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Super 7 patterns when turning

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Ron.p24/06/2009 19:49:19
9 forum posts
I have been suffering regular patterning when turning for some time I have tried many things to overcome this problem which seems to be about one eighth pitch. So now I have replaced the leadscrew and nut  stipped down checked everything ! and still see this pattern. Can anyone please advise me the     definitive way to set the machine up? 
Many thanks  Ron
Graham Horne24/06/2009 23:10:25
14 forum posts
Just a thought, doesn't cost a lot, try clamping a heavy weight on some part of the machine and seeing if the pattern changes. There may be a resonant vibration.
Someone once told me to lean on the tailstock when power feeding between centres and watch what happens to my carefully set-up machine. Anything is possible.
Ron.p25/06/2009 08:15:45
9 forum posts
Many thanks Graham I will give it  a try
Philip Rowe25/06/2009 10:15:10
248 forum posts
33 photos
Some years back I had a very similar problem, but only really visible when facing on brass - it was there with other types of cut and materials but not so prevalent.
Anyhow, lots of experimenting with tool angles, heights, speeds, asking advice even from Myfords, I eventually cured it by replacing both the drive belts.
My clue was the fact that the lathe had been standing unused for around 2 - 3 years and the belts had developed a "set" where they had been in contact with the pulleys and it was this that was creating some kind of resonance which in turn produced the patterning.
Hope this is of some help.
 
Phil
David Clark 125/06/2009 13:13:18
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3357 forum posts
112 photos
10 articles
Hi There
Try feeding towards the tailstodk.
Do you still get the same result?
regards David
 
Ian S C25/06/2009 13:24:55
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7468 forum posts
230 photos
Change from ordinary v belts to link belts ie nu T Link orPower Twist,this should help,try one belt at a time.It may also help if you can isolate the motor from the bed of the lathe with rubber packing(oil proof),if your motor is single phase these can cause vibration to a greater extent than 3ph.Good luck Ian s c
Ron.p27/06/2009 08:04:14
9 forum posts
Posted by David Clark 1 on 25/06/2009 13:13:18:
Hi There
Try feeding towards the tailstodk.
Do you still get the same result?
regards David
 

 Yes the pattern is not visible when cutting towards tailstock, what would the reason be ? and can the problem b e solved   many thanks . Ron

David Clark 127/06/2009 08:24:41
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3357 forum posts
112 photos
10 articles
Hi there
I would think that you have wear or slack on the carriage causing it to oscillate back and forth.
Have you adjusted the front gib strip?
 
If this does not work and you have a mill, you could lightly skim the edge nearest you and the middle edge. Make sure the carriage is set square on the mill before doing this
I believe most Myfords were run on the front of the bed.
 
I did this once a long while ago.
Can't remember the reason other than a lot of wear was present and the lathe bed had been reground so was perfect.
 
I used a small cutter so I only took material of the front and back, not the top face that runs on top of the lathe bed. You might need to pack the front gib afterwards with a bit of shim at the front.
regards David
 
Ian S C28/06/2009 11:23:24
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7468 forum posts
230 photos
If you can get MEW no8(Dec Jan 1992),there is quite a good artical called Chasing Vibrations by Bill Morris.It has a photo of the pattern generated on a bit of steel,and it shows the soft packing and bushings used to isolate the motor from the lathe.Do one thing at a time,and do the reversable things first before you start machining the saddle etc.Ian s c
Robbo28/06/2009 22:06:28
1504 forum posts
142 photos
If you can't get hold of MEW No 8 (they weren't numbered in those days but) email me and I'll send you a copy of the article, it's on;y 11/2 pages.    Is your motor not fitted with a resilient mounting with the rubber bushes on the endplates?   
kneedeepinswarf29/06/2009 16:13:49
3 forum posts
Hello,
Is the lathe motor a resilient mounted type? If not, you can get a pattern on the work due to motor vibration. Single phase motors do not turn smoothly but in a series of steps, known as cogging, which can cause the problem you describe. I had this problem with my ML10, which was immediately cured by replacing the motor with a resilient mounted type.

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