Dewalt 788 / Delta 40-690 front to back motion

[Block]

My new Delta 40-690's blade moves quite a bit front to back as it is sawing up and down. I placed a wood block gently behind the blade and it was vibrating towards and away from me - seems like a lot to me. I'll try to shoot a video of it this week. I thought this saw is known to have a very good straight up and down motion.

I'm surprised - is there is no vacuum attachment point on this saw? I didn't see one so I quickly/haphazardly taped an old vacuum's hose under the table near the blade/hole, and that worked well. I used the saw 3-4 times so far, and it was a mess under it each time.

Up late trying to master Google Sketchup...got what I wanted drawn finally. Really handy!

[wood-n-things]

The front to back motion is an inherent problem with the new delta and the 788. You are correct there is no vacuum port on either saw.

[mtnman]

I took my 788 into a service center for the front to back problem and they replaced it under the factory warranty. The new one is somewhat better. Good luck!

[sawdust11703]

You can't expect a lot on the lower end of scroll saws. The Delta is the same as the Dewalt, with just a different color. I'm wondering where you heard that the saw was known for a good vertical cutting motion? If I were in your shoes, I would really try to see if I could return it. Trust me, as a Dewalt owner, you're not going to be happy and cutting items with intricate detail will become difficult if not impossible with that excessive blade motion. 1 1/2 yrs after my dewalt purchase, I was forced to go out and buy another saw. Don't make the same mistake if you're not happy with it. I have quickly learned in the woodworking hobby that you generally get what you pay for.

[Block]

Maybe mine is "normal" then. I'm very busy this week so I'm unsure if I'll post a video before Sunday.
There is a local authorized Dewalt service center, but who knows if they are familiar enough to know what is considered "normal". I've never heard of this place before:
Syracuse Industrial Sales
1850 Lemoyne Ave.
Syracuse, NY 13208

I don't understand why scroll saws are not designed the same as sewing machines - why not have the drive mechanism and blade go straight up and down? Similar to a car's camshaft or some other up/down mechanism (or however sewing machines are designed).

This is a better saw then I can justfiy (The $180 Porter Cable likely would have been good enough). I wish it had a dust collection port though - basically a no cost feature if they had included it in the original design. I surmise people have engineered workarounds but I have not stumbled into conversations on it.

[Block]

The tune-up page has a fix for this (down aways):
Tune

Wouldn't simply clamping down the top or bottom of the blade slightly towards myself do the same thing as adjusting/moving the top or bottom arm outwards (towards me)?
In the link above, they slotted the yellow cover to allow the arm's position to be adjusted.

Is it ok to manually move the arms up/down by hand so I can determine if the top or bottom arm assembly is too far forwards? I'll need to have the blade all the way up and then all the way down to check front/rear movement. Perhaps they should have made the saw adjustable in this regard since they don't seem to be able to make it precisely enough.

[Bill Wilson]

wouldn't simply clamping down the top or bottom of the blade slightly towards myself do the same thing as adjusting/moving the top or bottom arm outwards (towards me)?
maybe, but i think you will find that the clamps will struggle to hold the blade if they don't get a good bite. The end of the thumbscrew is very small, so there isn't much room to play with.
in the link above, they slotted the yellow cover to allow the arm's position to be adjusted.

Is it ok to manually move the arms up/down by hand so i can determine if the top or bottom arm assembly is too far forwards? I'll need to have the blade all the way up and then all the way down to check front/rear movement.
i believe you can insert a screwdriver in the slot on the end of the motor and use it to manually turn the motor.
perhaps they should have made the saw adjustable in this regard since they don't seem to be able to make it precisely enough.
mine is a type 2 and it does not have the front to back motion problem of some others. Our scroll saw club has a type 1 that does exhibit this problem, so it isn't necessarily relegated to type 2 only. My personal opinion is that it is a tolerance issue. Each of the components may be within the tolerance spec, but if the key parts, related to the blade position are all at the limits of their respective tolerances, then the cumulative effect is that there will be variance in the finished assembly.

The biggest disappointment is that, despite repeated attempts of owners to bring this problem to their attention, DeWalt seems to show no interest in correcting it. Unfortunately, this attitude isn't limited to their scrollsaws. I fear that it is becoming pervasive within their company and they risk losing what has been a very good reputation for quality tools. Even more unfortunate is the fact that DeWalt is not alone, among major tool brands, when it comes to declining quality.

[Block]

I agree with your comment about multiple parts could be close to being out of tolerance, which added together sometimes produces a saw with too much forward/back movement. One would hope they'd test all saws seeing how cheap their QA labor is versus their quality, but China is known for cutting corners when nobody is watching ("quality fade")...

