This is my first lathe and I am having trouble with using a cut-off tool. I usually am cutting of mild steel, although I've tried stainless, brass, and some junkyard shafts. The diameter ranges from 6" to 1". On almost every cut I have the cut-off tool popping at times and chattering at other times. All of my cuts look as though I used a machete and chopping motions while the lathe rotated. I have made sure the tool is 90 degrees to the work, that the tool meets the work at or just below even with the center, and that everything is tight. I have broken a few cutoff tools, and once hit the wall over 20 feet away with the broken piece. (Yes, I wear safety glasses). I am using a tool by Wholesale Tool (wttool.com), page 156 of their latest catalogue. It is a "P-Shaped M-2 cut off blade". Specifically, the P4 - 5/32X11/16X5. I flood the cutting area with oil. I have tried almost every speed on the lathe - roughly 150 to 450 RPM. My lathe is a Reed-Prentice 16X54, and the toolholder is an oriental Alorix knock-off. I've used a new 15" four jaw and a 8" three jaw chuck. What do I check/change?
Your best bet is a carbide insert. Costs a bit more but the results will be sure to satisfy. The tool holder has a blade with a notch on the end the insert presses into and can be replaced by popping out with a tool included. These inserts have a geometry with folds the chips, making them smaller than the groove being cut. It makes for a free cutting action and prevents chips from building up in the cut.
try making your cutoff cut wider than your tool before your cutoff groove gets too deep in the material. for example, poke your cutoff tool into the material .025, then move the tool over about .050 then go another .025, then move back and poke in another .025 so your groove is .050 wider than the tool to allow relief so the material doesnt pinch the tool. also use lots of cutting oil and make sure your tool is sharp.
if you can use a saw instead, It would probably be better
I'm not familiar with the Alorix, is it ridgid? Carbide is the answer I'd bet if you have the ridgidity. I use a big-assed QC post with as short as possible carbide cut-off tool, very slow feed with flood oil...and it still scares the crap out of me. I prefer to saw! That Reed-Prentice is a WONDERFULL chunk of iron! I thought I had the only one. Would you have a book on it?
This is the first thing Id do. The "popping and chattering" indicates to me that something is seriously loose or the machine isnt rigid enough..so running it on the opposite side of the machine tends to tighten things up on a sloppy floppy lathe.
The centerline issue is also something that may cause this.
What kind of lathe is it?
Gunner
The aim of untold millions is to be free to do exactly as they choose and for someone else to pay when things go wrong.
In the past few decades, a peculiar and distinctive psychology has emerged in England. Gone are the civility, sturdy independence, and admirable stoicism that carried the English through the war years . It has been replaced by a constant whine of excuses, complaints, and special pleading. The collapse of the British character has been as swift and complete as the collapse of British power.
All of those suggestions help. Turning the blade upside down sounds counter-intuitive, as it seems as though it would be far less rigid, but it's worked for me. Maybe it has something to to with the chips clearing the groove more easily.
Upside down and on the Backside of the lathe, not the front.
Here is something that may help, from a gent (God rest his soul) that really knew his shit....
formatting link
Sound advice from Richard..to which I would add this:
Most people treat the pre-ground HSS parting blades as a finished tool, ready for use. It is NOT! No more than a ground, square, HSS tool bit is a ready to use tool.
Parting tools NEED side clearance. This must be ground into the blade before use. When re-sharpening has reduced the length of useable blade below the radius of the piece to be parted off..start again! Snap or grind off the short end and regrind side clearance on a new section. Fer Chrissakes..new blades are cheap enough to buy!
Lets belay all this crap about whether the blade should be at, above or below center. ANY and EVERY lathe tool should be set at dead center height..PERIOD. If you get better results by not doing so..you are doing something WRONG and need to re-examine the geometry of your tool bit.
Unless you are parting off SMALL diameters, and wish to reduce or eliminate the center "Pip", the nose of the tool should be ground SQUARE to the body. Any angle to the nose will, invariably, deflect the blade to one side, during deep cuts..resulting in binding, rough finish, non-flat surfaces or breakage.
More importantly, an angled cutting edge produces a chip WIDER than the slot..how the hell do you expect this to escape freely from the cut? Better, even than a square grind, is a slight radius, or as I use a broad "Vee" shape to the nose..This flows the chip in on itself, producing chips that are noticeably narrower than the cut and which clear the slot easily. If you want to add belt to suspenders, use a tiny mounted point to grind a shallow, radiused groove LENGTHWISE in the top face of the tool. Examine a carbide, inserted parting tool tip, to get an idea of the best geometry to achieve.
Chatter is reduced by INCREASING feed! Power feed will give best results.
Rigidity of the entire set up is next to Godliness! Lock all slides not in use.
Normal cutting speeds are the rule..Reduce ONLY if your rigidity is suspect.
Reduce overhang to a minimum..both in the tool setup and the workpiece.
Avoid Lantern type tool posts and Armstrong tool holders like the plague. Especially the angled parting tool holders..the worst abomination ever foisted on unsuspecting machinists. If you can't afford a rigid tool post..MAKE one!
Rear mounted toolposts have definite advantages..Deflection of the tool or workpiece tends to lift the cutting edge OUT of the cut, rather than forcing it deeper...this by dint of the geometry involved. Mounting the parting tool upside down, in the front tool post, and running in revers, has the same effect. This same arrangement works wonders with broad form tools too.
Part off as close to the chuck as possible.
If a long overhang is unavoidable, or the parted off piece is relatively long..use GENTLE pressure from the tailstock to prevent whipping and chatter. Remove this just before final breakthrough or you may get a jam up. Judicious use of a fixed steady, a wedge of wood 'twixt toolpost and job, or, (dare I say it,) a well lubed hand, (NO GLOVES PLEASE!!) will also help to reduce chatter in these circumstances.
Lubrication is a MUST except on free cutting brass and MAYBE good grades of grey iron.
Drip feed or flood lubrication..matters not. Just bear in mind that a happy parting tool sounds like frying bacon. The instant it starts sounding grouchy..add more lube.
Happy partings..
8^)
teenut The aim of untold millions is to be free to do exactly as they choose and for someone else to pay when things go wrong.
In the past few decades, a peculiar and distinctive psychology has emerged in England. Gone are the civility, sturdy independence, and admirable stoicism that carried the English through the war years . It has been replaced by a constant whine of excuses, complaints, and special pleading. The collapse of the British character has been as swift and complete as the collapse of British power.
I also tend to answer letters before they're finished. I have a photocopy of the manual from the people at the Yahoo Reed-Prentice user group. I don't know if there are any left. We have been bantering around the idea of getting it on the 'net so all can have one. Just haven't found the perfect avenue yet.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.