Negative Rake Scraper Basics

what's a negative rake scraper how can it help you as a woodturner when your project calls for the use of a scraper my name is Mike piece and welcome to my shop I'm passionate about wood turning and I want to share with you tips tricks and techniques to help you with your wood turning this time you're in student please click on the subscribe button I want to give a shout out to Gary McCord for suggesting this video thanks Gary have you ever used a scraper and gotten horrendous catch well this is where a negative rake scraper comes in that's just one of the many things we're going to talk about starting now okay I'm working on on a platter and I'm coming across here and very hard Bradford pear very dense dense grain and I'm cutting into side grain so it's kind of a tough going so let's come across here maybe very light now despite my best efforts it doesn't look too bad but I've got a few ripples here and that's where scrapers tend to come in very well for doing cleanup cleanup work where you have some small tool marks and as we've talked about in previous videos you're going to take very very light like pressure now with a very over the conventional scraper this is probably not a good example because it's a little on the small side but I haven't converted it to a negative rake to use it you're going to have to lift the handle up higher and come across if you don't and you could actually need to just to rest up a little bit you need to be cutting at or slightly below center if you don't have the thing angled down like this if you've got a catch it's gonna be self feeding and you're gonna get a you get horrendous catch if you don't generally operate in a negative rake and you're gonna you're gonna come across and clean up those tool marks well the advantage of the negative rake scraper with that secondary bevel number one you can come across flat and still not worry about self feeding because of that secondary bevel it's almost like it's going downhill some people think there's no difference between using a conventional scraper that in this manner first it's a negative scraper because they said the angle that touch is going to be the same I can't explain why but there is a difference number one is far less aggressive Stewart batty who is an outstanding instructor and a really very knowledgeable woodturning technician besides being an artist he says that if you use a conventional scraper you need to have a a overhang ratio of the tool to where it touches the tool rest seven to one seven times this this length compared to the distance between where the tool touches the wood and the the tool rest a seven to one ratio because there's so much leverage that you've got to deal with you get a catch he says that the negative rake scraper is far less aggressive and it can you can get by with a much shorter handle you only need a five to one ratio so that gives you an a pretty graphic example the difference in aggressiveness and these are primarily for cleanup cuts but you want a tool that's not going to get you in trouble and that's one of the serious advantages of a negative rake scraper is they're safer safer to use they're easier to use it's easier to hold it hold it flat coming across like this the other another advantage is you can engage a very wide part of the tool cutting normally when you're dealing with a scraper you only want a small amount of the tool touching the wood but with a negative rank scraper you can have a much wider band of of metal if you will touching the wood without getting in trouble and you'll find that most useful in the bow let me grab a bowl blank and give you a better better example so in a bowl you could have a French rake it's covering that's touching touching more of the the wood and it'll still be be safe we talked about the earlier video ten tips for a bowl scrapers that you don't want to come across a tool rest out here to the rim because that gets you in serious serious trouble this will start flexing the next thing you know it's going to explode on you if you're careful with a negative rake scraper because it is less aggressive you can come out a lot further out on the edge of either a platter or a bowl safely and then as we talked about Milutin a recent video if you're using a shearing shearing cut it makes it even less aggressive when you come out here to the to the edge some some folks argue that the negative rake scraper will also give you a better better finish than a conventional scraper some of that is a matter of how you put the burr on and how you sharpen it and and your your technique now that's that's the that's the pros it's user friendly and safer fewer catches it's easier to control you can gauge a wide area safely you can get a better finish and it's less aggressive and you can get away the shorter shorter handle now on the cons the burr is very fragile on a negative rigged scraper and you've got to refresh that burner about every 30 seconds to a minute or so for em to steal maybe a little bit longer weight on on some of the tougher m42 or 810 powder powdered metal scraper so I was researching this video I went on Doc Greene's website I'll show that on the screen he's a retired physicist roasted this book that I found very helpful fixtures and chucking for wood during done anything about scrapers on this book but he has some tremendous of ly good articles about scrapers on his website so I'll show that reference okay so we know negative rake scrapers we've got two bevels but what size should that bevel be should it be like this with a fairly blunt this is about 70 degrees and about 25 degrees on top with them somewhat longer bevel should look more like this with just very uh just a flat edge on it on the top not very long at all or should look more like this skew well there's not an easy answer as this chart shows we get a wide variation from an any number of noted Turner's with different opinions so I think it goes back to that that old joke if you asked 10 what Turner's you're gonna