DeWalt 788 knob upgrade

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

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.

Charley

I realize that this note is ten years late, but do you have any info on ordering bearings? I live 100 mi from anywhere, so need to order on-line.
I just bought a 788 last week and am learning how to use it. Here's a pic of my 3rd project being glued up.

That's incredibly good for only your third scroll saw project. Most people cut for years before they can follow pattern lines that well. The "Scroll Saw Village" www.scrollsawvillage.com forum is the best place to learn the strengths and weaknesses of the DeWalt 788, and they have a list of all of the bearings and part numbers to buy them with. You don't (shouldn't) buy replacement bearings from DeWalt. You can get better bearings through bearing and power transmission specialty stores or on the internet. These stores can be found in larger cities across the country. You will likely pay less than half what DeWalt charges for the bearings, and you will get better quality bearings this way too.

The tiny bearings in the short arms that move the blade up and down are bearings with no internal race. Then you buy the internal race (sleeve) as a separate part number. I found that getting some synthetic grease and putting a tiny bit of this grease in the bearing hole with the flat end of a tooth pick, before inserting the sleeve and bolt, will make these bearings almost last forever. Do not use automotive grease. Do this on your first disassembly and you may not need to replace any of them, ever. While at it, look for wear marks on the sleeves and turn each sleeve 90 degrees from it's original orientation as you replace it. Bearings wear when there is inadequate grease between the moving parts. The synthetic grease does not dry out, so it continues to lubricate and move around within the bearing, keeping wear to an absolute minimum.

The bearing on the end of the motor shaft and those in the rocker near the motor that moves the long rods to control the blade motion are larger sealed bearings that take a hard beating. If you truly need to replace a bearing, it will more likely be one of these the first time that you service your saw. There are bearing numbers etched in the bearings to help find the correct replacement. The numbers indicate the size and type of bearing. Any bearing company that makes this size and type of bearing will use this same number for it. Buy one of the better quality brands and you will have a perfect replacement. The connecting rod between the motor shaft and the rocking vertical arm can stretch from prolonged hard use. DeWalt now sells this connecting rod complete with bearings all assembled because of this. The bearings require a small press to push them in or out of this rod. If they slide out easily without requiring a press, it's time for a new rod. It's aluminum and the bearing holes elongate from heavy use. The bolt that the rocker pivots on sometimes loosens or breaks, so I suggest that you consider finding a stainless bolt of the same size and style that matches it and replace it. Lowes has them. Consider using blue Loctite on the threads to keep it from loosening in the future. The blue Loctite will still let you remove it the next time with a wrench. DO NOT USE red or orange Loctite or you may never get it apart the next time.

If your saw is no longer running smoothly, I'm almost willing to bet that your problem is back in the connecting rod and rocker arm area near the motor. Bad bearings and loose bolts in this area are the main causes.

Take your time, and take pictures with your cell phone as you disassemble the saw. Watch the Gwinnet Woodworkers videos on Youtube and you should have no problem fixing up your saw. Join the Scroll Saw Village Forum and share your experiences and projects with the rest of us like minded scroll saw woodworkers.

Charley

Interesting thread and amazing information about the saw maintenance/rebuild, thanks Charley - a man after me own heart.

I recently purchased a used 10" Rikon table top bandsaw and basically did what is suggested here - took it all apart, inspected, squared up everything, got the bearing part numbers and found a local supplier (who does mostly mail order). For $20 I got a package of superior long life bearings, enough to rebuild the saw 2 more times.

One other thing - about the bolt: I would caution against hardware store stainless bolts, as they are quite hard and brittle. A grade 8 bolt is much stronger, tougher and usually yellow zinc plated to be very corrosion resistant. If you look around, the worlds largest specialty fastener manufacturer is called ARP out of Ventura, California. They manufacture a wide range of stainless fasteners that exceed Gr 8 strength, and are available in most common SAE and Metric sizes. Expensive, but nothing better unless you go titanium. My highly modified V8 engine is put together using only ARP studs and fasteners. Most of the car is bolted together using their 12pt polished stainless affairs. Jewelry that happens to be used in Formula 1 engines etc as well. I visited their production facility 2 years ago and this past January. Chris the production manager previously worked for several Formula 1 teams in the UK, the whole place is top shelf in every regard.

Tech Info: https://arp-bolts.com/p/technical.php


You can mail order them from here, been using them for 30+ years. Measure the bolt dia, length and thread size and look it up on the filters on the left side of the page.
https://www.summitracing.com/int/se...s:in-stock&SortBy=Default&SortOrder=Ascending