[gdl357]

Hi guys, I just received my 4" 4-jaw chuck. I am getting some vibration when i go to speeds higher than 500. The jaws are placed even. Wondering if the backplate they supplied is off, or maybe the chuck. Is this normal. My 3" 3-jaw was vey smoothe. A little worried. The chuck is " FUERDO" bought from LMC.



thx

[Ken_Shea]

Do you see any wobble ?

I have seen these loaded to the gills with grease inside, may need cleaning.

[gdl357]

I unscrewed the backplate and rescrewed, it got better. Still wobbles a bit. It is cleaned well.
Taking me forever to center a 1/2 round bar. When I put my dial to the edge ov the chuck right before the adaptor plate I get a .003 displacement. 3 lines on the dial. Bad?

[Ken_Shea]

.003 is not bad, unless you need .0005

Actually, that is not bad at all. Give the jaw a extra snug at the high point and that may even come out.

Look for burrs, dings, metal chips, anything, on the back of the chuck mount holes, the face plate, and where it mount to the lathe, I bet you have a problem there. Maybe take some 600 grit paper and sand a little bit on the faces.

Looks to me like this is another job for the "SUPER MINI HAMMER"

[gdl357]

*****Update*****
Got the 1/2 centered at less than .0005 (barely moving) Good enough I guess.
It is now .0005 (barely moving) off at the adaptor edge. All i did was snug the 3 nuts to the spindle and tap at the high point with a tiny brass hammer and kept on doing that till the needle stopped moving. Then tightened up the nuts an ther u go. No shake what so ever! Now I'm Happy.

Ken_Shea I really thank you for always helping me. I hate it when I don't know what I am doing.

:cheers:

[Ken_Shea]

Glad I am able to help, if you did not do what I suggested or you did and the wobble is still there you need to get that taken care of or you will be fighting this forever.

[Ken_Shea]

In thinking on this it may be profitable for you to explain a little why it is so important to have a true running no vibration chuck.
1) Vibration is tough on bearings
2) Vibration is tough on cut finish
3) Vibration is tough on the tool cutter edge
4) If vibration is caused by chuck wobble then, for example, if it is wobbling .003 the chucked part will also wobble and the further it stick out the greater the wobble will be.

If you have a true running chuck, and say your bar is chucked up tight and it is .003 offset then that is what it will be at 1" or 6", assuming the bar is not bent

Ken

[gdl357]

Turns out I have viration between 700 and 800. From what I am told this is due to Harmonic vibation. At one point any machine with any heavy chuck will have a point where it vibrates due to harmonic vibration. Fix, just go past the speed and it will stop.

[HuFlungDung]

The error of the chuck mounting on the backplate itself should be zero runout (ya Ken, so I'm fussy ). The backplate should have been machined to exactly fit the recess in the back of the chuck, such that no amount of tapping with a hammer would ever move the chuck at all! That's how us professionals do it

After you've got more experience under your belt, you might redo the chuck mount some day. Just mount the backplate on the thoroughly cleaned spindle and machine it right on the machine it will be used on. You might have to face off the existing boss if its too small, or de-centered. There's usually ample thickness to the backplate casting so you can take a couple of stabs at it.

[gdl357]

I think the backplate is machined to exact fit, there is no play there. The problem is the studs that are slightly smaller than the holes in the spindle. That's where the excess play is.

I talked to Micro Mark Tech support. They said it is that way and that you always have to dial in the chuck once you remove and place it back again. Its all part of the setup on these mini-lathes, he said. Anyways I don't plan to take this chuck off as I will do all my work on a 4-jaw. The 3 jaw will never be this precise.

Right now the needle is moving a distance of the thickness of the needle itself, which I think is way less than .0005. On the chuck and on the workpiece. That is super for me. The Micro Mark Tech also told me that if the chuck was reading at .003, it would be considered very good. They accept and ship machines that have original 3" 3-jaw chucks reading up to ".020" !

So my setup will be ok for a noob like me.

:cheers:

[gdl357]

Well, Chris from little machineshop gave me a great tip today. The reason I was getting lots of vibration at certain speeds (700-900 & 1200-1300 & 2300-2400) is because the adaptor plate has 2 x 1/2" holes that are for hooking up a 3-jaw chuck. They are at one end of the adaptor, which is what was causing the viration. He told me to plug the holes with a brass plug. Sure enough, it worked. It is now super smooth from 0-3060 rpm. Also the needle on the dial is moving by a hair. Now I'm Happy. This 8.5 lbs beast better get ready for some major machining.

Great tip. thx