SCMS Accuracy?

[Wade Samuelson]

I have really enjoyed reading the other thread about whether a miter saw is a neccessity, but I didn't want to hijack it, so I'll ask my question here: I have a Bosch 10" SCMS and when I make long cuts (11" or so) the blade "drifts" to the right about 1/16 of an inch. I don't see any way to fix that--anybody have any solutions? And second, judging by the discussion in the other thread, it would appear that most folks don't really expect complete accuracy. Is that the case even when making straight 90 degree cuts? I can understand that a saw might be off a little when cutting compound angles, but when cutting the end off a 3/4" x 11" pine board, shouldn't I expect a square cut? :confused:

Thanks for the input!

[Jim Becker]

Your saw "shouldn't" be "self-adjusting" to a different angle than what you set it to. Something is amiss...IMHO.

[Craig Zettle]

I have noticed a number of potential problems that can happen when making a cut that big on your SCMS. I have a Dewalt 12" SCMS and run in to the same thing.

First, no matter how firmly I hold the wood against the fence, it still wants to move, so I usually clamp one side with a clamp that is part of the Dewalt system. It is made specifically for this purpose.

Also a blade that big will have a tendency to deflect, so I am going to try a thicker blade ( I am running a thin kerf Freud 80 tooth)

I have also found that slower is better with regard to the quality of the cut on a SCMS. Less chip out and a much smoother cut than when I just plow through.

With that said, I still could not imagine not having a SCMS in my shop. I cut my rough lumber to approx size before joining, and you can't beat a miter saw for that. And all my crosscuts of longer stock are done on it also.

[Paul B. Cresti]

I have really enjoyed reading the other thread about whether a miter saw is a neccessity, but I didn't want to hijack it, so I'll ask my question here: I have a Bosch 10" SCMS and when I make long cuts (11" or so) the blade "drifts" to the right about 1/16 of an inch. I don't see any way to fix that--anybody have any solutions? And second, judging by the discussion in the other thread, it would appear that most folks don't really expect complete accuracy. Is that the case even when making straight 90 degree cuts? I can understand that a saw might be off a little when cutting compound angles, but when cutting the end off a 3/4" x 11" pine board, shouldn't I expect a square cut? :confused:

Thanks for the input!

Wade,
Well my story is long so I will give the very quick abreviated version. I never seemed to get extreme accuracy out of my old Bosch. When I had to make a wide crosscut it was always a slight hair off. Eventually I started to do all my final croscutting on my Unisaw with a shop made sled. That was getting tiresome and cumbersome so..... I went down the road to the European format sliding saw. I now do all my rough & fine crosscutting (the most accurate manual weigh I know how), ripping, beveling, edge jointing, mitering and compound mitering... on it. The CSMS though does work for for rough cuts and for installing trim or crown. I just do not rely on it for any fine furniture projects. It actually is no longer in my shop.

[Richard Wolf]

I make my living with SCMS and always find them to work very well.
Let me ask you some questions. First you say it drifts to the right which really means that when the motor is pulled out it is off to the left? Becuase Wade, I don't mean to imply, but you are pulling the saw out, pushing down, and cutting on the push stroke, aren't you?
I have also found that using a heavy hand while pushing can defleck the blade to one side.
Also check both fences independently becuase one side could be square and one side out.
I bounce my saw around in my truck everyday, but spend two minutes setting them up with a perfect square before I start in the morning.


Richard

[Corey Hallagan]

I think most miter saws have a tendecy to move a bit. I have seen dewalts, Ryobi's Makitas that all will have deflection if when you do not lower it slowly into the piece and hold it firm that it will have a slight movement, usually the work piece as the blade crashes into it. I get fine cuts from my Ryobi when I handle it this way, if I just chop it down into the wood, i get the same thing.

Corey

[Wade Samuelson]

I make my living with SCMS and always find them to work very well.
Let me ask you some questions. First you say it drifts to the right which really means that when the motor is pulled out it is off to the left? Becuase Wade, I don't mean to imply, but you are pulling the saw out, pushing down, and cutting on the push stroke, aren't you?
I have also found that using a heavy hand while pushing can defleck the blade to one side.
Also check both fences independently becuase one side could be square and one side out.
I bounce my saw around in my truck everyday, but spend two minutes setting them up with a perfect square before I start in the morning.


