Parting tool help

Alex Alto

Alex Alto

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Not sure if this is the place to post this, so please feel free to move it...
I use hss cutters exclusively (tried some ebay bonded carbide but couldn't get used to them).
I can cut a few useful profiles, but every parting tool I have tried to make fails miserably, including one bought from a toolmaker.
I predominantly use cold rolled steel, but either the cutters are just the wrong shape or the machine isn't powerful enough.
All I get is the start of a cut, then chatter and the machine sometimes grinds to a halt.
I have a QCTP fitted to a 1950s Australian made Advance 7x20 lathe.
Any ideas on how to sort this issue?
 
Make sure you are on center. If your to high they seem rub and if too low the cutter digs in. Use a good amount of lube. Don't go to fast. Make certain your cutter is square to the chuck.

In my limted experance sometimes it takes a fair amount of pressure to get started cutting good chips then I back off just a little too keep it cutting good chips.

Tim
 
Making sure the cutter is ON CENTER and perfectly perpendicular is NO JOKE. Close doesn't cut it on smaller machines. I use an indicator to make sure I'm exactly 90 degrees to part, nothing else is close enough. .002 above or below and all hell can break loose. Plenty of cutting fluid and start around 180 rpm, maybe faster if your part is small diameter. I remember noting but problems early off, now I do nothing but Ti and SS with no problem. (I use carbide inserts however)
 
Does you cross slide have the extra T-slot in the rear? If so then you can use a rear mounted parting tool back there and eliminate all your parting woes. This has been done for decades on many smaller lathes and Myfords in particular; they also have that slotted cross slide top similar to the Advance design. I would definitely look into rear mounting your tool.
 
mikey said:
Does you cross slide have the extra T-slot in the rear? If so then you can use a rear mounted parting tool back there and eliminate all your parting woes. This has been done for decades on many smaller lathes and Myfords in particular; they also have that slotted cross slide top similar to the Advance design. I would definitely look into rear mounting your tool.
Click to expand...
Yes, there's actually 3 T slots on the cross slide of this machine. I'll have to look into rear mounting a parting tool for it... Hopefully that will fix it! Cheers.
 
Funny, everyone here stress on center. I will go below center ( steel ) on a small bench lathe. No one mentioned to go side to side opening up the groove, so it doesn't get jammed on a deep cut. On small lathe, I don't try to be a hero and part off a 2" or bigger piece. Only have the tool out about .800.
Used my saw to complete, then face it off. Sound like you have a lite duty lathe ? Inserts on a 5,000 lbs machine won't give you the same trouble.
 
Practice, practice, practice. I don't fear parting at all, but I used to. I part with the tool on center, or slightly below, but the big things, imo are getting the tool perpendicular to the chuck and then figuring out your feed. Your feed should likely be faster than you think - if it's not cutting a continuous ribbon, you're probably going too slow. Getting a 'feel' (assuming you're not using CNC) is probably the most important thing. I generally use HSS (because I can get a thinner kerf) but once you have it down, the same techniques work for carbide as well.

GsT
 
Like others said, on center and dead nutz 90 degrees to the work. Also important is a taper on the tool for relief or chips will bind the tool up when the cut gets deep. Make sure the tool is vertical as some holders taper to match a factory tool taper and some don't.
 
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