underpinner wedge sizes

learner6

Grumbler in Training
Joined
May 2, 2004
Posts
5
Loc
Norwich, UK
I am currently using a semi-pro hand underpinner & clamp & have suffered from mitre corners opening up after a few weeks. Corners have been pinned & glued with PVA but I think the problem is the short depth of wedges I have been using, combined with wood moulding that can be quite warped & stresses the joints. I am now using a deeper wedge (12 mm) which gives a good 75% penetration of moulding depth. What is a good rule of thumb for selecting wedge sizes that give good joint strength but does not risk break-out on the moulding face?
 
Welcome to the Grumble.....from another on this side of the pond.


What size moulding and what type of moulding!!!!!...... you can give me the UK ref No. and suppliers names.....if you haven't got the sizes....I can work it from there
 
Ta for a quick reply Dermot. The mouldings giving trouble were B1141 (7/8")& the wider C3645 (1 & 1/2") from Wessex Pictures (cream cushion in Obeche I think), nice mouldings but quite 'springy'. Regardless of size, there must be a guide to getting a decent depth/number of wedges into a moulding to get a really secure joint....
 
Below is from the instruction manual of my Cassese …..I can only guess that it would be the same for a semi-manual underpinned…….though how far the wedge is in has rarely caused me a problem of the miter opening….it generally has been a bad miter cut…..the glue should hold the joint……and in reality the wedge is only there to hold the joint together while the glue dries….I use Evo-Stick extra fast (the green bottle)

I never have problems with soft wood only some hardwood mouldings.

I’m gone to look for my Wessex catalogue….back soon…
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http://www.cassese.com/et/manuels/manuels/88-89/expcs88-89.pdf
The CS 88 / 89 is designed to join mouldings in one or two places (positions) without limitation of the number of wedges in any of those places. The selection depends on the width and thickness of the moulding to join.

As a general rule a MINIMUM 2 mm clearance (less than 1/8”) “above” the wedges shall be respected. Same sized wedges can be stacked in order to avoid to have to change the cartridge size when joining frames with different thickness.

AS A GENERAL RULE, THE JOINING MUST BE CARRIED OUT AS
CLOSE TO THE THICKEST MOULDING PART(S) AS POSSIBLE.
 
I think the second moulding should be C2645!!!

I cannot see why the joint should fail on those mouldings….. if you are getting a good cut/mitre and being reasonable generous with the glue…..if you use too much glue you can wipe it of with a clean dampish rag….use a clean rag on that light colour moulding or you may leave dirty marks on it.

I do not use Wessex but I have had similar mouldings….most of those mouldings are coming out of a few factories in Europe….. Spain or Italy…..my supplier in Ireland would have something very close to what you are using….

How are you cutting the moulding!!!.......what is going wrong for you is something very simple…..we will resolve your dilemma
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Rgs
 
Thanks again Dermot, I think you have me sorted...seems to be a combination of not being aggressive enough with the wedge depth & placement & using any old PVA, will definately try Evo-Stick in future
 
Yes, sorry C2645...they both clamp up really well but can be quite warped. I could not stretch to a Morso so am using a decent Elektra Beckum mitre saw - perhaps a factory work clamp would be a good investment to ensure spot-on 45 degree mitres as I have learnt early on that everything starts from a 100 percent mitre!!!
 
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