Banding on turned work

[MWParticipant @mw27036]

Posted by Phil P on 04/01/2017 13:08:26:

I then grabbed hold of the saddle and found I could rock it slightly (I am talking a few thou at most)

So I cleaned everything and re-adjusted the saddle gibs and the banding problem disappeared instantly.

Phil

Yep, unfortunately it's a problem that's caused by frequent use rather than infrequent unfortunately, so you're getting punished for your labours ​. But very common, I had the same problem (keep consciously avoiding the word issue out of context) and that's what I suspect is happening here, it's just a case of loose gibs which inevitably happens because it's not designed to be a perfect fit, and needs to be continually readjusted over time. In some manufacturing lathe manuals they recommend this check once a week. Which you might expect if you ran it eight hours a day.

This is why I suspect these myford experts wouldn't have found it, because the fit changes over time, if it really was as dire as a spindle error, I would hope they'd see something like that immediately.

Until we get an update on the situation then I think we've notified him quite thoroughly.

Michael W

 

Edited By Michael-w on 04/01/2017 14:21:44

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bazyle on 04/01/2017 14:09:30:

By 'not helecial' what do you mean? Are they bands going all the way round and repeating every 1/8 in as the leadscrew pitch?

.

Bazyle,

I think that was Frank's direct answer to my question:

[quote]

Frank … Could you just confirm, please:

are these individual rings, spaced at the leadscrew pitch?

… or is it a continuous helix?

[/quote]

MichaelG.

[old AlParticipant @oldal]

Is your tool sharp and at centre height. Do a facing cut on a bit of spare stuff. I recon the tool could be a little too high.

[John HaineParticipant @johnhaine32865]

Well, no leadscrew is going do be absolutely concentric, so if there is any play in the saddle gibs the eccentricity will produce a minute in-and-out movement of the saddle, at a rate of once per leadscrew revoultion.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by John Haine on 04/01/2017 15:57:43:

Well, no leadscrew is going do be absolutely concentric, so if there is any play in the saddle gibs the eccentricity will produce a minute in-and-out movement of the saddle, at a rate of once per leadscrew revoultion.

Yes, I had exactly the same problem on my Atlas when I first had it. Tightening the saddle gibs cured it but then there was binding at the tailstock end so some judicious scraping was required. Bed wear is always greater where the tool is near the chuck.

Russell

[brickyParticipant @bricky]

Thanks for all the helpful suggestions,I will look into these and try to find the solution.The tightening of the gibs seems like the place to start.The fitters had the saddle off and I presume cleaned out the half nuts.It turns accuratly over the full length of the bed,so solving this would cheer me up no end.

Frank

[AjohnwParticipant @ajohnw51620]

Posted by John Haine on 04/01/2017 15:57:43:

Well, no leadscrew is going do be absolutely concentric, so if there is any play in the saddle gibs the eccentricity will produce a minute in-and-out movement of the saddle, at a rate of once per leadscrew revoultion.

I'm not so sure as neither lathe I have had with this style of bed has had this problem. The raglan wasn't that sensitive to to gib adjustment. The ML7 was. Tightening everything up for some drag improved it a lot. No repetitive rings on either.

I've since found that slideway oil can help as well. It probably helps reduce clearances and also tends to hang around for some time.

Interesting to here mention of Atlas. Not popular for some reason so often cheap. An owner of a 10" described it as a Myford on steroids and the bearings can be changed. Not sure if that is true on all of them but he did get excellent work out of it.

John

–

[Gordon Brown 1Participant @gordonbrown1]

I had a similar problem on my ML7and it turned out to be due to axial play in the spindle, allowing it to move back and forth ever so slightly. Tightened up the left hand end and that sorted it. I checked it by putting a dial gauge plunger against the end of the chuck and giving it a bit of heave ho along the spindle axis.

[Martin ConnellyParticipant @martinconnelly55370]

This shows concentric banding on an aluminium alloy part cut with 0.2 depth at 35mm/min using a 0.2mm radius tip insert 800 rpm. You can't feel the banding and the lighting has to be just right to see it which is why the photo is lop sided. It polishes out with very little effort using some well used scotchbrite. The banding matches the cross slide lead screw pitch. I have not polished the part since it needs further work in the mill which will remove a lot of the face showing the banding.

