# Banding on finish when using powerfeed on G0602



## wannasteam (Sep 5, 2011)

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


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## steamer (Sep 5, 2011)

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


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## wannasteam (Sep 5, 2011)

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:


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## steamer (Sep 5, 2011)

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


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## cfellows (Sep 5, 2011)

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


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## steamer (Sep 5, 2011)

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


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## steamer (Sep 5, 2011)

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

Anyway...keep checking.

Dave


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## Jasonb (Sep 5, 2011)

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


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## wannasteam (Sep 5, 2011)

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


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## wannasteam (Sep 5, 2011)

Jasonb  said:
			
		

> 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


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## steamer (Sep 5, 2011)

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


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## wannasteam (Sep 5, 2011)

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


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## steamer (Sep 5, 2011)

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


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## wannasteam (Sep 5, 2011)

steamer  said:
			
		

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



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


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## mzetati (Sep 5, 2011)

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


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## Jasonb (Sep 5, 2011)

mzetati  said:
			
		

> 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]
> ...



"_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


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## steamer (Sep 5, 2011)

Good point

Check the tool
dave


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## ozzie46 (Sep 5, 2011)

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


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## Tin Falcon (Sep 5, 2011)

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


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## rustyknife (Sep 5, 2011)

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


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## steamer (Sep 5, 2011)

Show us a picture of the tool mounted ........please..... ;D


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## steamer (Sep 5, 2011)

Preferably up against a piece of stock..........


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## Jasonb (Sep 5, 2011)

I'll say it again why do we need to see the tool if the OP says its fine when fed manually

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

J


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## mzetati (Sep 5, 2011)

because the forces applied to the (possibly dull) cutting edge would be much greater than those applied to a (possibly) better tool, to say nothing about the (possibly) lower feed rates when feeding by hand.
The brass workpiece shows a lot of metal being pushed towards the HS, instead of being cut: that COULD be a sign of a bad tool.

Marcello


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## Ken I (Sep 5, 2011)

I have the same problem with my no name brand lathe.

Although it is nowhere near as bad as in the photos - more cosmetic finish changes rather than any real depth to the banding - but a few tenths of a thou to be sure.

Definitely leadscrew pitch.

I have tried snugging everything up to no avail.

However I have noticed that with the screw nuts closed (machine stopped) I can rock the carriage back and forth about 0.5mm - its not play in the half shells or the leadscrew - and it feels like a spring.

If I power feed (without cutting anything) if I load the carriage handwheel, I can see a momentary hesitation and again this "springyness" in the connection to the leadscrew.

Something is wrong here - going to strip it and see what I find.

I will be watching this post closely.

Ken


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## steamer (Sep 5, 2011)

Gotta agree with Marcello here.  I am suspect that it's dull, ill positioned , ill shaped or all of the above.

Though I would suspect hand feeding will be at a higher feed rate than .0024"/rev!

The added cutting force from a higher feed rate may be taking up the slack in the machine that wouldn't take up otherwise.

It's just a hypothosis....

WE need to eliminate it because WE'RE not there to look at it ourselves Jason.

It's exceptionally difficult to trouble shoot someone elses machine from half way round the world.

Leave no stone unturned.  I promise I'll not complain if you tell me I was wrong later ;D

Ken, I'm intriqued with your statements.....seems to be a theme here.

Dave


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## steamer (Sep 5, 2011)

Something else to check may be leadscrew alignment, either up and down or front to back with respect to the halfnuts


Dave


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## dalem9 (Sep 5, 2011)

my guess their is play in the head stock bearing and a high spot on one of the drive gears. Only a guess Dale


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## Mosey (Sep 5, 2011)

Off the point a little, but maybe interesting anyway... when I got my first South Bend heavy 10 back in 1990+-, I got similar rings in the finish when turning a bar. After lots of frustrating attempts to find the culprit, I called South Bend and spoke to an old timer- Mel- who was the guy who tested the lathes before they went out the door. Mel said "yup, it's what we call here a "ring-turner"". He said "they don't know what causes it, but if I ever figure it out, he'd like to know". Well I did figure it out. It was poor HS tool tip shape, height, and finish, any or all at a time. I switched to carbide indexible inserts, which are correct shape and finish of course and never got a ring again.
I guess Mel is gone by now.

I guess I should add that the problem seems to be that the chip starts to form, then welds itself to the work, then breaks off, then the cycle repeats. What I was seeing was the ring of welded broken chips.


