View Full Version : parting tool problems
08-17-2001, 01:40 AM
I don't even try to part off to the center anymore. I always stop when the tool gets to between .1 and .18 diameter depending on the size and length of the cutoff piece.
You are more likely to encounter problems when going smaller if your tool is not exactly on center. What's left you can wiggle and break off. This method also ensures that the cutoff is not going to get whacked by the jaws. If it is a threaded work piece being cut off the stock then it is definately the preferred method so as to not ding the threads.
One other benefit of carbide inserts is most are formed with a cup shape. This makes the curled chip narrower than the groove that it is cutting. I have never seen chips jam up using them.
08-17-2001, 01:57 AM
I just looked at the post that i just did a minute ago. Twilight Zone http://bbs.homeshopmachinist.net//eek.gif . I guess I'm a time traveller now. It also didn't go to the front of the list either.
Maybe I should hurry out and get a tank of gas. http://bbs.homeshopmachinist.net//biggrin.gif
this is 2004 isn't it? http://bbs.homeshopmachinist.net//eek.gif
08-17-2001, 04:55 AM
Looks like the site has been repaired.
[This message has been edited by suprdvn (edited 04-21-2004).]
10-02-2001, 04:56 PM
I am having problems setting up my parting bar. I have sharpened it the way they tell me in my book, but the tools just seems to overheat and get dull. I have a bunch of chater and the tool seems to taper itself, so the tip becomes norower then the shank. I am turning my work at approx. 870 rpm. Any sugestions as to what i might be doing wrong?
10-02-2001, 06:33 PM
Make sure the blade is on center and at 90* to the shaft. Your speed is way too high. Slow speed and cutting fluid work much better.
I use a carbide insert cut off tool set dead center to the work with only enough blade extended to part the work. Sixty RPM and the occasional shot of cutting fluid give me the perfect chip looking like a little toilet paper roll.
You may be overheating your bit when grinding it. For HSS an Aluminum Oxide soft bond (H) open structure wheel 80-120 grit grinds much cooler than the wheels supplied on most grinders. These wheels have less tendency to overheat the HSS and draw out the hardness. If it gets too hot to hold, let it cool down then continue after cooling off.
I hope this helps.
10-02-2001, 09:23 PM
I cut off at 250 rpm all the time, maybe try 60 rpm to get better chip control.Don't be afraid to push a little hard to get past chatter stage- keeping in mind that if tool grabs it makes a speedy wreck. I went with an upside down tool holder running spindle backwards.Don't even ask me what happens if tool jams with a screw on chuck OR how I found out.
10-02-2001, 09:36 PM
Slow down your speed. I work at about 90/150 RPM and use lots of cutting oil. If the metal jams in the cut and galls you are going to break a cutting tool and maybe ruin a project. Keep the tool sharp.
10-03-2001, 02:15 AM
You could also try your travelling steady to stabilize the shaft while parting. Opening up the cut by moving the parting tool over to the waste side and starting a partial width cut can be helpful in preventing pileup in the groove.
I bet it was exciting having a big chuck unscrew when you did not expect it!! At least you did not get hurt (I hope).
The upside down parting tool should be mounted at the rear of the slide. Hardinge HLV-xx lathes have this as a optional feature. It allows better clearing of the chips and lessens the chance of binding in the parting groove. Most of the time it will stay out of your way and it can be left setup back there for when you need it. Set it so it parts the center of the work with the top slide fully retracted.
Your chucks will never loosen again as they are always run in the forward direction. This technique works with threading tools too. (old Swedish trick - I think)
Have fun - play safe...
10-03-2001, 04:17 AM
Surface speeds and feeds are sometimes the most difficult thing for a person to master.
With high speed steel I start out at about 50 feet per minute suface speed and work up, depending on steel.
Quick formula that is close is [SFPM X 4] divided by diameter = rpm this is close approximation, easy to remember.
So if you were cutting off a 1 inch part start out around 200rpm, more if leadloy, and use plenty of oil.
Yes I run a bit faster most of the time, but 50sfpm is a safe starting point to work up from, especially with big expensive drill bits.
Yes, slow it down. Also think about getting a narrower cutoff blade -- that will help reduce the chatter. Cutting oil can help. Be sure you're on centerline, and at 90 degrees to the work. If you can grind a small vertical notch in the front edge of the tool, that sometimes helps as it breaks up the chip and keeps it from jamming in the groove, especially if the groove is deep.
