RAS precision crossing cutting wide boards
ennisdavis
| Posted in General Discussion on
I am coming to conclusion that it cant be done with precision. I tried over and over again, different methods. A few thousands high mismatch so I ran it thru my router/joiner table, perfect. It could be the wood. I am cutting MDF. But you figure the thin kerf blade has some deflection. I put the blade to the face of the cut and even backed out a few thousands, no good.
Replies
"RAS" and "precision" are antonyms.
I have had a RAS for many years and love it for certain tasks. Like most tools, there is variation in quality from brand to brand and model to model but, I have never considered any of them a precision machine; particularly with consistency. There are just too many ways for them to go out of adjustment. When using one, you must take that into consideration. If you need a precision cut, you need to do a precheck of alignment. Even then there are limits.
Youre worried about a few thousandths of an inch? In woodworking? And with MDF? I think you are in the wrong hobby.
1/64th is more than 15 thousandths. And that's more than enough for the vast majority of tasks.
I am still looking for that old cast iron 12 in. RAS That will replace my cheap DeWalt but in the meantime I tightened the rear post screws to lock it at 90 degrees, put an eccentric bushing at the rear of the motor to bring the blade parallel to the cut and still figuring how to tighten the motor tilt adjustment so it stays put. I get fairly good cross cuts in thick hardwoods, thin kerf blades are a plus, I see no reason it would deflect .
The RAS is not precision. You can tell by this crazy blade pattern. Blade is true but the thin kerf wobble causes issues in soft wood.
If it's blade flutter that's causing inaccuracies...although RAS's have multiple mechanical variables that make precision cutting a frustrating experience, might I recommend a pair of blade stiffeners which I use on all my thin kerf blades on the table saw. In fact I use them on all my blades.
They're simply heavy oversized washers...the diameters of which are about a third of your blade diameter. Sold at Lee Valley and I'm sure they're available elsewhere.
Not sure whether they can be used on a RAS...although I can't see why. Check first.
We had thin kerf blades in the 80's when I was engineer at a large furniture making plant, we ripped 1,000,000 board feet of hard maple a year glue joint quality, never had flutter. Blade alignement is key.
I guess I have been lucky. I have a Craftsman (Emerson) RAS that my Dad got for Christmas in 1973. I have had it for 35 years now and it still gets regular use. Once dialed in it produces clean square cuts ready for quality joinery and holds its setup. Blade runout and/or flutter has never been an issue. I recently upgraded to a Forrest Chopmaster and love it.
Caveat: I mostly use it for 90 degree crosscuts and very rarely for other angles. Once moved, it takes a few test cuts to get back to square, but then its good to go.
proof is in the pic. Alignment would not cause that mark, it looks like a plunge cut. For those with a RAS, try a half crosscut with a non square end and see how the flip aligns.
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