Marking Gauge Modification

now we're ready to start marking out the timber is prepared I've marked the outside edges you'll see that my datum surfaces are on the inside and the face edges are both pointing towards me the ends are also true and I'm going to be using three gauges it's good practice in a complicated job to preserve the settings and it gives you the opportunity of freshening up a line if it becomes indistinct part of the way through the job if you try to work with one gauge setting it to a previous dimension is almost impossible so having three is preferable to having one you may notice that some of my gauges look like a conventional gauge but they have in fact been heavily modified I've ground and sharpened the pin so that it's a crescent tipped knife with a flat side I've changed the position of the pin so that I can see it as I work with it and altogether I believe it now works as well some of the more expensive gauges now my first gauge is set to the thickness of the timber plus a tiny amount I'm very keen on thinking about these things it's almost impossible to set a gauge exactly and if we consider the options it may well become clear that slightly above or slightly below may be helpful in the future now if I set this gauge to t + slightly over the thickness it will protect the delicate tip of the mitre until the end of the job if I were to set it to t-minus I would in fact end up with a small flat on the end of my mitre which we certainly don't want so I'm going to set T Plus now I might try and quantify t plus for you with my students here I suggest something like plus 0.2 of a millimeter now I did some sums and I have an idea that this may be quite close to a hundred and twenty eighth of an inch for those of you who are fond of Imperial or to put it the final way a sheet of average writing paper is four thousandths of an inch thick so my plus becomes roughly eight thousandths of an inch or two sheets of writing paper but please don't worry too much about precision the only snag with going way over a setting is it will usually produce more work for you to do later what I'm going to do here is cut it in deep for most of the its length because at the end of the chopping out I'm going to be feeling a chisel drop into this line but at the other edge I'm going to make a faint scratch because if I cut deeply up to the edge it would encourage a small lump of wood to fall out of the top of my miter line I'm going to take the light scratch short way down the sides now I'm pretty clear that this depth of mark is going to disappear in the final cleaning up of the job if you're worrying about that this little scratch down the edge will be very helpful for lining up the mitre which is what we're going to do next both pieces are marked identically at this stage in fact all the way up to the marking out of the pins the pieces are treated the same little scratch little scratch and that's the first step there we go the next stage is the cutting in of the edge miter lines now this is an extremely important job in many ways the crux of the whole exercise and I have found it quite difficult over the years now you can buy engineers 135 degree miter squares or as I used to do in the beginning you may have to set up a sliding bevel perhaps up against a protractor you might wonder where I don't choose to use something like this beautiful little starett combination square but there are technical problems if I offer it up like this for marking the miter line I'm registering on the non face side of the board which breaks one of the important conventions which produce accuracy for us I want a square that will register on the datum or face side I have found the little scratch that we took down the edge to be helpful but the precise positioning of this square is very important indeed I do suggest that when you have some practice goes you look at your results with some magnification now I will be putting a chisel into this line eventually so I want it quite bold and deep now I mentioned that I found it rather difficult to position this might align and I dreamt for many years of an expensive piece of tool-making that would help but I've actually come up with this little wooden jig and it was adjustable by virtue of this screw here and I can now register the jig against the shoulder line which we cut in with the gauge and that makes an absolutely solid repeatable position for my mitre square so I'm ever so pleased with that I now say it my 2nd gage - t - L this is the thickness of the work - the thickness of the lap the lap line as I call it is marked right across the N grain of both pieces as usual I like to cut in quite deeply as that will help us in the future when we're trying to precisely work down to the flat side of the line I now have to drop this line down the edge until it meets the miter line I don't want to go past the miter line I don't want to Nick it and this is the sort of place where I find my bench light very useful that's done there and now I can do it there as well all this early marking out work is done on both pieces they remain completely symmetrical until we reach the marking out of the pins which I'm happy to say is getting a bit closer nice and deep from the miter line you finally down to the major line yep I'm pleased with that our third gauge is set to the distance between the end grain and the intersection of these two lines now I have a slight modification to conventional theory in that I like to set my gauge to be about two tenths of a millimeter larger than this dimension this is the result of much experience with joints that wouldn't quite close we frequently found that something was holding apart the shoulder lines or the mitre now if you follow conventional instructions the ends of your dovetails or pins are actually grating on the lap of the second piece by marking this line as d+ I am creating a tiny bit of space it's a space for excess glue it's a space which helps to ensure that our shoulder line and miter closed and these are not glue surfaces so it has no impact on the strength of the joint so here is my third gage which is set I mark across here being careful not to Nick the miter line I mark right across the face side and I mark the other edge this marking is of course reproduced on the second piece as I keep saying everything is done to keep the pieces symmetrical in the beginning you

Channel: David Charlesworth

Views: 54,221

Rating: 4.9459457 out of 5

Keywords: Hand tool woodworking, woodwork, hand tools, Marking gauges

Id: L-aT7WIdydg

Length: 13min 5sec (785 seconds)

Published: Fri Mar 18 2016