Articles

Article about problem solving. 

Strange Noises?

When ever you are in the workshop and turn on a machine and hear something strange then it is likely all is not right and needs investigating!    As you might expect until you accurately identify the cause of a problem the solution cannot be implemented.  This may sound trite but often I jump to the wrong conclusion too quickly and blindly attempt to resolve something that is totally unconnected with the real problem and even make things worse!  I think this is a curse all of us have to live with as it is so easy to jump in without adequate thought or proper investigative analysis.  This happened very recently to me with the acquisition of my new lathe, a Warco BH600G. I was a little disturbed when a strange ‘ticking’ noise occurred and progressively got louder as time went on.  My immediate thoughts were a faulty motor, probably influenced by reading odd forum comments about the quality issues with imported motors.  I then reflected that the motor on my imported band saw had suffered terrible conditions having been soaked on more than one occasion yet had refused to die after some 25 years of abuse.   My experience from past dealings with electric single phase motors told me it must be a loose plate inside which holds the starter mechanism but the noise was very cyclic and seemed to originate from other places as well.  I was maybe trying to over-convince myself this was the case since having spent so long installing the lathe close to the back wall, removal of the motor was going to be a tricky and painful exercise and even more so if it then turned out not to be faulty!  It then occurred to me that a  similar ‘ticking’ noise had happened on the milling machine (yet another Chinese import with 3 phase motor) and that was because the pulley keyed to the motor shaft by two grub screws had come loose allowing the pulley to oscillate and thus the resultant noise.  Yes, that’s it, but on checking both grub screws were very tight.  The next thought was the surrounding wires, metal guard plates and bits that were possibly being ‘caught’ as the pulley or belt revolved and I then thought about the ‘fix’ I had made to enable the motor to be easily raised for belt changing, but again after looking around, everything was as it should be and the annoying ‘ticking’ continued.  It must be the motor because everything else had by now been eliminated I convinced myself, but the thought of removing it was not popular as I had since injured my left arm and that would be needed to extricate the motor from its platform as it is very heavy, especially so at arms length. Reluctantly,  I resolved to pretend the noise was of minor concern and train myself to block it out of my hearing.  Unfortunately, I am not that easily satisfied and whilst I enjoy problem solving I hate to give in especially as every time I start the lathe it reminds me how inadequate I am! A few days went by and the ‘ticking’ continued and by doing so continued to annoy me!  I decided to start again and analyse the problem more carefully and decided the best approach would be to properly identify the real source of the noise.   By starting the machine I went about isolating the noise source and it soon became evident it was not the motor as the ticking was only heard when I looked down from the saddle area towards the motor but looking from either end of the motor the noise was considerably less, so this revelation absolved the motor of all blame.  So what the hell was it?  The back gear was not connected but even when engaged the noise was just the same and the counter shaft was completely silent which left the only other area the spindle and output gear train.  The latter was easy to check by disengaging all the gears.  The spindle was more of a problem to check and I dreaded to think about the consequences.  But the spindle was the only part left that rotated and so it must be the bearings - oh no not the bearings please no!  I placed my ear close to the back end bearing seat and rotated the spindle by hand and could hear the tick on each turn and then moved to listen at the chuck end and the noise was even louder - that’s it - the roller bearings are faulty!  This was not good news as I did not want or expect to strip down the bearings which had probably only a few hours running but it seemed I had no choice and so wisely, as it turned out, decided to leave it for a few days.  This tactic is one often adopted when all else fails as I hoped miraculously it would self heal.  Unfortunately not and since I was not keen to start stripping the spindle I listened again this time more closely to hear exactly when and what possibly could cause the ticking noise as I decided even a broken roller or even worse a missing roller in the bearing would on slow turning reveal its identity.  Whilst doing this I realised I had not checked all of the rotation parts and the one forgotten was the chuck which, of course, was fixed to the spindle end.  I removed each of the chuck jaws but still the ticking continued however by placing my ear close to the chuck body it was a joyful moment as it came obvious the ticking was from within the chuck body!  With chuck back plate removed the innocent looking scroll cover plate, a cast iron disc which has little purpose other than to stop swarf from getting into the scroll was loose!  The three attachment screws were very sloppy and the plate was rocking back and forth with what now was a joyful ticking sound and after tightening silence ruled once more.  Every now and then, the problem is new and from an unexpected source, proving there is always more to learn.  Total investigation time many,many hours, fixing time 10 minutes!

Other problems

Another related story about my new import lathe and resolving a problem, which I thought was inherent in the design of a typical import machine.  I mentioned before, knowing that the fitting of parts from the Chinese made machines often leaves a lot to be desired I re-scraped the cross and compound slides.  Prior to doing this remedial work the sliding surfaces showed the so-called scraping marks but in practice these were of no value whatsoever!  It takes time and some basic skill to blue a surface and scrape the metal to produce a flat surface which when mated to another flat surface will glide across with a ‘silky’ feel yet maintain a very accurate location and this is the ‘real’ purpose of the scraping indentions.  The aim is to have a flat surface to provide oil retention between the mating surfaces at random places such that the oil thickness is of almost microscopic thickness yet still effective in the task of providing essential lubrication.  This is what I call flat for sliding parts but certainly not flat for other, different purposes which, by design may require more accuracy.  This became very evident to me with the new import lathe, when I machined the end of a 2” diameter mild steel bar the finish ,whilst good, showed a rippling effect as though an image had been printed on the machined surface.  The ripples were of microscopic dimension but evident in the light reflecting and so, once again, jumped to the conclusion this was due to the roller bearings in the headstock!  Because this problem was of academic interest I thought little about trying to resolve it as that would probably entail replacing and using a higher grade of bearing which would probably cost more than the lathe!  It was some time later I removed the QCTP and was admiring the superb ground and blacked finish to the base of the main body that fitted on the compound.  Yes it was another Chinese import but I have to say of very high standard regarding the hardness and ground finish and yes the bottom surface was very flat!  Looking casually at the compound surface where the QCTP was fixed it showed some obvious machining marks which were either from milling or I rather suspect, rough grinding, but did imply that the surface had been machined for flatness.  Another wrong assumption again!  Checking the actual flatness revealed it was way out to such an extent that my small reference surface plate rocked about showing probably 1 or 2 thou. variance across the surface!  After a fair bit of scraping and bluing the surface was made flat not to very precise flatness but at least now the QCTP base would touch for at least 60% across all corners and edges.  Job done and next time I surface cut a 2 “ bar from the same stock using the  same cutting tool the surface finish was both flat and had no rippling effect even when examined with a light and eye loupe. That was the solution to a problem that never existed in the roller bearings but also a lesson that if a surface is designed to be flat then check to make sure it is as flat as required and never trust machine or scraping marks which often are done to imply quality but sadly do not live up real useful purpose.  It is so often assumed by seeing those beautiful artistic curled scraping marks that this demonstrates very high quality and precision but in reality few, even expensive quality machines, are scraped so artistically as the skills have been lost as machines are now capable to do these tasks better and cheaper.

GWH Engineering

creative engineering in a home workshop