Standard modern lathe misalignment

[aaronpadilla]

Hi there,

This is my SM 2000 series up and running with a noisy headstock right now.
I am doing a cut test and the result is bad.
It is leveled as good as possible with an ordinary level, I don't have any better now.
I got a taper of 4 mils in 5 inch.
The headstock is bolted dead-on on v ways, non adjustment is possible

Can I expect it to be better if I use a precision level? (I doubt)
If misalignment persists how can I workaround it?

 

[sdelivery]

Think of it from a side view...if the tool moves above or below the center line it will change the amount of material removed.
I would say a level job with a better level will help, when leveling a lathe the most important leveling direction is parallel to the cross slide.
Start at the headstock and dont be afraid to go back and re level it will settle some.

 

[Jim F]

Second picture, that has no bearing on the precision of the lathe.
You could have it at a 45 deg slope or standing on the head stock, as long as there is no twist, it will cut straight.

For reference.

South Bend 14

https://www.ebay.com/itm/South-Bend-Model-Fourteen-Vertical-Lathe-Optical-Lens-Alignment-Machine/313033743532?hash=item48e243dcac:g:DjIAAOSwLrletKYO

www.hobby-machinist.com

 

[DAT510]

From the first picture, what the shim material you are using under the tool bit?

 

[pdentrem]

Are you checking for twist at the two ends? Check under the spindle and at the far end, on the other side of the tailstock. It doesn’t matter if the lathe is level, it just has to have the same reading at both positions. Also don’t be surprised that the readings will be different a month from now. If there was some twist, it sometimes takes of time for the casting to react to the changes you make.
Pierre

 

[aaronpadilla]

From the first picture, what the shim material you are using under the tool bit?

Aluminium blocks

 

[aaronpadilla]

Are you checking for twist at the two ends? Check under the spindle and at the far end, on the other side of the tailstock. It doesn’t matter if the lathe is level, it just has to have the same reading at both positions. Also don’t be surprised that the readings will be different a month from now. If there was some twist, it sometimes takes of time for the casting to react to the changes you make.
Pierre

I will do

 

[DAT510]

Going just from the pictures you provided..... and not knowing the direction of you taper

1) I can't tell what type of insert your using, but from the picture it appears at least the holder has a fair amount of negative rake. Negative rake cutting requires a greater amount of pressure at the cutter face to cut, which could increase the deflection of your test bar.

2) If your test bar was cut without support from a live center and tailstock this could further increase deflection of the bar when cutting especially if item 1 is true.

3) I've never used AL for shimming cutter bits........ which makes me wonder if you could be getting some compression/deflection of your shims also?

In other words... Your taper may not just be an issue of lathe leveling.

Hope this helps.

 

[aaronpadilla]

Going just from the pictures you provided..... and not knowing the direction of you taper

1) I can't tell what type of insert your using, but from the picture it appears at least the holder has a fair amount of negative rake. Negative rake cutting requires a greater amount of pressure at the cutter face to cut, which could increase the deflection of your test bar.

2) If your test bar was cut without support from a live center and tailstock this could further increase deflection of the bar when cutting especially if item 1 is true.

3) I've never used AL for shimming cutter bits........ which makes me wonder if you could be getting some compression/deflection of your shims also?

In other words... Your taper may not just be an issue of lathe leveling.

Hope this helps.

Interesting, thank you
Right now I am upgrading to wedge toolpost, I will publish the outcome later

 

[Howard E.]

I've always used Rollie's dad's method-

http://www.neme-s.org/Rollie's_Dad's_Method.pdf

"Level" is not really a requirement- it's '"twist" and "droop" that are the enemies. Lot's of lathes have been installed on ship decks that were very seldom near level for any extended amount of time.