(Conventional) Scraping

welcome back everyone and thanks for joining me once again at the lathe I've been wanting to do a video on scraping for some time now and I finally sorted out how to present that topic so this time we'll take a look at conventional scraping you may not have heard the term conventional before but that's just the word that I use sometimes to differentiate regular old scraping from things like shear scraping and they get a rake scraping so without hesitation let's dive right in so what exactly is scraping and how does it differ from cutting well if you look at any cutting tool that for instance this couch there's always going to be two surfaces intersecting in the case of the gouge we have the flute and then we have the bevel that we've ground away and that's left us with a sharp edge and that sharp edge severs the fibers with a scraper instead of using that sharp edge to sever the fibers we have a little burr on the edge it's it's almost microscopic sometimes you can angle the tool just right in the light and you can see it but you can always feel that little burr on the edge and instead of using the cutting edge to this every we use that little burr to sever the fibers so why bother picking up a scraper why not just stick with cutting tools the whole time well I'm actually of the opinion that she tried to get as far as you can with cutting tools before going to scrapers because cutting tools they cut much more cleanly much more efficiently they very rarely leave tear out but there are several situations in which cutting tools just won't do the job one thing that scrapers are really good at is that if you've almost got your shape of the profile that you want and you just didn't take off a little bit of material scrapers are very good at being able to make very light very small cuts so they're very good for getting your final shape they're also some woods most woods will respond well to cutting but there are some woods from what I've heard things like dents exotics sometimes don't respond well to cutting they respond much better to scraping so that's another case where you might get a scrape or instead of a cutting tool and finally there's certain situations especially when cutting n grain cutting tools can only be so far because you can't get the cutting tool in the right situation specifically I'm thinking of hollowing endgrain you can as we saw in previous videos you can to some extent you can cut against the grain or you can try to reverse your cut from the center outwards that way you're not going cutting against grain another technique if you know how to do it it's kind of an advanced cut back hollowing but even that only gets you so far at some point when you're doing hollowing you're going to have to pick up a scraper to finish the job now understanding this tension between using a sharp cutting edge of a cutting tool and using the burr of a scraper is essential to being successful with scraping with a cutting tool not always necessary but whenever possible we want to have one of those one of those two surfaces that is forming the cutting edge usually the bevel in contact with the wood and that's going to give us a lot of control and a nice clean cut now with a scraper we actually want to avoid bevel contact altogether because if you notice the direction of the cut on the burr it's completely different if we were trying to do use this as a cutting tool so if I was to press too hard or if I was to drop the handle and that bevel started to become in contact with the wood all of a sudden it doesn't want to be a scraper anymore it wants to be a cutting tool and a cutting tool is in this position is going to have a completely different direction of cut then it will be than it would if it was scraping and that's where a lot of really bad catches with a scraper come so we want to avoid the bevel contact and use just the bird to do the work for us it's the easiest way to ensure that we don't make bevel contact with a scraper is to always make sure that whatever angle is formed by the top surface here and where the wood is contacting the cut the the burr should always be less than 90 degrees so that means we generally want tool to be slightly downhill now without side curves like this we also want to be at or below center line if we get too high even if we're uphill and we get too high we nope we no longer have that 90 degrees so on an outside curve at or below center and the tools slightly downhill now with inside curves it's the opposite so we still want the tool to be slightly downhill but we want to be at or above the centre line that'll guarantee that that angle is always less than 90 and with flat surfaces whether they're inside or outside doesn't matter as long as a tool is slightly downhill you'll have your less than 90 degrees formed by the top of the scraper and the surface of the wood perhaps the second most important thing to understand about scraping as opposed to cutting is that when reclining we very often have the energy that's being absorbed by the cutting edge some of it is actually trying to push a tool down as in leverage and but some of the some of the energy is actually coming down the tool and that energy coming down a tool is never a problem because it just basically pushes us off the cut scraping up that are they on the other hand because we