10-03-2001, 02:02 PM
I got fed up with HSS tools one day and went nuts buying carbide insert tooling. The parting tool was the scariest $350 - for the 1 1/4" blade, ten TiN coated inserts, and the 1" shank blade holder.
Busted a few inserts along the way, but I am tickled pink at what it can do. Eventualy I will mount mine upside down at the back of the slide so I don't have to set it up all the time. These REALLY have to be on center and at 90* to the work.
One nice feature with inserts, you can get them so that they cut the nub off completely on the right or left side depending on which insert is used. Leaves the parted piece smooth as a baby's bottom.
Carbide is truly awesome stuff...
10-03-2001, 07:26 PM
If you choose carbide the rules change. You have to run faster and control the feed rate carefully. When parting or facing on conventional lathes the surface footage will be constantly decreasing as you approach center. Therefore you will find that your feed needs to slow as you approach center. Excessive chip load can cause the carbide to chip and fail sometimes taking an expensive tool holder with it. Master the high speed first. Halfnut is right on with the 50 sfm, if you go to carbide you need to run 250 or faster for most steel, brass and aluminum will probably take all the revs you can muster. Set the tool length by putting blade next to face of workpiece and place tool holder as close to OD as practical then slide blade to a small amount past center.
10-03-2001, 08:45 PM
Nothing got hurt- parting tool just flexed about 1/8". pucker factor was about a medium,can't think of all the variables all the time. Have a 14" S.B. sure wish I could mount tool on back of slide. Upside down position has really made cutting off a pleasure.
10-04-2001, 01:49 AM
Perhaps a system like I have on my 1 1/2" x 8 TPI chucks would help reduce "pucker". My backplates have a split collar clamped by a Allen capscrew. The backplates have saw kerfs at 90* to each other to allow flexing when clamped. The collar rides on a shoulder and clamps the chuck back plate onto the spindle register. When tightened the chucks cannot be removed even with a strap wrench and much cussing. The chucks have never lossened in use resulting in a zero "pucker factor" for me.
I do agree with you, especially with your overhang statement. This is important when using any parting tool, HSS, brazed Carbide, or Cemented Carbide inserts.
Actually the recommended speed is 295-395 (SS) SFPM for insert tooling, and the infeed force should be backed off to .25x normal infeed near the center. Proper support of the work will reduce chatter and reduce the size of the pip as well. The insert is always in danger of Built Up Edge (BUE) near the center even if the insert is pushed past its limits at the start of the cut. The SFPM drops to zero as you approach the center no matter what speed you start at. These are Sandvik Coromants recommendations, not mine.
I am not in a production setting, and I do not like to run my cutoff ops at 2900 RPM with a manual lathe - I don't need that much excitement - even though in using inserts that is what I should do. I have mangled a single insert because I had not seated it properly in the blade. I have checked my inserts with a 50x microscope and do not get any fracturing, flank wear, or BUE running at slow speed with a high pressure cutting lube. It works, I have great chip control, and I am extremely happy with the results.
[This message has been edited by Thrud (edited 10-04-2001).]
10-05-2001, 04:10 PM
Thanks alot. The speed stuff is all new to me. That makes alot of sense. My blade has been wearing out and overheating. I will give that a try. I will also keep an eye on my blade when i am sharpening it. Thanks alot to everyone. I am off to give it a try....
10-07-2001, 10:30 AM
Well i am getting better. I seem to have problems cutting large pieces. Stuff over 1" in dia. I slowed my speed down to 160 rpm. At some points the work just stops dead in its tracks. Any insight as to why this is happening?
10-07-2001, 09:06 PM
You might just not have a big enough horse for the width of your cut off blade. I have stalled out my Logan many times, my Hendy with it's 5 hp and gear head just keeps cutting. You never said what kind of lathe you were running. If work is larger on my Logan I have to go to back gear and speed up belts, power transfer is more positive that way.
But if you go to a smaller width blade on deeper cuts it will have more of a tendency to wander and it will break easier.
I have parted off 4 inch material many times with carbide inserted tooling in the Clausing at work, machine has a 10 hp motor though, plenty of power and a good ridgid spindle.
Keep playing you will come up with speeds and cutter widths that will work with your machine. Cut off tools are ornery things sometimes.
10-08-2001, 01:37 AM
Don't know if anyone is interested but I'd like to share what I use with the list.
I've put a picture at:-
Not very clear as it's been cropped from a larger picture but here's a quick description.
The blade is a 16T carbide saw with 16 holes drilled in it to accept a peg to stop it rotating.
It's held by a central bolt and sleeve and the peg. The cresent shaped side plates have a small recess at the outer diameter to stop the unused tips getting damamged in clamping.