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## dalem9 (Sep 5, 2011)

with machine off engage feed drive turn chuck by hand and see if there is a tite spot.just to rule out a gear that is bored off center Dale


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## wannasteam (Sep 5, 2011)

:bow:

Thanks for all the input and thoughts. Very muchly appreciated.

I'm at work now and I will have a look at a few things when I get home tonight.

Just a few thoughts and comments from me:

I have a 7 x 12 asian lathe that I've had for about five years and get very good results even tho my saddle is quite "baggy".

I've had very good results finish-wise using both hand sharpened HSS tooling, indexable tooling and carbide tools. I am using the same tools on the bigger lathe.

I very strongly suspect that the problem is somehow related to the connection between the leadscrew and the cutting tool. I say this because if I hand feed as slow as what the leadscrew gives, I get very good results, although not with the same uniformity as one would get from powerfeed. To me, this eliminates the tool itself as the culprit.The banding occurs from heavy cuts, light cuts and very light cuts.

The pitch of the banding is the very nearly the same as the pitch of the leadscrew which indicates a problem somewhere in that system.

Again, thank you very much for your input, ideas and thoughts.

Cheers

Joe


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## Niels Abildgaard (Sep 6, 2011)

File a slot in end of leadscrew,disengage geartrain,engage powerfeed and try with an electric screwdriver.
Good luck and enjoy the feeling when localizing problem

Regards

Niels.


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## Jasonb (Sep 6, 2011)

Niels Abildgaard  said:
			
		

> File a slot in end of leadscrew,disengage geartrain,engage powerfeed and try with an electric screwdriver.
> Good luck and enjoy the feeling when localizing problem
> 
> Regards
> ...



As this is a brand new lathe I would strongly advise NOT to do this, if it needs to go back or replacement parts are required you could invalidate any warrantee.

Jason


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## Richard1 (Sep 6, 2011)

Cutting a slot in the end of the lead screw is probably not a good idea. If there is a way to drive it independently of the gear train without damaging it, it might tell us something.

Richard


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## Ken I (Sep 6, 2011)

This is the banding typical on my lathe.





Still haven't figured it out.

In this case I think it looks cool but generally not.

Ken


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## steamer (Sep 6, 2011)

Jason's right....no modifications please......

Dave


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## mzetati (Sep 6, 2011)

Joe,

now we know the tools have no faults, I'd try to remove some of the other variables: would You get bands if cutting forces were zeroed? a felt tip pen in the toolpost might give an answer.
Can You fit a hand crank to the spindle? Powerfeeding by arm would let You sense eventual tighter spots, while cutting, while moving parts with the tool retracted, no tight spots at all, ...
If You do that with the gear cover removed You might actually see the reason of them.

Marcello


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## steamer (Sep 6, 2011)

Additionally, if you have an accurate arbor, or a piece of ground stock that you can put in a 4 jaw and tram it, you could put an indicator on the toolpost and up against the bar and see if we can measure what's going on.

Dave


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## Jasonb (Sep 6, 2011)

Looking at the Grizzly manual teh gear on teh end of the leadscrew is retained by an Allen socket screw, either drive this with a hex driver or replace with a hex head bolt and use a nutdriver or socket, thats a non invasive way of cranking the leadscrew by hand.

One other thing I was pondering, if the OD of the leadscrew has minimal runout but what about the root of the thread could it be possible the leadscrew deflected while the thread was being cut?
 Would need something narrow on teh end of teh DTI to measure but worth a try.

J


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## Mosey (Sep 6, 2011)

Seems to me that as this is a new lathe, and you have eliminated user error, it is a problem of the manufacturer, and should be given to them to solve. What I mean is that you might inform them of the problem and ask them to fix it. if it means their replacing or repairing the machine, so be it.


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## Lew Hartswick (Sep 6, 2011)

Are the bands always the same pitch? 
Have you tried it with a center in the tailstock supporting the work? 
You should be able to see the tool or compound move when that happens it's big enough. 

That is a perplexing problem.
  ...lew...


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## 90LX_Notch (Sep 6, 2011)

Something has to be causing a change in the velocity of the carriage in relationship to the spindle rpms.

I would check for excessive endplay on the lead screw as well as excessive backlash in the halfnuts. Another thing to look at is wheather or not the halfnuts stay fully closed as the carriage travels along the bed. If there is slop in the lock cam for the halfnuts, they will open slightly as the carriage encounters heavier forces. This would explain the collars. As the carriage stalls the tool dwells and cuts deeper. Then, as the carriage moves it creates a high spot. My Atlas 618 MKII had such bad slop that the carriage wouldn't move. I was going to make new halfnuts, but when I really looked at the problem I found wear in the cam lock for the halfnuts. I made a new one and changed the centerline distance to increase the travel of the halfnuts when closed. 

