Angle and gap problems. Knife Block issue?

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coxsox
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Angle and gap problems. Knife Block issue?

Post by coxsox » Tue 13 Aug, 2019 11:29 pm

Hi,
I've been trying to fix a long standing issue I've had with my Morso where I sometimes get a gap in the join. I use quite a wide moulding and have spent many hours adjusting fences to try and resolve this. I've also just purchased a brand new set of Framers Corners Morso blades hoping this would resolve things. I've also bought a digital angle meter trying to make sure the fences are set correctly.

The latest thing I did tonight is to laser cut a 45 degree and also a 90 degree template. The 45 degree allows me to set the fences correctly in line with the blades either side. Once this is done I noticed that the fences were not in a straight line. Which explains why I get some issues. I also checked the angle of both blades together when fitted on the knife block and noticed that the angle is not 90 degrees, its more like 88 degrees approx. This doesn't sound right to me. the blades are new and bolted correctly to the machine. As the knife block is cast I cannot see any reason why this would be less than 90 degrees.

I will remove the blades tomorrow and double check the knife block, but if anyone has any ideas on whether this is right and I just don't know what I'm doing :head: , or the machine does have an issue,
many thanks

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prospero
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Re: Angle and gap problems. Knife Block issue?

Post by prospero » Wed 14 Aug, 2019 1:18 am

Forget templates.

Just because the angles on the Morso appear to be set perfectly does not mean it will produce a 45º cut.
The best way to do it is by trial and error.

Sounds slightly bonkers, but wood is a natural organic material and behaves strangely sometimes.

Blades start to dull as soon as you make a cut. As they dull the cut goes off-track. You have to compensate by adjusting
the angle of the LEFT fence. The right blade might be producing an off-angle cut, but it's futile adjusting the right fence
as the moulding lays along the measuring guide and will defeat any adjustments.

First thing to do is set the fences so they are dead in line. Cut four equal length pieces of any old scrap moulding - wide as possible
and quite short. Doesn't have to be moulding, PSE timber is fine.

The test fit the pieces. Look for gaps. Theoretically there should be no gaps along the mitres.

But if there is look to see if it's on the inner side or the outer. Chances are it will be on the inner.
Push three joints together. They will fit without gaps because the ends are free. The problem always manifests itself on the fourth
corner. Think about it..... A tiny deviation in one or both faces will be multplied x8. With three corners pinned the final join should
be just a tiny way apart. If it wants to overlap then the angles are definitely off. Pushing the joint tight will then cinch up the whole issue.
That's assuming you insert the v-nails on the outer edge first - which I always do. Pinning each joint all the way along restricts the possibility
of any angle variations equalising themselves over 4 corners.

Slacken the left fence locking bolt and move the fence end a tiny amount toward you. I'm talking gnat's whiskers here.
Lock it again and repeat the exercise. It will either have cured the problem or improved it. If it now shows a gap on the outside
then you have overcooked the adjustment. Keep doing this until the angles are right and no gaps.

This may sound an incredible embuggerment, but it's the only sure way. Setting the machine theoretically is going to be a frustrating
exercise. And I think you'll find once you have faffed about and got it right you get a sense of where it should be and next time you
can do it by instinct.
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Re: Angle and gap problems. Knife Block issue?

Post by Not your average framer » Wed 14 Aug, 2019 6:39 am

You should be aware that the wood you are cutting does have a measure of elasticity and as the blades cut into it, the wood on the outside of the blades tends to compress ever so sligthly and and the wood springs back also ever so slightly after cutting. I know that this sounds crazy, but the bevel ground rear of the blades does allow an ever so slight flexing of the blades and although these blades are produced using a substantial thickness of material, as an ex-engineer, I can assure you the very significant forces exerted of the blade and the wood create deviations that need to be corrected. This is just one of those basic facts of life.

Not only this, but as the blades start to lose their edges, the force applied to the blades increases and eventually you may feel the need to re-adjust the angle of the incoming fence to correct the result cut angles of the mitre joints. I know that to the natural way of thinking it is easy to think that settling the fences at 45 degrees to the blades should produce perfect 90 degree well fitting joints, but unfortunately that's not how it is. Generally speaking, when the blades are good and sharp, the differences that you get between cutting softer woods and harder woods are not significant, but if you let you blades get really dull the difference may become more noticeable.

I regularly cut oak mouldings and although the oak seem to still cut reasonable well with blades that are getting quite blunt, you are hammering the sharpness of your blades quite considerably and may after a little while notice the difference when going back to cutting softer woods like obeche. Particularly as blunt blades can cause tear outs very easily in softer woods. Getting to set your fence angle to get the right result involve trial and error as Prospero has already said and also there will be a bit of a learning curve, before it becomes completely natural and instintive, but don't worry, we all go through this and one day it all becomes so natural and easy.
Mark Lacey

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Re: Angle and gap problems. Knife Block issue?

