deep hardwood mouldings

[Nicole]

Is there a secret to underpinning these mouldings or another way? I have a pneumatic undrpinner that copes well with most of my mouldings but even on the highest setting for hardwood it will only just about fire in a 12mm v-nail and certainly wont stack two even though the depth of the moulding requires it. How does anyone ever mitre these together? Im talking about a one and three quarter inch depth ash moulding.

[prospero]

Are you using Hardwood v-nails?

If I were doing this type of moulding I would tend to put in one v-nail, just to keep the joint in alignment and then knock in a couple of nails near the top. That's the old-school hammer and nails. It does mean filling nails holes, but gives a good strong joint.

Lots of folks swear by a dovetail joiner, but that means buying new kit.

[Not your average framer]

Is there a secret to underpinning these mouldings or another way?

Well, sometimes there are a few tricks which can help, but a lot depends upon the particular piece of moulding that you are using. Personally, I don't like pinning and filling unless I have no choice. It looks so much better if you don't need to pin and fill the tops of the mitres.

If you can arrange it so that the mitred end grain of both lengths joining at a corner both have the grain travelling in the same dirrection in the wood, then the inserted wedge will met far less resistance as it is pressed into the wood.

This is of course easy to do for three of the corner joints, if you cut the first three lengths of moulding in the same sequence as these lengths are about to be joined, as these lengths were already adjacent to each other before you cut them from the full length of moulding.

Getting the forth to do the same can be less easy to do, but if you have some more of the same moulding left over, then often you can pick and mix to get a combination which is not too bad. This helps to reduce the force required to insert wedges into the mitre joins, but by it's self this is not usually enough and additional tricks are usually required to stack wedges in the harder wood types.

So here is my other trick! The resistance met by the wedge can be considerably reduced if the inside wedges are inserted very close to the face of the rebate, but beware this can cause problems if the two end grains meeting at the mitre joint are not well aligned. However if they are well aligned and you are well practiced at doing this you can stack a couple of wedges about 2mm from the face of the rebate.

You can do this because such a thin section of wood between the wedge and the rebate will give a little and by doing so create a slight bulge inside the rebate at each corner and as a result of the wood yeilding a little, the pressure required to insert two stacked wedges will be significantly less. Unfortunately this does not work for the outer wedge, so you can only insert one wedge in the outer position.

This usually works quite well for me, but there are times when a particular length of hardwood moulding just won't allow this to work. Fortunately most of the time it does work, but this is a technique which requires practice. If you get too close to the rebate, then the wedge can take the line of least resistance and exit from the moulding into the rebate.

Sorry, this technique does not always produce a perfect result, but most of the time it is successful. I always order enough wood to have some waste so that I can select the most favourable sections to cut my lengths from. I hope that this all makes sense!

[Roboframer]

You've heard the old one about the V nails only there to hold while the glue dries, right? Well I don't totally agree with that but I certainly do when it comes to deep hard wood mouldings.

My underpinner only takes V nails up to 10mm but it will stack two of them in oak as long as the pressure is at its highest (it's well 'ard), but I very rarely attempt that. I use one, in as many positions as it takes, front, centre, back etc, with a copious amount of wood glue and then band clamp it with one of these

[Graysalchemy]

I agree with RobGlue is the key. Line it the moulding fire in one hardwood wedge then clamp I use a ratchet strao the type you would use on a roof rack with plenty of corrigated card in the corners to protect the moulding. I also use the foaming PU Moisture curing adhesive like this

[prospero]

The problem with deep mouldings is that hangings are usually fixed to the back in the time-honoured manner. This means that because of the levering action of the sideways force the corners are under a lot of continuous torsion and the front of the frame takes the most strain.

On a frame of some weight it makes the integrity of the corner joints very iffy and more prone to failure than a shallow moulding. For this reason I like to have some form of mechanical fastener near the front. A glue bond can be very strong, but it's either stuck or not.

As Mark (NYAF) says, stacking pins toward the inside of the frame works. It's rather like pinning a reverse section moulding. But you have one chance. Pins can slip and go side-by-side instead of in line astern. If that happens the joint won't be very strong and you haven't room the have another go far enough away.

For the sake of drilling 8 holes and a bit of hammering and filling I sleep better.

[Nicole]

Some great suggestions from you all thank you. The moulding was ash by the way and so hard that I had to ask my husband to help push the foot peddle down on the Morso because even with my whole body weight on it I could still not cut through it. I think I might try the fail safe hammer and nails with this frame as it is large and heavy as it contains a woollen rug. I can't afford to have the joints fail.

[Roboframer]

If you don't own a mitre vice (which is a really useful bit of kit anyway) you may be better using screws than hammer and nails, and even if you do own a mitre vice you still may be better using screws.

You can pre-drill the holes completely through the mitre to the full length of the screw and use screws slightly larger than the holes (rub them over a wax crayon or a candle first, especially if you only make a pilot hole) - and if you countersink, the holes will be easy to fill, in fact countersunk brass screws look very neat anyway.

This, for me, would be after underpinning & clamping as per my first reply; could be done while clamped and I'm assuming a fairly serious drill, not a dremel type thing.

There are screws and there are screws too - http://www.diy.com/departments/turbodri ... 082_BQ.prd

[Nicole]

Thank you Roboframer great suggestions and I will certainly try this

[misterdiy]

We do a lot of deep frames in ash which is pretty hard. I got fed up of stripping the unnderpinner down to remove the buckled v nails. Sometimes they would come through the side of the moulding. I stopped stacking a long time ago and put one 12mm v-nail in which was reasonably successful and then cross nailed at the top of the frame. This was very time consuming so we invested in a dovetail router which is a dream for deep mouldings. if you only have one or two to do then its not really worth the investment. Just put one v-nail plus cross nails and loads of glue

[gesso]

If your leaving the moulding natural then you could dowel
the mitres with the same wood.
Do as robo said use a mitre vice and glue into the holes. If your going to stain your frame then
be aware of what effect the glue can have on the stain your using.
If dowelling don't use ribbed dowels but find smooth sided dowels
(there are plenty available on ebay. Finally if you want to hide your dowels as much as possible,
position them in the top and bottom of your frame so they don't show from the sides.
Otherwise you could make a feature of them by either using contrast woods........just a thought

This could also be done with spline mitred joints.......see youtube.