DeWalt bevel problem

[r&b]

I've been using a DeWalt DWS778 Compact Sliding Mitre Saw for the past 6 months and been very pleased with it. It is obviously well put together and suffers none of the sloppiness of the more DIY brands. However, recently I have noticed the bevel cut is not being made accurately. Typically across a 200mm board the cut is approx. 2mm out of square when cutting a 45 degree bevel. At 0 degrees, the cut is exactly square across the board.
I have checked with a set square the blade alignment across the bed from the fence and vertically from the bed. Both are spot on. The only way I can cut a bevel accurately is to mark a line across the work and manually set the mitre to where the blade shadow dictates.
This can't be right and I wonder if anyone could suggest if I'm missing a trick somewhere.

 

[ntb]

I'm not entirely sure I've understood you but if the board you are cutting is not completely flat the bevel will be out of square so check that first.

 

[r&b]

Yes, the board is completely flat and clamped to the bed.

 

[ntb]

Then I'm as stumped as you. The only other thing I can suggest is to clamp both sides in place to examine whether there is a taper in the kerf.

 

[r&b]

Now I'm not following you! Sorry for my ignorance but just what is a kerf?

 

[ntb]

The gap that the blade leaves as it cuts. If something is out of kilter it may show in the cut.

Have you checked for play in the spindle bearings or a loose blade? Do that first if you haven't already.

 

[r&b]

Thanks for explaining the kerf. But I don't think its part of the problem. My cut itself is clean and correctly bevelled at 45degrees but is not perpendicular to the fence, whereas the unbevelled cut is.
But now I've looked again, there is a tiny bit of play between the motor/blade/handle assembly and the traverse bars. This would certainly make the cut inaccurate. Do you know if there any adjustment available for this?

 

[ntb]

I'm not familiar with your machine. Unless a DW owner can chip in, a call to DeWalt or the place you bought it from is probably in order. I'd be looking for a replacement it it's new.

 

[big-all]

i wonder iff its a worn blade or stance[standing]position??
or even the rubber wheel on the fence guard
i have the dw712 and the wheel can throw the blade off fractionally as it goes up the "little slope" in its path

 

[gregers]

or it could be you yourself putting too much pressure on the machine itself as you start the cut,used to find a similar problem with my old elu chopsaw.

 

[r&b]

Hi Guys, and thanks for your replies. I am now more or less convinced the problem is with the sideplay on the traverse bars particularly when the saw is pulled right back. I've looked at the little wheel on the guard but I don't think it's interfering, because the worst inaccuracy is at the start of the cut and that's where the most play is felt in the saw assembly. I am cutting mdf (and that's all I've ever cut with it), so I'm happy the blade is not worn and as it cuts like a hot knife through butter I don't need to put much effort in at all. So folks, it looks like I'll be testing out the guarantee arrangements. Disappointing, as I thought De Walt was a cut above the cheaper brands. Once again, thanks everyone for the suggestions.