DW 788 Vibration

[Buey1]

I have a question re: the DW 788.  I purchased mine 2 years ago and it has performed perfectly with rather heavy use.  It now has developed a vibration which is seems to be up-and-down and is evident on the cast iron table. The vibration requires constant pressure on the work to hold it tight to the table.

Does this mean the arm bearings are beginning to wear?

[daveo]

hi
firstly check the screws that hold the main blade holder mech especially on the lower one, that they have not worked loose, If they have then you might like to put a drop of thread lock on them before securing.
Now you say
 "Does this mean the arm bearings are beginning to wear"
there a total of 16 bearings on the 788 all of which should have annual care
they are all needle bearings with a sleeve on each, if they are allowed to dry out then the needles dont roll and they start to chatter against the sleeve, all of which causes vibration
So in short I think a good overall  might be the answer
there is a good 4 part video on u tube about this if you search the problem
the sleeves for the bearings are available from the likes of   E replacement  parts
but alas the bearings them selves are not unless you buy the casting itself
but you will get them from your local bearing/belt supplier
they are made by INA bearings
hope that helps some

Dave

[Buey1]

Thanks Dave:

I've seen the videos on replacing the 16 bearings and that is what I'm afraid is needed. i don't think I want to tackle that kind of overhaul myself given its complexity. Their is a local authorized Dewalt repair service nearby and I am going to inquire about the cost of having it done.

Bill

[daveo]

Bill
well thats the way to go, using a dealer will obviously cost so I would suggest that you make sure that they replace all bearings regardless of condition, that way you will have peace of mind that the problem is not going to recurr in another few months.
also whist you are in maintanance mode, you might like to service the clamps.
All to often do we get people complaining about blade slippage, and indeed using wrenches and making there own levers to tighten them, and the answer always seems to be the same "degrease and rough up the ends of the blade" or "rough up the face of the thumb screw" all of which is not needed.
On the opposite side of the clamp to the thumb screw there is a small grub screw used to vertically align the blade as I am sure you know, if you remove the grub screw from any machine of age and good use the screw will have a shiny flat face, and this is the problem. A new (genuine part) grub screw will have a raised perimeter edge with a concave dimple in the centre and once fitted you will find that securing the blade takes nothing more than a nip with the fingers, in fact you will feel something of a cushioning effect when you tighten the clamp
and no more slippage
good luck and let us know the result

Dave

[Buey1]

Right Dave...I've already replaced and recentered the grub screws top and bottom with a drop of removable Locktite.  Also replaced the thumb knobs.  I know what you mean about the 'feeling' when the knobs grab the blade...a big difference.

Bill

[Buey1]

I finally bit the bullet and took my dw788 in to an authorized Dewalt Service Center for vibration repair.  The total for the necessary parts to repair came to $371.00 without labor.  I paid the $35.00 basic diagnostic fee and left with the machine parts in a box.  Their report was the various parts were bent and the bearings are fine.

I have now a new machine on order.

I have salvaged the Type 2 motor ($300). the variable speed control, and the cast iron table ($250) if anyone might be interested.