Metalwork - Lathe and Mill topics: February 2024

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

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........

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

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........

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Friday, 16 February 2024

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

I'm not a lathe expert or a real machinist, but I'd guess your deviation is in the middle of the cut & likely

from the shaft/work piece flexing. (can't read your measurements on my pc) the guys in the know here

will probably recommend a follow rest.

On Friday, February 16, 2024 at 10:00:55 PM CST, Mark Z via groups.io <bode528=yahoo.com@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

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........

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

Ooops. Over 17" max deviation is 0.0013" Missed a zero.........
--
1969 16" x 6' South Bend Lathe
Garage full of old Mopars........

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[SouthBendLathe] Set Up my 16" - Test Cut

I rebuilt my 1969 16" x 6' lathe some years ago with help from Ted! Thank you Ted! I bought it from work around 1990 - they had bought it new in 1969. But it was not in great shape. Ted provided many new parts and even quite a bit of labor. I had set it up in the old shop and it cut pretty good.

Built a new shop a little over 2 years ago and finally got around to taking a test cut. Started about 0.001" per inch. The worst part is around the chuck area (no surprise) but worst is around 0.002" per inch. But over 17 inches, maximum deviation is 0.013" . From 0 to 17" its 0.0011". I don't know what is typical, but this will work just fine for most of my needs.

What do you typically see from these lathes when in nice shape?

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

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Friday, 2 February 2024

Re: [Amateur-repairs] Creating a LSB and USB Test Signal!!

Hello, wow already February and so much to do in retirement! J

I wanted to share something with the group that I found interesting. As I prepare to dig back into my Collins 51S-1 radio, I mentioned that I would start the process over and test all the tubes again. Previously tested on a B&K 747 checker… Since then I have added to my tube checker collection and decided to use my Heathkit TT-1 tester, so I went and validated the calibration again.. Tested a 6V6 and 5Y4 as they were just sitting on the side of my bench and easy to get to. They both checked good!

Then the fun began when I grabbed a 6C4 tube. Being a 7 pin tube it went into a different socket than the 6V6 or 5Y4 tube.

The tube began to act very erratic, On-Off, low then high, testing it for shorts showed no shorts.. At first I suspected a bad tube socket but further inspection showed no issues??? The tube was marked on the box as good with a GM reading of 2150..

So I dug up 4 other 7 pin tubes like a 6BA6, and several others… All checked fine with no problems. Put the 6C4 back in same erratic problem.. My brain began to go in many different directions!!!

So out came my Hickok 6000A, Jackson 658 and Weston 978 Military version it was time to try that 6C4 and see what I get…

6000A said the tube was Good??? But the meter did move a little, like a ¼ of an inch on the needle..

Then I tried the Jackson, and same results, tube was good but again a very small amount of needle movement, like 1/16 of and inch…

!!!!!! Then a big surprise happened, tried it in the Weston 978, same version as the 981 series.. and wow, the tube was acting erratic like it did on the Heathkit TT-1,,, What is going on here??????

So after some coffee and a bit of a rest, we do that at age 76, LOL,, we began to look at some literature in my "How To Use, Calibrate, Repair And Upgrade Tube Testers by Igor S. Popovich" A nice Birthday present and surprise from my son last November…

Their it was in clear print, The Heathkit has a built in 5KHz Oscillators to place signal on the Grid, and the Weston has a 1 KHz oscillator to also place a signal on the tube Grid under test.. Apparently the 6C4 was not happy with this test signal… A good reason why having different tube checkers can help out a lot, or at least one of the Top Testers available…

So I will definitely be using the Heathkit TT-1 with the Weston 978 standing buy when I go back and re-check the tubes in the Collins radio, wonder what I might discover???? I will report back with a follow up, still a few weeks out as I have several other projects now on the bench, like I said Busy in retirement, J

If you have had similar experiences please do share it with the group… Like one of you said early on the only real test for a tube is when it is working in the circuit it was designed for.

Robert WA6PHN,,

What do they sing,, "It Never Rains In Southern California", Sure!!!! L

From: Amateur-repairs@groups.io [mailto:Amateur-repairs@groups.io] On Behalf Of Robert Lonn WA6PHN
Sent: Sunday, January 21, 2024 2:32 PM
To: Amateur-repairs@groups.io
Subject: Re: [Amateur-repairs] Creating a LSB and USB Test Signal!!

I will keep this all in mind for sure 👍!!

On Jan 21, 2024, at 1:31 PM, Don Root VA3DRL <drootofallevil@teksavvy.com> wrote:

Robert , that method likely wont to much. I was mainly suggesting that many applications of tubes are not at one bias voltage. Variable Mu tubes are often have the bias controlled by the AVC. For the tube to do its job, it has to work as intended over a wide range of bias voltages/ gains.
Your testers likely test that the tube can provide lots of transcconductance[Gm] [gain, sort-of]. however when the bias is say minus 20 V, they don't bother to do another test the Gm ,, But they do/ can test for gas. It the tube is gassy it mucks-up the tube operation so it cant operate at small gain/ plate current so the tube can't throttle-back to low amplification.
I think I just saw that a 6SK7 has a normal Gm of 5000, but should throttle -back to only 10, [micro-Mhos] I think.
reading back; many 1930's gas tests were not very sensitive, but likely your testers have a good separate gas test using a marked "gas"switch. I wonder if you have tried that on the tube in question?

On Sat, Jan 20, 2024 at 07:56 AM, Robert Lonn WA6PHN wrote:
Not sure about that till I get further into this.. Sometimes I will turn the Bias up and down just to watch how the meter responds.. Not very scientific..
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73 don va3drl