Parting tool chatter

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holmes_ca

........Edmund...Alberta
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I notice no member has mentioned the old spring parting holder design, I built one scaled down for my Taig lathe and you can't have a lathe much smaller than that it holds a 3/8 x 0.040 blade, it has improved my success immensely, sometimes new is not always better,

Edmund.........Alberta
 

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jack620

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Interesting Albert. My Hercus lathe (basically a metric South Bend clone) came with an Armstrong spring holder. I never liked it so I gave it away. I wonder if the improvement you saw is due to the spring design or the thinner blade?
 

goldstar31

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Interesting Albert. My Hercus lathe (basically a metric South Bend clone) came with an Armstrong spring holder. I never liked it so I gave it away. I wonder if the improvement you saw is due to the spring design or the thinner blade?
I scrapped pr lost mine. So long go, I've almost forgotten. My GHT mentioned here gives no complaints
 

SmithDoor

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The spring type holder die. If they where great everyone would spring type.

You find it how you sharpen the blade make cut. Just look at any saw blade it has a high rake angle.
Just type all the wonder cutters on aluminum cast 10 minutes old. They all failed with big glob of aluminum on end of carbide cutter. But band saw would it this new aluminum casting in seconds.

Dave

Interesting Albert. My Hercus lathe (basically a metric South Bend clone) came with an Armstrong spring holder. I never liked it so I gave it away. I wonder if the improvement you saw is due to the spring design or the thinner blade?
 

awake

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I have just been through this thread & cannot see anyone mentioning making 2 cuts.
I have had a very elasticated Warco 240 MV from new. (My Drummond M seemed more rigid.) One can watch the cutter dipping visually millimetres, not thous. I cannot run a low revs because the variable speed motor will constantly stop. That happens even for simple turning operations. That can make parting off an "interesting" activity to say the least.

If the metal removed can help cause a cutter to jam- & I believe it can- then making a second cut to increase space for the chips to clear makes sense, does it not?
I have found that I do better if I cut to a depth where I feel things getting tight when hand feeding (that is really a mixture of, nerves, feel, revs dropping & tool dipping) I withdraw the cutter, move over a cutter width, go in again but deeper. I can usually do this fairly fast & confidently, because the chips are clearing quickly. Then go back to the first cut again cutting deeper. Alternating, until finished, or giving up & resorting to the hacksaw.
Seems to work for me- most of the time that is :eek:
Yes, I often use this technique when parting deep depths.
 

tornitore45

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Edmund, we discussed the virtual hinge point being below the center. The tool holder you show move the hinge point above center changing the situation from positive feedback to negative.
 

tech610

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Try to push the crosslide in while advancing it into the cut and maintain the pressure while you are parting. You will not find this info readily available online, but because of backlash in the crosslide the tool moves in and out, digs in and out. Keeping the pressure on will not let cutting tool move back and forth.
 

SmithDoor

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You know they use cutoff tools for over 150 years with lots of slop
On most screw machines it is rake to feed the cutoff blade.

Dave
Try to push the crosslide in while advancing it into the cut and maintain the pressure while you are parting. You will not find this info readily available online, but because of backlash in the crosslide the tool moves in and out, digs in and out. Keeping the pressure on will not let cutting tool move back and forth.
 

holmes_ca

........Edmund...Alberta
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Interesting Albert. My Hercus lathe (basically a metric South Bend clone) came with an Armstrong spring holder. I never liked it so I gave it away. I wonder if the improvement you saw is due to the spring design or the thinner blade?


Jack, I'm pretty sure it is the spring tool holder,
The spring type holder die. If they where great everyone would spring type.

You find it how you sharpen the blade make cut. Just look at any saw blade it has a high rake angle.
Just type all the wonder cutters on aluminum cast 10 minutes old. They all failed with big glob of aluminum on end of carbide cutter. But band saw would it this new aluminum casting in seconds.

Dave
Jack610 you are right on, that is exactly what it does, keep the pressure on and the tool moves away relieving the cut

Edmund........Alberta
 

johwen

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Hi johwen from under.
Being a hobby machinest for quite along time and like everybody had trouble parting mild steel I came across the T section blade see here...Works fantastic use the blade upside down and the lathe in reverse you can even use power feed... Details here
"T" Type Parting Off Blades




The premium quality blades we stock are sourced from the largest manufacturer of repetition lathe tooling in the USA.


The blades have a slight hollow grind along the top (bottom) cutting edge which assists in curling the chip for easier ejection from the cut.


The industry standard height for 1/2" "T" type parting blades is actually close to 12mm.
Please be aware that some of the cheaper "T" type blades from China and India are 12.7mm (1/2") high and will not fit the FoR inverted parting tool holder.

Here is the website for the manufacture of the blade holder and blades
Hope this helps an happy parting
John
 

OrangeAlpine

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Ah yes, the old tyme springy parting tool holder. The device of nightmares. I learned much of what I know about machining "back in the day", using such devices mounted in lantern tool holders on clapped out WWII equipment.

No, thank you.

Bill
 

johwen

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John,
Eccentric Engineering don't make those blades. They are made by Somma Tools in the USA. See post #78.
And yes, they are fantastic blades.
They make the blade holders only the blade come from the US and are well worth the extra cost and better than a wrecked job which can often happen with a chattering blade or too thick a blade. John
 

scottyp

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Parting off always been a bit of an adventure on my mini lathe, sometimes easy, sometimes not so easy. I tend to run slower and lower (just a bit below center) with a T style tool, and maybe some lubrication. I like the idea of running in reverse, I think it would compensate for some slop in the cross slide and I may give it a shot, but I am going to first going to grind some rake into my cutters.

The more of this thread that I read, the more convinced I am that the shape (and sharpness) of the cutting edge is the most important ingredient.
 
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