forward angle of blade

[Albert]

What should the forward angle of my blade be? I note that on my Delta SS350 the blade seems to be tilted slightly forward. It seems to me that this would make it cut quite aggressively. I also note that the upper clamp can be adjusted using an allen wrench. Should I move the upper clamp back?

Albert

[workin for wood]

you could move it back, or it might be just fine. perhaps you have it set in the more aggressive oscilating mode. If it is oscilating it will still deliver a square cut, because it will angle on the downcut and straighten on the upcut. If your cutting thin fret stock such as portraits then I'd adjust it to go straight down, and for thicker hardwoods, I'd go for more aggressive angling.

[millwab]

Jeff, help me out here

you could move it back, or it might be just fine. perhaps you have it set in the more aggressive oscilating mode. If your cutting thin fret stock such as portraits then I'd adjust it to go straight down...

My only complaint about my Delta is that it has a slight forward-and-back motion of the blade that can be a bit annoying when doing very fine cutting. I wasn't aware that you could adjust the blade holders like this. The manual that came with the saw does not say anything about this. How do I go about correcting for this "oscilating" mode? Thanx.

[Rolf]

That front to back motion on my Delta SS350 is the reason I bought my G4 RBI.
There is some adjustment in the top clamp assembly but on my machine it did not have enough travel. When I have time I will look into that further. I still use the saw for our club meetings. Actually I will be doing some demos tonight at our semi annual round robin.

[CanadianScroller]

The rocking motion happens on ALL parallel arm saws due to the nature of the parallelogram. In the Dewalt and Excaliber saws the geometry of the parallelogram reduces the motion.
Even with extremely fine work the front to back motion should not pose a significant problem.

The Eclipse saw has removed this problem, so have some of the older scroll saws that had a spring plunger on the top.

Personally I wouldn't get too hung up on the front to back action of the blade. There are so many things that affect it. Even a slight build up of sawdust in the lower blade clamp can prevent the blade from travelling 100% true.
It is more critical that there is no side to side motion on the blade. This can really cause a problem when cutting fine work, not only will it increase the size of the kerf, it can make it almost impossible to start cutting on the pattern line.

I did have that problem with my Delta 40-540. It turned out I was not keeping the lower blade clamp free of sawdust.

[William Young (SE BC)]

Hi Carl.
I am a little confused with your statement . Please correct me if I have misunderstood what you are saying. My findings from having owned both are the opposite to that.

The rocking motion happens on ALL parallel arm saws due to the nature of the parallelogram. In the Dewalt and Excaliber saws the geometry of the parallelogram reduces the motion.

The DeWalt has a non adjustable front to back motion on the blade of 30 thou wheras the parallel arm system on the Hegner can be adjusted to 6 thou . I have my P-20 adjusted to 7 thou although I can set it anywhwere between 25 and 7 thou. The G4 RBI is probably about the same as Hegner and P-20 even although they wrongly advertise it as staright up and down because it is impossible to have the parallel design move exactly straight up and down from front to back. I beleive the older RBI Hawk saws had a two position setting for aggressive of finer but not adjustable between them.
For the Delta SS350 I am not sure if it has the same adjustment as a P-20 or not but I will look at one next time I see one in a store and I will know if it has the same adjustment as a P-20 has . I know a lot of P-20 owners had no idea that their saw had an adjustable back to front blade motion. It is not discussed in the service manual. I was one of them until I saw a discussion about it on a scrollsaw site and adjusted mine. What a whale of a difference it made for ease and acuracy of cutting when I went from 25 thou to 7 thou.

I did get used to the 30 thou front to back motion on my DeWalt because I didn't know the difference at the time. But after upgrading to a saw with less of that motion I wouldn't want to go back because of the ease of spinning the wood in place without getting the overcutting action of the more agressive front to back motion of the parallel link design of the DeWalt.
W.Y.

[CanadianScroller]

You could be correct Bill. I am just thinking mathematically not measuring.
Like I said though when we are discussing the motion being of by thousands of an inch I think we get too wrapped up in it for the purposes of scrolling.

I am not talking about cutting the gears of a clock, but even then I sincerely think my eyesight would probably make all my cuts of by a thou or two

I did have some frustration with side to side movement when cutting fine lines but cleaning the dust out of the clamp corrected it.

