The Pm-1440gt Has Landed

[jbolt]

I've done the first fine leveling with a machinist level. This is the first test cut. over 8" it is 0.0021" narrower at the far end. I will let the machine sit overnight, take another cut and adjust from there. Finish looks good for the single phase motor.

 

[mksj]

Hi Jay,
Machine looks great, and very clean DRO install, nice. A few things to consider checking the cutting alignment, you may need a precision level to check for any bed twist along the ways. I have some precision ground test bars and I look at the +/- TIR from 0 at different points along the bar. If the swing in the +/- value is skewed in one direction as you get further from the chuck, then you may need to align the headstock. Most of us have had to do this, it takes the slightest change in the alignment bolts. I would also do a test cut with the 4J chuck to see how it compares.

Overall, it appears to be a very fine machine, and that is close to a mirror finish cut on the test cut. Hopefully you have more room for a larger motor in the back if you go the VFD route in the future, Impressive, if I didn't already have a lathe, this is the one I would get today.

 

[koba49]

when I got my 1228 leveled I took a cut on a 1-3/16 chunk of steel with a HS tool bit over 5 in I got .0045 taper same direction you have small on the end big by the chuck this is with out a center in the part. by just lowering the front feet on the tail stock end I took out .002 taper I had to unbolt the machine and put a .006 shim on the back side of the foot at tail stock end, bolt it back down and I was .0001 high on tail stock end over 5.500 distance the machine is not dead level any more but it is aligned your machine is heaver than mine but try dropping the leveling feet or foot on the front tail stock end you may get it out by just doing that, it may not be level but I do not think dead level is needed to get a precise alignment

 

[jbolt]

Hi Jay,
Machine looks great, and very clean DRO install, nice. A few things to consider checking the cutting alignment, you may need a precision level to check for any bed twist along the ways. I have some precision ground test bars and I look at the +/- TIR from 0 at different points along the bar. If the swing in the +/- value is skewed in one direction as you get further from the chuck, then you may need to align the headstock. Most of us have had to do this, it takes the slightest change in the alignment bolts. I would also do a test cut with the 4J chuck to see how it compares.

Overall, it appears to be a very fine machine, and that is close to a mirror finish cut on the test cut. Hopefully you have more room for a larger motor in the back if you go the VFD route in the future, Impressive, if I didn't already have a lathe, this is the one I would get today.

Hi Mark,

The only problem with the DRO is it covers the lock screw for the X axis. I need to re-think that one as it is necessary for doing precision work.

I chucked up a 1" precision test bar and over 4" I get 0.0009" toward the operator at the far end. Unfortunately two of the head-stock jacking screws are blocked by the motor capacitors. For the moment the work I need to get to is 12" or less so I'll see if I can get it acceptable adjusting the bed twist. I'm finding the lathe too be too low for my height so I think I will wait on adjusting the head until I do the VFD and raise the lathe.

I haven't looked too hard for motors yet. The max motor body length is 11-1/2" with an overall length of 14-1/2". Max diameter could be up to 9". From what I can tell most 3HP #PH motors have a 1.125" shaft which will require a new pulley.

 

[mksj]

Hi Jay,
I have found the cross slide lock to be very important to maintain accuracy and often you want just a slight tension/resistance on the cross slide. I have seen two approaches, one is to standoff the DRO scale on blocks, and machine a threaded post with a lever arm or a hex nut head bolt which applies pressure on the gib lock, or you can put a friction lock on the other side. I did the latter and it works very well, I uses some naval bronze for the friction lock,very easy to set both a slight drag or a full lock. Since it is softer then the metal cross slide there is no wear. I subsequently added a rubber gasket between the mounting plate and cross slide so it does not get fowled with swarf. Also on the tool post slide, I made a small lever arm that is spring loaded, so it holds it position when loosened. There is a small ball bearing that is between the gib and the lock, do not loose it.

Example of lock with standoffs for scale: http://www.hobby-machinist.com/threads/installing-dro-on-pm-1340-gt.48653/#post-413797

On the 3 phase motor, a tight fit and probably only a TENV type motor will fit. The Marathon E470 motor or the Y541/Y527 inverter motors would be top of the line, but looks like it would be a tight. You would need to cut off the rear jack shaft, the main shaft would be 1.125". Pulley should not be a problem, but you want to go much smaller than stock, as I recommend running these up to 120Hz.

 

[jbolt]

I likey the friction lock. I don't like to have standoffs on the scale cross slide. Good thinking on using the follower rest mounting holes.

I'll take a look at the motors. How much smaller would you go on the pulley?

 

[jbolt]

I did not take much adjustment to get the machine cutting straight. I think I moved the front left foot about 1/4 turn. It took 4 test cuts to dial in. After this test cut I ran a TDI along the front and it had a 0.0003" difference over 8". I see no reason to mess with the head stock.

Even though the cuts are nice and shiny it does not tell the whole story. I ran some 400 grit lightly over the cut to highlight the finish produced. 700 rpm at 0.0026" feed, CCTG 32.51 insert. You can see the slight undulations. Nothing to complain about but not like my old lathe that was a 3 phase belt drive. It will be interesting to see if there will be a difference with a 3 phase motor.

 

[jbolt]

I don't have a manual yet so I'm not sure is this information is in there but I thought I would post it anyway.

Wires 1 & 2 are 24vac.
Wires S1 & R1 are 110vac.
Wires S & R are the 220vac in.

I have the light hooked up the the 24vac and the DRO to the 110vac.

 

[wrmiller]

Just my opinion, but I'm just a hobbyist and not looking for mil-spec finishes, so that would more that work for me. I'd be more than happy to take that thing off your hands for ya once I land somewhere.

 

[mksj]

You are not going to get any better than that unless you buy a 10EE, spec is something like better than 30 millionth of an inch. I still would check your machine with another chuck, and also check that the headstock is for the most part running true. I mark all my chucks so I always put them on in the same position.

On the pulley size it all depends on the motor and the maximum RPM, most 1750 RPM motors will do 2X their base speed, but the performance can drop off erratically after about 90Hz. The inverter motors maintain full Hp to at least 2X their base speed, the Baldor I use is rated to 6K RPM at full Hp. Still I think on an inverter motor 2X the base speed is a reasonable top end for the motor. Since the 1440GT already will top out at 2000 RPM, I would reduce the pulley size to around 50-60% diameter of the current one with an inverter motor, 75-80% with a standard motor taking it to 90Hz. The faster you run the motor, you have more poles per spindle RPM, so it should be smoother. Hp delivered to the spindle is 2X and torque 1X at 120 hz, vs. the a 60Hz motor at the same spindle speed using a higher gear. I would say the sweet spot is running in a higher gear and using either 30-90Hz or 30-120Hz depending on the type of motor. Braking with a VFD is also quicker when using a higher speed gear for the same spindle RPM, there is less rotational momentum. A VFD on the 1440GT, you will probably just use one of your speed levers to select a general speed range and leave the other in high.

A lot of factors affect surface finish, another gent that I helped convert his lathe to 3 phase on a G4003G, the surface finish improved about 70% by just going to 3 phase. Some of that may be pulsation, the cutter and cutting speed plays a significant role. Change the belts and play a bit with the tension/check the belt alignment. I use very sharp uncoated carbide inserts for Al, and can get close to a mirror finish with a skim cut. 1018 steel, forget it.

The 110VAC is usually off the transformer and fused, on my mill it uses a 3A fuse. Ok for a coolant pump and a DRO, but not much more.

Like Bill, I will be happy to stand in line behind him.
Mark