PM1340GT

[RandallsRaceShop]

I just got my 1340GT a couple (2-3) weeks ago. I haven’t turned much of anything on it as of yet. However, playing around with a piece of 6061 and also a piece of 12L14 I keep ending up with this spiral pattern when using the power feed. It absolutely does not leave a spiral pattern if I feed it by hand (who even does that.?.?.?) You can feel the grooves & if I drag a nail (finger/thumb) across it, there will be a white line of what was my nail.
Has anyone else with a 1340GT experienced this?

Thanks in advance
Randall

 

[RandallsRaceShop]

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[mksj]

I have seen that before a few times, in some cases it occurs with single phase motor pulsation showing up as a barber pole type of spiral finish. Might check your belt tensing and or changing the belts to something like the Gates Tri-Power belt (BX24 or BX25) as they wrap around the pulleys better. With the stock 1340GT, my recollection is I needed both. Typical solutions are trying to isolate the motor and replacing the motor with a 3 phase motor. There are a few previous posting on this some issue. Seems to be idiosyncratic as to the occurrence, but more commonly on lighter lathes. If you replace the motor with a 3 phase one, very few fit the motor space on the 1340GT, quite a few posts on the subject.

1340gt surface finish problem

O.K. guys, and gals, I've tried every speed/feed combo, every carbide insert I have, every HSS tool I have, I've even put vibration isolation pads between the stand and the floor...nothing seems to work. Here's what I get... Please excuse my photography skills. You can not only SEE the...

www.hobby-machinist.com

 

[wrmiller]

What's the feed rate?

 

[Dabbler]

It absolutely does not leave a spiral pattern if I feed it by hand (who even does that.?.?.?)

I do. I cannot remember the last time I engaged the power feed.

There is one other place that can create this effect. Check the gear train on the headstock, to see all the gears engage correctly (with about 3 thou of clearance, - you set it with a piece of 20lb bond paper). Check that every fastener is tight. If there is slop in *that* system it accumulates and then 'surge' back over a few rotations of the feed screw gearing, which is around 30-40 turns of the spindle.

 

[RandallsRaceShop]

I have seen that before a few times, in some cases it occurs with single phase motor pulsation showing up as a barber pole type of spiral finish. Might check your belt tensing and or changing the belts to something like the Gates Tri-Power belt (BX24 or BX25) as they wrap around the pulleys better. With the stock 1340GT, my recollection is I needed both. Typical solutions are trying to isolate the motor and replacing the motor with a 3 phase motor. There are a few previous posting on this some issue. Seems to be idiosyncratic as to the occurrence, but more commonly on lighter lathes. If you replace the motor with a 3 phase one, very few fit the motor space on the 1340GT, quite a few posts on the subject.

1340gt surface finish problem

O.K. guys, and gals, I've tried every speed/feed combo, every carbide insert I have, every HSS tool I have, I've even put vibration isolation pads between the stand and the floor...nothing seems to work. Here's what I get... Please excuse my photography skills. You can not only SEE the...

www.hobby-machinist.com

It’s a 3 phase lathe running off of a phase perfect. I will change the belt (happily). I actually meant to get a belt from Napa before the lathe showed up. I kind got busy unexpectedly & so I am running that stock belt at the moment.

 

[RandallsRaceShop]

What's the feed rate?

I have on .0025 at the moment. I’ll try it again, but I went through the gear box (1-8) on the “E” setting at least.
The reason I put it at .0025 was because I was trying to make a finishing pass. I didn’t want to have “ribbed for her pleasure”, but that’s what I’ve got at the moment.

 

[RandallsRaceShop]

I do. I cannot remember the last time I engaged the power feed.

There is one other place that can create this effect. Check the gear train on the headstock, to see all the gears engage correctly (with about 3 thou of clearance, - you set it with a piece of 20lb bond paper). Check that every fastener is tight. If there is slop in *that* system it accumulates and then 'surge' back over a few rotations of the feed screw gearing, which is around 30-40 turns of the spindle.

Right on.
Thanks for the suggestion. I did set the gears using a piece of paper. Honestly, I think I just grabbed some blank photocopier paper out of the ol’ lady’s office.

 

[wrmiller]

It’s a 3 phase lathe running off of a phase perfect. I will change the belt (happily). I actually meant to get a belt from Napa before the lathe showed up. I kind got busy unexpectedly & so I am running that stock belt at the moment.

I ran my 3-phase 1340GT with a VFD because I liked the soft start and braking functions. Among other things. It's been years since I bought my 1340 (2015?), but one of the first things I did was to replace that factory belt. Machine vibration and part finish was significantly improved. YMMV of course.

 

[RandallsRaceShop]

Ok, I’ve got some improvement.
Came out this morning checked belt, pulleys, motor cradle. Height/slack adjustment arm (motor cradle) had a little play at the top. A new bolt & washer & solid as a rock.
Fire up the lathe, take a pass, same thing.

So I go to pushing & pulling at top of my tool post. Sure enough a small knock was heard.
Fired the lathe back up, set the power feed & pulled on tool post while the machine was making a cut, nice & smooth.
So I set my mag base with DI on the cast web between ways with pointer resting on the back side of carriage. The knock I heard was about .001 movement on my DI.
Made a gib adjustment & it’s pretty good.

This is a good thing!

I appreciate everyone’s replies & insight.
Thank you all very much. Hopefully smooth sailing from here on out.

Randall