My new DeWalt saw running problem.

[KarlB]

I posted earlier about getting a new DeWalt saw under warranty.  see here:   http://www.stevedgood.com/community/index.php?topic=20132.0

Well I got the box opened and the first thing I did was check to see that the upper harm was straight.  It was.  But looking at the relationship between the upper an lower blade holder I found them to be out of alignment.  The lower holder was to the right of the upper one by at least a 16th of an inch, but closer to 1/8"!

I went online to find a solution and didn't find one. I told my wife I was not going to be sending it back to the service center!!!  So I tweaked it a bit here and there and got it pretty darn close.  I don't see an issue when it runs and the blade is now 90 degrees to the table.

Now I'm ready to turn it on!

I turn it on on the lowest setting and it is moving very slowly up and down (probably slow enough for Hotshot (Randy)!)  As I turned up the speed the steadiness of the slow speed was replaced by vibration between the 4 and 6 setting.  Moving on up the vibration slowly dissipated and it was stable at around 7.5 - 8.  I am not very happy about that, but I know this is a problem a lot of people have with the DeWalt. 

My problem is the speed at the highest mark doesn't seem as fast as I remember on my old saw.  There is no way to check it and I couldn't find an answer (or video) online to help me.  What I am looking to find out is the speed the saw is actually going!  The SPM should be 1750 at the 8 setting.

I need to know if anyone has a way to verify the strokes per minute (SPM) on the saw?  If it is accurate then so be it, but if not then I'll have to contact DeWalt again.

AS for the vibration I will anchor it to my bench to minimize it, but I think it wall always be there.  Something about harmonics I think.  When the saw it going certain speeds it will create this vibration.  (This is above my head for physics answers.)

I think I will figure out a way to put shock absorbers under the base of the saw to decrease the vibration.

By the way I can really observe the vibration by extending the articulated air tube away from the saw. 

Any ideas for determining stroke speed?

Karl

[hineps]

You could use a laser tach with some reflective tape on the side if the arm. Need to divide by 2 since there would be 2 impulses per stroke. The vibration is probably a resonant frequency in the saw and or the frame. You can move that resonant frequency by one of three methods. Change the stiffness by adding bracing. Change the mass by adding weight to the frame and or the table top. Change the forcing frequency which you can do by changing the speed of the saw as you have already found out. I use an old 20 inch craftsman variable speed saw and was able to decrease the vibration dramatically by adding weight to the frame and table, Also add some stiffening braces to the frame.


P

[jimp11]

             I allways run mine on max all the time . and put rubber blocks under  the saw mount holes and bolted through to the bench.

[jimp11]

      and line the blade up with the set screws