[Jeff]

Front-to-back blade movement

I have a question about this front to back blade motion. I recently "upgraded" to a DeWalt from a 16" Craftsman and the aggressive cutting action of the DeWalt caught me by surprise. Although the Craftsman has a slight side-to-side blade motion, it only moves about a half a millimeter front-to-back (measured at the table surface). Although the DeWalt has no side-to-side motion, the blade moves about a millimeter front-to-back, and about 2 millimeters 1 1/2 inches above the table. This gives it a very aggressive cutting stroke, so it cuts much more easily and faster than the Craftsman. It has no problem with 3/4" white oak, whereas the Craftsman really struggled. The problem is that the DeWalt is much harder for me to control in the "tight stuff". Maybe I just need to get used to it, but I don't see how you can cut a smooth curve of 1/16" radius (and that's very common, even for a novice like me) when the blade is moving back and forth 1-2 mm! The hole cut upon spinning the workpiece 180 degrees is also larger than on the Craftsman and is worse the thicker the wood is. Plus, because the blade is slanted forward on the downward cutting stroke, it doesn't cut squarely and this also causes frequent problems.

So, my question is...Is this something I'll get used to, or is it something I'll have to live with (no more tight turns!?). I was not aware of any saw with an adjustable stroke, except for the Hawk G4.

Jeff

[Rolf]

William,
How do you adjust the P20? The SS350 has a couple of screws that clamp the upper blade clamp assembly to the top arm. They can be loosened and there is limited movement.
I was taking my SS350 to the meeting last night and dropped it. Fortunately I dropped it on soft grass and only broke the tensioning screw off.
So I was forced to use someones Hegner for the demo's ( nice saw)

[Greenfield_Bob]

Rolf, My P-20 has two small allen bolts on the blade clamp holder, you can loosen them and move the clamp. That is on the top clamp.
If that makes any since, if it doesn't Bill will be in here to help.

Bob

[Albert]

In a mathematically true parallelogram, opposite sides are always parallel. Therefore, if the back bar is always vertical, then so is the front "bar", i.e the blade. So, theoretically, there is no reason, other than manufacturing slop, that the blade cannot be made to travel absolutely straight up and down. (This is the opposite of a "C" bar saw, that has an inherent rocking motion.)

Not being a mechanical engineer, I am assuming that there may also be a good reason for a forward slant, and the resulting aggressiveness. If so, then that is why the Delta SS350 and others have the adjustable upper clamp. Mine is currently set to minimum slant, i.e. with the two allen screws loosened, the clamp is pushed as far back as possible. I assume that by simply filing the two slots on the front edge to be a little longer that it then could be adjusted to true vertical. Whether or not this is desirable, I don't know.

Also, I am not sure that I am using the word "aggressive" in the same sense as others. To me, "aggressive" means that the forward slant has a tendency to pull the wood into the blade, making it difficult to "spin" in place and to make tight turns. As Carl points out, this may not be worth discussing if the aggressiveness is mild. My difficulty with spins and tight turns are probably just due to inexperience. I am getting better at both, but if an adjustment to the saw can ease my learning curve, then I surely want to take advantage of it.

The seeming consensus that I detected from the replies was: If you have the adjustment capability, then it should probably be set for minimum aggressiveness with thin stock and set progressively more aggressive for thicker stock.

Thanks to all who replied. I found all useful.

[chrispuzzle]

In a mathematically true parallelogram, opposite sides are always parallel. Therefore, if the back bar is always vertical, then so is the front "bar", i.e the blade. So, theoretically, there is no reason, other than manufacturing slop, that the blade cannot be made to travel absolutely straight up and down. (This is the opposite of a "C" bar saw, that has an inherent rocking motion.)

It's not quite the case that the blade must go "straight up and down" in relation to the cut, with parallel arms. The horizontal distance from the pivot point to the blade will lessen the further the arms move away from the horizontal so although the blade remains vertical at all times it moves slightly away from the cut as the angle of the arms relative to the table increases.

If this is hard to visualise, imagine that the arms go on moving up and up like the jib of a crane. Eventually they would be pointing towards the ceiling and the blade would be vertical over the pivot points, in line with the arms themselves. It would be nowhere near the table and the workpiece.

On my machine, the difference at the top and bottom of the stroke, compared to the centre of the stroke, works out at 0.14mm or about 5.5 thousandths of an inch. Of course I would need to be cutting wood where the full stroke counted. Thin pieces of wood would only use a fraction of the full stroke and thus the movement of the blade away from the wood would be even less.

You could adjust to take account of this by having a slightly forward leaning blade so as the blade moves away from the cut, the lean compensates. It can clearly only compensate in one direction as in the other direction, the blade is moving away from the piece even further. The obvious direction is on the downstroke so you might want a slight forward lean so the cutting teeth are always the same distance from the cutting point. However you might be undermining the effectiveness of a reverse-toothed blade very slightly if you did that.

This is all theory. In practise it's obvious that skilled scrollers do good work with their favorite saws regardless of whether it is a C-action, Parallel action or one of the more unusual proprietary actions.

Chris

[Albert]

Thank you, Chris. Yes, although the blade can be made to remain vertical to the table, it will still move back from the centerpoint. That is indeed a good reason to have a slightly forward tilted blade.