mcraigl Posted August 3, 2009 Share Posted August 3, 2009 Xxxx xxxx. Flat grinds are tough. I forged in a distal taper on about a 7inch blade (haven't measured the blade actually), and was having a hard time getting the bevel to be parallel with either the edge or the spine. Finally figured out that it was because of the tapering thickness. JPH says in his book that the flat grind is harder than hollow or cannel. I've got the cannel down pretty good. Just waiting for a contact wheel to arrive so I can try a hollow and couldn't wait so I went for a flat grind on the 2nd ladder-cablemascus blade. I'll post pix once it's done. But again, it did try my patience to get this grind to look decent, and I still ended up with some errant grind marks from the coarse belt that I will never be able to get out without thinning the blade way too much. Also a piece of advice -slash- observation. Be very, very carefull when threading the tang of a cablemascus blade. Cable don't play nice with threading dies... question: What grit do y'all like the best for the "rough" grinding steps? Seems like we're always talking about finishing grits around here. I've got 36grit blaze belts for my general grinding tasks and that's what I've used for the rough grinding steps on the few blades I've made. I'm thinking about going a little bit finer grit for a couple of reasons. first being that one millisecond of error with the 36g and you've got irreparable scratches at the least or completetly ruined grind lines at the worst. Second, and sort of still related to the first reason is to slow the process down a little bit. A new 36grit Blaze gives you very little room for error. It eats whatever contacts it, and does it in a blink of an eye. I'm thinking about trying an 80 grit Blaze. Any thoughts from the pros on that? Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted August 3, 2009 Share Posted August 3, 2009 I use a 50 grit blaze for ss rough grind. After they get back from heat treat i use a worn 80 grit blaze to align grind lines and thin the blade a bit. Then to 100,220,A45, A16 then buff. When the bps return I think the number is bp0235 and I outline with pictures all of the steps. Quote Link to comment Share on other sites More sharing options...
nonjic Posted August 3, 2009 Share Posted August 3, 2009 ive used 36grit, and kinda feel they tear the metal off. It feels much more controlled, and like its cutting, (rather than tearing) for me with a 60 or 80's for the bulk of the removal, then to 120, 240, 400 and hand finish. If it takes an extra hour with the 60 / 80 grit so be it. Most of what I do is complicated patternwelded, and its kinda depressing (and time expensive) when a 36 grit jumps over your plunge line! On forged blades, (flat grind) i grind the spine distal taper even, totally ignore the cutting edge of the blade untill the spines even. I then work back towards it. You need a datum of some kind to work to or your forever chasing errors! (works for me, y.m.m.v!) Quote Link to comment Share on other sites More sharing options...
mcraigl Posted August 3, 2009 Author Share Posted August 3, 2009 You're both confirming what I was feeling. My billet isn't nearly as purty as the beautiful pattern welding that you're doing John, but I still had a bunch of time in it. And it did jump the plunge a little bit. It's OK though as I'm pretty sure this blade suffered some bad grain growth and it didn't harden up nearly as well as I expected. So I'll be keeping it for myself. A first almost. Everything that's turned out nice has been given away. I think you pretty much described the process I went through to a "T". Rich, I vaguely remember that BP, and will be looking forward to their return. I'll look it up when they come back. I didn't get into the sharp cutty end of this work 'til after they went down. Here's the other issue... I forged the bevels, and forged a distal taper into the blade. Then when it came time to grind I remembered discussions about scribing the center line of the edge to give you a target to help keep the edge centered. I at first thought I'd just lay some shim stock next to the edge on a flat surface and then use it as a "fence" or guide to run the scriber along. Well, the distal taper made that impractical. So then I tried stacking a couple of peices of shim stock under the ricasso end of the shims but they were too flexible and needed to be supported all along. So I started stacking pieces under the tip end of the blade, but couldn't make the shim stock I had available add up to the required height to get the line scribed in the center of the edge. By then I was ready to say heck with scribing a line and just winged it. It ended up OK sort of, but am still interested in have a target to grind to. Or Datum as John put it. What do you guys do? Quote Link to comment Share on other sites More sharing options...
John B Posted August 4, 2009 Share Posted August 4, 2009 If you want to pack up an uneven or tapered piece of thinnish steel (Under 3/8") try using some modelling clay (plasticene?) to bed it down onto, you could use a total strip or just blobs at suitable increments, It is then relatively easy to hold stable whilst using a scribing block a) to ascertain it is horizontal to your marking out datum and b)to put a centre line on Quote Link to comment Share on other sites More sharing options...
nonjic Posted August 4, 2009 Share Posted August 4, 2009 trust your eye! its good to thous! Once I think im on the right track with levelling (trueing up) the spine of the blade I hold it against a straight edge, then flip it and see the difference, grind a bit more, check again, repeat lots of times! I think (personally) the center line marking is really only usefull if your starting out with ground flat stock. Quote Link to comment Share on other sites More sharing options...
devins Posted August 5, 2009 Share Posted August 5, 2009 I have not done this yet but I fab things off the cuff all the time. So as I see you describing the situation to scribe the center line of the edge so you can grind to it, I get a vision of a jig that could be easily made. You tell me if this will work. The tang will be flat unless tapered then the ricasso will be flat correct? If so you have a flat surface to work parallel to. You need to fix the flat part (tang if can for more stability and the longer flat area the easier, ricasso if that is what you have) in a jig that would hold straigt and parallel down the length of the blade. Then run one edge of the scribe down your flat jig surface(outside) and the marking scribe end would be adjusted to center at the ricasso and then scribe to tip. You could also use this to check for straight while forging prior to completion to make sure you are as straight as you think you are. This could be constructed from a piece of angle and flat stock with two screws for locking the blade in place. What do you think? Quote Link to comment Share on other sites More sharing options...
devins Posted August 5, 2009 Share Posted August 5, 2009 I drew this out very quickly but hopefully the pictures will give you an idea of what I am talking about. It should be adaptable to most situations. Quote Link to comment Share on other sites More sharing options...
mcraigl Posted August 5, 2009 Author Share Posted August 5, 2009 Devins, That just might work. Of course you're making the assumption that I'm so good as to have forged the parallel sides of my ricasso parallel with the centerline of the edge... One could always "pack" the tip end with some shim stock to get the edge in the center of your jig too. Might have to give something like that a try. Good idea. Quote Link to comment Share on other sites More sharing options...
devins Posted August 5, 2009 Share Posted August 5, 2009 That is what I was thinking too, you could check down the length with your scribe and if it wondered to one side or the other shim until straight and then scribe the mark. You will probably be ready to try it before me so let me know how it works, LOL. But I think it will. Quote Link to comment Share on other sites More sharing options...
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