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Post by Scrit on Oct 26, 2007 19:04:03 GMT
OK, so I think it's about time for me to stick my oar in and stir the pot a little............ ;D The reason for scribing, as some others point out quite correctly is to reduce the gap which forms when the timber shrinks - shrinking mitres tend to open up much more than shrinking scribed joins. The second thing is that these cornice mouldings are sitting on a solid oak moulding attached to a solid oak fascia which in turn sits atop blocks and packers. The whole is on top of plastered walls - which aren't perfect, although my blocks and packers damned nearly are - but the cornice moulding is supposed to butt-up to a plastered ceiling........ I don't know about others but a 2.5 x 5 metre plastered ceiling is hardly going to be perfect so mitres are out - whilst scribes can be "adjusted" (read "bodged" if you will, I say "tuned" when the client is around  ). On a 2in wrapped or veneered MDF cornice on kitchens this isn't a problem as Mitre Mate will hold together for the 10 years or so the kitchen is in - thios job will probably still be in in 100 years so I'm just being a bit more cautious. So why did I ask the question? Well thisweek I've busted three jigsaw blades, three coping saw blades and a couple of bow saw blades trying to find a quick and easy solution, if there is one, as I've got 29 scribed joints to do (half of them with 3m+ plus lengths, all at 10ft or more above floor level) - and they've all got to look right. So I'm starting to despair just a little. As for pinning or nailing them together, well I haven't a hope in hell of doing that. The solution I've come to is to purchase a Collins Coping Foot for my venerable Metabo jigsaw, to build a cramp and thereafter to machine scribe the lot. Wish me luck! I'll post again after the nervous breakdown. Ha! Ha! For anyone who's never seen one this is the Collins Coping Foot:  and this is the beast in action:  although I'm not sure I'll be letting my fingers get that close! Just to whet your appetite this is a sample of the work we're on with:  Sorry foir the poor photo, but it is a building site environment and consequently not the cleanest. Scrit PS A warm welcome to Richard! Don't let Jacob worry you, we can always ban him just like we have Senior......... ;D |
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Post by paulchapman on Oct 26, 2007 19:45:53 GMT
Blimey, that looks like a hell of a job, Scrit. Good luck with it  Cheers Paul |
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Post by engineerone on Oct 26, 2007 21:02:41 GMT
phil and all, you all have more experience than me i am sure, however sometimes one has to use the phrase wood for the trees ;D from what i have seen over the last couple of years, most second fix, or re-fix chippies scribe their skirtings, and in my case i did not glue the corners, only behind them, since even mdf moves a little when it is painted and in a modern centrally heated room. anyway recently i have found that scribing is made easier by using a small rotary sanding wheel in a dremel type drill. if you do the major undercut with whatever you are used too, then finish off with the sanding wheel, using those rubber drums to get the shape and size you want. worked very well on my table maybe this will help scrit cause on that job there could be some value in having a portable drill on high to finish off. as for your scaffolding, what about one of those folding stair units that they advertise in the papers or on one of the channels. paul |
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Post by Scrit on Oct 26, 2007 23:12:05 GMT
anyway recently i have found that scribing is made easier by using a small rotary sanding wheel in a dremel type drill. No doubt, Paul, although this oak is sufficiently thick that I was experiencing excessive breakage of coping saw blades so in this case I doubt that a Dremel would really help all that much. I intend to use wood rasps/wood files and sandpaper to do my finishing - partly because I'm already familiar with that approach, but thanks for the suggestion. as for your scaffolding, what about one of those folding stair units that they advertise in the papers or on one of the channels. Actually, Paul, we use a couple of large aluminium builders steps which have the advantage of being readily portable and offer good flat steps as opposed to rungs to stand on. Rungs are OK for half an hour but are agony after a day - and I've been up ladders for 2 to 4 hours a day for a number of weeks, now. Erm , how is a mitre going to open up any more than a scribe ? If anything it's better as you have more glue surface . End grain glue surface...? Strictly speaking it's somewhere between end grain and long grain, isn't it? It's certainly common practice to use glue and pins in that situation (as Jacob says) If these pieces were shorter I'd no doubt pre-assemble at ground level using mitres, Mitre Mate and 18 gauge pins. As they are so big they'll be slightly more of a challenge  Scrit |
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Post by dom on Oct 27, 2007 5:32:40 GMT
Lovely work Scrit, true craftsmanship.
Dom
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Post by johnboy on Oct 27, 2007 6:18:25 GMT
I saw an episode of This Old House where they had a machine to do the copes. Sort of a large key cutting machine using a circular saw to do the cutting. Seemed to do a good job but they were painting the mouldings so could use filler.