get 11 different answers I think in my case the product I'm going to experiment with it now it urge you to do the same and I think by experimenting I'm gonna start with whatever I've got no in this case this is a skew I want to maintain it as a skew so I don't want to go too far off from either the profile or the angle right now it's about 45 degrees I think I'll probably keep it at that experiment when I need a a really cute I think I'll probably pick up this and tune it up if I find that I get more use out of it as a scraper than a skew maybe I'll permanently change it to a French French Kirk as opposed to this Allan laser style skew now on this very large thick Sorby scraper it start off with an angle typical of of many conventional scrapers somewhere between 70 and 80 degrees I prefer more like 70 so I reground it especially when I put our negative rake on the front now this top edge is as I said 25 degrees so 70 plus 25 is 95 degrees so I've got an included angle slightly more than 90 degrees there's a lot of steel to grind here so I'll experiment with this a little bit as I maybe make the flat a little a little more acute going from 25 maybe closer to 30 and maybe then as they go back to the grinder I'll change that front angle from closer to 70 degrees to work it back to 60 but I'll do it is in degrees as I experiment with it and as I use it instead of just going whole hog and just grinding a lot of Steel away now this inexpensive Chinese steel Penn State scraper yeah the front of it is similar to the sorbus 70 degrees but I don't like this short bevel it may be good enough to get the job done but I'd prefer one a little bit longer because as I sharpen the front this is going to dissin disappear so I'm gonna have to go back to the grinder and put it on anyway so I want to make it a little bit longer so let's do that let's go over to the grinder and let me show you how we're going to do that and then let's talk a little bit more about birds because frankly I think maybe birds are more important how you put a burr on there may be more important than your particular angles so as a practical matter in my experimentation rat one of the factors it's going to assist me in choosing what that top angle is going to be it's gonna be the lowest setting on my particular Robo rest which I believe is somewhere close to 25 degrees and that makes it convenient to reestablish that so I'm going to start with that SIF that's good enough so let's give that a shot I'm just gonna hold this up here [Music] and now I've got a little bit longer longer bevel I like I like that better now you notice I'm using my very fine wheel you could be using aluminum oxide wheels same same principle but I'm using my finer grit wheel 180 because as we talked about in an earlier video one of the most important aspects of the quality that cut on the scraper is going to be just how fine a surface do you have here how polished and you're going to get much better more polished surface with a 180 grit then then I would with a 80 grit next I'm going to do the front front side again because I created a burr that was going in the wrong direction so I've changed this back to 70 degrees we're just going to lightly dress this [Applause] [Applause] [Applause] and I need to take a little bit more off here but I think I'll do that at a later time now that's raised a burr on the front and let's give that a try and see what it looks like in use now because the burro on the negative area scraper is very fragile you need to slow you speed down a little bit I'm not going to go much faster than that 650 so we will keep it flat we're just going to go very very light let's see what kind of shame none even services in this way the children between the nice fluffy sheep saving also getting a certain amount of sawdust they're fine very fine dust with some not necessarily a good thing [Music] the approach on how the birth that you would a little bit so I'm getting some very nice my shavings I think you can see so I'm gonna put those on the bed way now let's try something different with his birth now I'm an advocate of negative sharpening your tools the way they need to be sharpened but keeping them sharp but different people are going to disagree the finest bird comes from burnishing either with a carbide rod or or a diamond or CBN honed as I'm doing here the first thing we've got to do is take off that Burke it's by lightly rubbing this with his home now I'm going to come across this at a slight slight slight angle and just rub it would do that a couple of times trying to maintain the same angle and that reestablishes a Burke and it puts a very very fine burr on there that's stronger than the bird that comes off the grinder and a little bit finer so it should last a little longer but it's a little more effort to to make one so let's see what happens [Music] but beyond getting some very fine shavings just a tiny little bit of dust now here's those two piles of shavings the one on the top of the screen are the ones from the grinder burr the ones on the bottom are from the burnished burr and frankly I can't tell real big differences between them I've got to continue working with that but I'll keep working at it to see if I can get an improvement or otherwise I'm gonna go with the the the the bird that's the easiest for me to to make so now we're going to try that same experiment using the my skew or extreme negative rake scraper I simply ground the bottom at about a 23 degree angle and that raised a burr and it's a very significant burr I can feel it so let's see what happens with that [Applause] well the shavings are piling up as opposed to flying off I'm not sure what that says but they're very very fine fine shavings now because this is a fragile burl nibiru negative rake scraper won't last more than 30 minutes for a 30 seconds to a minute you want to use the entire surface so as I'm coming across I don't don't stay in the same place all righty move the tool slightly so I can use different aspects of the edge it won't