Joe W.

Very clever and nice design!

Kevin, Yeah, the bolt on the connecting rod is double nutted so no worries there on my unit. The problem reminds me of trying to find a chirping cricket in the house. It's gotta be in there somewhere!

Hi Paul, we will see - I ordered the connecting rod and will replace that for starters. I think I've found all the videos and reference material that's on the net and am always looking for more. with any luck, this problem will be solved in a few days.

Kevin, Yes, it does. Almost makes me want to put on ear plugs and ignore it.

Thanks Kevin, Your appraisal makes me feel better, as in, it is the machine and not me (I'm not going crazy). The person I bought it from said he was the original owner and that he never did any maintenance on it, so I assume it was assembled correctly at the factory. I am leaning in the same direction as your assessment of the cause being one (or both) of the bearings/sleeves in the connecting rod that attaches to the vertical rocker assembly. When it gets past the 4 1/2 speed setting on the dial, it sounds to me like it smooths out all the way up to full speed. I did - after I made the sound recording - readjusted the tension rod back, reversing the 4 counter clockwise turns I originally put on it, and giving it two more turns in the other direction (clockwise). Tried it again and got the same knocking sound. I'm going to order a connecting rod, with bearings and sleeves for it, and install it using the method Bob Brokaw did on his video. Even if that doesn't eliminate the knocking, at least I'll know those items are new.

Great idea (sound recording) and thank you for it - I am attaching the MP3 file will upload (fingers crossed) for all to listen to. The recording is a little over a minute long and starts at the lowest speed setting and goes to the highest and then back down again. And I appreciate your thought that I might be hearing a perfectly normal sound and just don't know it. I wish that were the case, but I don't think so. But as my mother used to say: "You are never so right that you can't be wrong". DW788 Sound.mp3

I adjusted - counter/clockwise (as per the suggestion on Rick's Scrollsaw website) another 3 turns and tried that - no change in knocking. So . . . I'm going to try going in the other direction with the tension rod adjustment and see what that does. While I was at it, I looked for marks on the underside of the tension rod cover plate and did not see any marks, so I don't think that is the cause. The range of knocking is on the speed setting I3 1/2 - 4 1/2) and not the tension setting. The tension setting does not alter the knocking sound. Still a mystery,

Ray, I'm seeking - if one exists - the service manual for the DW788 - - what the certified/authorized service centers would use - I assume DeWalt would provide that to them. I have an email request in to DeWalt and am awaiting their reply.

Yes, I tried that using my wife's stethoscope. The loudest knocking sound is heard near where the upper connecting rod connects to the vertical rocker assembly. I didn't find any sign of wear on any of the sleeves when I had it open, so I don't think that is the culprit.

Ray, yes, I did file down a goodly amount of the underside of the tension cover plate when I had the unit opened up. Figured I might as well do that then just to eliminate that as a possibility. It did not make any difference (dang it!) I will give the tension rod another turn or two, but I don't think that it the cause as the knocking kicks in noticeably starting at 3 1/2 on the dial and get worse thru till 4 1/2 on the dial and then smooths back out the rest of the way to full stroke speed. I think that's telling me something, but I don't know what - it does remind me of "harmonic resonance" where troops marching over a bridge made it collapse. And I am awaiting a response from DeWalt for a service manual. I figure an "authorized service center" must have something to go by when repairing them.

Thanks for sharing your thoughts. Here's some more information . . .

Happy New Year all! Well, after much deliberation, I adopted the practice of OCToolguy and like-minded scroll sawing addicts and bought a used DW788 (2016 on the motor) for a fair price. It did (and still does) have some knocking sound, but appears to cut well. Since it is used, I was OK with opening it up and seeing what I could see. Armed with camera/video, plastic bags, labels, tape, tools, every Bob Brokow video available (thanks Bob!), and a prayer, I disassembled the saw and examined most of the sleeves and bearings. This being my first time, I labeled and bagged every part/screws and took numerous photos throughout the process. The good news – 1) The bearings had minimal grease in them but/and the sleeves showed on signs of abnormal wear. 2) No leftover parts after reassembly. I cleaned out the bearings and sleeves and re-greased them using the suggested Valvoline synthetic grease. Reassembly, like disassembly was slow, but without any issues. Whew! Crossed my fingers, said another prayer, and hit the power button. Dang! Still have the knocking. Went to Rick’s ScrollSaw workshop and tried the “adjust the tension rod” tip without success. Stopped at only rotating it counter-clockwise one turn. There didn’t seem to be any improvement with the one turn, so decided to stop there, say Uncle! and ask for help . . . HELP! The bearings I greased: Front and rear upper and lower link drive bearings/sleeves Rocker Assembly vertical bearing/sleeve Blade Chucks upper and lower bearings/sleeves The knocking symptoms: Speed setting 1: Knocking 2: smooths out 3+ Knocking returns 4: Knocking gets louder 5: smooths out 6: smooth 7: Knocking returns 8: Knocking I have gone back over the forum postings to see if there was anything like this mentioned but came up empty. And looked elsewhere with no success. The knocking – smoothing out – knocking returning stumps me. A prize to the person who solves this mystery - an autographed photo copy of my very first scroll saw project. But seriously, any and all comments, thoughts, ideas are welcome. I could use it as is, but that’s just not me.

Brilliant! Now all I have to do is remember it for when I need it.

Welcome to the village!

Welcome Dave!

WELCOME!

Welcome aboard!

welcome to the village and love your works.

Welcome and look forward to hearing about your progress.

Your works are very good! Welcome.

Welcome to the village!

Welcome back!

Welcome and look forward to seeing your thoughts turn into patterns

Welcome to the village!

Welcome from Delaware.