Poor surface finish

[blowlampParticipant @blowlamp]

Still looks like chatter to me – as I said before, try turning some different metals with sharp tooling.

Martin.

[Chris TriceParticipant @christrice43267]

Try turning it at a much slower speed. If you've got slack in the saddle allowing .010" to .015" of movement, you need to seriously adjust your gib strips and/or feedscrews.

[WALLACEParticipant @wallace]

What’s it like if you manually feed ? I’m not familiar with your lathe but my l5 has a rack and pinion drive on the saddle that can be used to take cuts – the trick is to always keep one hand on the hand wheel so it’s always moving at a consent speed with no stoping.

If that’s ok, then it’s something to do with the feeds – and I’m still thinking a gear that’s been bored off centre somewhere…

Chatter you can usually?hear – I once bored out a 3″ diameter stainless bar and that rang like a bell – continuously !! I’ve generally found that chatter produces a finer pattern but that could be dependent on the lathe, tool geometry, speed etc etc so wouldn’t guarantee it…

W..

[Nigel McBurney 1Participant @nigelmcburney1]

I dont know how experienced you are,but I would suggest you try to find a really experienced turner for a second opinion ,if they cannot get good results then I think that you should dump the lathe on warcos doorstep stating that the machine is not fit for purpose, the tailstock height difference is a fault that should reject a lathe, I googled the lathe type and it appears tp have a vee and flat bed,a saddle traversed on this type of bed should not cause any of the deflection described particularly when traversing by hand .

refering to the comment on chatter and ringing when turning thin tubular shapes, this will occurr on any lathe,its the nature of the bell like shape, the work needs some vibration damping applied, during my aprenticeship I was making some 3 inch dia micrometer drums in brass . I bored them out ok but when turning the od and the taper where the numbers go it really sang and vibrated ,foreman showed me what was apparrently an old trick,fill up the Inside Dia with a thick greasy rag and ram it tight with a screwdriver handle ,vibration ceased, Of course depending on the job ,internal chatter on a thin bore is more difficult to cure ,a damping material can be clamped on the outside dia, or a larger piece of material used,bore to size,vibration should not occurr with the thicker wall material ,then turn the od to size.

[Chris TriceParticipant @christrice43267]

I turned up some rocket engine bells (non working) in aluminium and the ringing was deafening when boring them. Two thick rubber bands wrapped around the outside killed most of it.

[Martin CottrellParticipant @martincottrell21329]

Hi all,

Well, after more investigating today I think I have finally nailed the problem and as I suspected it is motor vibration that is causing the problem. I started by repeating the previous experiment but removed the motor drive belt to eliminate the gearbox drive train and spindle bearings from causing the vibration. The vibration was still just as severe when the motor was started so as I final trial I slackened off the motor retaining bolts so that the motor was no longer securely clamped to the back of the lathe bed. On starting the motor again there was no vibration and the DTI needle stayed motionless as I traversed the saddle along the bed. I refitted the drive belt with the motor still loosely mounted, refitted the 3 jaw and chucked the original test material and took a test cut using the same tool, speed, feed and depth of cut as before and to my relief obtained what I feel is a very acceptable finish! The image above shows the original poor finish with the improved finish on the smaller diameter using the same tool & settings as described previously.

I shall now contact Warco again on Monday and see if I can extract a new motor from them!

Regards, Martin. ( no longer p***ed off!)

[Neil LickfoldParticipant @neillickfold44316]

A part from motor vibration, also check the simple things like the pulley running true on the motor. On my lathe I had to bush and rebore the pulley. I have a piece of ruber between the motor and mount plate . I also have some rubber washer made also to help it become isolated. Now I can have the motor running and the dti does not move on the work piece.

I also changed the one piece belt to a segmented belt. When it comes around to replacing the current head stock belt, it will be replaced with the segmented belt as well.

My lathe had a problem with the adjustment of the 1/2 nut alignment on the lead screw. I put a dti on the screw and adjusted it , so the screw was not pushed in an up or down position. This did help over all .

Neil

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