Martin

Edited By Martin Connelly on 04/01/2017 19:18:17

[John ReeseParticipant @johnreese12848]

I had an old Pratt and Whitney lathe that did the same thing. I figured the badly worn bed and saddle increased the distance between the rack ant the feed gear. I assumed the banding was due to irregular feed due to improper gear engagement.

[HopperParticipant @hopper]

I've had banding like that on my old clapper and cured it by tightening up the headstock bearings. It might be worth putting a dial indicator on the spindle and check for movement with a 12" bar held in the chuck and grasp the end of the bar. Check/adjust both radial and axial play if needed.

Never assume that because something has just been overhauled/checked by the experts that it is 100 per cent OK. Nobody is infallible.

[Nigel McBurney 1Participant @nigelmcburney1]

As the band matches the leadscrew pitch,it must be the lead screw deflecting the saddle once per rev of the l/screw,to confirm this mount a dial gauge on the saddle with the indicator pin running on the vertical face of the rear bed shear,I would expect a very small kick on the dial hand every rev of the screw.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Ajohnw on 04/01/2017 17:41:04:

Interesting to here mention of Atlas. Not popular for some reason so often cheap. An owner of a 10" described it as a Myford on steroids and the bearings can be changed. Not sure if that is true on all of them but he did get excellent work out of it.

Not sure that I would describe it as a Myford on steroids but the 10" model is a very similar design to the 7 series Myfords and is a bit more substantial although the earlier US built models had a poor die-cast top-slide. The headstock bearings were always Timken tapered roller bearings and are still available, or at least were a couple of years ago. They were built in the UK under licence during, and for a few years after, WW2 and used for munitions work.

Russell

[AjohnwParticipant @ajohnw51620]

I think he saw it as mostly no need for the gap and easily changed bearings Russel. That style of bed is suitable for some one to do a light skim regrind on as well. Underside of the saddle too. Putting it all together probably a better option for a real refurb than either of the myford 7's mainly down to the bearings. The general geometry of the lathe may differ to them as well. That can change all sorts of things.

If anyone does start playing with pre load on dual taper roller bearing do take care. Really tiny adjustment of the nut make a difference. Go too far and the bearings will be wrecked pretty quickly. Mine took several adjustments to settle down. It pays to check for heat as well when the lathe is running at max speed. That can take well over 10 mins to reach it's max. I don't run my Boxford at max speed. I find there is no need. Somehow I doubt if it's possible to get one setting that is perfect for both but might give it a whirl at some point. I find the opposite to what some state at times – even super low cutting speeds get rid of problems.

John

–

Edited By Ajohnw on 05/01/2017 11:45:51

[Adam PhillipsParticipant @adamphillips50363]

If you take a look at Lathejacks album Chinese torture he had the same problem and fixed it with a modified worm bracket . I have the same thing happening on my Warco 918 and am in the process of modifying the worm bracket with 2 thin ball bearings. There are several design on the file section on the 9×20 Yahoo forum. The banding I get is quite regular and happens at all speeds and feeds infact I can hear the motor sound change tone when the band appears on the turned surface

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Adam Phillips on 05/01/2017 17:35:21:

If you take a look at Lathejacks album Chinese torture he had the same problem and fixed it with a modified worm bracket . I have the same thing happening on my Warco 918 and am in the process of modifying the worm bracket with 2 thin ball bearings. There are several design on the file section on the 9×20 Yahoo forum. The banding I get is quite regular and happens at all speeds and feeds infact I can hear the motor sound change tone when the band appears on the turned surface

.

Useful reference, Adam … although it took me a while to find the relevant photo.

**LINK**

Reply To: surface rust on lathe ways

I must, however, mention that Frank [bricky] has a Myford [with saddle feed provided by the leadscrew] so the suggested fix is unlikely to be relevant in his case.

MichaelG.

