DeWalt 788 blade clamp distance issue

[GearHeadOSU]

Hi Folks,

Have had a DW788 for about 8 years (not as active in use as many on here!), and always struggled a bit when installing blades: distance between blade clamps just barely gets close enough when untensioned.  Bought a different brand set of blades (Pegas, was using Flying Dutchman for some time) and now even more challenging.  While reading online last night on various DeWalt issues and fixes, read that the standard blade clamp center-to-center distance is 4-1/8".  Measured mine today and untensioned it's almost 5 inches!! (we'll call it 4.95").  Of course with 5" blades that barely gets the ends to the centers of the clamp screws if you're careful - which is why I found it frustrating that when installing a blade I had to get down on my knees with a flashlight to check bottom end in that clamp!  I also measured some blades, and the Flying Dutchman I had been using are a bit longer at 5.1", the new Pegas just a shade over 5"

In my research I saw mention of an issue with the tensioning wedge being out of spec for a certain period.  My saw is a Type 2 per motor tag, SN 200604-CJ14807 for those who may know how to decode this.  I couldn't find specifics of what dimension(s) are out of spec and what nominal is.  Could this be the issue causing my "daddy longlegs) blade clamp distance?  Other thoughts?

Thanks!
Rick in Oregon

[ddockstader]

Rick,
OK, I'm going out on a limb here and don't think I'm criticizing you, but that's just crazy. And I have an even crazier idea that I'll float for your consideration. My 788 arms were never more than about 4 1/8 inches apart. I just can't see how they could be. That being said, I did have a problem like what you describe when I couldn't get the blade to reach between the upper and lower clamp. I had upgraded my saw with the Pegas blade clamps. And being a typical American male who can recognize a wrench 3 out of 5 times, I installed the clamps WITHOUT bothering to read the installation manual. Lo and behold! The regular scroll saw blade wouldn't reach between them. I spent a couple of hours trying everything I could think of, releasing tension, checking for bent arms, looking for 6 inch scroll saw blades, you name it. I knew the blade clamps were installed correctly. Heck the Pegas name was right-side up. Then it dawned on me, what if I had put the lower clamp on the upper arm and vice versa. It took about 15 minutes to uninstall and then reinstall the clamps and suddenly my blades had stretched to fit once again. Is there ANY possibility that your blade clamps could be installed on the wrong arms? It's been over a year so I don't remember exactly what the original clamps looked like, but I know they were never as far apart as what you are describing. It's worth a check, anyway. Incidentally, the Pegas blade clamps are absolutely fantastic (if properly installed) and I highly recommend them. I hope you find the problem.
Dave

[GearHeadOSU]

Hey Dave, thanks for the input!  And I'm not offended (my ideas have been called way worse than crazy!)

At lunch today I took the table off my saw and snapped a few pics of the blade holders and arms.  I have a Jim Dandy arm lift, and thought for a minute THAT Was limiting how far down the upper arm can go, but it doesn't limit the motion.

So need some wisdom from the experts here...  From the pics is it obvious what the issue is?  Like do I have two upper arms instead of the proper upper and lower?  Something else look not-assembled-right?  I have not had my saw apart at all since new (not TONS of use over 8 years).

Thanks
Rick

[ddockstader]

Rick,
I just had to go downstairs and look at my saw to make sure, but that looks right - or at least it looks like mine. So my idea was crazy. However, I did measure my saw. From the bottom screw of the TOP clamp (the one just to the right of the upper thumb screw on your first picture) to the top screw of the BOTTOM clamp (the one just to the right of the lower thumb screw on your third picture), the distance is 4 1/8 inches. This was the most universal measurement I could come up with since I have Pegas clamps. But if yours is over 5 inches, something is definitely wrong.

