Understanding Woodturning Catches

right well that was a really fine example of a bad catch that kind of catch scares the daylights out of people when they first try the skew but you're actually pretty safe the woods held between centers it's not going to jump anywhere you're pretty safe whereas if you have a catch with a bowl guards they're much more dangerous you get hurt with those so I'm going to clean this up a little bit and then we'll come and have a look and see why that happened now this is the right way to use ask you first the bevel goes on the wood and you rotate the tool until the dust comes over the edge then you move the tool forwards and then I can roll a tool over and go in the other direction and notice here as the cut proceeds the bevel stays in contact with the wood if you raise the bevel then you'll end up with a cleanly cut surface which is rigid as I raise the bevel you'll hear the tool begin to chatter if you see cleanly cut ridges on a piece of wood that's always a sign that you haven't had the bevel rubbing either with a gouge or a skew chisel and also use the tool long point down the advantages are that any pressure you put in the cut are going directly towards the headstock and you've got much less pressure against the axis bevel on the word first roll the tool pivot it slightly until the dust comes over the edge that's a pretty good finish off the tool so that's all going along very nicely but let's have a look at why tools actually catch the simplest form of the catch is when you put the tool on the wood before the rest it's a quick bang and it usually messes up the wood so let's have a look at why the skew catches when you're using the skew you should be using the leading half of the edge and when you're doing that the wood is coming down on the far side of the fulcrum from where you're holding the handle that's represented by the line here so the fulcrum is where the tool sitting on the rest and there you have control of the leverage if you let the point of the cut come your side of the fulcrum then this space in underneath here and the pressure of the wood is on the unsupported part of the tool so just get that shaving out of the way that means the points going to dig in and the wood will just drag the tool down to the rest so if we look at that with the lathe running in slow motion we'll see it happening sometime when I'm cutting there I let the point of the cut come to this side shuttering around and then you can see that with the point coming in it's going to start jumping back speed goes up and I'll get rid of the original catch we look at the catch I had initially we can see how the same principle applies when you're cutting a bead that happened before I meant to the genuine article folks and generally when I do this I prefer to have an underhand grip when I'm cutting a bead so I have two options for cutting a bead one is to use the corner the tool comes along the rest as its rolled onto its side and so I'm using just the short corner of the tool and the only portion of the tool in contact with the wood is the lower bevel here if I let the bid I've just cut which I'll mark with a pencil up here if I let that area get on to the edge there then they're going to want to catch back every time yup so that was even better or worse if you liked on the last one and you should have seen the cameraman jump back so after that little gem we'll have a look at why you have catches when you're cutting v-grooves so what you're aiming to do here is to cut with the point of the tool and just have the bevel side in contact with a bit of wood you just cut over to the side of the groove now catch coming up as I come down here if I let the wood get onto the edge another real goody now just show you that from the other side over right so that's another gem and it's a matching set kind of ram's horn now the reason that caught is because I should have been using the Longpoint only if the wood gets onto the edge which it did somewhere in there then the edge is unsupported the space in underneath here and that's why it kicks and runs back so what we've got here is a little bit of a spindle with about every nasty catch you can you can have with a skewed chisel and we're still safe it's still between centers so as I said earlier on they're really not that dangerous they just mess up the wood when you're making a bowl there are lots of opportunities to have good catches with a gouge so first we'll look at the catch catching opportunities when you come around the corner when you first start to shape the outside and then we'll see how that applies on the inside a bit later when you start with the deep fluted gouge have it right on its side to start with and then you're going to roll it up into the cut as you swing it in to the edge if you bring it in flute up like this at first off there's space underneath the point of contact in there and you're likely to have a catch when you get better at it a little bit more experience then you can probably bring the tool in at this angle but to start with be on its side and then roll it up into the more dangerous position that's taking the outside off to really just two or three cuts now let's look at some finishing cuts so the aim here is to keep the bevel side rubbing against the wood is you've got to be very careful not to roll the tool too far over because if you start cutting up on the top edge there's space underneath the point of contact and the tool will catch guaranteed every time okay and now let's look at exactly the same cuts but with the spindle gouge again coming up the side I'm going to use this wing of the tool tool starts right on its side this is the half-inch spindle gouge drop the handle to get a better caving that's a typical roughing cut now if you get a smoothing cut move the rest of it lower have the tool pointing in the direction I want to go raise the handle to pivot the edge into the wood and off I go now you see here with a shallow gouge I'm using the nose of the tool to get the shaving if I bring the flute so it's upright in the same vision I had it on the deep fluted gouge I've got a guaranteed catch every time because the wood is done on an unsupported edge these aren't catches I like to show they're far too dangerous so having seen the outside cuts on the profile when I go and look at what happens on the base this is still a shallow garg's the spindle gouge and if you want a guaranteed catch just bring it in flute up if you do that the wood will come down on the unsupported edge and it will fall over every time and if you're doing that kind of thing you're probably hanging on white knuckled so the catch will be even worse what you have to do is to start the tool on its side get yourself a smooth surface on the rim roll the tool over and then take the shear cut back in the center hands on the wrist to squeeze the tool in gently get the bevel riding raise the handle pivot the edge into the wood then move forward we'll just show you how the shaving comes off the tool so it's coming off just above the nose of the tool now let's look at the deep fluted bowl gouge the deep fluted bowl gags this is the half inch deep fluted bowl gouge I'm going to use the left wing with a tool roll right over on its side so the flutes facing towards the the wood and just use that wing to trim up the edge then I can roll the tool over get the bevel writing now I've got two options here one is to use the top of the tool rather as I did with the shallow gouge or I can have a back cut which is using the higher wing here with the flute upright and I can do that I could do that because the inside the flute on the side here of the guard is steep so you really need to appreciate the difference between the two gouges when you look at them and on the shallow guards the spindle gouge doesn't have the steep bevel that the bowl gouge does right now we've got a another bit of wood and we'll have a look at catching a scraper this is a big bowl scraper and I'm going to be going across the bottom of the bowl so if you don't keep the tool flat on the rest you're going to have a catch and see too much of that there but it certainly did a bank the important thing with a scraper is the angle between the surface you're cutting here and the top of the tool is a negative angle which means it's less than 90 degrees if you tilt the tool up so this angle is more than 90 degrees that means the tool digs in there it's going to want to go through an arc through the wood and then what happens is of course you kicks back there's a current fad for negative reg scrapers this is a skew chisel which is an effect a kind of long beveled negative rake scraper but that means if you keep the skew flat then the bevel the little bevel on the top is going to make for a negative angle in there less than 90 degrees but you can still have a bad catch with a skew or with a negative rake scraper if you tilt it up steep enough negative rake scrapers are not a panacea you can still catch the tool with them

Channel: FineWoodworking

Views: 1,392,679

Keywords: raffan, free, catches, youtube, Lathe, woodtuning, turning, tiv632, Fine Woodworking, Understanding Woodturning Catches, Woodturning Catches, woodturning

Id: jOvF5f1phhY

Length: 12min 10sec (730 seconds)

Published: Thu Feb 27 2014

Reddit Comments

[u/jaybill]

Well, good to see I've made every single one of these mistakes at this point.

This is a great video, and I highly recommend his book, Turning Wood. I probably don't need to do that, though, because you already have it.

[u/givemehellll]

Great video, nice to see how the wood actually catches

[u/Uglulyx]

Thanks for the link. Helpful and informative, I think I now understand the trick to a skew.

[u/canamspike]

Fabulous video. I'm fairly new to turning so I don't know if it will go away with experience, but every catch made me flinch and wince