Homemade lathe tool holders

Made this QCTP three lathes ago. Just made some more holders a couple of weeks back.

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Greg

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ScrapMetal said:
Would you mind explaining why that would be?

Thanks,

-Ron
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I'm not sure I can give an explanation,but I have read a lot of claims that it is a better method for light duty lathes. I have used it on two different lathes, a 10 inch Atlas and light weight Grizzly and it works for me. One benefit is because the tool is upside down, the chips fall away.
I did a little searching and this explanation sounds reasonable too. Its from Practical Machinist forum.

"why a rear parting tool works better than a front tool you haven't included the real reason. Probably all of the reasons you give have some relevance, but the most significant is that the cutting forces on a front toolpost, whether or not a topslide is used, rock the toolpost down and towards the job, pushing the tool into the work - if the tool grabs, it dives into the job. The tool held in the rear toolpost is being lifted out of the job by the cutting forces.
The front toolpost gives positive feedback, the rear toolpost gives negative feedback."
 
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Mac1 said:
I'm not sure I can give an explanation,but I have read a lot of claims that it is a better method for light duty lathes. I have used it on two different lathes, a 10 inch Atlas and light weight Grizzly and it works for me. One benefit is because the tool is upside down, the chips fall away.
Click to expand...


And depending how large your cross slide is you can leave it on for the whole job, or just always there, and just move forward to cut off the part leaving your front setup same. Especially handy running several of the same part.
 
Mac1 said:
I'm not sure I can give an explanation,but I have read a lot of claims that it is a better method for light duty lathes. I have used it on two different lathes, a 10 inch Atlas and light weight Grizzly and it works for me. One benefit is because the tool is upside down, the chips fall away.
I did a little searching and this explanation sounds reasonable too. Its from Practical Machinist forum.

"why a rear parting tool works better than a front tool you haven't included the real reason. Probably all of the reasons you give have some relevance, but the most significant is that the cutting forces on a front toolpost, whether or not a topslide is used, rock the toolpost down and towards the job, pushing the tool into the work - if the tool grabs, it dives into the job. The tool held in the rear toolpost is being lifted out of the job by the cutting forces.
The front toolpost gives positive feedback, the rear toolpost gives negative feedback."
Click to expand...



Thanks for your explaination Mac1.
:thinking:
I could have an upside-down tool at the front if I wanted and have the cutting forces push instead of pull the toolpost. Just run the spindle in reverse.
A tool at the rear can be right-side up too thereby tending to dive into the work. That renders the reason from Practical Machinist invalid too.
The best reason I can think of for a parting (cut-off) tool at the back is to have it in addition to other tools if you need it often.

- - - Updated - - -

Marco Bernardini said:
An Italian lathe made in the '70, the Ceriotti, had a cut off vertical slide as extra optional.
You can see it here: http://www.lathes.co.uk/ceriotti/
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That really is something Marco. No dials! all levers. Must have been quite a producer in its day. The English even bought some! Colchester Shmolchester. :lmao:
 
I think back in the day when this started, it wasn't desirable to run the spindle in reverse, since a lot of chucks were screw on. All of the rear mounted cutoff setups I have read about had the tool inverted.
 
the old Brown and Sharpe screw machines often had their parting blades in this arrangement. It worked well.
Kevin
 
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