Mitre problems with Morso

[CalicoFraming]

Can anyone help me with a mitre problem?

I'm using a Morso with brand new blades. As far as I know, they're positioned correctly on the machine.

When I cut, the cut bows outwards ever so slightly in the middle of the cut then comes together again at the end. See pic for better explanation!

I'm making quite conservative cuts - not chomping great chunks out of the moulding. I'm applying the rebate supports so that they touch the underside of the rebate firmly but without lifting the moulding off the bed of the Morso.

The inner and outer corners are nicely closed - it's just this mid-way opening.

It's not massive, clearly, just annoying and I was hoping someone had some insight.

Thanks,
Calico

[silvercleave]

IMHO I would say that the moulding is rocking as you cut, ie the bottom of the moulding is not quite flat,
but someone might tell a different story....

Ian

[CalicoFraming]

Hi Ian,

I was thinking the same. Although I have the rebate supports as tight under the moulding as seems sensible, the pressure of the blades is clearly pulling the moulding down and away from me. I'm not sure what to do about it though

Calico

[stcstc]

it looks pretty flat on the top

try cutting it upside down and see if that helps

[silvercleave]

The rebate supports under the front edge of the moulding may be tooo tight, try screwing them up to just touching underneath then backing them off by a quarter turn

Ian

[JohnMcafee]

I'm guessing that the problem lies with the material, if it is a bit soft and springy it may flex a little as it is being cut.

Also, perhaps the blades are not as sharp as you think.

Do you see the same effect when the moulding is of a harder wood?

[CalicoFraming]

I've been making chevrons all weekend and it's pretty much the same with all the mouldings I've tried so don't think it's the wood, although most noticeable with the square section mouldings. Will try loosening the supports a little. Anyone else with any suggestions, I'd be most grateful.

Thanks

[Roboframer]

Welcome to the forum.

Are you saying the cut is curved or that the mitre is open at the centre?

A curved cut would be very strange and yours looks straight, plus if the blades had some sort of curve in them, then that curve would be in different places on different widths of moulding and not always in the centre.

Maybe it's a joining problem.

[CalicoFraming]

Have a closer look at the picture - there's a hairline gap then the moulding comes together again at the outside corner. It's pretty much this way on any size moulding. Weird, huh?

[Vince442]

I've seen this problem on a frame recently in a nearby gallery, having noticed the wood filler under the finish in all the corners but only in the centre of the moulding. The inner and outer edge spot on. So you're not alone in whatever is causing it.

Unfortunately, I can't spread any light on the cause or the fix - sorry!

[CalicoFraming]

Thanks Vince, good to know I'm not going mad at least!

Anyone know what to do about this?

Thanks again,
Calico

[framemaker]

What underpinner are you using?

Do rebate supports wear out? maybe there is some play in them and the moulding is shifting/moving as you bring the blades down.

sorry I can't be more help

[prospero]

The only thing I can think of is, as Ian said, the moulding is rocking somehow. This might occur if you get a bit of a chipping on the bed under the moulding. But if it does it consistently on all mouldings and you have the rebate supports set right, I would be more likely to suspect that the blades haven't been ground to the correct spec.

Try cutting a piece of flat wood (no rebate) and see if it does it with that.

[JohnMcafee]

Does the bottom look the same?

[Roboframer]

Yeah, show us your bottom

[prospero]

[Vince442]

Try cutting a piece of flat wood (no rebate) and see if it does it with that.

I have to mention that the frame I saw it on was a very flat moulding 80mm wide x 30mm deep.

[Roboframer]

But that wouldn't rule out a problem with the rebate supports; a flat batten would because you'd not need them.

We still don't have all the information though, are you using an underpinner and if so which one? Does the back of the join look the same? Are you saying you are getting a curved cut (yes 'weird') or a gap in the middle (not so weird)? Have you tried a different (freshly sharpened) set of blades? ....and were you breast or bottle fed as a baby?

I have a pneumatic underpinner with a rebate clamp, it pushes the mouldings tight in to the fences so it is held very firmly both at the back and the front. But if I selected the wrong pressure pad - i.e. too short, then the hammer would hit (and lift) the mouldings before the pressure pad hit them, instead of vice versa. Same would apply to a manually set pressure pad if it was not screwed down far enough.

The best way to calibrate both your Morso and underpinner is with a flat batten as wide as they will both take, when you've cut a mitre, just put the two sides on a hard flat surface and push them together. if they don't butt up to each other perfectly, without having to be lifted at the ends or at the centre, then it's a Morso problem. If they do but don't look the same after pinning, it's an underpinner problem. Then again, they could look perfect all bar the last corner of a frame, in which case it could be either, but probably the Morso; not the blades themselves, but the angle of the left hand fence. If your underpinner has adjustable fences they could need re-calibrating with a set square, if they are fixed then use the underpinner as the 'hard flat surface'.

[CalicoFraming]

The problem is apparent before underpinning, so guess it's a Morso issue.

Curved cut? Gap in middle? Well, seems to be one and the same problem. The cut definitely seems to hook inwards over the last few mm of the cut, leaving a gap in the middle. It does seem however that the gap only occurs on the top.

A couple of observations which I wonder might be relevant.

1. When I operate the Morso I'm holding the moulding tight with my left hand whilst my right hand stays on the lever, with the exception of the final cut when I set the lever then grip the moulding with both hands.

2. There's loads of play in the rebate supports - the right hand one especially rocks away from the blade under pressure and I can feel the moulding being pulled away from me when I cut. Now I've tried to set the supports as firmly as possible under the rebate to counter this, but too high and there's obviously rocking going on. This is my first Morso, and it's second hand, so I don't know quite what to expect from the supports - is there always play? should they be rock solid?

Hope this information helps and someone can help me get to the bottom of this.

Thanks everyone,
Calico

[JohnMcafee]

Looks like it might be blunt blades.