always have the tool slightly downhill there's never any energy going down the tool all the energy being observed by the burr is leveraged straight down so we want to be careful about how much of the burr we engage at once when it comes to scrapers I'd say as a general rule of thumb I try not to engage more than 3/8 of an inch at one time so we do have a lot of burr here to use and we want to use all of that at some point but at any one time maybe three-eighths maybe a most half an inch do you want engaged at a single time because if we engage too much of the burr we're going to have a lot of pressure and the woods going to want to push the tool down probably the third most important thing to understand about scraping is that because we have the two absorbing 100% of the energy as the birds doing its work it's very susceptible to vibration so if you're about an inch over the tool rest a quarter-inch thick scraper shouldn't give you too much trouble but you'll find as you get further and further over the tool rest with a scraper or turn scraper is going to vibrate quite a bit and so for purposes of just refining your work in getting rid of santaro quarter-inch thick scrapers are fine because you've generally have the tool rest pretty close to the work and you can get that job done without any vibration but as you get further and further over the tool rest you really need to go with thicker and thicker scraper 3/8 which you're good four inches over the two arrests without any vibration now that the the downside is that thick scrapers like this can be really expensive but if you have some kind of particular work you're doing over and over again you need to get in deep you might want to consider investing at least one scraper that's really really thick like that now as far as those bits on using a scraper that is always keeping the tool slowly downhill make sure your contact with work is less than 90 and only using a small portion of the burr at a time it's not very controversial pretty much any turner I've talked to or watching the video was pretty much an agreement but when it comes to preparing a scraper that all changes because it's another one of those situations where ask 10 Turner's get 11 answers which is kind of interesting because there's only two parameters to consider there's the bevel angle and there's how do you raise the burr so the first parameter we can talk about when setting up a scraper is the bevel angle I've seen all over the place from 80 degrees all the way to 45 which is close to what this one is and now I want to talk about the bevel angle if the whole point with the scraper is to not rub the bevel not to have unavailable contact and that's precisely the first function is that it keeps the bevel away from the burr so that we can make contact with the burden the burden to his job without any risk of getting a bevel contact now with a flat surface like this it's not going to be that risky you could probably have a seven degree bevel angle here and have no risk of contacting that bevel but as you start to do Halloween especially if you're doing blind hollowing you might not be able to see what you're doing so much and so that extra clearance is a good thing so as long as you don't go too thin this is about this clearance angle is about forty degrees if you go any further than that you start to thin out the material too much and you could get vibration now the second function of the bevel is it affects the shape of the burr at the end of the tool if you have a narrower bevel angle like this the burr tends to come out off the tip more and I found that it slightly leaves a slightly cleaner surface but the bird isn't last is long it's a much more fragile burr as opposed to if you have something more like a 70 degree bevel angle the hook that little bird tends to come up more and it's much better for it doesn't leave is clean the surface but it's much better and for hollowing because the burr will last a lot longer now I've kind of tried both and for a lot of times I find the difference negligible but if you did have trouble if you were having trouble getting a good finish and you were using a 70 degree bevel angle you might want to try something narrower see if that helps get rid of the taro there's a little bit of a of a conflict of interest here because we may want to have a narrow or wide bevel angle because we're doing hollowing but at the same time we might want to have the advantage of having a lot of clearance so we don't accidentally come in contact with the bevel so is there a way that we can get the best of both worlds and what I've been doing lately and the reason I have this bevel all the way out to about 40 degrees that's just for clearance and that's happening to be there happens to be where is my grinder firms are normally set so the purpose of this Bible here in this case is only for clearance and if you look at the side or look at the very edge here you can see I actually have a secondary bevel and that's the one that's actually doing Newark in this case it's probably about 45 degrees so I basically grind at 40 degrees first to remove to remove some of the material here and I look to handle just a hair and I'll regrind it just to get the micro bevel at the edge that's about 45 degrees or I can lift it up even higher and I could get whatever bevel angle I want here