bad finsh

[JT.]

bad finish

dit some testing and i got a strange finish on my metal .it is like a
wave (i saw identical finish before over here but i can not findthe post)
vibrating finish

the same finish if you do a long tube and you got vabrations in the part

but my lathe does it even on small parts 1"out the chunck ore between centers
i tried diferend cutters, other speed other feedspeed
i can not feel any play on the main bearings no special play on apron ore compount
it get wors if i increase the feed ore the amount ore cutting dept

 

[Pitchfire]

Carriage lift/banding from power feed/bent leadscrew?

 

[Mike Gibson]

This might be the thread you are looking for. http://www.hobby-machinist.com/showthread.php/6263-What-causes-this-finish-on-6061-aluminum

 

[Richard King]

What brand machine do you have, is it a Chinese machine? Did you buy it new or used? Have you eve run another machine? What's your experience? If your new to running a lathe, do you have a friend or teacher who can stop by to help? Do you have a mag base dial indicator? Chuck up a 1" shaft. Then put your spindle speed in lowest rate. Put the mag base on the compound and put the indicator on the shaft on tailstock end of shaft and turn on machine and feed the saddle as if you are taking a cut. Be sure the spindle speed is slow as if you run the spindle fast the indicator will vibrate very badly.
See what happens. I would suspect your chuck could have some trash under it, the spindle bearings are loose, your tool bit is sharpened wrong or not centered. Something is loose.
Check it out and let us know.

 

[JT.]

it is a sheldon 10x56 (army truck style)

i am a maintenance mecanic (formaly car mecanic) doing al the lathe work on my job for years now
spend many many hours practicing on a lathe
got a mag bases dail indicator no problem
tried about everything low speed/ high speed above center on center below center etc
HHS cutters /indexible cutters etc
got no play on the spindle (that i can feel )
i will try your methode

when taking realy shalow cuts it is only visible on the part you can not feel the waves anymore
but when cutting 0.05 ore so you can realy feel the waves

 

[JT.]

This might be the thread you are looking for. http://www.hobby-machinist.com/showthread.php/6263-What-causes-this-finish-on-6061-aluminum

looks about that
i will check all the stuff in the post
motor vibrations definitly there( i need to leave the door from the engine cabinet open do a resonace noice from the lock ) and also not enuff tension on the belts


the compound was broken when i bought it i grinded it off and put on a big plate but there is 3/4"missing from the base
i got a replacement compount in the mail

 

[Richard King]

looks about that
i will check all the stuff in the post
motor vibrations definitly there( i need to leave the door from the engine cabinet open do a resonace noice from the lock ) and also not enuff tension on the belts


the compound was broken when i bought it i grinded it off and put on a big plate but there is 3/4"missing from the base
i got a replacement compount in the mail

View attachment 44012

If your having that much vibration, solve that problem before anything else. Also check the repair compound and see if it is flat with a straight-edge and feeler gage. If new ground compound it is high in middle or convex the tool could rock where the turret mounts. Heating the compound to weld no doubt has warped the compound too.

 

[ScrapMetal]

looks about that
i will check all the stuff in the post
motor vibrations definitly there( i need to leave the door from the engine cabinet open do a resonace noice from the lock ) and also not enuff tension on the belts

Yes, figure out what's causing the vibrations but also get proper tension on the belt as maybe the combination of the two is causing a bit of slippage.

Just a guess, good luck!

-Ron

 

[JT.]

spend a few hours on the lathe testing al the above
had some play on one of the V-belt pulley tighting the allan screw toke care of that
still same vibration sights
tighen up al the V-belts GRRRRRRRR no diff.
to mutch play on the appron ???
took the appron off and notished nothing broken ore weared out so back
on the lathe filled up the oil and the appron worked way more smouth with some oil in
(i lubricated all the points but dit not notised that there is a sort of reservoir in the appron )
i quickly give it a go but nope still the same problem
tried with the feed in 3-4 speeds reverse feed manual feed always the same signd
so the problem was not in the feeding system
dissembled the crossslide and the compound cleand everything took aut the lash as mutch as possible and
took away all the play with the gibbs .
still the same problem
n the main bearings no play
put some more oil in the mainbearing cups
spinned the lathe and the oilniveau from the main bearings stopped half way the cup
added some more and saw it dropt to half in a second
filled up the cup and again it dropt imidiatly
had to fill it up several times till it stayed on top in the cup
yes i think the problem was lack of oil in the main bearings have some oilspills comming out of the bearing now so i now
they are well satuated an lubricated
give it a go and YES!!!!!!!!!!!!!!!!!!!!!!!!!!! the waves are gone finish is smooth like butter
1"SS tube on the pics (same part , diff angle from pic)

 

[Richard King]

A few things I noticed. 1) If you skipped the vibration in the motor you still have an issue. The motor problem has to be fixed before you can tackle a issue. Take the belt off the pulleys and turn it on and see where the vibration is or is it gone? Your motor could be loose where it is mounted, the motor needs to be insulated with rubber pads on some machines. The motor shaft could be bent. Check it with an indicator and not eyeballing it. Look at the pulley, are the V grooves smooth and the same pitch angle? Many worn pulleys have a step in the V. Inspect your belt for cracks and broken areas.

2) Looking at the part, there seems to be a ridge at the end of the cut on the left . before you feed with power move the tool into the part manually. move into the part and slowly by hand and check 2 things, do you feel a change in the vibration, does it get worse? Now stop feeding and turn off the spindle not moving the cross-slide or saddle. Please check the tool where it meets the right edge with a magnifying glass. Use a flashlight to really look good. Is there a ridge? If there is the tool is dull or the rake is not steep enough. Or the top of the tool is not angled steep enough and "dragging" on the bottom and not cutting from the top of the tool. One last thing. The finish isn't all that bad. Maybe your expecting a "ground" finish that can't happen on a lathe.

The bottom line for me is you have to repair the motor vibration issue before I can help anymore. If your ignoring something obvious and "wishing" it will run OK with the vibration, your dreaming and jumping ahead of yourself. If oil is running out the spindle, you have the oil level to high or the seals are bad. If you have a friend who can come over and watch, I am a firm believer in the old saying, "2 heads are better then one".