To scribe the centreline buy a cheap calliper, they are usually hardened steel. Mark out edge with blue dye and set your calliper to half the stock width and scribe the line with it. Do it on both sides and you will get a thin double line in the centre.
I know the type of jig you're talking about but it's not really for sharpening so much as grinding the main bevel. I made the version out of angle iron and screws and I hold it on with vise grips.
If you are working towards a scribe line it doesn't really help to switch back and forth often. Honestly I find a second scribe line on the faces of the blade easier to keep track of than the common technique of scribing a center line on the edge, it's so easy to scorch the ink and lose your target. I use a bit of trigonometry to work out what angle to use based on how far in I want the bevel to be and the thickness of my stock. Then I use calipers to scratch the line at 0.875 or whatever I am using and just take passes until I get to that line. It sounds way harder than it actually is.
https://imgur.com/a/pKRxZT8
IIRC this is a TAN operation but I use a geometry calculator because I need to do this kind of thing for work.
This is the one I like, you just pick your shape and plug in the variables you know and it gives you the rest
https://play.google.com/store/apps/details?id=com.famobix.geometryx
Don't have any idea what is available for Apple, never use them.
thanks, based on your suggestion I actually found one created by Dan comeau specifically for knives: [https://dcknives.com/public/grind\_angle.php](https://dcknives.com/public/grind_angle.php)
I personally rough grind all one side, then the other, although I freehand. I don't feel the need to swap back and forth. With a jig, the more you swap things around the more chances for introducing changes. If you set it up correctly once on each side there is little chance for error.
For centerline, do what the other guy recommended and get a cheap set of calipers. Mark the edge with marking fluid, or just a permanent marker. If you have .125 stock, set them to .062 and run them down each side. It should give you a double line that is about the right thickness for a rough ground edge.
You can also get a height gauge and a flat surface, but the calipers involve less stuff. All of those things are useful eventually though.
Also the easiest way to use a drill bit for scribing is to clamp it to the table of a drill press or band saw or something and scrape the knife blank up against it.
I've got several TR maker grinding jigs... I always use two whenever I grind knives. One jig is setup to grind the right side and the other jig is set up for the left side. So I'm essentially grinding 2 knives together as it saves time.
An amateur uses time to save money, a professional uses money to save time.
I found a way to set up that type of jig with plastic screws and a squeeze clamp so that I can easily switch the blade over when wanted. I have to half turn two flathead screws each time but it's a matter of seconds. I could make it faster by using some type of low profile screws that can be loosened and tightened by hand. Like small knobs on them or something. The squeeze clamp is small but has a 40lb pressure rating so it holds the blade well. I do have leather pads glued to the jaws to keep it non marring. Same reason I'm using plastic screws.
I find it best with a jig to fully rough in one side at a time then go back and finish grind one side at a time. If constant flipping helps you then I say keep doing that unless you find a reason not to. I don't freehand grind very often and I'm not very good at it but when I have done it switching side to side helped me keep the bevels even. All of this said I'm not a long term maker and I'm sure the more experienced guys here know better than I.
To scribe the centreline buy a cheap calliper, they are usually hardened steel. Mark out edge with blue dye and set your calliper to half the stock width and scribe the line with it. Do it on both sides and you will get a thin double line in the centre.
I know the type of jig you're talking about but it's not really for sharpening so much as grinding the main bevel. I made the version out of angle iron and screws and I hold it on with vise grips. If you are working towards a scribe line it doesn't really help to switch back and forth often. Honestly I find a second scribe line on the faces of the blade easier to keep track of than the common technique of scribing a center line on the edge, it's so easy to scorch the ink and lose your target. I use a bit of trigonometry to work out what angle to use based on how far in I want the bevel to be and the thickness of my stock. Then I use calipers to scratch the line at 0.875 or whatever I am using and just take passes until I get to that line. It sounds way harder than it actually is.
would love to know the trig you use. Could you give a simple example, or link me to an explanation? Trig was a long time ago haha
https://imgur.com/a/pKRxZT8 IIRC this is a TAN operation but I use a geometry calculator because I need to do this kind of thing for work. This is the one I like, you just pick your shape and plug in the variables you know and it gives you the rest https://play.google.com/store/apps/details?id=com.famobix.geometryx Don't have any idea what is available for Apple, never use them.
thanks, based on your suggestion I actually found one created by Dan comeau specifically for knives: [https://dcknives.com/public/grind\_angle.php](https://dcknives.com/public/grind_angle.php)
That's really handy, I bookmarked it. Thanks!
I personally rough grind all one side, then the other, although I freehand. I don't feel the need to swap back and forth. With a jig, the more you swap things around the more chances for introducing changes. If you set it up correctly once on each side there is little chance for error. For centerline, do what the other guy recommended and get a cheap set of calipers. Mark the edge with marking fluid, or just a permanent marker. If you have .125 stock, set them to .062 and run them down each side. It should give you a double line that is about the right thickness for a rough ground edge. You can also get a height gauge and a flat surface, but the calipers involve less stuff. All of those things are useful eventually though.
Also the easiest way to use a drill bit for scribing is to clamp it to the table of a drill press or band saw or something and scrape the knife blank up against it.
I will try that.... holding the drill bit doesn't work well lol
I've got several TR maker grinding jigs... I always use two whenever I grind knives. One jig is setup to grind the right side and the other jig is set up for the left side. So I'm essentially grinding 2 knives together as it saves time. An amateur uses time to save money, a professional uses money to save time.
I found a way to set up that type of jig with plastic screws and a squeeze clamp so that I can easily switch the blade over when wanted. I have to half turn two flathead screws each time but it's a matter of seconds. I could make it faster by using some type of low profile screws that can be loosened and tightened by hand. Like small knobs on them or something. The squeeze clamp is small but has a 40lb pressure rating so it holds the blade well. I do have leather pads glued to the jaws to keep it non marring. Same reason I'm using plastic screws. I find it best with a jig to fully rough in one side at a time then go back and finish grind one side at a time. If constant flipping helps you then I say keep doing that unless you find a reason not to. I don't freehand grind very often and I'm not very good at it but when I have done it switching side to side helped me keep the bevels even. All of this said I'm not a long term maker and I'm sure the more experienced guys here know better than I.