John
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Post by Alf on Oct 27, 2007 8:23:43 GMT
End grain glue surface...? Strictly speaking it's somewhere between end grain and long grain, isn't it? It's certainly common practice to use glue and pins in that situation (as Jacob says) Sigh. I don't deny that it's common practice to glue and pin, I was merely wondering at the specific idea that a mitre would be better because of increased gluing surface. It might be better for all sorts of reasons, but that one struck me as unlikely, s'all. Should have skipped the levity concerning the wisdom of pros, shouldn't I? Might have known I'd get clobbered for that one... Cheers, Alf |
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Post by Scrit on Oct 27, 2007 9:53:15 GMT
I saw an episode of This Old House where they had a machine to do the copes. Sort of a large key cutting machine using a circular saw to do the cutting. It's quite probably a Copemaster or similar machine, which at around £1500 + VAT (imported) is probably a little rich for the amount of scribing work I'll ever do - unless someone comes and asks for 5 or 6 scribed breakfront kitchens with 20 joints a time to install. In that case I'd possibly view things a little differently....... Strictly speaking it's somewhere between end grain and long grain, isn't it? It's certainly common practice to use glue and pins in that situation (as Jacob says) Sigh. I don't deny that it's common practice to glue and pin, I was merely wondering at the specific idea that a mitre would be better because of increased gluing surface. It might be better for all sorts of reasons, but that one struck me as unlikely, s'all. All right then. I'm not really sure about this at all  I was taught to glue and cross-pin, so belt and braces? I was also taught to use mitres on short lengths and scribe on longer ones because it is possible to assemble, glue and cross pin the cornice for a breakfront cabinet a heck of a lot more easily on a bench than on the piece. Possibly because in the days of hide glue the joint couldn't be guaranteed to last forever (much the same as the reasoning behind using wedged mortise an tenon joints in door and window construction), but the other thing that folk tend to forget is that traditional woodworking glues such as hide glue and the more recent UF/RF glues are gap filling which for a mitre cut by hand and then quickly trimmed may well be a plus point. If you've only ever used PVA that's a point you'd possibly miss Should have skipped the levity concerning the wisdom of pros, shouldn't I? Might have known I'd get clobbered for that one... ;D Scrit |
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Post by engineerone on Oct 27, 2007 9:57:56 GMT
;Dscrit whilst i understand you dismissing the dremel as a practical tool in your application, why not think laterally?  ;D how about modifying one of the 500 watt trim routers to allow you to machine away a lot of the back before you finish with the files and rasps??? they are small enough to be easily used at height, and the only aggro is that they need to be mains connected  as for the steps i do understand, was just thinking about adding scaffold planks paul who would like to be helpful with this font of something floating round my lazy brain |
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Post by mrgrimsdale on Oct 27, 2007 10:15:25 GMT
Well yes because you want to keep the conspicuous mitre joint tight, which also implies (and I've only just thought of this) that the scribed end, tucked away in a less visible internal corner, is your expansion joint
cheers
Jacob
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Post by Scrit on Oct 27, 2007 10:25:44 GMT
How about modifying one of the 500 watt trim routers to allow you to machine away a lot of the back before you finish with the files and rasps??? They are small enough to be easily used at height, and the only aggro is that they need to be mains connected The amount of material to be hogged away really makes a small router a no-no, Paul. I'd already considered using a laminate trimer, but they simply don't cut fast enough nor are they good tools to freehand on next to no support. Incidentally I'm looking for each cope, including cutting to length and fixing to take no longer than 20 to 25 minutes. More than that and (as there are two of us to lift, position, glue and pin) the job starts to get expensive, as though it isn't already...... and the cable problem is another one of those bits of aggro I can well do without! It's bad enough being up a ladder with a Passy, hand tools, oh and 3 metres of cornice moulding balanced on my bonce (good job I have an ogee shaped recess in the top of my skull). I think that with the coping foot I've probably found the best technique in the short term - a Copemaster would be nice but the job just doesn't warrant it I'm afraid. I've found it easier to mark the scribes with a pencil and bring the workpieces back down to ground level, if only because it's a bit unnerving trying to file or rasp anything on top of an 8 foot high ladder...... We tend to hop up the ladder only to fix and mark and the ladder seems to get moved every 6 to 8 minutes. The other problem is that the area we're working in is an access area for other parts of the site which makes it a bit like working in Picadilly Circus at times. I think the Site Manager would have a blue fit if we were to stop the flow of traffic with scaffolding towers or stagings (planks are out as they are too narrow - we are obliged to use proper stagings these days) Scrit |
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Post by Sgian Dubh on Oct 27, 2007 11:06:22 GMT
...I think that with the coping foot I've probably found the best technique in the short term... Scrit And don't forget the angle grinder trick I suggested for fast 'refinement' and trimming after the jig saw. If you don't have an Arbortech-- very fast and efficient-- then coarse abrasive disks might do as a substitute. When I used to do quite a bit of this stuff in the US for built-in furniture, I liked fast and efficient, hence the Arbortech. Slainte. |
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Post by mrgrimsdale on Oct 27, 2007 11:07:18 GMT
I expect you've already sorted this but if not these are good; www.screwfix.com/app/sfd/cat/pro.jsp?cId=A335516&ts=82470&id=14003Operable with one hand - clamping up and releasing, but too short for your ceiling so you'd have to prop them from the staging etc. Abt the job in general - can't help thinking you've got the sh*tty end of the stick, first of all in being asked to do something presumably "designed" by someone, without consideration for trad (easy) practice. They should have consulted the joiners at an earlier stage or planned for the whole thing to be prefabbed in the workshop. Secondly the site prob - insist on being undisturbed - make it their problem, not yours? Getting the job done efficiently is what a site manager is for after all. I've been in that situation several times, but with jobs not quite as intimidating as yours. e.g. I've had to insist on scrapping the architects drawings etc. On one job there was a clear (to me) structural problem and I insisted on a clear disclaimer if they wouldn't bring in an engineer. Don't let them T*ny you about! cheers Jacob |
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Post by Sgian Dubh on Oct 27, 2007 11:09:59 GMT
A dose of sceptiscm can be a good thing now and then, and it amuses me even if it does occasionally annoy others ;D cheers Jacob I agree. Sceptism has a useful role, and I was rather jerking your chain for fun. Slainte. |
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). On a 2in wrapped or veneered MDF cornice on kitchens this isn't a problem as Mitre Mate will hold together for the 10 years or so the kitchen is in - thios job will probably still be in in 100 years so I'm just being a bit more cautious.
;D
