Metalwork - Lathe and Mill topics

Monday, 19 February 2024

Re: [SouthBendLathe] Set Up my 16" - Test Cut

Brilliant! I'd planned to do the two collar test and the 12" long cut test, but I'm going to add this one to the list, probably at the beginning. Still have to mount my chuck, making the back plate this week.

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Sunday, 18 February 2024

Re: [SouthBendLathe] Set Up my 16" - Test Cut

To be clear once I used the 2 1/2 inch bar and skimmed the final coat, over 9 inches I got measurement error. So roughly within 0.00005". That is crazy good for a machine like this.
--
1969 16" x 6' South Bend Lathe
Garage full of old Mopars........

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Re: [SouthBendLathe] Set Up my 16" - Test Cut

Tailstock ram must also be level. You'll find a lot of tailstock bases worn on the front end from heavy handed operators shoving them around. You might have to shim

it level and then you should shim it so the center is .0005"- .001" high.

If you're only out 2/10's of a thou along the length of that bar....that's as good as that machine is going to be. It's not a Hardinge.

Bill

On Sunday, February 18, 2024 at 07:28:24 AM EST, Chips <sakr4360@sbcglobal.net> wrote:

Assuming the twist is out of the bed here's an easy one to set the tailstock.

Say the diameter of the quill in the tailstock is 1.4985 inches.
Turn a short piece of metal in the chuck to that dimension.
Put the tailstock at the far end and lock it down.
Set up a dial indicator in a tool post and zero it on the piece you turned to 1.4985.
Run the carriage down and put the indicator on the tailstock quill. It should read zero.
Now you just tweak the tailstock alignment screws until it reads 0.
You don't need an x feet long bar to work with, just a 1 inch stub of scrapbinium.

Re: [SouthBendLathe] Set Up my 16" - Test Cut

.0002" taper sounds pretty good on a 55 year old machine.

What are you trying to test because your setup has at least 5 variables?

On 2/16/2024 11:00 PM, Mark Z via groups.io wrote:

Having problems with zeroes! Worst is 0.0002" per inch. Missed a zero there too! Its late............. LOL!
--
1969 16" x 6' South Bend Lathe
Garage full of old Mopars........

Re: [SouthBendLathe] Set Up my 16" - Test Cut

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Saturday, 17 February 2024

Re: [SouthBendLathe] Set Up my 16" - Test Cut

THANKS!! that was the Best I've seem!! Figures!! It'd take a meticulous girl

to show us how to get it done!! lol

On Saturday, February 17, 2024 at 10:59:32 AM CST, Rogan Creswick <creswick@gmail.com> wrote:

For aligning a lathe, I use the process Blondihacks describes:

https://youtu.be/H0MwCyWeP7I?si=xxxzUihtQkf_h402

On Sat, Feb 17, 2024, 8:24 AM Mark Z via groups.io <bode528=yahoo.com@groups.io> wrote:

For sure deflection is a problem in the middle so I discarded the numbers that I felt would have been affected. But the number I stated included everything but the actual middle.

In retrospect if I was totally serious about this I would cut a 2 1/2" diameter 18" long piece of aluminum and use it to minimize deflection. Might actually do that at some point. I started the testing by only cutting a 1" wide cut at the ends. Once I was happy with that I did a full cut to get a better profile and eliminate tool position error from the DRO.

What do others do?
--
1969 16" x 6' South Bend Lathe
Garage full of old Mopars........

Re: [SouthBendLathe] Set Up my 16" - Test Cut

Thank you Rogan! That was very helpful in making me understand that I had a brain cramp. I should of know better. My tailstock center alignment was way off and really skewed my numbers.

I redid it with a 12" long 2 1/2" diameter aluminum bar without a center. I did it just at the ends (9 inch measurement difference) and got it to measurement error. I then skimmed the whole 9 inches and did a final cut taking 0.002" off the diameter. Measured every inch over the 9 inches and every measurement was within measurement error (50 millionths of an inch or half a tenth). I am shocked that its is that good.

--
1969 16" x 6' South Bend Lathe
Garage full of old Mopars........

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