what size wedges

[muffinski]

From a book I have read they suggest at least 2mm of wood above the wedge when under pinning to avoid splitting. Now there seem to be more sizes available I was wondering if there is a more accurate guide regarding what wedge size to use. For example should you aim to leave a quarter of the moulding above the wedge or 50% or should you aim to fill most of the moulding with a wedge. This is in reference to plain wood mouldings. In addition, I wanted to know what would the effect be of using standard wedges in hard wood such as ash mouldings or should I really use hard wood wedges in this example? I am using a Cassese 88 foot operated under pinner.

[easypopsgcf]

Hard wood wedges in anything that is hard. As for depth, you'll do well to stack hardwood wedges high anyway, easier on softer woods to stack them but stick to 3 or maybe 4 high occasionally. I only use 10's and 7's hard and normal and normal 15's to save doubling up the 7's. I try to stay 3-4mm from the top, but happy to be 10mm away as it'll be fine if the cut is good any it's glued properly

[prospero]

I always go by the rebate hight. Ideally, the wedges should go past this. Of course, it depends on the shape of the moulding. In most mouldings I always do all the outside ones first and then the inner ones. This way, the faces toward the inside get squeezed together rather than the outer ones being prised apart.

For hard woods, use hardwood wedges. If you use softwood ones they will sometimes split, especially if you try to stack them. And it's best to not place them as near to the back edge as you would softwood ones.

For deep, narrow mouldings the best way is to stack two near the inside first and then one nearer the outside.

[StevenG]

You do all four corners - outside first? Never tried that but I will today

[prospero]

It's just my way of working. Others will no doubt disagree.

If all your moulding was dead straight and all angles perfect it wouldn't be so important. But that never really happens so if you pin around the outside first you can check if the frame is flat. If it is, and there is a slight twist in one of the rails you'll see a slight misalignment on one or more corners on the inside. Adding pins around the inside at this stage will level the faces and at the same time spread the tiny error around four corners where it should become less or not noticeable at all. Putting all the pins in each corner in turn means that any twist will manifest itself in full on the last corner. And putting the last pin in will tend to try to open up the other corners. I'm talking tiny errors here.



As for doing the outsides first - think of this.....

Get some scrap moulding and cut a little frame. Pin near the outside. Stand the frame on end and try to rock it sideways. It will be rigid and the joints won't open. Now do the same, but with pins only on the inside. Rocking it now will allow the outsides to open and the whole thing will be generally wobbly.
Now if you have your cutter set right and pinned three outer wedges, the last two faces of the frame should be just a small amount apart. Pushing them together makes the three wedges you already placed act as a fulcrum and gives an extra little squeeze to the inside of all the joints. All the better for the glue bond. If you did the inside wedges first, then the opposite will happen. The outside of all the joints will tend to get pulled apart.

That's the general practice I've always worked to anyway.

[Glimpse]

Do you glue all frames? I try to avoid glue as it has a habit of fouling the hammer mech on the underpinner, but generally use a small dab Evostick on larger frames...

[pramsay13]

I always glue everything. It is my understanding that the wedges are in to hold the frame together until the glue sets, and if you are leaving anything out it should be the wedges rather than the glue.

[easypopsgcf]

Yes, glue every time, no exceptions. The way I see it is, the wedges hold the frame together, the glue keeps the join tight