and is from knowledge?A rear-mounted tool-post is one of the best ways of reducing parting-off chatter.
and is from knowledge?A rear-mounted tool-post is one of the best ways of reducing parting-off chatter.
Absolutely! My 8tpi even with the setscrew set tightly will come loose and make a disaster. However, I am waiting, praying and waiting for a new lathe with which I can test this rear cutoff idea out. In the mean time, some times I can cut maybe 100 thou in but I have to make a cut about half the blade thick extra, that is, I use blades about 50 thou so naturally, I needs a cut about 75-100 thou wide which virtually eliminates side friction problems. Also, sometimes, I have a problem (where I needs to eliminate all the probs spoken of above) in which I must be some how work hardening the material for it acts as if it has a tough skin. Once I gets thru the "skin" it cuts well but I have to feed faster than I would like. When I first started doing cut offs, I broke more blades than I could count (in Chinese anyway.)As stated several times above, rigidity of the whole setup is key. This is not just the toolholder, cross slide and saddle, but also the whole machine, spindle bearings, chuck and the workpiece itself.
Sometimes it is possible to reduce or eliminate chatter just by changing speed. Everything has a natural frequency and if the frequency of your setup is close to the spindle speed, chatter is more likely.
Beware of suggestions to run in reverse - if you have a screw-on chuck, it is a disaster waiting to happen.
I'm using a rear mounted parting tool blade, projecting an 1" to part off round mild steel bar 2" in diameter but am using it as a lathe tool proper as my front tool is set to cut a chamfer in a bit of 3/4" round bar- down to 1/2" round at one end and the rear tool to reduce the stock to 0.3125". Both ends are going to be tapped. The thin end- with a female 2BA thread and the thicker end M6 female .
It's for the forerunner to the Worden grinder- called the Kennet. Lubrication? Good old lard lard oil.
Ironically, both tools were by the same guy as wrote and designed the GHT Rear parting tool.
Basically, i'm merely following 'the book'
Norman
There lay the learning process. Is a fine line between too aggressive a feed and digging in and to timid a feed and scraping which result is chattering.but also by increasing the feed.
Primary importance is properly adjusted spindle bearings including preload. Solid tool & holder with “textbook” grind ( On Center ) will help you get the best results. Good luck.What advice can you give me
I have a Drummond Roundbed lathe.
Discuss....
Nothing wrong with using the tailstock center, but make sure you pull it back before cutting trough. If the cut off piece is heavy protect the ways with the protector you have built. You did build a way protector for when changing chucks, did you?
The big problem : is with lots of helpers but the questioner has solved the problem yet ?
I saw some people asking questions and then disappear.
The big problem : is with lots of helpers but the questioner has solved the problem yet ?
I saw some people asking questions and then disappear.
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