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DWS718 / DWS780 slide action very rough?


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First post here, but I've used a 718 before in a past life building sets for my daughter's HS musicals...  I was impressed with how nicely that saw moved on the slides, and recently decided to purchased one.  

I bought one (DW718SP) and struggled thru this past weekend with it. The sliding action is just awful.  There is a great amount of initial 'stiction', followed by chunky-bumpy sliding - enough to show blade marks in the wood where it wobbles on thru.  Yes, the locks are off.  I tried adjusting the single 4mm set screw on top, but within an 1/8 of a rotation we go from locked-up to sloppy loose.  And even when sloppy loose, it still seems to bump along.  Inspection of the polished rails shows no obvious divots or damage.  The issue must be within the bearing set.

I went back to Lowes, and then Home Depot to try out the floor models.  One 10" Dewalt slide nicely, while the 718 and 780's available to touch were pretty rough, although I don't think they were as rough as mine.  By comparison, the Hitachi, Ryobi, Bosch, Makita, Ridged, Lowes house brand, etc., all slide like butter....  A one finger operation that on some saws even seemed to improved when you pulled down on the handle and thus placed some additional load on the sliders.  I even purchased another Dewalt and dragged it home only to find another disappointment.

What's wrong???  Do they just start out tight and improve with use?  Or does Dewalt suddenly have a problem with bearing?  I desperately want to love this tool, but right now I'm quite disappointed.

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My 10" DW717 also did not have the smoothest slide action when I got it in 2008.  I found though, that a large portion of the stiction originated from the 6 dust seals around the slide bearing/bushings.  When I loosened the plates on the front and back of the trunnion assembly (where the slide bearings are) and temporarily slid 4 of the dust seals up the rails away from the trunion (the other 2 seals are fixed to the linear bearing assembly), I noticed that the sliding action loosened up considerably.  I also own an old Craftsman Professional 8 1/2" sliding compound mitre saw that slides like butter, but it does not have any additional dust seals around the bearings meaning less durability.  My DW717 did smooth out with use, but after the warranty period I decided that i could likely improve the sliding action further.  The porous bronze bushings in the right hand side of the trunnion come from the factory impregnated with some oil, but I found them to be on the dry side.  I experimented with a few lubricants including light greases and different grades of oil and found that a lightweight oil (10W or ISO 32) has worked the best.  I also added several drops of oil to the inside of the linear bearing by removing the rails, since I also found very little lubrication in there.  As for the 4 mm set screw, I set it so there is maybe a few thousanths of an inch play, but no tighter.  The saw is much smoother now than it ever was.  The additional oil has not only smoothed out the bearing/bushing action but also eliminates most of the stiction from the dust seals.  I wouldn't recommend tinkering with a brand new saw on warranty, nor should you have to, but it does appear that the issue you are experiencing may not necessarily be with the bearing but rather a combination of tight seals, break in period, and inconsistent factory lubrication between batches.

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Thank you for your reply and comments.  Here's the action that I have taken in the past two days.

1) I called Dewalt and opened a case with Customer Service.  They promised to have one of their tech guys give me a call to talk about options.  One is to take it into an authorized repair shop (there happens to be one within 5 miles of here!) and have it evaluated.  While I'm not nuts about doing a rebuild on a brand new item, it might make more sense than going thru the boxes at the stores looking for one that rides smooth.

2) After seeing it for themselves, several store employees now share my concern about why the Dewalts slide so much worse that the competing products on the shelf.  Unfortunately, I think I'm starting something here....

3) I had ordered an XPS light for the 718, and another brand stand for the saw.  Once I became 'fully educated' that I could get this as a package (780 comes with the light, and HD is giving away free stands), stepping up to the 780 makes good technical and economic sense.  HD even matched an internet price, bringing it down to $540 from $599.  I'm returning the 718 today.

4) I'll try working in some lubricants and fiddle more with the 4mm adjustment over the weekend and see how it goes. 

Thanks again!

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  • 11 months later...

I just got the DWS780, love it.  Rails glide smooth right out of the box.  I did notice the Ridgid slid extremely smooth, however, my experience, history and knowledge with Ridgid products tell me it's a purchasing gimmick.  Eventually those rails will probably have more problems and worse problems than DeWalt's rails.  The rails are built tight for good clean accurate cuts on the DeWalt, loose bearings will eventually become more loose and problems will envelop in my opinion.  780 is dead on with mitering, dust collection is way better than 718, and the XPS light is awesome.  Better to start with a nice tightly built tough tool, than a tool that might look catchy, powerful and fast at first, but in reality is a dud over the long haul.  (TTI products).  This once again is why I love DeWalt and Makita products, they know what they're doing when it comes to power tools. 

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