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01-13-2008, 03:02 PM #1
Setting tool on centerline on CNC turning center
Several posts back someone mentioned they had a turning center and noticed the tool was .004 thousanths high. How do you determine this so accurately? On my lathe I can use a hight gage but how would this be done on a turning center with a slanted turret?
01-13-2008, 04:24 PM #2
have you tried facing off a piece of stock and scribing a line on the face with the tool using that axis? I dont know if you will be able to see .004 thou. unless you scribe it lightly and use a comparater or something of that nature.
01-13-2008, 09:28 PM #3
I believe the post to which you are referring involved an OD threadder that was .006 or .008 below center on a small dia thread. Nonetheless, some machines can be locked by pushing a button (spindle lock) or in MDI; M110 or M19 or G28 C0. or M10, etc. Basic idea is to lock spindle and lightly scribe a line with a qualified face tool. Jog suspect tool to face and meaure from there. While I doubt the exact measurement can be made, an aprox is close enough. The Hardinge T42 Super Precision has a turret that has slots where a .75" ground bar can be mounted to set boring bars, ID threadders, groovers and such can be set so you can clamp the ID tools at any height-desired at .01 above centerline. Most slant beds require a line to be scribed on the face of the set-up part and tools set from there. That method is close at best.
01-14-2008, 02:23 AM #4
If I thought I had a problem that would require measurement of turret position, I think I would make a block with an indicator attached that I could set on a surface plate and set with gage blocks then transfer that indicator block to a tool slot and indicate over a test bar of some sort at each position, otherwise checking the tool holders with the insert on a surface plate would show if holder/insert had a problem. But facing something off to a tit and comparing is all I have done so far, and not very often. Someone told me the other day that my 3 year old lathe has less than 10% use on it and I have never smacked it, so I just mostly assume everything is OK.
01-14-2008, 10:01 AM #5
I take the practical approach.
I start shimming untill ot's right.
Might not be the "Mathmatical" method, but it works
01-14-2008, 10:27 AM #6
I measure the pip, then divide in half and use that size shim.
01-14-2008, 10:32 AM #7
there is a tool
Mori at one time made some kind of a tool to make sure the tool was on center. Everytime I help set a job up my operator mentions it because he thinks Okuma should make the same thing so we don't have to eyeball things, or bring a tool down to the tit. I would imagine you could buy something somewhere. I had the same problem the other day with a live tool drilling at an angle so that 180 degree holes were like .150 off. If anyone finds anything for sale please post!
01-14-2008, 11:05 AM #8
My Lathe came with a button that I insert in the turret then I install a dial in the spindle chuck and dial myself on the button in the turret until it read zero sometime it take longer than other. Even if your turret wasn't crash it doesn't assure you that you are dead center.
01-14-2008, 11:41 AM #9
Checking Turret Centerline
First you need a coaxial indicator mounted in the chuck. Using the indicator sweep a ID pocket on the turret; bringing the turret to spindle centerline. Then sweep down on the pocket this will tell how high/low the turret is. Anything over .003" should be adjusted for by turret radial alignment.
Turning tool height should be checked by surface plate and height gage. I have found that the reason for leaving a tit on the part was due to the tool being cheap and the height being off .005' to .01".
01-14-2008, 11:49 AM #10
It may help if you say what kind of turret it is. VDI to Inch holder can be a bit different when centering.
01-14-2008, 11:55 AM #11
Hi turn a dia set tool at x0.0 & z0.0 then with depth mic measure from o/d down to your tool sould give you half the dia.
01-14-2008, 02:04 PM #12
Use a magnetic base with a .0001 indicator and check the tool slot on the turret, run it back and forth in X axis to make sure the turret has not been whacked. You decide how accurate you want it, I think .003 is way too much, I would want no more than .0005. You could also check the machine accuracy report to see what it was at the factory. A co-axial indicator is fine for checking a diameter, ID or OD, but not accurate enough for .0001 and certainly not good to check a linear surface.
01-14-2008, 07:50 PM #13
Thank you all for your posts, I should clarify a point or two. I own a Haas toolroom lathe so I can check the hight with a hight gage, no problem. However I have operated some CNC lathes that were slant bed or vertical slide and the only method I have used was to face the part and shim until the tit was gone.
With some people talking about measuring the tool I was wondering how this was done. The same question applies if you have a small boring bar or other small tool. I understand sweeping the tool holder pocket but the tools I have seen are not always exactly centered.
I was just wondering if there was some geewiz way that I had never heard of before. Thanks again for your responses. If anyone else has a different approach I would still love to hear it.
01-14-2008, 07:57 PM #14
If the turret pockets are indicated in straight, but they are either all low or all high and the boring bar holes are also high or low, then the head needs to be moved. On a slant bed with an adjustable headstock, moving the head rearward will raise the tools in relation to the spindle and moving it forward(toward the operator) will lower the tools. This is assuming that the head and turret are in parallel alignment already.
01-17-2008, 01:15 PM #15
Adjustable head stock.....? Please explain more. I've never paid attention to the head stock...just the turret and slanted bed and slide...and never saw any adjustments there.
My tools are all off...due to a crash...I've been shimming ever since. And...I've been programming to remove the taper in Z.
So, the head moves....OMG! I never thought about that. I've got to figure this out...no more taper...no more mis-aligned tools. It's a happy day!!
01-17-2008, 08:03 PM #16
Rob - since it's turning a taper, it safe to assume the the headstock got knocked out of line. You manual should show you where the adjustment points are. I'm sure someone else can describe this better than I, but here's the basic process. Adjust the head until a test bar held in the chuck or collet is turned to the same diameter over it's full length (same as a manual lathe). Then indicate your turret square to it's travel, and indicate the bottom of the tool slots parallel to their travel. Try to indicate the boring bar holders concentric with the spindle, see if they are all high or low. If so, place two dial indicators against the headstock, one at the spindle end, one at the chuck actuator end, and zero both. Now move the headstock evenly at both ends inward or outward until the boring bar holders can be indicated true with the spindle. IF everything is perfect, the bottom of the tool slots will now be 1" below the spindle centerline. Nobody has perfect machines, so you may need to compromise on the adjustments, or shim a few holders occasionally.
01-17-2008, 11:12 PM #17
Here is a link for a tool I came across a while back. I havn't gotton one yet, but it looks like it might be a quick way to get your tools on center. They say it is a "precision" level, but again I don't have one so I don't know how accurate it is.
sorry--don't know how to post a picture.