sliding toolrest

discussion of the niceties of turning on a bow, bungee or pole lathe.

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sliding toolrest

Postby roosstoi » Sun Jun 10, 2012 9:24 pm

maybe I am making a big mistake in using my skew chissel but I had to solve a problem and either my solution can help or you can tell me what I did wrong in the beginning.

problem:
When I fix the chissel with my hand to the toolrest and bring the tip of the chissel towards the wood it works well, but at the very moment I try to cut an ankle to the left or to the right
the chissel bites into the wood and the tool together with the toolrest is sliding to the left or right and is "destroying" the object by cutting a deep spiralshaped trace.

my solution:
I cut a new toolrest, drilled holes into the bottomline and glued 10mm pegs into the holes at a distance of 10 cm.
Foto 1.JPG
toolrest with fixed pegs
Foto 1.JPG (109.41 KiB) Viewed 7472 times


Now I first slide the toolrest to the stop at the left or right and if the chissel now bites into the wood, my grip to the fixed toolrest also keeps the chissel in place and no more "cursing" at the end of a turning piece.
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Re: sliding toolrest

Postby Bob_Fleet » Sun Jun 10, 2012 10:45 pm

If you put a peg through the toolrest into one of the poppets that fixes it in any position you need to use it for.
It also stops it falling off so often.
Here's mine
pic-4.jpg
pic-4.jpg (20.36 KiB) Viewed 7459 times

The peg at the other end is slightly lower so it can rest on it and remain level.
Hope this makes sense.
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Re: sliding toolrest

Postby roosstoi » Mon Jun 11, 2012 3:01 pm

the solution with your big peg would not work with my toolrest, which i built according to Mike Abbotts plan and has got a very thin edge of ca. 2 mm. Although, I admit, that prohibiting the downfall is an added benefit and worth to make another, a broader, toolrest which would solve another upset.
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Re: sliding toolrest

Postby gavin » Mon Jun 11, 2012 4:07 pm

roosstoi wrote:problem:
When I fix the chissel with my hand to the toolrest and bring the tip of the chissel towards the wood it works well, but at the very moment I try to cut an ankle to the left or to the right
the chissel bites into the wood and the tool together with the toolrest is sliding to the left or right and is "destroying" the object by cutting a deep spiralshaped trace.

For avoidance of doubt, please show picture of your 'skew chisel' .

If you always make sure only the bottom third of the cutting-edge is in contact with the spinning work, you should get no dig in.
Also be sure to work 'downhill' (auf deutsch: nach unten) from thicker diameter to thinner diameter. I gather you wish to make grooves? If so, take a tiny cut on (say) the right side, then a slightly deeper one on the left side, and gradually alternate sides to make a progressively deeper groove. The bump in the middle of 2 grooves is called a 'bead' .

You must also fix the tool rest to one poppet head. A pin or dowel as Bob Fleet suggests will work well. You report the top edge of your tool rest is circa 2 mm - well you can still put a pin through that tool rest. It does not have to leave the tool rest through the 2 mm surface!
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Re: sliding toolrest

Postby roosstoi » Tue Jun 12, 2012 3:30 pm

For avoidance of doubt, please show picture of your 'skew chisel'

I upload a picture of the tool I am talking about from another thread, Donald Todd had originally uploaded
SD531554_1.jpg
SD531554_1.jpg (194.01 KiB) Viewed 7388 times


with the 2 mm edge I ment that the whole toolrest is very slim and ends up in a small edge.
Drilling a hole for a big peg "could" break it if I hit the peg too hard - what I do sometimes with pegs or other sticks pushed down in holes, this has happened as resently as last weeks when I wanted to fix a drilled handle onto an iron for bowl turning. ;-)
I think I cut a more massive toolrest than I can follow Bobs advice AND I hope that my skills with the chissel hopefully could improve over the years
Last edited by roosstoi on Wed Jun 13, 2012 6:40 am, edited 1 time in total.
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Re: sliding toolrest

Postby gavin » Tue Jun 12, 2012 3:57 pm

Thanks for pic.
Try a broader skew chisel - they come up to 50 mm wide.This one would be a tough one to learn with.
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Re: sliding toolrest