Now I'll give you some advice that just HAS TO WORK! Get on your computer, open your browser, and Google "Gwinnett scroll saw service." This will bring up several YouTube videos made by the Gwinnett Woodworking Club outside Atlanta and particularly done by a guy named Bob Brokaw. Bob knows more about the Dewalt 788 than Dewalt does. Since each of these 7 or so videos (4 from 2014, 1 from 2018, 1 from 2019, and 1 from 2016 on "DeWalt Scroll Saw Repair Up Keep Maintenance") runs an hour to an hour and a half, I don't suggest you view them all. But the 2018 and 2019 updates will probably at some point go over what you need to know to take your saw apart. The 2014 videos are COMPREHENSIVE, but they take about 4 hours. But somewhere in these videos you will learn how to take your machine apart (including the tools you'll need. You probably have them all except may the T27 torx bit. That I had to find), what it looks like inside, how it works, what goes wrong that you can fix (essentially everything), and (more importantly) how to put it back together. This is the best advice I can give you from Illinois. If I could, I would love to travel to Oregon and help personally, but we're not allowed to go anywhere right now. So good luck and keep posting so I can follow your progress.
Dave

[GearHeadOSU]

Hi Dave,

I ran across the Gwinitt service videos last weekend researching this topic.  Watched the first "intro" one then realized the others totaled HOURS as you describe.  Very thorough!  I also ran across info on Rick Hutcheson's site (scrollsaws.com) with tune-up info on the 788.  That is where there is info on the tensioning wedge and issues within a certain manufacturing "range" with that part being too large in some dimension causing issues that sound like mine - but frustrating never describes the issue in detail.  I'm tempted to go ahead and order a new wedge, as I can get one for ~$6 plus shipping.

I may put more investigation on hold (while I wait for that part), since upcoming Christmas + grandkids = toy and puzzle projects.  Then tackle a more in-depth tear-down once that "production pressure" is past.

Thanks
Rick

[KCSteve]

I'm almost certain I'm wrong, but just in case.

I had a similar problem with blade length on my 18" Jet for a while.  That was before I figured out how you actually set the tension on a Jet.
That big knob at the back of the arm?  That's just for getting the arms parallel.  It does have an effect on the tension, of course, but that's not how you set it.  You set it by spinning the lever that closes the blade clamps and pulls them up.

When I was trying to use the knob at the back to set the tension I kept having problems with the length of the blades.

Like I said, I don't think this is  your problem, but I figure it's worth tossing out there just in case.

[GearHeadOSU]

OK folks, back for an update...  Based on web research a couple months ago, I suspected that my saw was from a batch with an out-of-spec tensioning wedge.  I never could find details on the issue, but was able to order a new one for about $11 with shipping, so worth a gamble.  After finishing up Christmas gift projects, and watching (studying!) the great DeWalt scrollsaw repair videos by the Gwinnett club, I felt ready to tear into my saw.  Followed the video advice to clean and re-lube all the bearings (all in OK condition thankfully), then tackled my blade distance problem. 

In one of the attached pics, you can see the wedge at the top rear of the saw.  Cranking the tension lever pulls the wedge forward, forcing the upper arm of the saw upward, increasing tension.  Since the replacement wedge I received was exactly the same size as my old one, I first tried adjusting the rod connecting the lever to the wedge "longer", going up to 8 turns (at about 1mm per turn) to where the edge was back about as far as it will fit under the upper plate, and only gained about 0.3" on blade clamp screw distance; still about 4.7" center-to-center.

I figured what the heck, and used a large flat file to cut down the top surface of the wedge.  It's aluminum, so easy to file (a milling machine would have been even easier!).  After multiple tries, I ended up taking the top surface down about 0.1" (2.5mm) - see original and cut down replacement pic.  I got my blade clamp C-C distance down to about 4.25".  Still a bit over the nominal which I believe is 4.125", but MUCH better than the "barely close enough" I had before.  Haven't tried cutting yet, but will tomorrow after finishing re-assembly.

Cheers and happy new year!
Rick

[KCSteve]

Definitely seems worth a try since you already have the replacement in hand if it doesn't work.