if I'm doing Halloween I could have a 7 degree secondary micro bevel near the edge and still have all this clearance right there and also the advantage of that is you can switch back and forth because it's very little material to move to remove to change back to say something like a 45 degree now you'll see some terms will have a pretty strong opinions about which bevel angle is the best for scraper but where the opinions really start to diverge is what's the best way to raise a burr on a scraper but most methods will at least start on the grinder and so my platform is set to 40 degrees and I'll start by just moving a little bit more of that relief and then depending on whether I want a 45 degree of her at a 45 degree angle and might list lift up cool just a little bit off the cool rest and I don't cost too much over precise angle I think more in terms narrower is better for for difficult grain if I'm trying to get a nice finish and a wider angle is better for for calling so if I want to do some hollowing I'll lift the two a little bit more and I'll just take a little bit off the edge and it'll give me my 60 70 or whatever I need I know you can go right to using this burr in fact that's what I do most of the time there are other further preparations you can do and but I find for the most part the amount of time it takes to do those it doesn't really buy you anything in the end because generally with this edge I'm after this I'm going to say 150 180 grit sandpaper and as long as there's no real as long as no tear out this will leave I find a perfectly suitable surface to start standing with now that being said if I'm having trouble if I have some particularly difficult grain and I and I continue to get tear out I'll try any and all other methods to prepare the burr in an attempt to try to get rid of that tear out before I move on to the sanding phase so one additional preparation that some Turner's like to do that will actually refer to it is taking off the burr they'll take something like a diamond home like this one and though rub that though they'll actually remove the burr from the top so it may feel like you've remove the burr from the top but what you've actually done is you've pushed a little burr out off the end of the scraping edge and what this does a lot of times if you're trying to get a really really clean surface and avoid sanding this sometimes work but I find that sometimes it will actually if it's certain really tight grain woods it might actually start to tear out again so you can always give this a try trying to get her fine get a really fine surface but beware you might actually end up having problems as well now it some turns will do after they've taken off the burr like this is it will actually rear A's the burr using the diamond home just by always pushing up and this is actually very similar to using that secondary bevel right off the grinder but instead of making your secondary bevel with the grinder you're simply doing it with a diamond cone and what that will do is it'll give you a very fine non jagged very smooth edge which will work really good on some woods may perhaps dense exotics but I find that sometimes that extra smooth that non jagged edge will actually again start causing santero it's kind of like using a serrated edge when you're using right off the grinder it's kind of like using a serrated knife on a tomato it tends to not rip the tomatoes so much and this tends to be more like a regular chef's knife then I see with the edge it really depends on what you're cutting what kind of results you're going to get out of it now yet another preparation is kind of borrowed from woodworking and card scrapers where very often you'll you'll you'll draw out the bird similar to what we're doing when we take off the bird with the with the a diamond home and then you use some kind of bar a burnishing rod to push up a burr but because we use high speed steel in most wood turning tools your rods going to have to be made out of carbide it has to be harder than immature we're trying to turn the burro I've tried this a little bit and some people like to do this but I find for turning tools it's not really worth the effort of burnishing I don't get that much benefit out of it compared to how much time it takes me to have to stop and and set up a burnishing tool and then one last way to prepare the burr to raise a burr turning tool either in from Jimmy Clues he sets the platform up like this and he grinds the scraper upside down and whether that does it'll produce a very aggressive BRR probably not good for refining work but if you want to do some hollowing and you want a really aggressive burr you can give that a try as well now one thing I found that works that helps regardless of how you decide to raise the burr on a scraper is to polish the top edge now you don't have to top polish everything you only need to polish the very edge and I usually do that with a diamond hone and if you can't get all the way out to the edge very easily I even cheat I raise it up just a hair just to make sure the very edge is polished now you don't have to do this every time you sharpen scraper only when the scraper is new or if you've changed the shape or if you've been using it for a while and it starts to grind back to where there's no more shiny edge anymore just come back with the diamond