trouble seeing knife lines when dovetailing

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madge

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Hi all, I'm dovetailing an oak toolbox and am struggling to see my knife lines in both the end grain and long grain when transferring tails to pins. As a result I'm being over cautious when sawing and leaving myself far too much paring. I tried applying electrical tape before transferring tails to pins and this makes the pins far easier to see; the problem is that the tape springs back a little when cut and so I don't really trust the lines. Applying the tape is also a hassle. Does anyone have any recommendations for making knife lines more visible?
 
Hi Madge

Deeper lines and a low angled light should help, a fine propelling pencil can be used to fill in the knife lines 0.3mm would be good.
Derrick Cohen used blue masking tape which won't stretch when applied, normal masking tape will work.

Pete
 
Yes the obvious answer is to make deeper lines. Personally I'd use a scribe. Mine's an old dart (without the feathers).
Another alternative is thin square chisel-edge craft-knife of the Exacto type. You can locate it, then tap it lightly for a deeper cut. It works well in small pinholes, where trying to slice a line with a knife is difficult - especially when you find you are slicing the sides of the hole.
 
I fill my knife lines with a pencil sharpened to a chisel point on sandpaper. I find this much finer than a propelling pencil lead, although I only have 0.5mm leads, not 0.3mm.

This makes the lines very easy to see and the knife lines all get removed on final planing after construction.

HTH
 
Another option that I have seen suggested is to go over the end grain with white chalk or white coloured pencil before marking the lines. I must remember to try this!
 
Or you could dust the ends with white chalk after marking the lines so that the chalk fills the knife lines.
 
Hi Madge
Another hint that might work for you is to rub medium grade abrasive paper along the end grain.
This will give you scratches in the opposite direction to your knife lines, which will then show up a little better.
(The chalk method is good for darker timbers)
Cheers John
 
Hello madge, I dovetail oak frequently and I agree it can be difficult to see the scribed lines. Here's my take on the problem,

-Deeper scribe lines sound appealing, but I'm not sure that's the best solution. Best practise is to just scribe once, so you'd have to achieve that deeper line with a heavier cut, and a heavier cut will almost certainly be a less accurate cut.

-Pencil isn't always that visible on oak end grain, red biro is better but in my opinion neither will really give you the accuracy you need to fit tails to pins straight from the saw.

Consequently my preference would be for glancing side light, and sure enough I always use a desk lamp when dovetailing, repositioning it throughout the exercise to give the maximum visibility.
 
Get yourself a pair of plus 4 reading glasses from Tesco £6, they work like a magnifying glass. I use a scalpel, cuts a nice deep fine line.
 
My answer may depend on how wide your pins are i.e, what tool can you fit in between the pins, some ideas.

I cut tails first and then mark pins from them, if I can fit a carved 2H pencil in, I will use this or
if it's a dark timber and the pencil marks don't show up, then you can use a white chinagraph pencil.

Most of our sockets are too small to fit a pencil in so I use a Swann Morton scalpel No 4 with a No 26 blade - long and thin and very good for getting in the corners.

Another couple of ideas you can try but not my own preferred methods are cut the tails with the saw as usual but before removing the waste, place them over the end grain of the pins and cramp in position. Either pull your saw through the previously cut saw kerfs or use an old cabinet scraper and put it in the saw kerf and hit it with a hammer to mark the end grain.

Cheers Peter
 
Hello,

Have you thought of cutting the pins first? Obviously you can do it either way, but unless you have a good reason not to, cutting the pins first leaves bigger gaps to mark through. Then sharpen your pencil into a knife shape and mark the tails with that. The end grain can be marked with a small square and pencil from the transferred marks, so is easier to do and see what you are doing. I never use a knife to mark dovetails and can get them as tight as a gnat's chuff, so there is no accuracy problems doing it this way.

Hope this helps.

Mike.
 
Hello,

Oh and just remember when you saw to the pencil line, is to leave all the pencil line behind.

Mike.
 
If the knife bevel is too steep it wont make as deep a line as a slim bevel like a scalpel, this might sound insulting but are you sure the knife is sharp, as in shave hairs off your arm sharp? I find anything less wont really make any decent line. The low angle light is a good tip but a lot of light on the area is a better tip, done be left in the dark!
 
woodbrains":1haxnj5w said:
Hello,

Oh and just remember when you saw to the pencil line, is to leave all the pencil line behind.

Mike.
T'other way around surely? Whether you've marked through a pin hole or between pins you want to cut exactly to the outside edge of your mark i.e. take away all the pencil mark. In theory anyway.
Pencil is good too. Knife sometimes the worst option as it's so easy to be slicing the side of the pin or hole. I don't like using a knife unless against a steel edge, but woodworkers are a bit fixated on knife marks!
 
Jacob":2nfdc8zn said:
woodbrains":2nfdc8zn said:
Hello,

Oh and just remember when you saw to the pencil line, is to leave all the pencil line behind.

Mike.
T'other way around surely? Whether you've marked through a pin hole or between pins you want to cut exactly to the outside edge of your mark i.e. take away all the pencil mark. In theory anyway.
Pencil is good too. Knife sometimes the worst option as it's so easy to be slicing the side of the pin or hole. I don't like using a knife unless against a steel edge, but woodworkers are a bit fixated on knife marks!

NO!

The pencil line is on the piece you are keeping.

Mike.
 
woodbrains":3hdjvxmk said:
Jacob":3hdjvxmk said:
woodbrains":3hdjvxmk said:
Hello,

Oh and just remember when you saw to the pencil line, is to leave all the pencil line behind.

Mike.
T'other way around surely? Whether you've marked through a pin hole or between pins you want to cut exactly to the outside edge of your mark i.e. take away all the pencil mark. In theory anyway.
Pencil is good too. Knife sometimes the worst option as it's so easy to be slicing the side of the pin or hole. I don't like using a knife unless against a steel edge, but woodworkers are a bit fixated on knife marks!

NO!

The pencil line is on the piece you are keeping.

Mike.
Oh yes so it is! But you have to make sure you are on the right side (outside) of the line - that's what confused me.
 
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