Looking for a recommendation on PM1340gt alignment

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GunMonkey

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Im setting up my new lathe and working through bed leveling and headstock/tailstock alignment. I have a MT5 ground test bar that reads with no movement/runout at the headstock. At 11.5" down the bar it reads with .0003 showing a slight bias toward the rear of the lathe. I moved on and aligned the tailstock between centers with a straight ground test bar. I then mounted a Bison 4 jaw direct mount D1-4 chuck and put a 3" aluminum round stock 14" long in and turned a barbell. I am getting a taper of about .0025 over 9" smaller at the headstock and larger at the tailstock.

Now for the question.

Am I better off adjusting the headstock or adjusting the feet on the lathe? or both? or is this as close as I will get it? My Starrett 98 shows the bed to be level front to back. Im hoping someone familiar with the lathe can give me some pointers before i loosen the headstock bolts.

Thanks, Jeff

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First it is important to get the bed ways level front to back AND headstock to tailstock at the same time. this is before you try to align the headstock.

Then you need to align the tailstock side to side and up/down.

Next, depending on the provenance of the MT5 test bar, it could be out. Usually you check with a parallel test bar between centres in addition, just to be sure...

Because your tailstock is in alignment cuts between centres can be made to get the head into perfect alignment. I haven't done this in 30 years, but those are the basic steps.
 
Thanks for your reply Dabbler.

The ground rod came from India and has a listed tolerance of .0002. It reads consistently as I rotate the spindle and increases gradually as it is moved from the headstock so I believe it is ground pretty true.

I did check with a parallel test bar next after seeing the slight offset of the headstock. I adjusted the tailstock about .0007 forward into alignment using the rod. The rod is being held by new carbide Bison MT5 and MT3 centers.

My last lathe was a South Bend heavy 10 and the bed would flex enough that adjustments could be made in the bed that would effect taper. Is this the case with a PM1340GT? I watched Tom Liptons video where he could not adjust taper from the bed of his Yam lathe and had to adjust the headstock.

I believe the headstock is slightly out of axis with the ways. Im not sure how difficult it would be to control the movement after loosening the bolts to improve the way that it rests on the bed casting. The .0003 is being read probably 15" from the first set of bolts so the movement required in the headstock would be a fraction of that I believe and could be hard to control and lock down.
 
If you are out of parallel 3 tenths at 15" from the bolts - you are in. That is better than a Hardinge I worked on once. It takes a very experienced machinist to turn all but the most basic shapes to those kind of tolerances. I wouldn't mess with it. You could easily mess it up.

Your next step is to turn a bar between centres, say, 12" long, and measure the diameter at each end There a great videos on this on youtube, but essentially you first relieve the middle so the only heat you generate is at the ends. You also lock your cross slide so the tool remains true to the V ways. If your two diameters are within .0003 then your lathe bed and ways are a close as you can make them.

If I remember the video correctly, Tom Lipton was a little surprised about the bed thing, but his lathe is very heavy - I vaguely remember a very large number, could it have been 5000 pounds? This is a very unusual situation. Almost any lathe I've heard of, except the very heavy toolroom lathes and a few CNC lathes need their beds adjusted so they are flat. This should apply to your PM1340GT. My lathe is a 12X37 and weighs almost 1000 lbs, but it needs careful alignment whenever I move it.

My friend bought an 18" X 60" Mazak lathe, 6000 lbs. Very strong an heavy base. It took >2 hours to get the lathe bed flat in both directions after it had settled on his garage floor for a week.

Your rod may well be in line. I was being cautious, because I had a bad experience with an American made alignment bar.
 
Dabbler, nice job on helping Jeff with this. Good advice.

Jeff, happy to see you found a lathe in better condition. Looks like you will get it dialed in accurately.
 
GunMonkey said:
Im setting up my new lathe and working through bed leveling and headstock/tailstock alignment. I have a MT5 ground test bar that reads with no movement/runout at the headstock. At 11.5" down the bar it reads with .0003 showing a slight bias toward the rear of the lathe. I moved on and aligned the tailstock between centers with a straight ground test bar. I then mounted a Bison 4 jaw direct mount D1-4 chuck and put a 3" aluminum round stock 14" long in and turned a barbell. I am getting a taper of about .0025 over 9" smaller at the headstock and larger at the tailstock.

Now for the question.

Am I better off adjusting the headstock or adjusting the feet on the lathe? or both? or is this as close as I will get it? My Starrett 98 shows the bed to be level front to back. Im hoping someone familiar with the lathe can give me some pointers before i loosen the headstock bolts.

Thanks, Jeff
Click to expand...
When my 1340gt was new(this year) I had almost the exact same issue as you did. I contacted Matt and he said probably I need to adjust headstock.Unfortunately you cannot expect the headstock to be dialed in.Also my tailstock is about 4 thousanths " high(was told by PM that this is standard for this lathe:confusion:), not anything you can do except scrape the bottom of tailstock(I left it alone)
It's not too difficult to adjust the bolts but can take several hours.
Basically use 2" steel about 8" long , no tailstock.Make cuts ,adjust, check--and so on.This has been covered in previous posts. Eventually it will go to 1 or 2 ten-thousandths of taper mover the 8".
 
pacifica said:
Also my tailstock is about 4 thousandths " high(was told by PM that this is standard for this lathe:confusion:), not anything you can do except scrape the bottom of tailstock
Click to expand...

The LeBlond 15" toolroom lathe always came shipped with the tailstock .003 high. This is to allow for wear from sliding on the slantway (sort of an asymmetrical Vee way) and the flatway. You can scrape yours in or use a boring bar holder to hold a dead centre .003 below centre in the tailstock.
 
Here's a funny but very informative video on leveling a lathe that was cutting a .002 taper in 8 inches. Enjoy!


(he is trying to talk to all levels here - but he does a great job!
 
Thanks. I will be back at it tomorrow. The test bar I made is from 3" stock and I don't have 2-3" micrometers that will read tenths. I decided I should have some and they arrive tomorrow. I dont have any other scraps of stock long enough to use to make something in a smaller size that I could measure so it was buy material or a new tool.
 
This is the set-up I used when actually moving the headstock. Just tightening the cap screws can give a movement of .01". I tighten 2/3 rds of the way and then tap with a rubber hammer for incrementel movement, watching the movement on the indicator. That way you can gauge how much you moved the headstock.
If available you can replace the stock cap screws with USA made holo-krome or unbrako.A poor quality cap screw can cause unexpected jumps in movement.

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