Super 7 patterns when turning

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Super 7 patterns when turning

This topic has 11 replies, 7 voices, and was last updated 29 June 2009 at 16:13 by kneedeepinswarf.

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24 June 2009 at 19:49 #42028
Ron.p
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@ron-p
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
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24 June 2009 at 19:49 #4701
Ron.p
Participant
@ron-p
24 June 2009 at 23:10 #42034
Graham Horne
Participant
@grahamhorne65034
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.
25 June 2009 at 08:15 #42037
Ron.p
Participant
@ron-p
Many thanks Graham I will give it a try
25 June 2009 at 10:15 #42039
Philip Rowe
Participant
@philiprowe13116
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
25 June 2009 at 13:13 #42040
David Clark 13
Participant
@davidclark13
Hi There

Try feeding towards the tailstodk.

Do you still get the same result?

regards David
25 June 2009 at 13:24 #42041
Ian S C
Participant
@iansc
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
27 June 2009 at 08:04 #42057
Ron.p
Participant
@ron-p
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
27 June 2009 at 08:24 #42058
David Clark 13
Participant
@davidclark13
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
28 June 2009 at 11:23 #42081
Ian S C
Participant
@iansc
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
28 June 2009 at 22:06 #42091
Robbo
Participant
@robbo
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?
29 June 2009 at 16:13 #42097
kneedeepinswarf
Participant
@kneedeepinswarf
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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