use the entire verb before I have to go back and refresh it this looks to me to be getting finer shavings in appearance but it's again it's not anything to tell now just remember when you do go to the grinder for this type that with with the skew you have to remember to sharpen the side that's going to be on the tool rest because you that burner is formed on the top of the tool so you want to make sure the top of the tool is going to be is going to be the the up side when you when you use it in other words I can't do the turn flip it over and do this without going back to the grinder because the burr is going in the wrong direction so similar to last experiment we're going to take off the bird that we created with the grinding grinding wheel very like light pass and don't get rid of that and now we're going to I'm going to use a little different approach I had a class with Eric Bostrom and he he showed how to make a burnishing tool from a carbide you know how to make this bursting tool out of a dremel dremel tool so we're going to bring it up a little less than 90 degrees and we're just gonna come along and we're gonna do that a couple of times trying to maintain the same angle with steady pressure not too heavy and we'll see we have that best [Music] Wow I would say these these are wider shavings but they seem to be very very very nice they're a little bit larger so I'm not sure that it's cutting better but they sure seem nice and fluffy now I bet let's look at the surface of wood because that's what really counts and and and I've just got a flawless flawless surface here I've had no tear out it's just very smooth and I think I could I could start sanding that I believe with to 220 without any problem at all all right let's try one more thing with just one of these one of these scrapers we already bring us up it's a negative rake scraper but we're going to bring it up on its side and bring it across and use it as a shear scraper or shear scraping technique and let's see if we get any difference because of the bevel this thing I'm gonna pull this back just a little bit [Applause] you know these great these shavings are finer than what I had before because they're they're not as thick so again it gave me a very smooth surface but frankly I had a very good surface before because this is this is flat and we're not running in to ingrain most of this is side side grain I don't know that it makes a whole lot of difference to come up as a shear scrape I think I'm gonna do just fine coming across so okay not maybe not the best experiment but let's while we're at it let's go ahead and try with the other one and I believe this bird needs to be defeated redone because I was getting mostly sawdust so but one of the things I pointed out in earlier video just want to stress again negative Reiki still use it as a shear scream you want to make sure your tool it doesn't have sharp edges here along the bottom so when you bring it up it will glide across your tool rest now if negative rake scrapers are so great shouldn't i regrind all of them well the jury's still out here's a few scrapers I know I'm going to keep in the present present form number one a box scraper I want that to have a nice sharp corner so I can control it when I go down the wall of a box or shaping the inside wall up near the mouth I'm not gonna change that one here's one of the original scrapers I had a little small for big bowls this round round scraper I use it for a lot of small items boxes inside boxes boxes inside the lid inside the bottom and on the bottom of bowls and small areas I'm comfortable with it I think I'll probably just just leave that one my spear point scraper I'm not sure I think I'm gonna leave it for the time being but if I ever get in a situation where I'm catching both both sides it's liable to send me back to make this a negative rake scraper because as we've talked about negative rake scraper is less aggressive and this is a great tool for getting in corners but you got to be real careful not to be getting cutting on both sides and a negative ring might make that safer but I'm gonna hold off on sharpening this is a negative break well it's been a good good series so far I've learned a lot about scrapers and going through this process because there's an old expression that says to teach us to learn twice and I think I learned an awful lot from making these now to learn an awful lot from y'all's comments if you got any comments please leave them below on your your thoughts the experience on negative rake scrapers but before we round up let me just touch on a couple summarize a couple of things again little very light pressure no more than the pressure you put on your hands under under a hairdryer negative rake scraping got a very fragile burst you got to refresh it about every 30 seconds or a minute or so you also want to slow your turning down don't go as fast as you normally would because that'll keep that burr protected it's just a little bit a little bit longer use the entire edge of that burr you use all of it so move the tool across the the entire edge so that will last a little bit longer and as we learn about negative rate scrapers they're not as aggressive as a conventional scraper they don't take off as much wood but it's a fishing tool just to get rid of tool marks and imperfections and refine the surface a little bit so thanks for visiting with us stay safe y'all come back here

Channel: Mike Peace Woodturning

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Keywords: negative rake scraper basics, what is a negative rake scraper, negative rake scraper, how to use negative rake scraper, beginning woodturning, woodturning tools, wood turning tips, wood lathe, wood working, lathe tool, Woodturning lathe, basic woodturning, Mike Peace, mike peace woodturning, woodturning tricks, wood turning tricks, mike peace woodturner, woodturning projects, woodturning, wood turning, Wood turning lathe

Id: 9Hai4ia7UX0

Length: 23min 11sec (1391 seconds)

Published: Fri Jan 19 2018