Help Mitre Cuts Gapping

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JRAM1

JRAM1

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Feb 13, 2007
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I have a Brevetti Prisma CE Mitre saw that recently has been cutting poorly. The outside corners of my cuts are gapping from the front(top)
of the frame and progressively getting worse towards the back (bottom) of the frame. I have never adjusted the alignment but have checked it with the angle tool provided and it seems fine. I have newly sharpened blades. It seems to be worse with simple square, flat mouldings. I reviewed the manual, but it seems to be little help. Can anyone explain what might cause this, and how to fix the issue. Any help would be greatly appreciated.
 
It could be clamping problems, poor blade sharpening, and a host of other problems. Call the Brevetti distributor and tell them what is going on. Send an e-mail to the Brevetti company and ask them.

John
 
I thought clamping too. I get cuts like you describe when there's side to side play in my clamp. Does the mitre line up perfectly with the stop but then after you clamp, it juts away from the stop a little?

Also, do as John suggests and contact the manufacturer.
 
My thought is that you are dealing with a poorly sharpened blade or blades. When you check the blades not running and not engaged in the wood they can be fine. When the dull blade it cutting or tearing through the wood it can deflect the blade enough to ruin your miter.

I would try another set of blades before adjusting the machine itself.
 
Also be sure that you check the length of each leg. If they are not exactly the same length it will cause you joints to gap open. Lay the legs on a flat surface back to back (long sides touching) to check for length differential.
 
Brevettis don't have an agressive clamping system unless you have the pneumatic model. The stock can still move side to side as the blade is drawn through the cut. What you describe sounds much more like a bad sharpening than something being out of line on the machine especially since you are experiencing it now after you have changed the blades.
 
you might try fresh blades, new if possible and maybe cut a little slower. also on larger moulding it always helps to cut each miter a sixteenth long and shave it back to finished size. hope this helps
 
The Brevetti Prisma CE is not a pneumatic machine. I have one too, and it's the best cutting machine I've seen.

My first thought is that it's the underpinner, not the saw.

Second thought would be to swap the blades, could be a bad shapening.

Third thought, if those don't pan out, is to open up the front of it and check the motor mounts and the sliding blade mounts. Perhaps something has broken or come loose, allowing the blades to move a little sideways.
 
I'll tell you what you should definitely not do: Don't try to adjust the saw yourself, or at least don't if you aren't 100% sure you can fix it. My Prisma CE was purchased used and the previous owner had clearly messed with the saw; it cut good, but not perfect. I tried to adjust it myself, and it has been nothing but headaches since. I'm ready just just pay someone to fly down here and fix it.
 
It sounds like you first need to determine if its the saw or your underpinner. What do the joints look like when you clamp them?

If they have a gap when you clamp them, its the saw. If there is no gap, then its the underpinner.

I had a similar issue and mine was the underpinner. If its the underpinner, you can make the adjustments yourself.
 
JWB9999999 said:
The Brevetti Prisma CE is not a pneumatic machine.
Click to expand...

I have the Prisma Maxi and there is an optional pneumatic clamping and cutting attachment available. In looking at the system at the last Decor Expo I believe it was attached to a CE model for demonstration purposes. Could be wrong, it was a while ago.
Question to the OP: Was the saw exhibiting the same tendency before you changed the blades?
 
You might try clamping the frame in a miter vise if you have one (I join almost all my frames in a vise before vnailing) just to see how it lines up. If it lines up fine in the miter vise then it might point to the underpinner as the problem.
When the blades were sharpened, did they check them for run-out?
If they are not flat it could cause a problem. I'm more familiar with the CTD D45AX pneumatic saw.
Also make sure the backside of the blade and blade mounting surface are clean when installing. Good luck. :kaffeetrinker_2:
 
OK, you've used the angle tool, and the blades line up tightly when you check them, so the saw alignment is probably fine.

And you mentioned fresh blades, so those are probably fine too.

It could be a clamping issue -- some movement in the moulding when the blade passes through. Body language does make a difference. Make sure your stance is proper and solid.

It could be warped or twisted moulding -- you might check for that too.

If none of those issues are to blame, check the settings on whatever joining system you are using. My underpinner (the Cassesse CS299M) allows for adjustments if the miters gap at the back, at the front, the top, or the bottom. I'm sure other decent underpinners have similar capabilities.

I had the same problems as you describe, until I made adjustments to my underpinner. It seemed to me that the underpinner required a lot more frequent tweaking than the saw.
 
I have Brevetti CE saw and one piece of advice I will offer you is not to even think about adjusting the cuts yourself. I thought I was fairly smart, read the manual and went to work and made a complete hash of it. The "guage" provided with the machine is junk - useful for drawing lines or as a paperweight only.

The tool required is a "Dial Guage" which is mounted on a mitred piece of timber. The tip of the guage presses against the stationary blade which is then pulled through as if cutting. The dial records the changing pressure against the blade and movement of the needle should be minimal. Adjustments need to be made to the set of nuts at the front and rear of each track in the correct sequence to get a perfect mitre and this is best done by a technician. My guy took about half an hour to accomplish what I had struggled with for a couple of hours.

If you have a guillotine a simple way to test your cuts is to press the cut edge against the guillotine blade and use this as a square.

As regards the underpinner, if you are getting joints which flare open at the base of the moulding there are a two possibilities:

You are placing your V-nails too far back in the wood.

The timber is too hard (common these days) and more aggressive clamping both laterally and from overhead is needed to stop the moulding lifting when the V nail is driven in.
 
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