Also, it could be something as simple as the belt slipping. That or there is flex somewhere, but I would think that would give chatter or a bad surface finish (pulls, tears, etc.).


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## wannasteam (Sep 6, 2011)

Thanks a lot for such interest in this problem. I am very impressed by the assistance you have given.

Ken: That is EXACTLY what I'm getting. Does it go away if you manually feed with the saddle wheel? How about turning the leadscrew by means other than the gears?

Marcello: I will try your suggestions on the weekend. I will rig something up on the gears end of the leadscrew and drive it with a battery drill and see what happens.

Dave: Another idea I have is to mount 3 lasers on the toolpost pointing in X Y and Z axis and shine the lasers on the walls and ceiling. That will amplify any movement and maybe that will give me a clue. I'm not sure what this will tell me but it would be interesting to play around with this. 

Lew: Yes they are the same pitch as the leadscrew. I agree...this is certainly a head-scratcher. :-(

Jason: I'll take the saddle/leadscrew assembly apart on the weekend and report back. Notch's idea about the camlock is interesting, thanks.

I bought this unit from an ebay store based in Adelaide, South Aust and returning the unit is not an option as the freight costs involved would far outweigh the benefit. I want to try to fix this problem with everyone's help and maybe help someone else with the same prob.

I am sure that by taking a systematic process of elimination, we will find the solution...As Dave said "We will leave no stone unturned" 

(I wonder if I will get the same banding if I turn a stone) :big: :big:

I'll try to do a few things this evening but I'll leave most of the disassembly stuff until Friday and hopefully get some positive result.

In the meantime, keep the letters coming folks! 

Cheers and thanks again.

Joe


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## wannasteam (Sep 7, 2011)

I hope I'm not violating forum rules by placing this link to another BBS forum but it might be of interest. If I am, mea culpa, mea culpa, mea maxima culpa.

http://bbs.homeshopmachinist.net/showthread.php?t=36425

Consensus seems to point to a bent leadscrew. I'll take mine off this evening and check it carefully.

Cheers

Joe


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## Ken I (Sep 7, 2011)

Joe, it goes away if I feed manually - but only on finishing cuts, wierdly I am also getting banding on face cuts.

I was also incorrect when I stated that its definitely leadscrew pitch - its not !

Since I am trying to diagnose this I have started to consider everything.

I now realise that my lathe is a lot noisier than it was when new and has a cyclic vibration to it - the periodicity of that vibration matches (I think) the banding.

I am begining to suspect spindle bearings.

Since yours is a new lathe I would not think this to be the case - but then again I have seen brand new bearings with brinelled or corrosion pitting of the raceway.

The amount of noise this can kick up is amazing, I once changed my car's gearbox mainbearings in an attempt to cure a serious noise/vibration problem - the wear/pitting on the bearings was almost nothing but it turned out to be the culprit. 
I had a similar experience on a brand new industrial fan unit - the supplier (tried to say it was normal) would not change them - I said I would pay if there was nothing wrong - this thing was screaming like a banshee - again it fixed the problem and again the pitting was so microscopic it was hard to believe it could have caused so much noise.

New bearings can be brinelled (dented) by rough handling / installation and corrosion pitted by temperature swings causing internal condensation or by induction due to rotation in a magnetic field (as occurs in unshielded electric motor bearings).

I'll let you know what I find.

Regards,
      Ken


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## wannasteam (Sep 7, 2011)

Hello Ken



			
				Ken I  said:
			
		

> Joe, it goes away if I feed manually - but only on finishing cuts, wierdly I am also getting banding on face cuts.



Yours is even weirder than mine is!  

I take it that you have powerfeed to the y axis? You might be on the right track with that cyclic vibration you describe as it seems to affect both axes.

My lathe seems to run pretty smoothly but I'll disengage the drive to the spindle and see if I can feel any roughness there.

Cheers

Joe


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## Omnimill (Sep 7, 2011)

I apologise in advance. But not related to your problem Joe, your lathe looks like it's NOT variable speed - maybe belt change? Anyone know if this type of Lathe is available in the UK?

Sorry for butting in ... :-\

Vic.


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## Ken I (Sep 7, 2011)

Joe, I have powerfeed only in the Y axis - not crossfeed - thats what made me think its not powerfeed related and made me look at the pitching of the bands which appears (hard to tell for sure) related to the up/down harmonic vibration.