home and get that shiny edge once again and this improves the surface regardless if I decide to raise the burr and it's even if it only improves a little bit it's so little effort to do that it makes it worth the time so you can see there's quite a few ways that Turner's like to raise the burr on their scrapers and you can probably go out and Google for and find quite a few more now if you're pretty new to scraping don't be overwhelmed by all these different possibilities if you're if you're new to scraping new to turning I would say just try going straight off the grinder the way I make my relief bevel and then lift the handle just a hair to get your secondary bevel to raise the burr and go from there and use that burr for a while see how it goes and if you start to run into trouble with certain kinds of wood certain kinds of work that you do try some of the other preparations and see if those solve the problems for you all right so we know how to use your scraper and have our bird turned up so it's time to make some shavings and let's see how scraping reacts and the various screen orientations and I think I'm gonna start with an green and spindle work so I have my tool lot in a tool rest but not wait this is actually a wide cutting angle going into endgrain can we do that after all the tirades i've made about cutting directly into end grain and how dangerous that can be and how you can get leverage catch why would you take a scraper and do the same thing well it turns out you can scrape with a wide canang go directly into endgrain and here's why now the wood fibers are kind of like this straw and when I'm cutting end grain and spin to work I'm cutting directly across the fibers now with a cutting tool if I could guarantee that I'm on taking off a very small amount of material I might be ok but that's really hard to do with the cutting tool what tends to happen is the cutting tool will go in a little bit deeper and the deeper it goes the more resistance you get it can't get rid of that all of that material and that's where you get your leverage catch now with a scraper because we're cutting with a really tiny burr that Birdsall I'm going to take off so much Imperial I can only cut so deep and because it's only cutting a little bit of material off that waste always remains flexible and it doesn't cause us any trouble and that's why we're able to scrape directly into end grain now that's really good news when it comes to doing end grain and spin the work because even though we have a lot of trips we can try with a cutting tool as we can try cutting against grain we can try cutting from the center out and if you know how to do it you can even do what's called back Halloween but those techniques will only get you so far so if you're doing say a goblet that goes much deeper or a box you're going to have to pick up a scraper at some point to finish the job the other thing that helps when you're scraping and green and smooth work is because all the it's pretty steep a pretty stable operation because the grain is always completely parallel to the to the right bit so we're always cutting the fibers directly across the end grain so it was a little bit of stability and predictability going on there so I like any time we use a scraper we're going to have the tools slightly downhill we simply engage the bird and the wood the other nice thing about scraping is it doesn't matter which direction we go and we can go either way because we're usually because we have a wide cutting angle there's no issue of the fibers being supporting the fiber being cut this o is going to be supported by the one directly above it so this matter which direction we go and when your Halloween you can try to hollow laterally like this or you can use a stress straighter and you can plunge directly in really nice to be able to cut directly into n green with the staple no what about scraping side gradients been to work now whereas cutting and grading spindle work is probably the most useful place to use a scraper cutting saw Granite's been to work is probably the least useful usually you can get pretty results with cutting tools directly and they're also sometimes some problems when you're trying to scrape a side grain and spin door again because the fibers were always exactly parallel to the lathe bed sometimes what can happen is that Burke and underneath the fiber and start tearing them away so very often you won't be able to improve the surface that much the spacing although sometimes if you have some tricky grain scraping in two side grain might be the answer you can see that surface is not as nice as as with cutting tools the other thing is I find usually if I'm trying to improve the surface in longer and it's fun to work a peeling cut with a skew there's a much better job than scraping now there are the sides of beads and stuff not technically that's that's N green just like it was here and so this would respond well to scraping so if you're trying to improve the valleys of your beads and coves you could certainly try to do some scraping there the trick is that you don't want to come in directly you don't want to come directly in this way because you remember you have to keep the surface top surface of the scraper at 90 degrees with the work and if I come in sideways I'm not doing that so I have to find a way to move the tool