DeWalt 788 knob upgrade - Router Forums
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post #1 of 7 (permalink) Old 06-19-2017, 05:24 PM Thread Starter
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Default DeWalt 788 knob upgrade

Recently a fellow woodworker sent me a note about an upgrade someone did to his DeWalt 788. Seems as a Marcus Bailey has come up with a over sizsd knurled knob cap for the Dewalt Scroll saw. He is making these and for more information you can contact:

Marcus Bailey

404-274-2532

Or: [email protected]

They come in 2 sizes,1.125" and 1.00" , I bought 2 small ones, here are the pictures,thats about 2 min. to install.

Herb
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post #2 of 7 (permalink) Old 06-19-2017, 07:22 PM
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I've seen them before, Herb.

While they look nicely made and should work well, I'm concerned with the added weight putting a significant additional load on the tiny bearings and mechanism of the saw. I prefer a tool, or one of these that you use to turn the saw knob, but then you remove it before running the saw. The lower blade grip runs very close to the bottom of the table when the saw is at it's maximum up position, so I'm also concerned that something like this, if left on the saw, might hit the table bottom or surrounding parts too. DeWalt 788 bearings need re-lubrication or replacement about once a year if the saw is used heavily. It would likely be more often if these were added.

If I felt that I needed a tool to loosen or tighten the blade grips, I might get one of these, but I wouldn't leave it permanently attached to the saw. I've also seen where someone had hollowed out the end of a file handle to fit the knob on the saw.

Charley

Central North Carolina

Last edited by CharleyL; 06-19-2017 at 07:26 PM.
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post #3 of 7 (permalink) Old 06-19-2017, 07:37 PM Thread Starter
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They are made of aircraft aluminum and weigh about as much as a copper penny, the diam. is only 1/16" larger than the wing nuts and had plenty of clearance under the table. They seem to work good, I am not a heavy scroll saw user so you probably have a point in the lubricating idea. There was no detectable vibration or noise when I turned on the machine. Only time will tell, sure makes it easier to tighten the blade.
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post #4 of 7 (permalink) Old 06-20-2017, 10:34 AM
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I agree, but I wouldn't mount them permanently on the thumb screws. I would use them like a wrench and just slip one on when it was needed, then remove it when the tightening or loosening was completed. The tiny bearings will thank you. They don't last very long without this added load.

I have used some DeWalt 788 saws where these thumb screws were very hard to break free, and these metal tools would have helped both me and the other saw users. For whatever reason, my DeWalt 788 doesn't have this problem. My fingers have always been adequate without any tool needed to assist them. I can't say this about the wing nuts that I use on my shop made clamps that I use when cutting compound scroll saw work. My fingers can get quite raw from them if I do compound scroll sawing all day, or for several days straight.

Rebuilding a 788 with worn bearing problems is a half day plus job that costs about $60 for the bearings - about 3X as much if bought from DeWalt or a tool parts source. If I service my saw and re-lubricate the bearings about every 6 months I can do it in about 3 hours and not need to replace any parts at all. Most of the bearings in a 788 do not rotate a full 360 deg. They rotate back and forth over a partial revolution, gradually working the lubricant away from the area receiving the loading. The result is dry bearings that wear quickly after the lubricant has moved away from the loaded portion of the bearing. A bearing that moves a full 360 deg. will continually move the lubricant all the way around the bearing, keeping even the heavily loaded areas well lubricated.

When I re-lubricate my DeWalt 788, I remove the sleeve from the center of each small bearing one at a time and use a tooth pick to apply a tiny amount of synthetic instrument grease to the tiny rollers inside the bearing. I then clean and inspect the sleeve for any signs of wear, then install it back into the bearing, trying to orient it differently from it's former position, in an effort to use less worn areas for the next few months of operation. I also check and tighten the rest of the linkages in the saw and replace anything that shows any wear.

Charley
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post #5 of 7 (permalink) Old 06-20-2017, 12:25 PM Thread Starter
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That is good information, Charley. You use your machine a lot more than I do. But this is good to know, I don't have a problem tightening as much as loosening the wing bolts. Didn't even know a scrollsaw had bearings, never thought of it.
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post #6 of 7 (permalink) Old 06-21-2017, 07:12 AM
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Youtube has some good videos on doing major re-builds of DeWalt 788 saws. The best is in 4 parts and made by Gwinette Woodworkers in Atlanta. It's a bit slow and drawn out, but covers all of the details very well.

If you need to service your 788, you need to know that the frame of the saw is the covers, kind of an exoskeleton. There is no internal frame, so one side of the covers needs to be left on to keep the saw from falling apart. With more experience, this won't matter as much, but to someone new to servicing the 788, it could be a mental disaster if they should take both side covers off at once. Inside it's just a bunch of linkages, a crankshaft to convert rotary cam motion into back and forth motion, and bearings at each pivot point. Some bearings near the blade are very tiny. Back near the motor there is a vertical arm that pivots on a large cap screw, and this is a design weak point. This bolt can loosen, and has been known to break on a few occasions. I now keep a spare, but mine hasn't broken, yet. I also keep a complete set of bearings, bought from a local bearing distributor, and not from DeWalt or a tool parts supplier. Why pay list price plus when the same bearings are available much cheaper from a local distributor. You can actually buy better bearings than the originals, if you give them the original bearing numbers and ask if better quality bearings are available. I have the bearing list somewhere, and I'll find it if you need it.

If you have trouble tightening or loosening the blade wing bolts, get those knobs, but don't fasten them to the wing bolt. Just use one when you need to loosen or tighten the wing bolt like you would use a wrench. Those wing bolts are special. They have a flat pivoting end on them, so they don't cut into the blade as they are tightened against it. I also keep a spare set of these, just in case. On the opposite side of the blade arm is a set screw. You can adjust it, with the blade thumbscrew loose, to slightly move the blade grip right or left so that the blade movement is perfectly vertical. These set screws can loosen, so I now use Blue Locktite on them to keep them from moving, yet still be adjustable.

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Last edited by CharleyL; 06-21-2017 at 07:22 AM.
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post #7 of 7 (permalink) Old 06-21-2017, 09:10 AM
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I agree with everything Charley has said but I didn't read it all. I trust what he says to be good information. If Charley didn't mention it my concern would be getting the clamp screws to tight. Getting them to tight is the number one cause of stripping the screws out. Also Steve Good has a pattern on his web site to make your own if that is what you want. My personal opinion is don't use them unless you have a medical reason.

Don in Murfreesboro,Tn.

Measure once cut twice and it's still to short.
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