The lathe didn't used to vibrate and nothing is bent or out of line - so I stripped my headstock this morning and am popping out to get new bearings all round.

Can't say that I feel anything wrong with them but experience has taught me that doesn't mean much.

http://www.homemodelenginemachinist.com/index.php?topic=15669.msg160811#msg160811

I busted the cast iron locknut and posted a caution.

Ken


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## wannasteam (Sep 7, 2011)

Ken, what a shame about the locknut and thanks for the heads up. How would you suggest to undo it without busting it...for those that live by the big hammer ;D



Vic...variable speed drive is the next project. Having one on the mini lathe sure spoilt me. ;D 

 ;D ;D ;D ;D

Eureka!!!

I think I found what's causing this banding thing.

I took the L/screw off to check for straightness. No prob.. .003" TIR in the middle. So put it back on and went to the gears compartment and tried to figure a way to spin the L/screw (without unscrewing the allen screw) with a battery drill when I checked the tightness of the L/S by turning the L/S gear with the halfnuts engaged. 

Hmm...that felt a bit tight so I gently lifted up the halfnut lever just a bit to take some tension off the l/s and it smoothened out. :idea:

Tested it with a light cut on some steel and voila! No bands!

The halfnuts were a bit on the tight side and were binding with every turn of the L/S somehow, which would explain the pitch of the banding being the same as that of the leadscrew.

Without delving into the innards of the saddle, I can't tell whether the nuts are in fact too tight or if there is a mis-alignment between the upper and lower half nuts or something. It might be caused by the cam lock mechanism but that is to be investigated on the weekend.

I hope this helps someone else with the same prob.

Cheers

Joe woohoo1


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## Ken I (Sep 7, 2011)

Joe, Glad you got to the bottom of your problem - now I have to get to the bottom of mine. I've been living with it for some time but your thread finally got me off my Butt to do something about it.

I wasn't hitting the nut to get it off - simply using it to protect the thread while hitting with a copper hammer to drift the shaft out of the bearing. Ah Well.

As regards the split nut alignment mine were out back to front which was only a case of adjustment - but they were also out up/down and to fix that I needed to machine a bit of the apron.

Let's see if new bearings cure my problem.

Ken


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## 90LX_Notch (Sep 7, 2011)

I was in the process of writing up a detailed explanation for this problem when I lost it. I'll make this brief for now and when I get time I'll go further into detail. My lathe started producing the dreaded bands after I crashed it due to my own stupidity. The cause is play in the halfnuts when closed. The leadscrew acts as a plane/wedge and raises the nut(s) open slightly as the carriage encounters resistance. Then, the halfnuts close up tight until the leadscrew opens them again. This causes the carriage to move with a jerky, but consistant pattern. The pattern translates into the bands as the carriage jumps forward.

-Bob


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## steamer (Sep 7, 2011)

Cool!

QED!

Dave


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## 90LX_Notch (Sep 7, 2011)

Dave,

What's QED?

Bob


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## around (Sep 7, 2011)

"Q.E.D. is an initialism of the Latin phrase quod erat demonstrandum, which translates as "which was to be demonstrated". The phrase is traditionally placed in its abbreviated form at the end of a mathematical proof or philosophical argument when what was specified in the enunciation  and in the setting-out  has been exactly restated as the conclusion of the demonstration.[1] The abbreviation thus signals the completion of the proof."

Cheers,

Adrian


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## mklotz (Sep 7, 2011)

Adrian,

You really should identify the source when you quote from Wikipedia or others.

We don't want to get in trouble with the big guns.


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## 90LX_Notch (Sep 7, 2011)

Adrian,

Thanks for the explanation. However, in my case ironic applies better! I sure didn't want to prove my original statement by messing my own lathe up. Especially when I was .001 from the target dimension on a deep hole that I was boring. But as fate would have it....

Bob


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## arnoldb (Sep 7, 2011)

Good to see you got your lathe sorted Joe Thm:


 Q.E.D. = "Quite Easily Done"; easier than Latin which is all Greek to me :big:

Kind regards, Arnold


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## steamer (Sep 7, 2011)

Actually Arnold...I like your translation better! :big:

Glad it worked out!

Dave


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## wannasteam (Sep 7, 2011)

To the collective wisdom: Please accept my appreciation and gratitude for all your help and advice.

Now that we've discovered the cause, the hunt goes on for the solution.  

I'll dismantle the saddle and have a look at the halfnut cam mechanism and see if there is anything obviously amiss.

Bob: How did you eventually uncrash your lathe? I might be able to take some more ideas to my shed for the weekend.

