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Parting off -- what went wrong here?


Posts: 15
Topic starter
(@rongiordano)
Active Member
Joined: 2 years ago

I was trying to part-off a section from a 5" diameter piece of wood using a diamond-shaped parting tool.  The wood was in spindle-turning orientation. Everything was going fine until I got about 75% through the piece.  At that point, the wood grabbed the parting tool and pulled it (and my hand) forcibly into the side of the wood. You can see in the picture where the ferrule of the parting tool dug into the wood and took a chunk out of it.  I made some initial widening cuts to help prevent the tool from binding but apparently that was not enough. So..... how are you supposed to safely part-off a piece of wood like this? 

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7 Replies
(@chriscohen)
Joined: 2 years ago

Active Member
Posts: 17

@rongiordano for what it’s worth, when I am parting off something like that I stop about 3/4 through and finish with a saw. (Lathe off of course. Had that happen to me once and it scared me.

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(@rongiordano)
Joined: 2 years ago

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Posts: 15

@chriscohen Thanks Chris. I will definitely be more alert next time and use a saw.

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Posts: 53
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(@jldawadm)
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Joined: 2 years ago

Ron,

    There are others who would know much better than I, but the first thing I noticed is that there is a lot of the tool overhanging the tool rest. With that much tool overhanging the tool rest it's very easy to lose the proper angle on the tip of the tool and cause a catch.

It is also possible to have the tool lose it's parallel position to the sides of the slot. A small degree change or a slight twist of the shaft would cause a catch on the side of the tool which can be exacerbated by the smaller piece 'flexing' or wobbling as it loses contact around the edges. Even though it's supported by the tailstock, the tailstock applies pressure to the center, not the edges and really does more to help it stay in the chuck. If I had to guess, it looks like this is what happened. When I have a piece like this with a deep parting cut, I just grab a saw when I'm getting close. Whatever works is my motto.  

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(@rongiordano)
Joined: 2 years ago

Active Member
Posts: 15

@jldawadm Thanks, Jim for your comments.  My parting tool is 16" long and, as the cut progressed, I definitely was fighting to keep the tool level to counteract the downward force on the tool tip. Adjusting the tool rest up or down did not help much.   I did have the tool rest close to the wood, but pulled it back for picture taking.  The wood is very dry and the tip became quite hot during cutting.  I was hoping for a nice smooth peeling cut, like you see Carl Jacobson and others doing, but my experience was anything but smooth.  Although my hand got some pretty bad lacerations, none were deep enough for stiches thank goodness.  In the future, I'll just take the wood off the lathe (with chuck attached) and cut it on the bandsaw with my round-stock cutting jig.

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(@kevinbassett)
Joined: 2 years ago

Trusted Member
Posts: 60

@rongiordano can you show the tool.

when parting with a parting tool you can ant to cut on the tangent. If your boring in on the mid line the piece can drag the tool under the spindle. Best to finish off the last 1/2- 1/4” as suggested above. If it’s a diamond pointy carbide probably the same but I don’t use that kind of a tool for spindle turning.

KB

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(@rongiordano)
Joined: 2 years ago

Active Member
Posts: 15

@kevinbassett Here is the tool I used.  I think, as I got further into the piece, the wood on either side of the cut began to wobble and eventually both sides clamped down on the parting tool.  I was going to include a photo of my hand after the accident, but it was rather gross. View a Larger Image of Cryogenic 3/16

 

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(@kevinbassett)
Joined: 2 years ago

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Posts: 60