Mitred Corners side gaps WHY?

[Fellows Framing]

Hello,


I recently have been having a problem with the mitre join. The face is good and the top of the side but a gap appears down the side getting larger towards the bottom of the moulding.

It is slightly more pronounced in hard woods. The blades are relatively sharp and the cuts are clean.

The logic to me is that the blades are not cutting down quite at 90 degrees on the vertical.

Does anyone have advice as to why this is happening and how to overcome it please?

Thanks

[David McCormack]

It could be the underpinner is pushing the joint open. Check that the fences on the underpinner are set up correctly. If there is a vertical adjustment the fence should be tight up against the back of the moulding. After cutting on the morso what do the mitres look like if held together on a flat surface? I'm no expert but just trying to think how I would approach this problem.

[prospero]

Two things spring to mind.....

Not enough pressure on the top pinner clamp.

V-nails to near the outside.


The first one mainly appears with hard woods. As the v-nail bites the joint can be lifted a bit which separates the two faces. As it penetrates
it will pull the front together, but the back remains open. My money is on that. Try it with a bit more pressure.


It appears there is a touch of the second in the photo. The v-nail position looks OK, but see how the gap is greater between the outer v-nail
and the back of the moulding. If I were doing that section in oak I would v-nail one-deep on the inside and then use hammer and nails crossed
over near the top.


All in all I think the problem may be a combination of those two things.

[vintage frames]

If it's happening on hard woods, could it be that the moulding is not being held firm enough on the morso fences during the final cut?

[Fellows Framing]

The underpinner thoughts are useful and I am sure it is slightly exacerbating the gap but the problem is with the morso.

When I push the mitre tight before underpinning there is a gap down the side as shown in the photo.

[David McCormack]

With it being a flat profile are you cutting it upside down, i.e. without using the rebate support? I would try it this way and hold it tight against the fence, really firm, on the final cut as suggested by vintage frames.

[IFGL]

Looks to me like the outer v nail is too close to the edge, the wood is being displaced outwards.

[Fellows Framing]

The moulding actually was cut upside down and held tight.

The gap if there before underpinning.

[IFGL]

Then your blades are probably Tosh

[vintage frames]

I wouldn't say there's anything wrong with the blades, per say. If they were not as sharp as they could be, however, then this would cause a turning torque on the moulding as they cut. Try perhaps a really fine shaving cut as your last.

[Graysalchemy]

Could be a number of things twisted moulding, blades not sharp enough but I would have said it was pins too close to the back. The other thing is can you adjust the angle of the back fence of the underpinner? Mine 3099 you can tilt it and if that isn't vertical then that can cause the same problem.

[prospero]

what model pinner are you using?

I only ask because on my old Euro the guide is a one-piece cast item. Sometimes you get a build up of gunk in the corner which stops the two outer ends of the rails going right into the corner and you don't get a tight join. I used a hacksaw to cut a little slot right in the corner of the guide and clean the dried glue of by running the blade into it.

I still reckon it's the wedge position issue.

[vintage frames]

Look at what Fellows said - the gap is there before underpinning.

[prospero]

This pic - http://viewer.zmags.com/services/resour ... 1376/224/1 was posted on the Grumble.

This was in a framing suppliers mag.