Banding on finish when using powerfeed on G0602

[wannasteam]

Hello all

I just got a brand new G0602 lathe.

It is all good except when I use the leadscrew with powerfeed.

I get these bands (see photos) on the surface. They are quite rough as can be seen on the pix.

I tried the ff:
1 changing gears,
2 different tools,
3 hard/soft materials,
4 various speeds
5 check the run out of leadscrew (.003" TIR) and is the same with/without the halfnuts engaged.
6 running the cut without the bearing block at the tailstock end
7 do a cut without the powerfeed. Results were as good as I could get it manually but no banding.
8 cleaned the leadscrew real well
9 slackened off completely the gib adjusters for the half nuts, first one, then the other then both

As close as I can figure, it seems to be related to the leadscrew somehow. The pitch of the bands/ridges seems to be the same as that of the leadscew.

There is no discernible in/out movement of the saddle/compound as it traverses.

None of the steps I did made any difference. :'(

I'm kinda stumped here so any ideas from the collective wisdom?

regards and thanks in advance

Joe

 

[steamer]

Hi Wannasteam,

Your feed rate is WAY too high. Slow it down to .005"/revolution or slower, and the bands should go away.

If you don't know how, post a picture of the lathe, and we'll talk you through it.

Dave

 

[wannasteam]

Hi Dave

The feed rate was set to .063mm/rev (.0024") by default so I put a bigger gear on the leadscrew to slow it down even further. I went from 104 tooth to 120 tooth. It didn't make a bit of difference. :-(

Cheers

Joe

BTW this is the lathe in question:

 

[steamer]

Thanks for the picture!

OK, No seperate power feed clutch, so you engage the half nuts for power feed ...correct?

Additionally, can you take a picture of the feed selection knobs/settings?

Is there a stud gear change and what have you go on the stud?

Is the banding spiral in nature...like a thread? or is it in the form of "collars"

Are the saddle gibs adjusted correctly?....if the table is fishtailing....it will cut like that also

Does it do the same thing if you reverse the feed?....ie feed left to right ?

Dave

 

[cfellows]

I get those on my old Logan lathe when I use the power feed on the lead screw. For power feed, I have a separate gear motor which drives the lead screw from the back end. As you say, it doesn't matter how fast or slow you run the power feed, the banding is the same. My lead screw has a slight bow in it which is probably causing the problem. I have a replacement lead screw, but haven't gotten around to installing it yet.

Have you tried to see if you have any discernible bow in your lead screw?

Chuck

 

[steamer]

Actually he did Chuck...he stated that it has .003" or perhaps less.

I'm wondering about the gibs on the saddle Chuck....Do you think their loose?

Dave

 

[steamer]

Actually....I wonder if the leadscrew has a drunken thread too.

Anyway...keep checking.

Dave

 

[Jasonb]

Put a DTI on the carrage with the base on teh lathe bed and see if that moves up and down as the power feed is run, this will show if the leadscrew is lifting the carrage. You may not see actual runout if you are measuring the leadscrw off the carrage, or while its got the half nuts clasped around it.

Any chance it was lifted with a sling around the bed and leadscrew, thats how they often get bent.

J

 

[wannasteam]

Hi Dave

OK, No seperate power feed clutch, so you engage the half nuts for power feed ...correct?

Yep, that's right

Additionally, can you take a picture of the feed selection knobs/settings?

Done.

Is there a stud gear change and what have you go on the stud?

ermmmm...stud gear change? Not sure what that is...

Is the banding spiral in nature...like a thread? or is it in the form of "collars"

Like collars.

Are the saddle gibs adjusted correctly?....if the table is fishtailing....it will cut like that also

Checked them. Nice and snug

Does it do the same thing if you reverse the feed?....ie feed left to right ?

Unfortunately, I don't have the facility to cut L to R..No reverse tumbler (yet) :-(


Hi Chuck

The leadscrew seems pretty straight. I checked for runout in three places and got the same result...around .003" TIR. I'll check it properly if/when I have to start dismantling things.

Cheers

Joe

 

[wannasteam]

Put a DTI on the carrage with the base on teh lathe bed and see if that moves up and down as the power feed is run, this will show if the leadscrew is lifting the carrage. You may not see actual runout if you are measuring the leadscrw off the carrage, or while its got the half nuts clasped around it.

