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closing the gap on mitres

Nick Tonks

Mar 4, 2006
I am finding that some times when I glue and underpin the frame corner the mitre is not as closed as I would like it (some times if the moulding has a slight twist in it. Has anyone found any tips to fix this, mabe clamping and what sort of clamps work well.
Are you using a vice?
I am using a Hanson Guilotine and a pnematic morso underpinner (old model). I some times find the mitre could be tighter. Does it make much difference with the V nails if they are for hard wood or soft wood most of the mouldings we get are soft wood and we are using hardwood V nails. The person I bought the equipment off uses hardwood V nails for everyting.

Hardwood nails are for hardwood and softwood nails are for softwood. It does make a difference!

Some underpinners clamp the joint and make the joint better than others. I am just experiencing this difference with a new Cassese machine. Joints with this machine are enormously better!
If the moulding truly has a "slight twist," there is probably nothing that's going to give you great corners.

I use a vice (the name of which escapes me at the moment 'cause I've only had it about 25 years - Kwik Klamp, maybe or something equally cute?) that allows you to hold both rails in position with both hands while you push a foot pedal to clamp the corner. You can adjust it to exert a tremendous amount of pressure, but it won't untwist a moulding.
Somebody should start a Snopes for Framers and put to rest many of these urban legends that framers are always asking about. You can't un-twist a twisted moulding nor can you un-warp a warped moulding!! Putting weight on a frame leg or clamping it in a vise strong enough to hold a Sherman tank will do nothing to take out the wrong direction that the moulding leg is heading. As soon as you relieve the pressure the squirrelly grain that CAUSED the defect in that piece of wood will take over and cause it to return to its "natural" state. After all, the tension in that piece of wood was there for a reason.

When the tree grew from a seedling there were certain things that happened to cause the tree to bend one way or the other, twist towards the source of light, and generally grow out of a normal straight grained direction. It would take more space than Bill has on this host site to go into the aspects of how a tree is formed and what affects the grain direction and pattern of a resulting board from that tree. But what took years to shape isn't about to be undone by a day or two of clamping or heavy weight on the wood.

And whomever asked about whether there is a difference in "hardwood and softwood v-nails" I can only reply, ................. Well, DUH!!!! I can't figure out why the v-nail guys would confuse all of us with these mundane details if it really didn't matter.

(That would be like saying all paint is alike. No matter that some is enamel and some is polyeurethane and others are laquer, it all works on a surface that needs paint.) :rolleyes:

Softwood v-nails are sharpened on the forward side so as they are inserted they actually draw the mitre closed. Using these nails in hardwood causes them to split from the top down.

Hardwood v-nails are dull on top so they more or less smash through grain of the moulding. Using hardwood v-nails in softwood doesn't draw the corner closed when inserted. That is the reason for the gaps.
Mitre problems usually start with the cut ... try using a mitre sander to true up the chop before joining.

If the moulding is twisted toss it ... garbage in garbage out.
Here's another thought:

Each piece of steel inserted by your underpinner acts as a wedge. The more fasteners you insert, the more the corner will tend to tighten on the inside and separate at the outside, even if your miters are perfect. So, use enough fasteners to hold the corner together, and no more than necessary.
Jim that suggestion you just gave does that amount to the same advise we are always told that the V- nails and/or brads are just a temporary fastener to hold the corner together until the Glue dries. That is to say that the strenght of the brad or v-nail isn't intended to hold the corner to a secure fit ,even if they do squeeze ? No matter how many you use or where you place them. In fact as you sound to me to be saying sometimes it can work just the other way around.

Also It seems to me that if the two mitered corners don't meet exactly even when placed together ,why would you want to force them. Doesn't that seem to say that one or both were cut wrong to start with?

But then I need a lot of fitting instruction myself.
And Tom your suggestion has been wanted by old framers for a loooong time.It might be a good place to put some of our Framing Myths Threads .LOL
My method:
Cut on miter saw
Sand on miter sander
Glue and clamp. I use either a strap clamp or a miter clamp as show above. set for 10-15 min.

For me at least, the sander was the key to tight joins.