G0602 finish issues

[photomankc]

I have been battleing with an issue and have not been able to really figure it out or even exactly were to look for it. Since I have found some decent ground inserts and im able to get some decent finishes with them I noticed an issue with power feed. Every time I use power feed I get a wavy surface with peaks and valleys I can feel. Its a repetative standing pattern that repeats in the same postion no matter the spindle speed or feed rate which leads me to suspect something in the leadscrew/drive train/(please no) Gear Box.

I am talking with Grizzly to see if they can help me track it down but as it stands, power-feed is useful for only roughing cuts. I have to hand advance the carriage to obtain a decent finish on the final passes. That's a bit of a pain. I'm also afraid it will impact thread quality.

The pattern seems to stem from the carriage digging in by about 0.002" and then coming back out and repeating this pattern as it moves down the bed. It takes a manual pass with a 0.002+" advance to skim off the peaks.

I have some photos of what Im seeing.

First is a manual 0.005" pass.

Second is a powerfeed pass at the same spindle speed and DOC

Thrid is 1/2 manual and then 1/2 with power feed to show them side-by-side.

I hopeful that Grizzly will help me get this fixed and hopefuly without (god forbid it) having to return this beast but I wondered if the folks here had seen anything like this and maybe had some suggestions at what to look at.

[hoss2006]

Could be a slightly bowed leadscrew moving your carriage a little bit every rotation.
Can check it with a magnetic base dial indicator while it's running with a flat tip.
Try tightening the saddle gibs a bit.
Shown on page 40 of the manual.
http://cdn5.grizzly.com/manuals/g0602_m.pdf
A new leadscrew is only $52.50.
http://www.grizzly.com/products/G0602/parts/4
Hoss

[photomankc]

That improved it. Didn't clear it up but did reduce it by maybe 50%. I tightened them down as tight as I could do without stripping something and added some drag with that front right lock and it's still there. Put a DTI on the tailstock and ran it across the side of a parting blade and you could see the rythmic movement plain as day. was a bit over 0.001" with the gibbs looser. Tighten them down real hard and you get down to 0.0005" but that still makes a wavey surface.

I'll report all this to Grizzly in the morning and see what they will do. Gave me fits tonight tring to bore an aluminum sleeve. I knew the 3" overhang was pushing it on the 1/2" boring bar it really seems to jack up a bore on aluminum worse than steel. I couldn't do the bor manual since it was blind and I had to clear the chips or they would keep getting bound up around the bar and cause it to skip and leave big rings inside. I guess the softer material really shows the issue more than steel.

[photomankc]

Since I always hate when a thread has my problem but then dead-ends I thought I would update the situation. Grizzly is sending me a new leadscrew. Did some other tests one of which was to disengage the gear banjo and manually turn the leadscrew with a DI mounted in the tool post. It showed the same inward movement when turned by hand and at the same point in the rotation each time. Partly engaging the half-nut eliminates the problem while fully engaging brings it back. Hoping that the new leadscrew will fix the issue for me.

[cubep]

Did you find a solution at your problem because i get this lathe and I also have this problem? And what inserts and holder do you use?

[Hans_G]

my G0602 does the same thing w/ power feed. I was about to ask the same "how to fix this" question. Any progress? Thanks!

[photomankc]

In short. No, it's not gone completely. The new leadscrew did diminish the issue a bit but it is still there. For instance, even when a surface looks pretty good to the eye, if you touch it with sand paper, the pattern will almost immediately show itself. I have found that it takes about a 1 thou reduction in diameter with sanding to remove it visually.

I have been making TTS holders lately and it's been a bit frustrating because even after sanding when you turn the shank and use that in a collet, you can clearly see the rings in the wear marks which means it's not getting into contact over the full shank. Best as I can tell it's a ghost image of the leadscrew produced by alternating increasing and decreasing pressure on the tool as it moves. How to fix it...... don't know. I have to sand stuff that really needs a good surface and there are things I can't sand so there are things I can't do.

[Astroguy]

I had the same problem with mine and I noticed when I engaged the lead screw it was bending the screw up about 3/16" or more so I shimmed the mechanism down and the problem went away.

[photomankc]

You're talking about the interface between the apron and the carriage right. Good point, I'll have to check that.

[Hans_G]

Astroguy- checked my power feed 1/2 nut and it does exactly what you're describing- bends the leadscrew as it engages. Not sure when I'll get around to relocating it, but I'll update if it fixes the problem. Thanks again!

[Fastest1]

I have seen a few threads where people have had to shim the apron. I didnt understand the problems they were having. Your pictures make it very clear. When you checked for movement of the carriage, you said you had tightened the gibs and gib lock. Did you try to see if the carriage moves when just the gibs are tight and not using the lock? I have seen a thread or two on the yahoo forum about modifying the gib strip clamp. Some use brass flat stock between the gib strip and the cast piece that bolts on underneath the carriage to tighten the space. Good luck with the repair.

[photomankc]

I was just farting around and it seems like there is not any real serious bend upwards when the nut is engaged, but there may be some outward movement. I'll take a look at that when I have some spare time.