Ken: I'm glad I motivated you to do your bearings. If you get a minute, would you please describe what mods you did to get the halfnuts sorted on your lathe?

I'm thinking that these adjustments will be self-evident when I dismantle the apron but I'd appreciate a heads up. Thanks



			
				Ken I  said:
			
		

> As regards the split nut alignment mine were out back to front which was only a case of adjustment - but they were also out up/down and to fix that I needed to machine a bit of the apron.



Cheers

Joe


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## 90LX_Notch (Sep 7, 2011)

Joe,

I kept adjusting the fit of the half nuts and lead screw until I got it moving smoothly. Put an indicator on the bed and have the plunger against the carriage. Run the lathe, and as the carriage travels, impose a load against the carriage with your hand (safely) and see if a jump occurs on the indicator. If one occurs you'll have to play around with how the nuts lock up on the leadscrew.

Bob


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## Ken I (Sep 8, 2011)

Joe, On my lathe the apron "hangs" under the carriage on 2 x M8 cap screws - the clearance holes are elongated in the X (crossfeed) axis - so some adjustment front to back is possible.

The half nuts run in a dovetail and are opened and closed by a rotating cam so the up down position is not adjustable.

You could change it down by putting shims between the apron and the carriage (between the joint held by the M8 caps) - which I have seen on this model lathe.

Mine needed to go up.

One method would be to rebore / bush the hole that the cam runs in to raise it - but in my case I noticed my rack & pinnion handweel drive had a lot of lash - enough to allow me to skim the top of the apron to raise both the half shells the amount required and improve on the rack / pinnion lash.

I measured the error by dial indicator on the screw - by closing the half shells and measuring the deflection - repeated at 180° from high / low leadscrew positions (bow in leadscrew) and averaged it out.

I also checked at the headstock, centre and tailstock extents of travel to make sure the leadscrew was paralell to the bed - which it was. (If that was out you would have to rebush the tailstock end leadscrew bush to correct whatever the X & Z errors measured out to be.)

Another problem that developed as the machine "aged" - the lever/cam mechanism that operates the split nuts has no detent and relies on the cam going overcentre - this developed a habit of coming out of engagement - a PITB when turning but a disaster when screw cutting. I installed a "friction washer" under the lever - but with this teardown I am going to look at adding a spring loaded detent ball / detent for the cam.

Since your lathe is new - if there are "fundamental" errors in its construction maybe you should make it your suppliers's problem.

Hope this helps.

Ken


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## bob ward (Sep 8, 2011)

I had a similar surface finish problem on a new generic 14 x 40 lathe. If I hand cranked the carriage I got a nice smooth finish on the job, using the power feed the finish looked very much like that in the OP's pictures. I couldn't figure out the problem so I got the lathe suppliers out to have a look.

I forget the details now, this was 2 years ago, and the solution is quite counter intuitive, but what they did was replace the cross feed screw and nut and the problem no longer existed. YMMV


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## wannasteam (Sep 12, 2011)

Hello all

Ken: Thanks for all the info. It sounds like you've done a lot of work tweaking your lathe. I guess I am fortunate enough to not have had those problems on my 7 x 12. 

Apart from the standard mods, mine worked pretty well out of the box.

Bob: Replacing the cross feed nut and screw was definitely counter-intuitive. 
I would have thought that the problem was with the main power feed screw.

Here a few pix of how I solved my particular banding problem.

Firstly, the picture is not flipped. The lathe has the leadcrew lever on the left side of the saddle and the wheel on the right. The model sold by Grizzly (my original pix) is the other way around. Hmmmm...I wonder if this is because we drive on the left side of the road here. scratch.gif

First thing I did was to remove the lower part of the saddle to see what was going on inside there. Nothing unusual so I nipped up a couple of gibs and oiled everything. 

However, I noticed a hole kinda in between the 2 gib adjusters. (see pix) and noticed that it was tapped 6mm. I put a 6mm setscrew in it and lo and behold, it was a stop screw for the cam lever! Adjusting this screw allowed me to adjust the "tightness" of the half nuts. Kinda the same effect as slightly lifting up the cam lever. After a bit of trial and error, success! See pix of final result.

This seems to have solved the banding. Yay!

Another thing: I had to elongate the holes fixing the bearing block at the tailstock end of the leadscrew to relieve the tension on the leadscrew when the half nuts were tightened when the saddle was over at that end. The end of the leadscrew wanted to lift up about another 2mm.

On a different note, I also added one of those racheting handles to operate the carriage lock.

I hope this helps somebody else out.

Cheers

Joe


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