Planing a straight edge

[Music] the first thing I'd like to show you is the what I call the edge exercise you've already seen me taking a number of shavings off this edge and the question is is it flat now I've got a precision straight edge here starett and we can see immediately that that's pivoting about the center indicating that this is actually a bump now what I was taught 40 years ago was though that the way to get a straight edge was first to deliberately plane it Hollow I do this with what I call stop shavings my shaving will start just inside this end and it will finish just inside that end and as you can see if I continue to do that I will be getting rid of the bump and as it were attempting to hollow this edge the shavings you saw me take earlier which went right through I call through shavings so I put some pencil marks at either end and I'm going to do a squiggle on the surface when you're when you first try this exercise don't try and stop and start too near to these marks because if you get it wrong and remove them you defeat the object of the exercise starting in the right place is not too difficult the difficulty comes in trying to stop in the right place because I can't see the timber so it may help you to have a little telltale on the bench which indicates when you should lift the plane the other point to make is that it's important that the plane is moving when you lift it it doesn't matter how slowly it's moving but if you stop and lift the shaving remains attached to the wood pulls back through the mouth of the plane and it can often take a minute or two to clear it the squiggle shows you where you actually started and stopped it's important that the plane with its curved blade is centered on the timber and I use a thumb on top and my fingernails form a fence underneath so this is a sort of pinching action on the plane when you start the shaving it's the thumb pressure on the centre over the centre of the work that's doing all the work some beginners grip the back handle much too hard and they tend to twist the plane off the surface when I'm doing this I can actually open that hand completely it's only at the end that the thumb is released now when I have live students I say what's going to happen in a moment if I carry on like this do you see it stopped cutting there and it's stopped cutting here and in a few more shavings it will in fact stop cutting altogether you're perhaps noticed that I'm trying to play with my legs as much as possible my arm is jammed against my ribs and I try to do this by rocking backwards and forwards on my legs they're stopped cutting I think we can assume that this is hollow and it might be fun to try and measure this hollow now many years ago I decided to start measuring with ready readily available cheap things like thin cigarette papers newspaper writing paper the thin cigarette papers one thio use papers about do thou of an inch good writing papers about fourth hour and a business card is about 0.3 millimeters which is twelfth hour so to try and find out what's going on well have a bit of fun I'll put the business card in there we are the straightedge is pivoting and rocking up and down it's nothing like 12th oh my TP fourth are the straightedge is on the point of spinning on the paper so this hollow is nearly four thousandths of an inch if I put two thousand er Neath it pulls straight out no I can't leave my edge in this condition there are in fact little steps here where I started my shaving and finish my shaving and it's got the pencil scribble on it so what I do is allow myself to have one or two teen up shavings there's still some pencil so I will take to clean up shavings and what this does is to reduce the hollow slightly I'm now clearly spinning on the fourth eye Jim I can just feel the mm grabbing a little bit so this edge is now two thousandths of an inch hollow over twenty inches long and I consider that to be straight I think it's a remarkable tolerance for a hand tool on timber

Channel: David Charlesworth

Views: 17,684

Rating: 4.9826465 out of 5

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Id: vqPP6-0jkws

Length: 7min 35sec (455 seconds)

Published: Wed Oct 31 2018