I always sacrifice the first tooth and grind it back to provide clearance as I've found that starting off with a full blade won't give enought chip clearance on larger diameters.
The face of the tip must be square and not ground at an angle. This is because although very rigid vertically it will wander off sideways if not square.
In any case I always grind parting tools square especially on small lathes because if you grind the tool at an angle the face width is wider than the groove and the chips jam up.
This tool can manage to part off 5" steel bar in a 10" swing lathe with no problem.
10-08-2001, 02:32 AM
Cool tool, dude! I have seen guys take a cheap carbide blade and cut it up into about 12 single blades - they do work well.
My insert type cut-off blade (UGHN262 & KGT2N Neutral inserts) is made by Mitsubishi and is 2mm at the tip. Produces perfect chips evertime.
If the entrance angle is off of 90* with a parting tool you get a slightly (or not so slight) curved surface.
10-08-2001, 04:36 PM
Parting tool update,
First of all i want to thank everyone for their help. I keep comming back and re-read the info. So here are some of the problems i faced, or at least solved.
1. My belts were slipping. I guess all that cuttingat 860 rpm realy uses up the belts when it jams.
2. The angle on my cut off blade was too steep. It was forcing the blade over into the wast portion of my work.
3. This was the big one. My work wasn't centered. It had about .010 run out on it. That realy shakes things up i guess. That explains why it always seemed to cath in the same spot. I fliped my work around and that cured it. I guess my work wasn't perfectly round when i put it into the chuck. I tried to reposition it a couple of time but that didin't help. I have a self centering chuck so i couldn't adjust it to make the work center. Ah the things i have learned...rather i am learning.
Next on my list....thread cutting...Oh boy!!
10-08-2001, 06:15 PM
All the normal sources sell 'feeler gauge stock' pretty cheap. Some shimming with various thickensses of that on the chuck jaws will get your work REAL close to center.
10-09-2001, 12:54 AM
your chuck should have four allen head bolts at 90* from each other to center your chuck use these by putting an indicator against the work piece and finding where you are out of center then tighten and loosen the bolts opposite of that point. This takes a little practice and patiance but is good to learn. it is the same as zeroing in on a four jaw chuck. hope this helps with that problem.
10-09-2001, 09:07 AM
Let me clarrify what toolpost is talking about, he is refering to a tru- adjust 3jaw chuck. They are adjustable a few thous. more expensive than the average 3 jaw chuck, they have 4 adjusters on the outside, dial them in kinda like a 4 jaw. Anyone out there wants to get rid of a 8" tru adjust with a D1-6 back plate, cheap I would gladly take it off their hands.
I have shimmed in a 3 jaw many times, quicker to use a 4 jaw but I have done it. Have used shim stock, paper, I keep cigarette paper in toolbox, it is about .001 thick. Handy.
You never said what kind of lathe you are running, don't be ashamed, odds are one of us is running one like it, and know the quirks of the machine.
I've ran some klunkers, and some really fine machines. Klunkers made chips just fine, just not as easy to run. Main thing is to make chips and to learn.
10-09-2001, 05:24 PM
So what you are saying is that i might need to put shims, where my chuck jaws grab the work in order to have it centered. And cigarette paper is a good substitute. Don't smoke. I don't think i have an adjustable jaw like toolpost was talking about. So halfnut thanks for the explanation. I was pretty lost there.
I own a craftex 3-1. I bought it at BusyBee machines. I don't know if they have that down in the states but there is one here in Ottawa and other Canadian cities. I know it isn't one of the best machines out there but i know nothing about machining. So i figured it was a great stepping stone. A 2500.00 stepping stone. hahah
I want to thank everyone for their advice. I come back everyday and there is always something new. Thanks guys.
10-10-2001, 08:39 AM
Not familiar with this machine, related to Smithy? I'll do a search on it for curiosity sake.
Those 3 in 1 machines, some people hate them, others love them. Sure is the cheap way to get started and learn. Take good care of it, if you get serious in this endevor of making chips I have to warn you, machines are contagious. When I started looking for machines for a small machine-welding shop back in 86 I had a terrible time of it, got a bargain on a mill, got shafted a bit on a Lathe, I learned about rebuilding on that one, turned out OK. I don't run shop full time anymore, sold my big building, have a fair sized shop at house. As I warned you, it is contagous, I have more machinery now than when I was running it full time, things just follow me home.
So when your shop gets full of other machines that are bigger faster better if you have kept this machine well, it will be resalable, then you can get another one.
