The Framers Forum

Hello all,

I have been making some oak frames (pw160 wessex) with an immes unperinner using 7mm hard nails.

The mitres are not tight enough - when you hold the corner up you can see daylight!

Does anybody have any tips or ideas please to get a tighter join?

Thanks
Sarah

Have a look at the mitre from the underside. If the join is tight, then the fault is in the cutting. If the joint is open on the underside also, then it may be you have to consider clamps.

Make sure your fences are nice and snug against the back of the moulding. I'm not familiar with the Inmes underpinner but on a Cassese you can adjust both the angle and the slope of the back fence. Hardwoods resist more as you drive in the wedge compared to the likes of obeche etc. and want to open up so it helps if the fence is right up against the moulding.

Also, don't position your wedges any further back than half way, see pic. Sometimes when working with hardwoods you just have to think... loads of glue and clamp

Thanks Vintage Frames - the is an even bigger gap on the underside so is the resistance from the wood pushing it apart so will try clamps.

Thanks David - will try re positioning the nails.

This is a perennial problem.

There is more resistance with oak and you need a tad more top pressure. As the nail bites it can tend
to 'lift and separate' the two ends. A hard pressure pad is preferable.
Hardwood wedges are not 'splayed' and won't pull the joint together.

Are you trying to stack the v-nails? Although this is technically possible, it asking a bit much when it comes to oak.

You could try using soft wood v-nails. It is sometimes better.

Personally, my method is to put in one shallow nail and the drill/cross-nail near the top. With a hammer and ordinary nails.
Filling the hole is not a huge job and on oak hardly shows at all.

A mitre vice is handy when doing this.

It took me a very long time to figure out how to solve this problem. I made up a wooden right angle piece that fits inside the usual fences and lined the inside faces with some medium grit abrasive paper. The abrasive paper was glued in place and when the oak was clamped in place using the rebate clamp on the underpinner, the force that was parting the two lengths of moulding in the underpinner was countered by the sandpaper gripping the oak.

Not all underpinners suffer from this particular problem, some rebate clamps won't allow this sort of movement at all.

I had this problem with a previous underpinner but is solved with my current one which has adjustable clamp pressures.

I did the same as prospero and a mitre clamp will save you you a lot of fiddling.

To fill small hole, i would just put a dab of glue in the hole and then sand gently over area and it will fill hole with oak sawdust so will make it virtually invisible.

Nick

I use softwood wedges when there's a problem and through trial and error, I put the wedge nearest the outside(the one that's no more than half way) first followed by the inside wedge. For some reason this has helped.
A Hoffmann dovetail router will also cure this!

Nick, do you mind if I ask what underpinners you changed? I am looking for a new one and numerous searches for personal opinion are few and far between..