Experiment: Fix tool rest with wedges and chain-loops?

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Experiment: Fix tool rest with wedges and chain-loops?

Postby gavin » Fri Mar 14, 2008 9:46 pm

I am interested to hear how others get on with an idea that has been working pretty well for the last month.

I find I get really good adjustment for tool-rest positioning :) by using chain-loops and wedges. The tool rest is locked absolutely solid when you drive the wedges home.

In these images, the tool-rest happens to cross under the turning axis, rather than just at an angle to it . That allows me to get really close to the work for a smoother surface. :D I have only just tried tool-rest crossing the axis , and I find the hook sometimes digs viciously :oops: , but I will persevere.

Anyway the point of this post is not where the tool rest lies in relation to the axis, but how you fix it.


Image
Left-hand view of lathe - I did not need to use a chain-loop to fix the left-hand wedge, but I could have done.
Image
My poppet heads have 200 mm long 'needles' of M20 threaded bar, with tips turned to 60 degrees on a metal-worker's lathe and 'T' pieces welded to them. (Having two of these needles in a poppet head give you variable height, but so far I have not used the upper one.)
Image
Close up of wedge - unfortunately wedge is white, like the wall behind.
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Fix tool rest with wedges and chain-loops?

Postby Robin Fawcett » Sat Mar 15, 2008 7:48 am

Looks very interesting Gavin . . I'm all for some R&D.

I turn bowls on a normal pole lathe but with a T shaped tool rest which clamps to the bed. Not long ago I realised that if I cut off one of the arms of the T I could fix it at right angles to the bed and get that "really smooth finish" just using a bowl gouge. Haven't got round to it yet though!

I've spent quite a while poring over your photos but can't work out what the wedges are wedging into or the significance of the chain loop?
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Postby Terry in Ottawa » Sat Mar 15, 2008 1:22 pm

It looks like the wedges sit on top of the horizontal bed members so the wedging action is between the bottom of the tool rest and the top of the bed. It is difficult to see in the pictures because, as Gavin mentioned, they're painted white the same as the background wall.

Can't see how the chain is tightened though.

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Postby simon » Sat Mar 15, 2008 3:15 pm

Looks good to me. The right way to do something is the way it works for you. Using what you have got, is another good principle, rather than saying "If only I had ......."
Keep on experimenting

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more pics to follow when I work out how to put in a url!

Postby gavin » Mon Mar 17, 2008 9:00 am

Sorry for the confusion above!

I took some more pictures to show this wedging . But before I put them up here I want to mark each one with my website's url, so you can see the image behind and through the url.

How do I do that? What is it called?

Apparently this is not called "watermarking", so I have yet to find it in any help menu on my editing programs. :(
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Postby Robin Fawcett » Mon Mar 17, 2008 10:40 am

Over to you......Hugh
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Postby robin wood » Mon Mar 17, 2008 12:48 pm

When I started bowlturning 15 years ago I worried a lot about having a fixed tool rest close to the work. I think it is a natural carry over from spindle turning. Now I rarely even bother to fix the left hand end of my rest and the whole thing is actually easy to slide in and out. Lailey also did not fix the end of his rest something that confused me so I had to work out my own method of fixing. Japanese bowlturners have a completely free rest that they lift and position just where they want it. The thing is as your technique improves you find that the only force on the rest is directly downwards so it no longer needs fixing...saving time. I am sure a solid rest helps beginners feel more confident though...one less thing to worry about.
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Tool-rest fixing

Postby gavin » Mon Mar 17, 2008 1:39 pm

Lailey's right-hand poppet head and tool-rest fixing:
Image

Both Robin's and Lailey's lathes fix the right-hand end of the tool rest to a pin on the top of the right-hand poppet-head. The left-hand tool-rest end also slides along an under tool-rest rail or beam, which is at right-angles to the lathe bed. Robin points out that downward push for the experienced turner is enough to keep the left-hand in place. He is right, and I would add that that having a softwood under tool-rest helps to give more friction between it and the tool-rest.

With Robin's and George Lailey's layout, the toolrest is at a constant height to the lathe's turning axis.

My wedge and chain-loop idea is for those situations when you want to vary the height of the tool-rest, just as powered lathe turners constantly do for optimum performance.

I have found that a hook which does not cut sweetly with the tool-rest at one height will completely change into a very happy smooth-cutting hook just by moving the rest up or down an inch or two relative to the turning axis.

So if you are just starting out and only have a few hooks available and don't know how each one will perform on a variety of bowl diameters, you may wish to experiment with differing tool-rest heights.

When you have Lailey's or Robin's experience of turning and of hook making, then you are just not going to need to worry.

When I have put up my other pictures to explain the idea better and a few other folk have tried the idea, we'll know if my idea is worth persevering with.
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