The magicmitre website has comprehensive tips and downloadable instruction manuals.
Brian Sharrock said here:
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I applied coving (can one say 'coved'?) to my bathroom .. the results weren't bad ... before doing the kitchen I bought the "Magic Mitre" as demonstrated on QVC .. I wouldn't be without it ... not many corners are exactly ninety-degrees but the 'Magic Mitre' makes all mitres a piece of ... For joining lengths of coving .. whether it's two or more metres long .. Magic Mitre recommends scarfing the joints rather than butt joints .. the scarfed joints are less visible and easier to smooth down with polyfilla.
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[1] sells the 'Magic Mitre' box, complete with a jack-saw that does exactly what you want ... that is transfer an angle off a wall onto a mitre-box and permit you to cut skirting, architrave and coving. You can do internal and external corners with ease ... albeit with a certain head-scratching 'that'll be an external _right_ so I offer up the work-piece this'a'way'. The device is manufactured somewhere and huge quantities get shipped to QVC in batches, these batches tend to get pre-sold. So get you order in quickly ... see WebPages. [1] there are other vendors but only QVC include the (free)jack-saw :) *Remember there is no such thing as a free lunch!
I haven't read all the destructions, but IIRC from watching the demo you hold the angle apparatus up to the wall and lock it into position, then take the angle to the cutting bit and cut.
"It" doesn't - "You" (perhaps that should be 'one' for an Earl?) does!
The apparatus includes a plastic hinged angle-finder; this is offered up to the angle (corner internal/external; banister angle; dado rail; ... whatever) and pushed against the two defining walls: the angle-thingy is then locked off and placed over spigots on the arms of the adjustable mitre box; the mitre box is then locked off - the mitre box has thus been set to the exact angle required. [Remember the adage; measure twice - cut once]. The angle-of-the-corner isn't so much 'found' as the machine sets the coving up for an exact meeting/mating joint. { the internal/external settings do require some head-scratching but the .pdf instruction manual is excellent ].
If a Liverpudlian like me can produce mating coving joints ... then an Earl (of Derby) should be able to d-i-y his entire mansion ....
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