rest and another unknown another direction so I can come in and make sure I'm having less than 90 degrees and here you sometimes can reprove maybe you can't get that the shape of your Cove just right or your be just right and you can come here with a scraper and you work some extent but you might want a whole lot you can try this but you might want to hold off because when we get to doing negative rake scraping or or shear scraping a lot of times that's a much better option for in here but you can you can use a commission scraper to clean up the end green on your beads and coves now what about side green in face work now you might think just like side grid spend the work it doesn't work very well but it actually works really well inside drain and face work and the reason has to do with the grain orientation unlike spindle and spend at work we're always hitting the fibers exactly parallel that only happens for a brief moment when you're doing side grain and face work most of the time we're sharing across the fiber at an angle and only when we get to that one spot directly when when the green is exactly parallel across the blade bed do we actually go across the fibers exactly parallel that's only for a brief moment so most of the time we spend shearing across the fibers and that leaves a really really nice finish it works on us on the surface like this say this is the bottom of the platter but also the bottom of a bowl is also beside grading so if you have a bowl that's really deep you can't get a gouge to the bottom or you have an inner covering that keeps you from getting the gouge in position or even read the bevel you can use a scraper to finish the bottom the bowl and just like any scraping we can go in any direction even though from outside in or inside house doesn't really matter because we have a wide cutting angle again the fiber is always supported directly by the one just above it and you can see even in this curly maple which is often troublesome when it comes to trying figurative taro it left a really really nice surface you could probably start setting this with two twenty three twenty easily so what about endgrain interface where can we scrape directly into n green and face work well this is kind of a gray area it gets tricky bit again because of the green orientation changing as it spins around when the grain is in this orientation be exactly perpendicular to the cutting edge that's not a problem as I come around and I start slicing the five s or 45 still not a problem and when I get to here when I'm exactly perpendicular it's just like end grain and spending work that's not a problem the problem happens is when I start to come directly in head-on into the fibers and I can start exploring it's quite a bit of resistance there now some Turner's do will scrape directly into end grain and face work if you're going to do it though make sure that you're really close to the two arrested don't get the tool over any further than necessary and make sure you're very light to the touch but I generally don't do that because as we'll see when we get to doing a shear scraping and negative rate scraping those are much better options for scraping directly into in grain and face work there also there's also the issue of in-between here when we're transitioning from face work to end grain I would say as you're getting to about 45 degrees as you come around from from side grain into anger and you can go to about the 45 degree more 45-degree angle because you're still slicing across the fibers somewhat and doesn't end up being too much trouble so basically you can scrape on side grain you come around to your about 45 degrees and you'll be okay but I usually stop right about there well I won't I won't eventually straight any further into Ingrid okay so that's my primer on scraping or as I sometimes call conventional scripting to distinguish it from other kinds of streaming we still I'm hoping to cover very soon to other kinds of scraping one is a negative rake scraping and the other is shear scraping now one last bit of advice regarding scrapers as you look through the catalogues or at the store you'll notice that there's some standard sizes and shapes that they come in and those are usually a good pretty good place to start but as you start getting more into a say a particular kind of work don't hesitate to change the shape your scrapers to fit your needs I have this one scraper for instance where I've scraped both sides so I have a 90-degree corner and then it radius is off just slightly and I use this for getting into the bottom of end grain boxes to get a nice square corner at the bottom as well you can make scrapers out of almost any kind of high speed steel you can get your hands on I buy a lot of bits from the machining industry from and from my website called Enco and off very often fashion my own scrapers like this half inch one that I used to get into undercut rinse so that's what I have for this time so get out in the shop try to do some scraping and see what it can do for you

Channel: Brian Havens

Views: 38,053

Rating: 4.9525423 out of 5

Keywords: Scraping, conventional scraping, bowl scraper, end grain, side grain, spiindle work, face work, shop-made, shop made, round nose scraper, square end scraper

Id: Pq5uUDMFi5M

Length: 30min 37sec (1837 seconds)

Published: Fri Aug 28 2015