Skew sharpening

[woodpig]

Some years ago I bought a couple of Skew chisels. Due to a house move etc I've never got round to using them but as I'm hoping to be able to get a Lathe set up soon I decided to check out some of my tools. The 1/2" one has a standard grind and the 3/4" one came radiused. I decided to resharpen the 3/4" one as it seemed a little rough. I sharpen most of my tools on a modified belt and disc sander and the shallowest angle I can set on it is about 18°. It was soon clear that the radiused Skew was sharpened at a much steeper angle, probably around 20° or perhaps a little more. The 1/2" version was a perfect match for my grinding setup at 18°. So, is 18° good enough or should I try to go as low as the 15° as often reccomended? I may have to make a new jig if required. Your thoughts gentlemen. If my Lathe was set up I'd just try them out but I'm not in a position to yet.

 

[Random Orbital Bob]

How topical!!! A master turner from my club was round only yesterday and we had this same debate.

We ground a large skew he was returning to another club member at 20 degrees. That gives an included angle of 40 degrees and we then went ahead and tried it versus my normal grind of 15 degrees.

The bottom line is the 15 degree is clearly a "sharper" edge as the taper is narrower. It will therefore give a better finish on planing cuts. However the edge won't last as long because it's "weaker" than the 20 degree bevel. Equally, you'll notice a greater difference in hard versus softwoods and the general advice is for skew work in hard woods go 20 and for softwoods go 15. Since that's a quite a considerable pain in the wotsit, many turners just split the difference and grind in the middle at a theoretical 17.5 but your 18 is clearly just fine.

As a result of this dialogue I'm switching my grinds because I experimented and found it really lasted longer (the edge) at the blunter angle.

 

[woodpig]

Thanks Bob, pretty much what I've found. This piece is quite good.

http://www.almather.com/skewdemo.pdf

I don't intend to turn softwoods so as you say my 18° tool rest should be fine.

 

[marcros]

any comment on the angle for plastics, bob? I would have thought towards the hardwood side?

 

[Random Orbital Bob]

Now you're just being difficult Mark

I honestly have no idea. Thinking it through....the challenge with turning plastics is heat isn't it ie they melt if you're not careful. That would lead me to think the sharper the tool the better and be damned with the longevity of the edge since melting substrate trumps anything else. So I'm inclined to hedge towards 15 degrees but I've never actually turned plastic except for two acrylic pens some time ago.

I guess if the plastic was seriously hard and very heat resistant then you'd go the other way and treat it like an exotic?? For those pens I used my regular skew at 15 degrees if that helps. Nothing melted in that case and I had the lathe going pretty fast (circa 2k).

Polishing was a bit different too...wet n dry actually dipped in water and up to 12,000 grit. It did give a very nice finish but I chickened out of using ca glue as the hard finish.

 

[Random Orbital Bob]

Thanks Bob, pretty much what I've found. This piece is quite good.

http://www.almather.com/skewdemo.pdf

I don't intend to turn softwoods so as you say my 18° tool rest should be fine.

I enjoyed reading that...thanks. Did you check the YT of the potato turning...excellent

 

[woodpig]

No, I didn't spot that Bob. Good wasn't it!

Here's the direct link for anyone who wants a look.

http://youtu.be/0XMBbYM11I8

 

[Richard Findley]

I did an article on the skew a while back so had to measure the angle I use. Mine has 25 degree faces, so inclusive of 50 degrees. Works fine, but then my preference is for a beading and parting tool, so it works harder than a standard skew, so needs to be a bit tougher.

Richard

 

[marcros]

I was playing about last night, and I would agree that the 20 degree bevel lasted much better. So much so that I tool the time to swap over a second, small skew to this angle too.

One other thing that I tried, and I think it was from one of your posts on the Sorby forum bob, was to sharpen the skew right through the grits, and right through the trizact grits until it was a mirror finish. Then use it and touch it up very often on the finest grit belt. The theory being that if it is too blunt to allow this, it needed sharpening sooner. I found that for me it worked very well, and only took a few seconds to touch it up after every few passes on a pen blank. The finish was noticably better than I had achieved before.

 

[Random Orbital Bob]

great. The old adage applies...little and often.

I have a credit card diamond file in my smock pocket and if I just cant be arxxx to down tools, walk over and boot up the PE I'll just gently stroke both sides of the edge with that and it brings it back to do a final planing cut or another finishing cut. But if I get it wrong, if I'm tired or the lights poor etc, it can just fold the edge over and then its useless so there's a bit of a lottery involved.

 

[Random Orbital Bob]

But Richard, your input is interesting as a pro. The master turner I referenced before (Yewtube from this very parish) and I, are both closet fans of Mr Raffan and he, like you seems to keep a fairly blunt angle on his skews. I've found that whole discussion really useful as it just never bubbled up the attention of my world before now. I will try a 25 just to see how it feels for me because the skew is my favourite tool for rolling beads. I suspect you're rather better at it than I

On that issue I'm going to be cheeky and ask if you've any tips on how to avoid the problem of what I call the "goofy" direction of bead rolling. When I roll my beads right to left I'm fluid, feel comfortable, I go quick, the bead is a fair curve and all is well with the world. When I do the other side and go left to right, I feel "goofy" uncomfortable, more like it's going to catch, stiffer, just the opposite of the more natural side. Consequently my beads have a tendency to be out of balance and then require adjustment using a scraping cut which is of course a complete no-no.

I'm right handed by the way. Is there something obvious I'm missing or is there something visual on YT you could point to that helps with this cack handedness. I do get my stance at the finishing position before I start, its more to do with failing to lift my arm whilst moving the upper body I think. Very frustrating.

 

[Richard Findley]

Hi Bob

It's quite natural that one direction feels easier and more natural than the other. Only practice will make it feel more natural. That said there are a few things that you might be able to adjust to make it easier.

I haven't seen you turn so this is purely based on common issues ive seen.

Firstly, stance is important. Very easy to get in your own way, so make sure you are stood to the side, not directly behind the bead, and that your tool stays fairly well into your side. Your whole body should be used to make the shapes, not just hands and wrists.

Another common issue is the ability to roll your wrist. Make sure your starting grip will allow you to make the full roll of the tool. A tiny adjustment here can make a world of difference!

HTH

Richard

 

[Random Orbital Bob]

Thanks Richard, good advice

 

[CHJ]

great. The old adage applies...little and often.

+1 for that philosophy.

I have a credit card diamond file in my smock pocket ..... I'll just gently stroke both sides of the edge with that and it brings it back to do a final planing cut or another finishing cut. But if I get it wrong, if I'm tired or the lights poor etc, it can just fold the edge over and then its useless so there's a bit of a lottery involved.

I too have a set of cards for this but prefer a cheap diamond coated steel plate to avoid the risk of rounding the bevel edge, when using skew I have it sat on the top of my grinding station and it's easy to give the skew a few strokes across it, the flat on the skew being more than enough to provide a good register.


As a matter of interest after seeing this thread I checked my 'go to skews' for angle today when in the shed, 25 deg. or there about, no specific reason other than that I remember some time ago deliberately increasing the angle to a chubbier look as I was not getting on with the slim line profile I had.

 

[Dalboy]

+1 for credit card on the skew just lay it flat and rub the skew over as above little and often very rarely does it get to a grinder.
Not sure about the angle on mine must check not that I will be changing any as they work just great for me. "If it ain't broke why fix it"