I am having trouble after installing my QCTP. I used the lathe and a 4 jaw chuck to cut the t-nut for this new setup (just faced the plate down and then cut the sides with a band saw to fit). Other than the old toolpost slipping, and not having the correct angle holder it worked fine. These are the reasons I am replacing the tool post, I was apparently using mis matched stuff and was missing some shims. I know NOTHING about being a machinist, but it was working fine before and now it seems to be going crazy. I have some steel rod that I have been turning down just practicing on and I was cutting nice little spirals of material off, and leaving a fairly decent finish, now it seems like I am making ez-outs! Thats what it looks like anyway. Also the machine is making a chattering noise, the headstock seems as tight as new, and nothing seems to have changed. I still dont have the machine bolted to the floor (keep forgetting to grab a concrete bit), but it wasnt before either! I made new tools, more correct tools, tried using some tools with carbide cutters, tried different speeds ETC. I have no idea what to do next. Maybe something has slipped in the 3 jaw and it has a lot of runout, I guess maybe I should try to find a test bar. Any ideas? I will try to take a picture of what I have going on.
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Having trouble after QCTP install.
- Thread starter jtb51b
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- Mar 19, 2014
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If you just changed the tool post. Then maybe the new tool post did not get secured properly? Maybe it’s still lose? And please STOP that chatter testing…PLEEEEEEASE! You could easily damage other parts of your lathe with that kind of improper cutting, thank you, Dave.
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Also make sure that the top of the t-nut is not clamping to the tool post. The tool post should clamp down tightly to the top of the compound rest. Pull the t-nut up with the tool post bolt and see if it protrudes above the top of the compound rest. If so, it needs to be machined until it stays below the top of the compound rest. It sounds like something is loose and not rigid in your tool post mounting.
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I will check it out, I did check for shaft protrusion prior to tightening and had none, Thought I checked the t nut center height also. The tool post is VERY tightly mounted to the top of the compound. it seems like the workpiece is no longer running true, I checked with a magnetic base holding a dial indicator and it confirmed that the bar is NOT turning true AT ALL. Could my 3 jaw chuck have gotten out of whack just by threading it off the spindle shaft? I didnt drop it or handle it roughly, just removed it and layed it aside to use the 4 jaw. I would love to stop this chatter testing, trust me..
OK, went and checked the toolpost mounting, it is VERY tightly mounted to the compound, the shaft does NOT protrude, the t-nut does NOT touch the bottom of the tool post. I may have found the problem, I gave everything a good shake and the carriage moved--a lot.. Somehow the bolt that tightens the carriage to the ways (I believe this can be used as a lock?) had been backed off a couple TURNS. I tightened it back down to where it should be and we will see later this week what that does for me. Who knows how that happened. FYI the 3 jaw does still look to be not running true, I will tackle that problem next I guess..
Thanks for the quick help!
Jason
Thanks for the quick help!
Jason
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- Oct 31, 2015
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The bolt on the saddle that lies just to the right of the cross slide is the carriage lock. It should be loose unless you want it locked. If that's the bolt you're talking about, it's not the cause of your chatter.
Check the tightness of the cross slide and compound gibs.
Check the tightness of the cross slide and compound gibs.
That is the bolt I am referring to, it was VERY loose. and when its very loose so is the saddle. I ran it down just until it took the slack up in the carriage. Your saying that this bolt is either ON or OFF basically? It should ONLY lock the saddle down, not provide any adjustments? Reason I ask is because if so, something is wrong and I need to be looking for the correct place to adjust that.
Jason
Jason
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Hi Jason,
If your bar did run true, then you removed and replaced the chuck and the bar is no longer running true, then I would suspect a some debris on the threaded spindle nose or on the chuck internal threads. Perhaps a chip is not letting the chuck plate seat squarely on the spindle nose shoulder.
Are you using a tail-stock centre? It might help. Sometimes the jaws of the 3 (or 4)-jaw chuck get worn to a taper. They then only grip over a small contact area. It is called bell-mouth. The pressure of your cutting tool can push the work backwards, as the lathe rotates the work it keeps getting pushed backwards, and actually can work itself loose from the chuck. The best solution to that is to regrind the jaws with a tool-post grinder, but certain precautions need to be taken; keeping the abrasive grit off the lathe and pre-loading the jaws.
That chatter is most likely caused by some thing loose or flexing in your tool setup. It could be anything from the tool bit, to the holder, to the top-slide, the cross-slide or the carriage. Try the shortest tool stick-out you can. Try adjusting the top, cross and carriage gibs/slides so that they just slide easily with no binding, but no slop.
What is the diameter of your test bar and what material?
What material is your tool bit?
What is your speed, feed and Depth- of cut (DOC)?
Has your tool just gotten dull and therefore can no longer cut properly?
-brino
If your bar did run true, then you removed and replaced the chuck and the bar is no longer running true, then I would suspect a some debris on the threaded spindle nose or on the chuck internal threads. Perhaps a chip is not letting the chuck plate seat squarely on the spindle nose shoulder.
Are you using a tail-stock centre? It might help. Sometimes the jaws of the 3 (or 4)-jaw chuck get worn to a taper. They then only grip over a small contact area. It is called bell-mouth. The pressure of your cutting tool can push the work backwards, as the lathe rotates the work it keeps getting pushed backwards, and actually can work itself loose from the chuck. The best solution to that is to regrind the jaws with a tool-post grinder, but certain precautions need to be taken; keeping the abrasive grit off the lathe and pre-loading the jaws.
That chatter is most likely caused by some thing loose or flexing in your tool setup. It could be anything from the tool bit, to the holder, to the top-slide, the cross-slide or the carriage. Try the shortest tool stick-out you can. Try adjusting the top, cross and carriage gibs/slides so that they just slide easily with no binding, but no slop.
What is the diameter of your test bar and what material?
What material is your tool bit?
What is your speed, feed and Depth- of cut (DOC)?
Has your tool just gotten dull and therefore can no longer cut properly?
-brino