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A question for the actual machinists here about tool pressure.

SKWERLZ

On a front and rear spider setup like this with eight 1/4” brass contact points how much tool pressure would you run as far as depth of cut?

Is it fairly secure or dancing or walking on thin ice?

Thanks.


1745855370680.jpeg
 
Machine power and depth of cut are factors. I use a similar setup in a Precision Matthews belt driven lathe and run .010. When you're accustomed to running machines that can take a heavy cut with high feeds, these hobby machines are exercises in patience. A heavier production machine, the tenon diameter on a barrel is two cuts.

Didn't initially catch the threading op instead of a straight turning cut. Straight in, agree with Mr. Schmidt, not a lot of pressure with that tool..
 
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I would think from your picture, the tool pressure will be negligible with that threading tool.

Of course, this is predicated on your insuring that the screws in your spiders are tightened sufficiently as you reach the final indicator readings.

Only you can determine that.
 
ChristianSilver said:
What alloy are we dealing with.
Size of lathe / rigidity
Tooling
Inserts
Precision of your machine
Click to expand...
It’s standard SS or steel barrel material
Hardinge HLV-H
Almost of my tooling is neutral or positive rake and small nose radius except the threading inserts and those never see more than .010 cut at about 800 RPM.

Most I’m asking about how aggressive I can turn down the tenon before threading.
My normal insert for that task is a 42.51 dcmt.
 
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A more specific scenario
My average barrel requires me to cut the shank .190 to get tenon diameter ready for threading.
I’m wondering if the spiders will be ok splitting that .190 in three equal cuts of .063.
 
I find .020 - .030 DoC @ .004-.006 IPR at 600 rpm works fine on my G400G in a twin spider setup. I could probably take more but I don’t want to risk moving the setup and the above has been pretty bulletproof
 
On my Hardinge, I use a spider on the back and a Buck chuck on the front. From a 1.250 I turn to around 1.150, reset the digital and go to 1.060 on the next pass. It is rigid and accurate enough that it is rarely off by .001. Turning at 800 rpm.
 
Walt Krafft said:
On my Hardinge, I use a spider on the back and a Buck chuck on the front. From a 1.250 I turn to around 1.150, reset the digital and go to 1.060 on the next pass. It is rigid and accurate enough that it is rarely off by .001. Turning at 800 rpm.
Click to expand...
That’s definitely more than I trust my front spider to take, eventually I’ll get a proper Chuck for it.
 
SKWERLZ said:
On a front and rear spider setup like this with eight 1/4” brass contact points how much tool pressure would you run as far as depth of cut?

Is it fairly secure or dancing or walking on thin ice?

Thanks.


View attachment 1655673
Click to expand...
I don't ever go more than .010" if I am in a hurry for some reason, maybe on barrel contouring or something.
Usually I go .005" per cut.
Just saves on everything, tool life, bearing pressure, deflection, surface finish etc.
I cannot....................have down time on my lathe for any reason, so I figure safer is better than sorry.
------------------------------
One time I was hogging some material, maybe turning a 2" shaft down to 1.25" or something
so didn't care about any deflection or surface finish until I got close to final dimensions.
All the hogging of material in large cuts likely compromised the shear pin right before I started threading.
and the brass shear pin broke on the Lead Screw while I was threading. Messed up a lot of work
So never again.
------------------------------
.005" depth of cut per pass for me ....Saves on everything but time
But when i work on a gun i make sure I am never in a hurry and have hours to spare or go home and come back again fresh tomorrow.
The few hours amount of work on a gun is years of use. A good trade.
When we get in a hurry is when S--- hits the fan and mistakes are made, thread depth not correct etc.
----------------
I WILL however take large cuts on plastic and brass, but still within reason, maybe .020 on brass and .050 on plastic
 
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You can use a black marker and make 2 marks on the barrel.
One around the diameter of the barrel where the chuck and barrel meet. That will tell you if you’re pushing the barrel into the chuck. The second mark draw a straight line on the barrel and the chuck, that meet. That line will tell you if the barrel is spinning in the chuck.

Hal
 
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