But where to put it, I have a surface grinder trying to come home with me now, I could move that over there, that there, see what happens.
Have fun learning, keep asking questions, it is a learning experience for me just learning how to word things and finding these letters on this keyboard.
10-10-2001, 04:35 PM
I love trying to figure out problems. Right now the best part is going to bed and spending my last minutes awake trying to figure out how to do something. Because i am so new at this, just the basic functions are sometimes difficult. I am realising quickly that building your own parts to help you is the way to go.
I still have yet to try my mill but i am holding off on that. I figure i will learn on how to fix stuff with the lathe before i start breaking stuff with the mill.
10-12-2001, 03:23 AM
If you're using a high speed steel blade I have had the best results from grinding a chip breaker just behind the cutting edge. Don't run much slower than regular cutting speed or you are inviting tool breakage. Coolant of some sort is a must. The tool binds when chips start to weld to the cutter.
10-12-2001, 04:29 PM
I am getting the hang of the parting tool. I am sure there is room for improvement. I can do small work but big thick stuff doesn't seem to be worth it. Somehow i think throwing the stuff in the cut-off saw and then using the lathe to face it would be the best.
Maybe i am missing something. It might also be that my 3 in 1 can only do so much. Lowering the cutting speed has helped alot. I go as slow as i can, 160 rpms and no chater.
So all the info i have gotten has realy helped
10-13-2001, 03:52 AM
160 rpm, with high speed steel you are limited to 1 1/2 dia or less, maybe a little more with 12L14. And then go easy.
A parting tool sure does tell the rigidity and strength of a lathe, just takes good hoss to do parting on larger diameters. Been there done that. Just a little play in the spindle bearings and vibration from hell.
Have fun everyone.
I read on a forum somewhere that some folks use a hack saw for parting. I don't know exactly how they do t his, but it sounds like it might be good for big things that exceed parting tool ability. I asked them about the saftey aspect and they tell me it is perfectly safe, but takes a little practice. Anybody here use that technique?
04-18-2004, 12:53 PM
The only way to part with a hacksaw is with the lathe in its lowest gear and the machine TURNED OFF. Some of us have probably tried it with the lathe running but that’s like parting between centers, you’re asking for a problem. If you get into carbides then things speed up dramatically. I use carbide inserts for parting everything, I find it quicker to part off in the lathe material then using my abrasive saw (even square). My first Carbide insert parting tool was a blade I bought on e-bay with a couple of inserts. I drilled (solid carbide drill) 2 holes in the blade and bolted it to a block of aluminum as a holder. I stuck the blade out about an inch which took care of material up to 2 inch diameter. It worked great until I finally ran out of inserts (I'm looking on e-bay for more). If you have a milling machine you can mill your own holding block.
[This message has been edited by coles-webb (edited 04-18-2004).]
04-18-2004, 09:47 PM
Parting off is certainly a skill to be learned. Halfnut touched on something which has a lot to do with most all lathe operations, and that is rigidity. Do what you can to improve that, without over-tightening anything. My lathe needed some modification to keep the rear of the carriage touching the rear way. This improved things for me.
I am one of those who uses a hacksaw for cutoff. I cut a groove first, to guide the blade, then run the lathe slowly, finishing the cut with the lathe stopped. I have developed the skill to hold the hacksaw at 90 deg to the work, and also consciously maintain my grip on the hacksaw, so I don't lose control of it when it jams. I'm always ready for that, if fact, I'm expecting it to happen. I keep my grip very strongly, with the result that muscles get tired fairly quickly. I take a rest often, of course, depending on the length of time it takes to get the cutoff done. I take a stance that lets me stay out of the way of a possible projectile, yet maintain alignment of the blade in the cut. This is much like preparing to take the recoil of a rifle. When the shock load comes, it's under control. It has taken me years to learn how to control handsaws properly, so if you aren't comfortable with them, don't ever try this method of cutoff on the lathe, especially if it's running.
04-21-2004, 10:06 AM
04-21-2004, 02:16 PM
I like to cut to the Left side of the desired cut-off position (off center) about 0.01" - 0.20" to about 1/4" deep then move back to center and cut another 1/4" deep, and repeat till done. This really helps to reduce binding.
I don't have one of those carbide insert things, I don't think this would work with them (or will it?).
04-22-2004, 11:57 AM
It will work but is not necessary. The insert and holder have ample side clearance. Binding is never an issue.
In fact the extra side clearance helps it cut straight if you need a groove wider than the insert.
[This message has been edited by suprdvn (edited 04-22-2004).]