[Maurice Cox 1Participant @mauricecox1]

I've come a bit late to this thread, but it might pay you to examine the pinion which engages with the rack. It was very worn on my S7, unknown to me, and ridges had formed on the teeth which caught on the crest of the rack teeth as the saddle was traversed toward the headstock. This caused a brief drag on the saddle followed by a jump to the left which generated rings on the work. A brief test of this would be to "help" the hand wheel to rotate while the self act is working, just enough to take up the backlash. See if effects the problem. Mine was cured with the purchase of a new gear cluster for the apron. While waiting for it to come, I had a length of cord tied to a spoke of the hand wheel then wound anticlockwise onto the shank of the hand wheel, with a small weight tied on the end and allowed to dangle, to take up the backlash, and keep the worn teeth away from the rack. It did get in the way a bit, but I was able to use the lathe while I waited.

Maurice

[Maurice Cox 1Participant @mauricecox1]

At the start of my post I should have said" traversed toward the headstock by self act". Sorry.

Maurice

[Carl Wilson 4Participant @carlwilson4]

Someone told me Myfords are made in China now. Is that true?

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Carl Wilson 4 on 07/01/2017 13:00:42:
Someone told me Myfords are made in China now. Is that true?

Some parts of them are but then that's true of nearly everything.

Russell.

[MWParticipant @mw27036]

Posted by Carl Wilson 4 on 07/01/2017 13:00:42:
Someone told me Myfords are made in China now. Is that true?

Apparently they aren't producing lathes at the rates they used to. I think they sell the odd one or two every now and then but they focus on spare parts rather than production.

The bed castings are made in china but they are machined here in the UK.

Michael W

[Steamer1915Participant @steamer1915]

I had experience of this many years ago on my S7 and I can do no better than repeat Phil P's post verbatim.

Best regards,

Steve.

[HopperParticipant @hopper]

Could it be the halfnut adjustment? See the below file from the Myfordlathes Yahoo group, note the last paragraph re banding:

Myford ML-7 Half Nut Adjustment.
When re-fitting the saddle to the apron you will need to adjust both the saddle to
apron fit and the lead screw half nut adjusting screw.
1. First unscrew the half nut adjusting screw right out.
2. Move the apron as far to the right as it can go and engage the clasp nuts – it
will be tight.
3. Undo the screws securing the apron to the saddle and these two parts will
self align.
4. Nip up the screws and then tighten the screws.
5. Move the apron to the mid point along the bed and engage the clasp nuts.
6. Hold the lever down with your left hand and screw in the adjusting screw
until it stops, then take your hand off the lever and screw it in a further ¼
turn.
Note: If you do not adjust this then you may get tracking marks when
taking fine cuts – these will be at 1/8 inch? The lead screw pitch?
With thanks to Keith Higgins, and Malcolm from Myford.

[Maurice Cox 1Participant @mauricecox1]

I would still urge the examination of the gear in the apron, that engages the rack on the front of the bed. I have not measured the pitch, but it looks close to 1/8", and when my gear was worn it had ridges across each tooth, that caught on the tips of the rack teeth as the saddle was traversed by the lead screw. and produced bands on the work as the movement of the tool was briefly delayed.

Maurice

[Andrew Moyes 1Participant @andrewmoyes1]

I have a 2001 big bore machine too. After attention to the headstock bearings, the results have been excellent, much better than my previous ML7. There’s no reason why Bricky’s lathe shouldn’t be the same.

If the banding is at leadscrew pitch, it’s almost certainly induced by the leadscrew. Any leadscrew of ¾” diameter held at 2’6” centres is likely to have eccentricity in the order of a few thou. That shouldn’t translate to the work if the saddle is correctly adjusted even if the half nuts are 'tight on'. So I’m in agreement with those who have suggested readjusting the saddle.

I had trouble with the workpiece diameter not tracking the cross slide DRO reading. I traced it to a slightly loose saddle. I mounted a DTI on an extension to the left, clamped in the toolpost with the DTI touching the workpiece. Having adjusted the saddle as per normal instructions, I forcibly rotated the saddle clockwise and anticlockwise viewed from above and was surprised by the movement seen on the DTI. To take up the last few tenths of a thou, I had to rotate the outer gib adjusting screws and locknuts as one using both a spanner and screwdriver. That eliminated all movement, consistent with the saddle being free to move of course. It made a noticeable difference to the accuracy I was able to achieve and the finish. It’s worth a try.

Andrew M

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