Postby jrccaim » Fri Jun 15, 2012 5:08 am

If understand you correctly, the width of the chisel is 2mm(?). Gavin is right as usual. This is far too small for anything except miniature work. And even for that, it is very small. My skew is 12mm wide. This is quite convenient for most of my purposes. A skew chisel is a bit difficult to master. If you do not hold the edge exactly parallel to the work (assumed to be a cylinder - you did rough the work out to a cylinder I assume? :) ) you risk digging in. It is the longer point that digs in. Sometimes you want this. Mostly you don't. When I cut grooves (say to decorate a tool handle) I use the skew chisel at 90 deg to the tool rest, on edge. Just like a parting tool. What I did as a learning exercise was to rough out a cylinder with a broad gouge. This gives you an irregular scalloped cylinder. Then I undertook to make a perfect (within reason) cylinder with the skew. Ruined quite a few pieces. I recommend such exercises for every learner.
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Re: sliding toolrest

Postby trollwumple » Fri Jun 15, 2012 7:51 pm

I think what Roosstoi is saying is, that the top of his tool rest is 2mm wide, "see above" and not the skew chisel, however, without anything to give us a sense of scale it would be a bit difficult to guess what the width of the chisel actually is. I reckon its about 12/15mm

will
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Re: sliding toolrest

Postby roosstoi » Fri Jun 15, 2012 9:24 pm

trollwumple you're right its the width of the toolrests top edge.
But because the bottom width is also very narrow (less them 3 cm) I would not
dare to use one big peg, it could easily split my toolrest.
But also many thanks to Alaska, jrccaim, for your hints
I will try to exercise your advices
btw my skew chissel should be about 15 to 18 mm.
Last edited by roosstoi on Sun Jun 17, 2012 11:39 am, edited 1 time in total.
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Re: sliding toolrest

Postby jrccaim » Sun Jun 17, 2012 5:06 am

Lieber Herr rosstoi, you are not wrong at all. Thing is, consider a skew chisel. It has a "long point" and a "short point" as you look at it from above. If you held the thing perpendicular to the rest, the long point would touch first, of course. If you pushed in some more, still holding 90 deg to the tool rest, the long point would dig in. Your foot is just not powerful enough to overcome this. So you must hold the chisel at some angle to the tool rest. Suppose you held it so that the edge were perfectly parallel to the thing you are turning. assumed to be a cylinder. Then you would reduce the diameter of the cylinder over the contact of the chisel. Very well. It would not affect any other part of the turning. So now you want a taper. It will be very obvious if you do it on a pole lathe, but if you vary your (parallel) angle you have two choices. (a) you can make the long point cut first or (b) you can make the short point cut first. If you do (a) you will get dig-in. (b) is much better. This is what Gavin meant by saying"cut downhill" or Bergab in German. Flip the chisel if necessary, so that you always cut Bergab, not Bergauf.The short point goes towards the smaller diameter.
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Re: sliding toolrest

Postby roosstoi » Sun Jun 17, 2012 11:49 am

Danke jrccaim,
I´ll do my very best

As you have obiously connections to Germany, maybe you know were this quote comes from ;-)
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Re: sliding toolrest

Postby jrccaim » Mon Jun 18, 2012 4:10 am

Well, in my youth I studied German very, very hard, in spite of being an engineer:). Rather rusty now, though. Anyway, what I wanted to add to my last post is that it is indeed possible to cut uphill. Bergab. There is a wonderful video on YouTube, of someone (I do think it's Bodger's own Hugh) cutting gypsy flowers on a treadle lathe. His alias is "Buckingham Boy" on the video. He uses the tool exactly opposite from the way I recommend. But he is far more skilled than I am! We build skills gradually. We must not be afraid to make mistakes. I always think I learn more from mistakes than from successes. Until you do master the skew, I would recommend Bergauf, simply because it minimizes small errors in holding the chisel. Aller Anfang ist schwer, I seem to remember from German 1. All beginnings are hard. So do not be discouraged. Soon you will be showing us all how to do it.
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