thought was to have both drives run in opposite directions, to cancel any vibration but I am not sure if the design would allow that.
The length of the throat is limited only to the length of the arms and drive shafts. There would be no lateral play since the arms themselves don't move.
This is just an idea I am not sure if it is possible. |
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doug
Starting Member
United Kingdom
7 Posts |
Posted - 22 February 2006 : 16:03:47
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Hi Canadian Scroller and others re blade clamps and the operation or movement of the blade arms etc
a collet type of blade clamp would be very limited in blade width and thickness it would be very time consuming in operation and in most scroll saws the bottom blade holder is very difficult to get at a collet would not take pin end blades now study the Diamond blade holder it has a hook to take pin end blades a countersink hole for fret blades and a 1/16" slot accross the whole width of the clamp which can take blades of 1/2" wide or more and up to 1/16" in thickness also the blade grip is adjustable not only by the wing nut pressure but also it has an adjustable kink system thus making it impossible to pull out - try bending a length of wire around a corneror other sharp bend dont clamp it in any way - now try to pull it around the bend any electrician will tell you its almost impossible to pull a cable around a sharp bend this is how the diamond blade holder works for a test clamp a fret blade in a bench vise and the other end in a diamond blade holder --now pull very hard try to jerk it out of the blade holder --it will pull out of the bench vice first or break the blade
in the past many systems have been used to drive a fret blade with little viberation if possible the high cost of gears plus the drive system and scotch yokes would I think put the machines cost out of most peoples price range the diamond uses a balance arm in opersition the the saw arms driven by a con rod and a ball bearing eccentric which gives a very good balance with no back and forward motion which you get with the flywheel type balance |
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doug
Starting Member
United Kingdom
7 Posts |
Posted - 22 February 2006 : 16:05:05
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Hi Canadian Scroller and others re blade clamps and the operation or movement of the blade arms etc
a collet type of blade clamp would be very limited in blade width and thickness it would be very time consuming in operation and in most scroll saws the bottom blade holder is very difficult to get at a collet would not take pin end blades now study the Diamond blade holder it has a hook to take pin end blades a countersink hole for fret blades and a 1/16" slot accross the whole width of the clamp which can take blades of 1/2" wide or more and up to 1/16" in thickness also the blade grip is adjustable not only by the wing nut pressure but also it has an adjustable kink system thus making it impossible to pull out - try bending a length of wire around a corneror other sharp bend dont clamp it in any way - now try to pull it around the bend any electrician will tell you its almost impossible to pull a cable around a sharp bend this is how the diamond blade holder works for a test clamp a fret blade in a bench vise and the other end in a diamond blade holder --now pull very hard try to jerk it out of the blade holder --it will pull out of the bench vice first or break the blade
in the past many systems have been used to drive a fret blade with little viberation if possible the high cost of gears plus the drive system and scotch yokes would I think put the machines cost out of most peoples price range the diamond uses a balance arm in opersition the the saw arms driven by a con rod and a ball bearing eccentric which gives a very good balance with no back and forward motion which you get with the flywheel type balance |
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another idea
