• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Need a sanity check from the machinists here.

A little insight into what I am doing and why.
I've had a DRO PRO digital readout for my lathe on the shelf for a while and finally decided to get it installed. X axis scale and reader went on the cross slide like a piece of cake. Z axis scale and reader were a whole 'nother story. My lathe is set with it's back to a wall in my garage. This portion of the install was about to cripple me as bending over the bed to mount and level the scale on the back of the bed as well as fabbing the reader mount on the back side of the apron was just adding agony to the situation so out comes the sections of black pipe and I roll the lathe out into the middle of my single car garage so I can actually work on the back from the back. I finish mounting the scale and reader and now it's time to put the lathe back where it was. After rolling it back into place I start to level the bed after which I will tweak it so the center axis of the spindle is parallel to and level to the bed ways.
Back to the leveling of the lathe, this is where my sanity comes into question.
I'm using an Starrett 8" machinist level which I bought new many years ago, it has never been dropped or abused in any way. I decide to check it so I place it on my Kurt vice which is on my Bridgeport. Picture 1 shows where the bubble is after about a minute. Flipping the level end for end, picture 2, shows the identical position of the bubble and the fact that the level is adjusted correctly. Yeah, I know my Bridgeport isn't level with the world.
Moving the level to the ways of the bed, picture 3, shows the bed is very close to level on the X axis.. Flipping the level end for end in the exact same location on the bed ways is where the wheels come off so to speak. Keep in mind that the bottom of the level as well as the ways are squeaky clean and location is exactly the same.
Thoughts?

Level 2.jpg

Level 4.jpg

Level 3.jpg

Level 1.jpg

A suggestion from forum member ljmontano was to put 1-2-3 blocks on the way flats and check the X axis level. As can be seen, the bubble offset is the same when the level is flipped end for end.
THANKS LARRY!!!

Level 5.jpg

Level 6.jpg



I am still confused in regards to the difference in bubble location when the level is placed on the inverted V ways of the bed.
Anybody have an explanation?
 
Last edited:
Leveling the ways perpendicular to their main axis is not what I do. I just level the head of the lathe in that direction. It is pretty hard to twist the bed.
 
Lathes do not have to be level. Roughly level them then take a cut on a piece of material held in the chuck, no tail stock center. Twist the bed until the cut has no taper, or has the taper you want it to have. The idea behind leveling them is to achieve the taper free cut, but not all lathes cut taper free when level.
 
Lathes do not have to be level. Roughly level them then take a cut on a piece of material held in the chuck, no tail stock center. Twist the bed until the cut has no taper, or has the taper you want it to have. The idea behind leveling them is to achieve the taper free cut, but not all lathes cut taper free when level.
I will be making a test cut before it's all settled. How far should the round stock protrude from the chuck for the test cut?
 
I will be making a test cut before it's all settled. How far should the round stock protrude from the chuck for the test cut?
I assume your doing barrel work, so duplicate that. You will start to fight push off with a long piece. Id actually do it on your next chamber job. Just keep taking light cuts and measuring until you get what you want.
 
I use a large thickwall pipe,actually its a steering linkage tube off of a 3500 truck. I chuck it up sticking out about 8" and then relieve the center portion leaving a ring at about 1'' from chuck and another about 8'' I do my test cuts on these raised rings. When they measure close enough to same diameter suit me Im done. Oh yeah use sharp HSS for cutting the test bar! One time I had my head stuck way up in a shady spot that smelled terrible and tried using a worn carbide because that what was already chucked! Deflecto!
 
Lathes do not have to be level. Roughly level them then take a cut on a piece of material held in the chuck, no tail stock center. Twist the bed until the cut has no taper, or has the taper you want it to have. The idea behind leveling them is to achieve the taper free cut, but not all lathes cut taper free when level.
A good lathe properly leveled & tailstock alined will cut streight.
 
Spitballing here but the pic of the level on the mill the mill might be so far out that the level is “maxed” out so when you flip it it’s still maxed out and does not show a difference. Now when you go to the lathe it’s not out as much so the out of calibration of the level shows up. Try to find a flat somewhere that you can set up your level where the bubble is centered and test it by flipping. As mentioned lathe doesn’t need to be level but straight is a good starting place then tweak it in
 
Spitballing here but the pic of the level on the mill the mill might be so far out that the level is “maxed” out so when you flip it it’s still maxed out and does not show a difference. Now when you go to the lathe it’s not out as much so the out of calibration of the level shows up. Try to find a flat somewhere that you can set up your level where the bubble is centered and test it by flipping. As mentioned lathe doesn’t need to be level but straight is a good starting place then tweak it in
You got my curiosity up so I checked the level, here is a pic of it seriously off level. Thanks for the guess.
I'm still stumped!

1622868383011.png
 
A piece of granite countertop will do in a pinch. 18"-24" square or so. What can I say? Poor men have poor ways.
 
Do you have a surface plate to check the level for flatness? I had one with a warped base that would teeter.
I do and have checked the level for flatness.
What mystifies me is the fact that when placed on the V-ways I see a big difference when I turn the level around, as seen in pics 3 and 4, but when I place 1-2-3 blocks at the same location of the bed but on the flat ways, pics 5 and 6, I get the same bubble reading when I flip the level end for end.
I have a headache now, going to lay down in a dark, quiet room. o_O
 
The top horizontal surfaces of the V-ways may not be relevant to the horizontal way surfaces.
 
Here is a rookie input.

I use the level to get me close, then chuck what started at 2x12 inch aluminum round bar stock. Stick out is 10 inches and just do skim cuts as I do the final leveling adjustment. 10 inch stick out is not needed for chambering purposes (2 inches?), but since I do a few AR15 barrels for our junior team, I want that section from the gas block journal shoulder to muzzle (a little over 7 inches) fairly straight.

I've used this bar stock since 2015 on all 3 lathes. As you can see it has been used a few times.

The pictures were taken on the last periodic performance check on the PM1440TV.

20200507_014956.jpg20200507_015012.jpg

The last step is align the TS to the HS. I cut a 60 degree center in the chuck and use the ground alignment rod from PTG held between centers to tweak the TS.

Sometimes I use the Blake to sweep the live center and adjust the TS at the distance I use it. The Blake is held by an ER32 collet chuck with a long shank. I said at distance I use it, TS alignment on older lathes with wear is only good where you adjusted it, at least it is in my older 90s vintage 1236 ATrump. YMMV.



Just a rookie hacking away at it, real machinist most likely have better way to skin the proverbial cat.
 
Last edited:

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
165,802
Messages
2,203,315
Members
79,110
Latest member
miles813
Back
Top