Any chance it was lifted with a sling around the bed and leadscrew, thats how they often get bent.

J

Hello Jason

I'll try that later.

I measured the l/screw runout by resting a ruler against the rotating leadscrew and put a dial indicator on the ruler. I did this with the half nuts disengaged and also engaged. Not very precise but effective...

I know what you mean about the lifting around the leadscrew. I unpacked the unit myself and lifted it up carefully.

Cheers

joe

 

[steamer]

OK

Do as Jason has suggested and mount a DTI on the bed or the bench...NOT the saddle.

Set the dial indicator plunger on the front saddle and for a short distance feed the saddle right to left....DON'T CRASH YOUR INDICATOR!

I'm looking for a rise and fall of the saddle.....Which I am suspicious of....which it MUST be doing.

Additionally, I know you said you checked your saddle gibs....but while the indicator is on the saddle, and with the machine off, pull up and down on the saddle with about 10 pounds of force...and tell me how much the saddle is moving?

Dave

 

[wannasteam]

Would an imperial leadscrew fit on to a metric halfnut enough to work badly..or vice versa? Or is the size difference too big for a No-Go situation?


Just a thought.

Joe

 

[steamer]

I doubt it. Half nuts are usually 3 or 4 diameters long. 3 mm is. 118" while 1/8 is. 125". That's a lot to make up.

Anything is possible I suppose.

Dave

 

[wannasteam]

OK

Do as Jason has suggested and mount a DTI on the bed or the bench...NOT the saddle.

Set the dial indicator plunger on the front saddle and for a short distance feed the saddle right to left....DON'T CRASH YOUR INDICATOR!

I'm looking for a rise and fall of the saddle.....Which I am suspicious of....which it MUST be doing.

Additionally, I know you said you checked your saddle gibs....but while the indicator is on the saddle, and with the machine off, pull up and down on the saddle with about 10 pounds of force...and tell me how much the saddle is moving?

Dave

Hi Dave

I've just measured the saddle and compound movement in relation to the bed and I can't get more than a thou movement in any direction. In a way this is good but not for the purpose of this exercise :-(

Joe

 

[mzetati]

What tools are You using, are them set at the correct height, do they have sharp edges and the correct rakes for the materials?
Depth of cut?

[edited]
Looks like the tools is 'refusing' to cut and being pushed away from the workpiece: when the forces are too strong, it goes in again.
You should see the turret going to and fro, if that's the case.
[end]

Marcello

 

[Jasonb]

What tools are You using, are them set at the correct height, do they have sharp edges and the correct rakes for the materials?
Depth of cut?

[edited]
Looks like the tools is 'refusing' to cut and being pushed away from the workpiece: when the forces are too strong, it goes in again.
You should see the turret going to and fro, if that's the case.
[end]

"do a cut without the powerfeed. Results were as good as I could get it manually but no banding"


I think we can rule out the cutting tools.

J

 

[steamer]

Good point

Check the tool
dave

 

[ozzie46]

I have the same lathe and it seems to be a common problem with it as others owners have the same complaint. It is my feeling that the 2 bolt hold down for the compound is the culprit. When I take my compound off of the cross slide I can see marks where it has been rocking back and forth.

I have not done so yet but have been thinking of trying the 4 bolt compound mount mod that the 9 x 20 lathe owners have done. See link

http://bedair.org/clamp/9x20clamp.html

I know that the 10 x 22 doesn't have "T" nut slots but you can drill and tap the cross slide.

Of course I may be all wet on this to. :big: :big: :big:

Ron

 

[Tin Falcon]

Here is the manual


http://cdn0.grizzly.com/manuals/g0602_m.pdf
Page 33 shows the correct gear configuration for turning and has imperial feed numbers on the feed chart. the feed rate seems to be the same as in the posted picture just imperial equivalents. so if the gears are set up right the lever settings pictures should give. a .0025 inch/rev feed.
Tin

 

[rustyknife]

I've ran into this exact thing before and found the culprit in my case to be incorrect cutter geometry. Played with all kinds of speeds and feeds, and it would not do it if fed slowly by hand....changed the angle of the cutting tool and all was solved.

Just a thought.

Regards
Eric