Post by coxsox » Wed 14 Aug, 2019 2:19 pm

Thanks, I'm actually cutting polcore (yes I know its not to everyones taste, but it suits the application I have) I did try your suggestions and has lead to some more queries, relating to how you actually cut the moulding and which fence you are lining up the cut with.

This is how I see things at the moment, In an ideal setup, the right hand fence should line up with the ruler, the left hand fence line up with the right hand fence at 180 degrees. The blades would be at a perfect 90 degrees and perpendicular to the moulding, then chop away, bobs your uncle and so on.....

Anyway breaking down the cutting process as far as I know it......

1, New moulding goes into morso, left hand fence dictates angle of the first cut. If the fence is 180 degrees to right fence then no query.
2. If the left fence is slightly back from right fence, then first cut may or may not be over 45 degrees
3. Shift the moulding to the right against the stop.
4. Now depending on if the fences are 180 degrees then the moulding will sit flush, if not and the left fence is back slightly, which fence am I holding the moulding to, presume the right fence.
5. Now I cut, but what this does is give the left side of the cut a difference angle to the first cut made on the left if the fence is slightly back.
6. Totally confused now. Do I need to then recut the left side again before moving it through to the stop ?

Doesn't seem right to me, to have to double cut each left side. Again probably over complicating the whole thing here, but by backing off the left side out of 180 degrees, unless I double cut I will always have the first left cut different to all the others....if you see what I mean.

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Re: Angle and gap problems. Knife Block issue?

Post by Steve N » Wed 14 Aug, 2019 4:54 pm

Dosen't matter if one fence is 46degrees as long as the other is 44degrees , so both add up 90degrees - A Right Angle

as been said before the right hand fence MUST line up with the measuring arm, so you always start with the right hand side, using a straight edge along the measuring arm on to the fence, once you have that done and tightened.
Move on to the Left by moving the straight edges along to the left, if possible have the straight edge along all three parte, measuring arm, Right hand Fence and Left Hand Fence , adjust the left fence so it's in line with the right fence and measuring arm, if so, you are set up
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Re: Angle and gap problems. Knife Block issue?

Post by coxsox » Wed 14 Aug, 2019 7:47 pm

Agree as long as the blades are 90 degree on the knife block, but it doesn't look like that, appear to be very slightly less, even with new blades, so not sure whats going on there, but is enough to notice a gap once framed. Have removed them, checked and refitted. Moving the left fence back will result in the first cut being out, if just cutting the left side mitre, unless the moulding is passed onto the right fence, held on that side and cut that way, but does waste material.

I've managed to resolve the issue by only cutting left or right angles and get a perfect finish, adds a little more work but rather this than poor joints.

May speak to Framers corner about their blades, but find it hard to believe new blades would be out.

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Re: Angle and gap problems. Knife Block issue?

Post by Steve N » Wed 14 Aug, 2019 9:27 pm

How was it before you put the new blades on
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Re: Angle and gap problems. Knife Block issue?

Post by coxsox » Wed 14 Aug, 2019 9:35 pm

Always had issues to be honest, which is why I bought new blades hoping that would fix things. Re reading some of the advice, it may be down to the possible material deflection someone mentioned, i.e. if I cut both angles at the same time then more force is required rather than just cutting each end/angle seperately and may be the material is bending slightly, after all its only slightly out. So will just adopt the single angle cut method I think.

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Re: Angle and gap problems. Knife Block issue?

Post by Steve N » Wed 14 Aug, 2019 10:28 pm

Some Polcore is not Morso friendly, ( also the same thing with some wood mouldings ) also you use much smaller cuts than when cutting wood
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Re: Angle and gap problems. Knife Block issue?

Post by prospero » Thu 15 Aug, 2019 1:56 am

Poly moulding does not cut as wood does. It's more a controlled break. Often it will crush before the blade bites
and spring back. Pinning it can be tricky as well. All-in-all it is what it is and nothing more. :roll:

Poly moulding is aimed more at mass produced readymades where it is cut on a production line with a saw setup
with negative-rake blades.

It also dulls the edge a lot quicker than wood. Same applies to some far-eastern moulding with rock-hard ornaments.
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Re: Angle and gap problems. Knife Block issue?

Post by Mark Thornton » Thu 15 Aug, 2019 1:50 pm

Also bear in mind that a Morso was designed on its final cut to only shave the face of wood mitres some plastic mouldings prefer a much wider final cut as the shave cut can disturb the surface on man made materials.

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Re: Angle and gap problems. Knife Block issue?

Post by coxsox » Thu 15 Aug, 2019 3:18 pm

thanks but I'm finding it does require a ver small shave.....

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