Richard

Yeah, I am using it correctly (and no offense taken--I am learning everything as I go here, and often getting things wrong!).

Both fences are square.

I put a framing square up against one fence and slid the blade along the square (power off, of course!). When pulled out, the blade was touching the square, but as I pushed in, the blade stopped touching and finished about 1/16" away from the square.

[Bill Neely]

Wade, I've got a Hitachi not a Bosch but I believe you need to square your fence (both sides) to the blade. If the saw is in the 90 degree detent then that's the only solution that I know of.

[Ian Barley]

I don't have your saw but I have had a similiar problem. Is the fence detachable? Can you check that both sides are still in alkignment - use a known straight edge laid across. In the past my fence has moved in the middle section causing it to lay as an extremely shallow V rather that as a single straight edge. Worth a look anyway.

[Brian Jarnell]

I have the 12"Dewalt and have no problem cutting square.

The blade is the DeWalt 80 tooth which has negative rake,I have found that it cuts with less effort than the positive rake.

[Chris Giles]

Wade,

First I would suspect the sawblade. The mitre saw needs to have the absolute sharpest in the whole shop because it has the least support. Take it to a sharpening specialist in your area that specializes in ww tooling and explain the problem. You may have to pony-up for a new blade, but you won't regret it when you see the difference. If this doesn't solve the problem, you either have an underengineered carriage or a defective one. At least you will know.

[Tom Hintz]

One thing I have found helps on all miter cuts, long and short is to make a first cut 1/8" or so long and then trim it to the final dimension. That seems to help elmininate the stock creeping and any blade deflection. Of course a good blade helps that as well.
The advice about being certain the fence is square to the blade is important as well. When I got my Bosch it was off just a tiny bit but that showed in the final cuts. I aligned the fence and it has been fine ever since.

[Walt Pater]

You need to square your fence to the blade. I have two Bosch saws, a 10" slider and a 12" fixed base. Can't live without 'em. Your 10" fence is a one piece assembly- loosen the hex nuts behind it, and with a dead-on square, making sure you are resting on the blade and not it's teeth, square it with relation to the blade. I need to do this about once every 6 months. Also, check the fence to make sure it is straight- if not it should be replaced. One of the reasons I bought the 12" fixed base saw was because it had one less axis to worry about. In general, a SCMS will not cut as accurately as a TS with a sled. On a recent cabinet job, my chop saw sat unused as I made all my crosscuts with a sled in the shop. Once on-sight, though, for the remodel part of the job, I used my chop saw all the time. Apples and oranges, the TS vs. Chop saw debate.

[Richard Wolf]

It sound like technique to me. If the blade is square when you pull it out, how can it not be square when you push it in? The only thing that come to mind is you are pushing the whole carriage to the right, which is easier than you think. Is there any slop in the blade/motor assembly if you try and twist it?

Richard

[Bill Neely]

Wade Samuelson wrote:

'I put a framing square up against one fence and slid the blade along the square (power off, of course!). When pulled out, the blade was touching the square, but as I pushed in, the blade stopped touching and finished about 1/16" away from the square.'

Sounds like he needs to loosen up that fence and align it to the blade.<!-- / message --><!-- sig -->

[Kent Cori]

My Bosch 4410 SCMS is spot on over its entire travel.

[Wade Samuelson]

Wade Samuelson wrote:

'I put a framing square up against one fence and slid the blade along the square (power off, of course!). When pulled out, the blade was touching the square, but as I pushed in, the blade stopped touching and finished about 1/16" away from the square.'

Sounds like he needs to loosen up that fence and align it to the blade.<!-- / message --><!-- sig -->

Fixed it! My fence is actually two pieces--one big section and one small section (only about 3 inches long and it sits on the far left edge). I was measuring/checking/yelling at/verifying the big section, as it's the part that is behind the blade. It was square. That little piece, however.... *sigh* More time lost and more lessons learned.

[Wade Samuelson]

By the way, thanks everyone. Just when I am about to chuck it all, have a garage sale and go back to fishing, somebody here bails me out.

I do appreciate it. This is a fine group.

[Walt Pater]

My 3915 has that little extendo-fence too, Wade. I pretend that it doesn't exist.