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Journeyman
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    Posted: 10 Sep 2019 at 4:37pm
I'm relatively new to turning. but not, I should emphasise to woodworking - I've been contributing to woodworking journals (both tehcnical and project articles) since 2004.
 I've got a Record DML18SH lathe, and have watched Alan Holtham's accompanying video many times. Over a period of a few weeks I've been practising bowl turning - just working through a succession of bowl blanks, turning just th outsides at this stage, to practise the gouge movement, aiming to get a smooth, continuous cut and a good finish straight from the tool. I've made pretty good progress, and the last few bowls i turned had a very nice finish that required very little sanding - beautiful spiral  shavings coming off the blank and a lovely gentle hiss al suggested i was getting something pretty damn right.
As part of this, I've also familiarised myself with my Sorby ProEdge, and have certainly found much benefit from the 'little and often' approach to sharpening.
Today, i did all the same things, but for some reason am having terrible problems that seem like vibration - the gouge starts to vibrate alarmingly as I get about half-way round the cut. A hand on the spinning blank and also on the top of the headstock detects no sign of it - it's only manifest as the gouge cuts through the timber.
I've resharpened the gouge, adjusted the position of the rest, checked all the levers etc are tight - and yet it keeps happening.
The same thing happened a few days ago, and i abandoned the session. When i returned the next day, sharpened the gouge and started again, all was well.
I'm baffled as to what the issue might be.
Any ideas welcome.
Check out my stuff at www.michaelforsterwoodwork.weebly.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dalboy Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2019 at 8:14pm
If a bowl is turned quite thin this can cause the problem you have described as the wood is flexing. If this is the problem it can be difficult to get rid of the undulations. One way to reduce this is when turning is to hold your hand on the outside as a support, not to much pressure as your hand will get quite hot.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Handcrafter Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2019 at 9:00pm
Thanks - that will be good advice to bear in mind when I get to doing the insides - but at present I'm just trying to perfect the technique for the outside, so the 'bowl' is still solid.















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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dalboy Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2019 at 9:17pm
One thing that can also happen is if you lift the heal away from the wood allowing the tip to cut in without rubbing the bevel which cause small ripples so on the next cut the chisel will bounce. The ripples may not even be that pronounced. I have had this happen where I turn a number of bowls and then have one where I am not paying attention to the bevel. With the outside, I normally do a pull cut and then lead into a push cut as this helps me by not having to lean over the bed too far.
Sorry if you have already eliminated this problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ian Thorn Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2019 at 10:15pm
As Dalboy I think you are losing the bevel this can happen part way around the out side of the bowl when shear cutting or the tool rest is not up close or both

Ian
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bodrighy Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2019 at 10:34pm
Oncde this happens you need to reshape the wood or all you will do is bounce of the ridges that you have made. Easiest way is to shear scrape, or if you feel confident do a reverse cut from the centre to the edge. Best thing would be to get alongside an experienced turner and be shown as some things just better felt than telt.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ian Thorn Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2019 at 12:46am
If you are going to shear cut from the centre out do it left handed with the tool handle against your left side feet slightly apart stand where the cut finishes weight on the left foot move your body not feet back to start the cut ,cut with your body moving forward not he arms . tool angle should be about 45 Dge . try see how it works . Relax enjoy it you where doing good then we over think it or try too hard
Ian
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Handcrafter Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2019 at 7:25am
Thanks, for all those helpful replies. I'm still experiencing intermittent difficulties, so shall certainly try those suggestions.
One thing that rang true with me was the comment about the gouge bouncing off the ridges I'd created earlier. That has a definite ring of truth for me because of another experience i've had which is when I take a heavier cut - sometimes doing that enables me to take beautiful shavings and get a great finish, and I surmise that maybe that might confirm the ridges theory in that by cutting deeper I'm actually going in underneath the ridges rather than across the top of them.
I know from my wider woodworking experience that tools and timber, just like people, prefer a manager who is 'firm but fair'! It's finding the narrow line between assertiveness and aggression!
I did wonder whether there was a vibration problem on the lathe itself, but since in my better times I've actually got a remarkably good finish, even on the end grain areas, that seems less likely to me to be the cause.
Thanks again, folks - I'd actually got myself quite depressed yesterday and wondering whether to persevere any further. You've lifted my spirits and I think I might keep at it a little longer. :)

Cheers all - once again, I really appreciate all the help.
Michael

Check out my stuff at www.michaelforsterwoodwork.weebly.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dalboy Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2019 at 10:13am
Don't give in as you have already found it is all down to practice. Even after a number of years turning I find that I occasionally do what you have done, but just stop and then have a cuppa and start afresh.
The more you do the less this may happen and when it does a simple fix is all it takes to get back on track.
Good luck with your turning and just have fun
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Handcrafter Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2019 at 11:32am
Thanks, Dalboy,
I don't think I'm ever likely to give it up in despair - I enjoy furniture making too much to do that - it just feels like a losing battle at times, but then at other times it goes swimmingly. 
There seem to be so many things that can go wrong, but I remind myself that there are thousands of woodturners out there enjoying the hobby or even making a living from it, so it can't be that close to impossible.
Yesterday I had been trying to turn a 10" platter from oak and it hadn't been a pleasant experience - maybe stick to smaller diameters and softer timbers for a while! Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gregmcateer Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2019 at 5:29pm
I've lost count of the number of attempts I've had at avoiding the dreaded bouncing bowl syndrome - So don't despair and definitely persevere.

I would definitely join a club, (or at least visit and see how you feel about joining) and consider investing in a lesson or two with a pro teacher - e.g. Richard Findley in Leicester - not a million miles from you. He's VERY patient, encouraging and an extremely good and accurate turner - You'll come away feeling much more capable.
I hope you like my son's caricature of me! If you want one of you - PM me.
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