Picture frames require precision reducing to acquire 45° mitred edges. This picture frame underpinner is typically completed with the aid of using the use of a guillotine, which leaves flawlessly easy 45° edges. The subsequent step is to correctly be a part of the 4 identical mitred edges collectively to shape the body.
Traditionally, this was completed with the aid of using hammering photo framing pins in from the edges of the body and became now no longer the maximum green manner of making best joins. You every now and then encounter very vintage frames which have been joined this manner and, despite the fact that they’ve lasted an extended time, their corners typically display gaps. The enterprise makes use of underpinners to insert V-nails, and smaller sorts of over/below pinner are to be had for the hobby/fanatic markets which do an similarly top job, albeit possibly at a slower pace.
V-nails themselves are made from hardened metal (for tough woods) and softer metal for smooth woods. They are available in quite a few heights to mirror the huge type of moulding thicknesses to be had. They generally picture frame underpinner are available in 7 mm, 10 mm, 12 mm and 15 mm heights. The energy of a photo body joint comes from major factors – the selection of V-nail length and additionally the adhesive that holds the be a part of collectively. It’s certainly a blended effect. Wooden mouldings use PVA wooden adhesive. Other types, like plastic mouldings, use different sorts of adhesive, eg speedy bonding first-rate glues.
To be a part of a wood body moulding, the PVA glue is squeezed directly to the mitred faces of wooden. If those faces had been joined like this, the glue might probable be squeezed up and onto the wood face which isn’t always desirable. This is specifically so in case you are the use of wooden stains because the PVA leaves regions which withstand wooden stain penetration. To save you this, and to create a well bonded joint, it’s far high-quality to unfold the glue out easily and thinly on every face you’re approximately to be a part of, running the glue into the grain. You ought to additionally ensure to wipe any extra glue off earlier than joining. This guarantees an optimally glued joint and decreases the opportunity of the PVA creeping onto the face of the body.