My upper clamp looks crooked (leaning towards my left), but I did not feel like measuring it (yet). Could have been the lighting fooling me. The box was in good shape, so shipping damage is probably not an issue.

[Block]

I moved the bottom of the blade towards me and reclamped, and later tried the top, but the forwards and back motion did not seem to get better. It seems to be moving away from me (farthest from me) in both the full up and full down positions. If so, it is simply moving in an arc (normal, right?), but I'm not convinced yet. Also, the upper blade seems to move less (forwards (towards me) and back) than the lower part of the blade. I'll be using the saw tomorrow and will try to convince myself what it is doing.
Would be a lot easier to judge with a 100+FPS video camera. Well, if there is enough light to get a fast shutter speed, I could take 20 stills and by chance all positions would likely be captured. I have a F1.4 lens for my SLR...

[GladeFade]

There will ALWAYS be front to back motion on any scrollsaw that the action pivots around a point or pin. The manufactures try to minimize this by limiting the travel and the placement of the table in relation to the movement. there is NO way to eliminate this motion on these saws. The only saw that has a true vertical motion is the Eclipse saw you can see this at Lowest vibration, Precision bearings, More safety features. But it is a top of the line in price.
Even the RBI saw has this problem, I was told by their service dept that it will always be there.
Bill

[Carl E Jacobs]

Amen

There will ALWAYS be front to back motion on any scrollsaw that the action pivots around a point or pin. The manufactures try to minimize this by limiting the travel and the placement of the table in relation to the movement. there is NO way to eliminate this motion on these saws. The only saw that has a true vertical motion is the Eclipse saw you can see this at Lowest vibration, Precision bearings, More safety features. But it is a top of the line in price.
Even the RBI saw has this problem, I was told by their service dept that it will always be there.
Bill

You are exactly Right,That is exactly what was causing ,spiral blades to self destruct cutting straight backwards I had to readjust the table to seriously reduce that V or front to back movement,reversing the cutting angle of the blades,I would have posted but did not seem any interest.
My very best!
Carl

[Block]

I'm confused as to what the table has to do with it.

Maybe mine is only moving 1/16" but it just looks like more when looking (too) closely at it. My near vision is going out the door so lookign closely at the blade is a struggle (42 year old eyeballs). I'll try to measure it via pictures soon.

[Bill Wilson]

Yes, the arcing motion of a scroll saw blade is pretty much a function of the design of the saw. Some are more aggressive than others, due to the location of the pivot, as Bill mentioned, but it is inherent to all saws except the Eclipse.

The problem with the DeWalt has to do with the front of the blade not cutting perpendicular to the table. Even if it arcs, the end result should be a perpendicular cut. If it isn't, then you experience the over or under cut that is the problem with some of the DeWalts. It may only be a slight difference between the bottom of the cut and the top, but on some projects, it's critical. It's this fact that seems to be lost on DeWalt. They don't seem to understand that if a blade cuts deeper on the top of the wood than it does on the bottom (or vice versa), it directly impacts the quality of the cut and may well ruin the project. I presume their QA engineers simply check their parts for conformance to spec, but have no idea how critical these tolerances are when the parts are assembled.

[Carl E Jacobs]

Relationship

I'm confused as to what the table has to do with it.

Maybe mine is only moving 1/16" but it just looks like more when looking (too) closely at it. My near vision is going out the door so lookign closely at the blade is a struggle (42 year old eyeballs). I'll try to measure it via pictures soon.

Think about it,You have a vertical plane the blade,and a horizonal plane the table ,moving to form 90 degrees ,moving blade in or out top or bottom,changes what ,the angle to the table .everything references off of the table surface .moving the table front or back up or down effects the degree of angle to the blade having the same effect,to throw some more stuff in the game ,this meeting point is not in the center of the table ,so correcting ,this angle in the front requires less than if you try to correct it in the rear ,because of the difference in distance to the hole in the table where the blade come thru. Direct relationship one to the other ,you ought to try looking thru these,72 yr. old eyes ,if it were easy anybody could do it ,now it's your choice how you fix it! I for one would like to hear how you make out !
My very Best!
Carl

[Block]

OK, I read about that somewhere or another but I consider that to be a seperate issue, so I got confused. I did a quick measurement and my table seemed OK for front/back tilt angle issue.

BTW, when cutting, the "arc" is less noticeable than when "unloaded".
I can cut well with my saw, especially compared to my friend's woeful Ryobi oro whatever it was that I us last year . Very hard to keep the blade 90 degrees to his table and maybe the blade was not tight enough but I did ntto know better and did not want to mess too much with his saw. Part of the saw even fell off...I think it was part of the lower clamp that just needed to be tightened more.