I Hate Leveling Machines

[Chewy]

I noticed that I have been cutting a lot of tapers lately. I wanted to get the lathe dead on to do a steam engine and taper in the cylinder bore isn't a good idea. The mill has been hit or miss but hasn't bothered what I made. The lathe was leveled originally with a Starrett 98-6 level. I made this plum-bob to tryout. The idea came from Dale @ Build Something Cool. Building it was an adventure. I wanted to get really good tolerances on the mill so the item would sit straight. Come to find out, my vise was crooked and the bed out of tram. And the whole d*** machine was out of level. Got that taken care of. Have .001 over 7" and my Coffee doesn't slide down the bed.

The plum-bob is worth it. I made a sliding scale with a center line and grooves every .030". 001 out of level is about 1/2 a division. Real easy to adjust vs the level. The lathe is about .002 down in the front but dead level along the X axis and no twist. Cut the taper down to a very little. A few tenths over 3" in the chuck and less than that over 8" center to center. I Use the level for the X axis and the plum-bob for the Y. Works great! You can stop the plum-bob in 1/2 the time it takes for the level to settle. The fun part is watching the plum-bob swing back and forth from the earth rotation. 20" of fishing line is enough to show this. I should have realized this as there is a science museum in Winston Salem with a big plum-bob that swings back and forth across a circle all day.

Three days later I have a level Mill and Lathe and a plum-bob for quick checking that won't break if I drop it. On to making keys for the vise so it can't move again.

 

[KevinM]

You need to ask a Navy machinist about lathe leveling.
(I stole that from someone else).

 

[graham-xrf]

I have seen the video before, and I thought it really cool. Congratulations on making it happen.
It does beg the question about the Starrett 98-6. Do you not have it around anymore?

The basic accuracy of the Starrett 98-6 is 0.005" per foot, or 86 arc-seconds. At around $125, I thought that was just too much compared to the Chinese level that I bought. I have learned that about the most useful level sensitivity is the approx 9 arc-seconds type. (0.0005 per ft.). One of mine (0.02mm/metre) is 4 arc-seconds sensitive, so it takes a long time to settle, and has to be used very carefully to progress at all.

The Starrett should have been OK for simple leveling with the aim to stop bed twist taper. Something must have moved, or changed.

 

[Jim F]

Just as a PSA,

Y axis is with a milling attachment.

 

[graham-xrf]

@KevinM
For a lathe on a ship, my mind is telling me that the thing about ships is that they can hardly help but be self-leveling, on average. They don't spend long enough in a list to let the machine twist. Must be different though, doing machining with the substrate underfoot heaving about!

 

[Braeden P]

You need to ask a Navy machinist about lathe leveling.
(I stole that from someone else).

If you ask they will just smile and laugh

 

[Chewy]

I used the Starrett to initially level the lathe and mill. I used it again as I was building the plum-bob. With a little experience, I know now that the plum-bob is easier and faster for the X (thanks Jim.) The level is faster for the Z. Using the graduations, I can now guess the shims needed quicker. Beats what is needed for 2/3 a division on the level.

 

[Jim F]

Actually, X is the only one that needs checked.
If Z is out, it does not affect the cut.
If X is good and it still cuts a taper, the tailstock alignment is out.
It can be out in the X or Y axis.

 

[Bi11Hudson]

@KevinM
For a lathe on a ship, my mind is telling me that the thing about ships is that they can hardly help but be self-leveling, on average. They don't spend long enough in a list to let the machine twist. Must be different though, doing machining with the substrate underfoot heaving about!

On a ship, the only thing that could cause "twist" is if the hull structure was bent or broken. In which case, the lathe truth would be way down near the bottom on a list of priorities. On a ship, the lathe is mounted (framed) to a steel deck (floor). As the deck moves through the pitch and roll comensurate to ships, everything, including the lathe, that is attached to the deck moves along at the same time. It is literally a part of the ship.

If the lathe is mounted while in a shipyard, there is a solid reference for level. A shipfitter's level is adjustable to the "level of the day", that changes as parts are added or removed. There is a pair of pegs (on my ship) that were mounted to a watertight bulkhead(wall) at true level as referenced to the ship. The very first thing, even before filling a coffee cup, a shipfitter would check and adjust his own level. Same thing after returning from lunch. This was done both in drydock and "dockside availability", since a drydock itself is afloat when raised.

Something as sensitive as the lathe is referenced to the "standard" as it is installed. Then no matter how the ship moves, the lathe moves with it. If twist occurs, the lathe has come loose from the deck, or the entire ship is twisted. Which leads to the error going waayyy down the priority list.

As an aside, when in port after a long voyage (mine were 6 mon each), the sailor walks down the sidewalk following the roll of the ship. Since the sidewalk doesn't move, the motion of a man walking is very similar to being drunk. Sometimes this is the case, but very often the man is just returned from time at sea.
.

 

[Chewy]

Most of the taper problems are with the chuck. Center to center is pretty good. Most of my stuff is less then 4" and done with the chuck or chuck and tailstock. I did about a hundred pen turning bushings for the wood lathe. The longest was 3 inches, with most being about 1". I used an ER 32 collet. Where I really noticed the taper was in making tools for the shop. Started having a .001 taper per inch and that was going to stop fast!

Anyway the plum-bob was a fun build. It is really fast to do a spot check on the ways.