Re: Turning Troubles

Thomas G Brandl

Basically neither is good. I would say tool below center line is the lesser
of two evils. The tool above would cause more problems of the tool digging
in. The aligning with the dead center should be correct tool height.
Smaller diameter work pieces are more critical of tool hieght, but 1/2
diameter isn't too finicky. I don't know if it was mentioned before, but
check tool over hang. I think you are using a rocker type tool holder. Keep
the length of the holder as short as posible. ie closer as possible from
the cutting tip to the tool post. The rocker post is a bit more flexable or
less ridgid than other toolholders, still it is a good idea to keep this in
mind with other setups. With a rocker type, you are rotating the rocker up
or down to achieve center hiegth. This affects the tool clearance angles.
If to great, you need to shim up the tool holder to keep the tool
angle/geometry correct.
As too 1/2 stock, what type of steel is being cut? Check the spindle
play or clearance in the headstock. It is adjustable. Check this in the
tailstock. I don't know if you are turning between centers or with a chuck
and center. Not any real difference though. Are you using a diamond tipped
(CBN) insert or some brand called 'Diamond'?
Another thing to look at is the tool nose radius and depth of cut.
Different materials are better or worst for finish. You depth of cut should
be over twice the tool nose radius. This keep even load on the tool. Just
some thoughts. Hard to give good advice without seeing whats going on.

jem1043 <> on 06/24/2003 08:20:25 AM

Please respond to

Subject: [southbendlathe] Re: Turning Troubles

--- In, "jem1043" <millermohr@w...>
I am not very experienced at machining and I have a problem with
turning a outside diameter with my South Bend 9" lathe.
I have turned the gibs so tight that it is not easy to turn the
but I still get gouges in a cylinder that I am trying to get to a
specific diameter.
Also, if I power feed towards the headstock and then power feed
the tail stock the cutter removes material in both directions?
I generally use the rocker tool mount and I have used cutting tools
that are HSS, the "tangential tool" and carbide tipped tools. The
tangential cutting tool seems to give me the best control and
I have tried moving the cross slide towards the back of the lathe
then towards me to remove as much "play" as possible and that seems
be the best. But what a pain to find a place to get the tool closer
the turning center line and then move it back to the setting I need
Maybe this lathe is just worn out. I don't use it much but I would
like to be able to use it when I need it.
Any suggestions would be greatly appreciated.

Thanks for all the comments.
I was turning a .5 inch diameter steel rod that was about 5 inches
long. One end was in a 3 jaw chuck with the other by a "dead center"
in the tail stock.
The tool might have been at the wrong height, but it was aligned
by eye with the "dead center" which had been aligned with a center in
the head stock. One of the tools I was using was a brand new
carbide with a 7 degree clearance angle. Another was the "diamond
tool", which gave better results.
Which case would cause the tool bit to "dig in" more. The tool above
center or below?

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