shoptask turnado lathe to acorn

[brittfussel]

October 25, 2019

Kevin

It would be easier for me to explain with pictures (or maybe be a video). If you can wait I can do this Monday when I'm back in the shop. I'm currently enjoying the excellent weather on the Central Coast of California and I do not have my machining tools with me. I'm not going to rule out that you may have a mechanical problem but I would want to rule out that your x-axis glass scale is not the culprit. I'm pretty confident that my glass scales are not accurate in the z-axis (lathe) direction.

I bought my gage block set just for this purpose.

Curiosity question, are you coming up long or short? If short, could you be losing steps in the stepper motor? Are you able to return to zero repeatably?


Britt

[KevinTaylor]

Hey britt,
I found this pdf of using guage blocks. Is this what you are talking about?

What I dont understand is if my z axis worked using a dti and the machines supplied DRO, why would that same method not work for my x axis?

And aslo if I set my revs per inch for my x axis and my DTI says it moved 1 inch after a 1 inch command, why would it be out 24 thou at x9.5?

I just dont get it.

[martyscncgarage]

First remember its a lathe, lathe software starts in diameter mode. So if you call x-1.0 the X will actually move .5" (half the 1" diameter)

I looked at your report file.
Axis Label Motor Encoder Lash Comp. Limit Home Dir Screw
revs/in counts/rev. (inches) - + - + Rev Comp
1 Z 5.0932 2000 0.0000 0 0 1 0 N Y
2 X 10.1852 2000 0.0000 0 0 1 0 Y Y

You doubled your X revs/in. What is the Threads per inch of the ballscrew? Is the motor direct driving the ballscrew or do you have a 2:1 reduction on the pulleys between the Screw and the axis motor?

[brittfussel]

October 25, 2019

Kevin

The pictures on page 9 is what I'm talking about. In absence of having gage blocks you could use your 1-2-3 blocks.

The approach you used should work for both axis. That is, unless one of your glass scales is giving you a defective reading on your DRO.

If you can use a third approach to making the measurement you should be able to identify where the problem is.


Britt

[brittfussel]

October 25, 2019

Marty

There is a two to one reduction on the z-axis on these machines. The numbers he has for turns per inch is consistent with my machine (I have the same machine only it's a mill turn or a three in one machine).


Britt

[martyscncgarage]

His Z shows 5 turns per inch, while his X shows 10 turns per inch.
Just asking for clarification because I can't see that in his pictures.


Marty

[KevinTaylor]

First remember its a lathe, lathe software starts in diameter mode. So if you call x-1.0 the X will actually move .5" (half the 1" diameter)

I looked at your report file.
Axis Label Motor Encoder Lash Comp. Limit Home Dir Screw
revs/in counts/rev. (inches) - + - + Rev Comp
1 Z 5.0932 2000 0.0000 0 0 1 0 N Y
2 X 10.1852 2000 0.0000 0 0 1 0 Y Y

You doubled your X revs/in. What is the Threads per inch of the ballscrew? Is the motor direct driving the ballscrew or do you have a 2:1 reduction on the pulleys between the Screw and the axis motor?

It is direct drive, motor to ball screw on the x axis. The z axis is a pulley, I think thats why my x is double. The ball screw according to shopmaster is and I quote "The ball screws are metric, but very close to a 5 pitch."

October 25, 2019

Kevin

The pictures on page 9 is what I'm talking about. In absence of having gage blocks you could use your 1-2-3 blocks.

The approach you used should work for both axis. That is, unless one of your glass scales is giving you a defective reading on your DRO.

If you can use a third approach to making the measurement you should be able to identify where the problem is.


Britt

So in that pdf, the DTI is setup in a mill spindle. How is this done with a lathe? I'll pretty much try any method at this point.

[brittfussel]

October 25, 2019

Kevin

You'll need something to hold the DTI such as a Noga Dial Gauge Holder or something similar. You would attach it to the casting or pull back the way protector and attach it to the ways. Or pull the jaws out of the chuck and attach it to the chuck making sure the lathe spindle doesn't rotate on you messing up your measurement. In my case I can use the mill spindle as shown in the picture. I have found that with the filler and paint used to smooth the casting, the magnet does not stick very well. I ended up attaching steel flat bars to the casting for the magnet to adhere to.


Britt

[KevinTaylor]

October 25, 2019

Kevin

It would be easier for me to explain with pictures (or maybe be a video). If you can wait I can do this Monday when I'm back in the shop. I'm currently enjoying the excellent weather on the Central Coast of California and I do not have my machining tools with me. I'm not going to rule out that you may have a mechanical problem but I would want to rule out that your x-axis glass scale is not the culprit. I'm pretty confident that my glass scales are not accurate in the z-axis (lathe) direction.

I bought my gage block set just for this purpose.

Curiosity question, are you coming up long or short? If short, could you be losing steps in the stepper motor? Are you able to return to zero repeatably?


Britt

I have no problems waiting at all.

I am coming up long as in at x9.5 im +24 thou, but I can repeat back to zero...or so says my DRO. but every time i do a g0 x0, it goes back to zero or maybe 2 tenths+/-. Maybe my DRO scale is off/bad in the x axis. Its just wired that at x1 its 1" on my DTI and DRO and each inch after that just keeps increasing by a couple thou until I hit the limit of my x+ axis and its 24thou more. Im not sure. I'll wait for you to post some pics when you can. As I have no idea what to do next.

[brittfussel]

October 25, 2019

Kevin

Will do on Monday when I'm back in the shop.

Did you look at Marty's post above? Your report is suggesting that you have your x and z-axis swapped?


Britt