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  1. #1
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    Default Using a scraper upside down while running in reverse

    Hi all,

    when turning the outsode of a silky oak bowl I was having the usual end-grain problem. I also noticed that the side grain was very smooth when running my hand one way (ie: how the chisel cut it) but was pretty rough the other way. I am fortunate enough to have a lathe that has reverse on it and I often sand by alternating between forward and reverse so I thought......

    why not run in reverse and turn the scraper upside down? I also lowered my back hand so the scraper was pointing upwards (maybe twenty degrees). I was a bit tentative but it did seem to work. I was using a square end scraper on just a small section. Due to the bowl size I could only get around 400rpm before the machine started shaking.

    As a related question am I better off trying to do the finish off the tool at a lower speed with zero shake or a bit faster with minimal shake?

    Are there safety (and other) issue I have missed? Does anyone else do this (perhaps no one else needs to ) but currently I seem to need all the help I can get with the finish off the tool.

    thanks

    Mick

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  3. #2
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    Default

    Wow cool technique! I hone all my tools gouges and for tear out just before final cut rehone for a light skim and sometimes I hone my scraper to make a smaller burr which works for me. I also don't have reverse on my lathe

  4. #3
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    You can't swing your banjo & toolrest around to the other side of the ways and stand at the back of the lathe to use the tool in the normal fashion?

    It'd be safer, in case of a catch or a knot working loose...
    I may be weird, but I'm saving up to become eccentric.

    - Andy Mc

  5. #4
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    Mobyturns is offline In An Instant Your Life Can Change Forever
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    Default

    The scraper in that orientation is more like a "negative rake scraper".

    I'm puzzled why you would want to try this in reverse? Yes there are safety issues but you don't give sufficient information to form a real opinion one way or the other on how safe it is with your method. Are you standing on the normal or front side of the lathe? Holding the scraper down to the tool rest? or performing this task from the rear or the back of the lathe?

    My interpretation is that you are standing in the normal front position and turning in reverse. If you are then you must be forcing the tool down against the tool rest to counter the rotation forces - tiring & not what I would call safe.

    Be very cautious when performing any sanding operations in reverse on a lathe as you can unwind the chuck off the spindle. Most chucks these days offer a securing grub screw to lock the insert onto the spindle, however the insert can unwind from the chuck body. Turning in reverse increases loads and hence the opportunity to unwind the thread.

    A keen edge on your bowl gouge should give a good edge for shear scraping with a normal curved scraper.

  6. #5
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    Quote Originally Posted by Mobyturns View Post
    The scraper in that orientation is more like a "negative rake scraper".

    I'm puzzled why you would want to try this in reverse? Yes there are safety issues but you don't give sufficient information to form a real opinion one way or the other on how safe it is with your method. Are you standing on the normal or front side of the lathe? Holding the scraper down to the tool rest? or performing this task from the rear or the back of the lathe?

    My interpretation is that you are standing in the normal front position and turning in reverse. If you are then you must be forcing the tool down against the tool rest to counter the rotation forces - tiring & not what I would call safe.

    Be very cautious when performing any sanding operations in reverse on a lathe as you can unwind the chuck off the spindle. Most chucks these days offer a securing grub screw to lock the insert onto the spindle, however the insert can unwind from the chuck body. Turning in reverse increases loads and hence the opportunity to unwind the thread.

    A keen edge on your bowl gouge should give a good edge for shear scraping with a normal curved scraper.
    To answer the above:

    - I am still standing in the normal position at the front of the lathe
    - My chucks have grub screws. I admit I had not thought of the inserts unwinding and am glad for this information and will keep my eye on this. As I expect to be only taking finishing / light cuts I am happy with this risk. For the piece I am currently doing it has a faceplate but that could unwind.
    - I did reverse the angle I was using the scraper, so instead of angling it down to the wood, I am angling it up. If I have got this wrong, perhaps I am losing the plot!
    I don't understand why this would not be the same as normal scraping. As best as I can work out I am doing the same thing just with the wood spinning the other way.

    Also, (to answer skews question) it would be difficult for me to do it (I am talking about using my scraper ) from the rear of the lathe.

    thanks

    Mick

  7. #6
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    Mick,

    If the grain direction is as you say, I'd forget the scraper and use a bowl gouge in sheer-scraping mode. You'll get a much better finish than using a scraper in reverse. If you're not sure about the cut, do a search. I also think Brendan Stemp demoed it on one of his You Tube videos.

  8. #7
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    Quote Originally Posted by jefferson View Post
    Mick,

    If the grain direction is as you say, I'd forget the scraper and use a bowl gouge in sheer-scraping mode. You'll get a much better finish than using a scraper in reverse. If you're not sure about the cut, do a search. I also think Brendan Stemp demoed it on one of his You Tube videos.
    Jeff,
    thanks for the above. I gave it a go (after sharpening my tools) and the shavings came off nicely but the finish was still not very good. I think the main problem (apart from me that is) is that it is a heavy bowl and I was trying to finish the outside before hollowing but the lathe still has a bit of a shake so I can't get a nice clean smooth cut. I'll go down the path of hollowing and then finishing the outside later.
    thanks
    Mick

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