View Full Version : Parting is such sweet sorrow
02-22-2005, 10:09 PM
Arghh. I am trying to get the new King lathe working, but parting with the steady rest is a nightmare. It is a crappy steady, no end bearings, just brass points. You have to tighten and oil it every 30 seconds. Even so there is enough flex to allow the parting blade to gouge into the aluminum and jam the workpiece in to the front two steady bushings and stop the lathe, belts burning, me panicking and throwing switches and levers like mad. After 4 times in one inch and a half piece of aluminum, this gets old fast.
The parting blade is a normal shape, relief on each side and the front, and the cutting edge ground parallel to the workpiece. It is sharp edged, and would thus tend to gouge aluminum (which is why you round the corner of a knive tool)but I don't think parting blades should be rounded on the edge? It wouldn'd cut unless it was sharp on the cutting (front)edge. Is there any way to keep the parting blade from grabbing the aluminum and gouging in?
I am just a hair under center height, as suggested by Sparrey. Maybe this is a problem. Or maybe, I should just buy a decent lathe in the first place? Sigh.
02-22-2005, 10:23 PM
I notice your parting blade has been ground on,that is a no-no,avoid the temptation,they are tapered for a reason.
Aluminum doesn't like plain bearing steady rests,make some new or modify your existing steady rest fingers to accept ball bearings,the wider the better.
I setup my brass tip steadies at work with a brass oiler,fill it with oil,set the drip rate and that frees up a hand for other things.
If you have gummy aluminum it is just a PITA reguardless of the lathe or the operator.WD-40,Pam,kerosene even anti-freeze work good for lube on aluminum.
I set the parting tool either dead on center or .005" above.Never below.
Hope this helps,parting can be a real bear.
02-22-2005, 10:25 PM
Just wondering, is there a reason you're parting like that? You'd be better off cutting that stock off and chucking it up shorter and parting close to the chuck. You're putting a butt-load of thrust against that steady. I usually grind a little angle on my cut off tools with the sharp end away from the head. It keeps you from having a little ring hanging on the part.
What is a King? I'm not familiar with them. I've seen some fantastic work come off some pretty simple machines. Don't give up!
Hoffman in Warner Robins Ga
[This message has been edited by hoffman (edited 02-22-2005).]
02-22-2005, 10:45 PM
Probably parting off like hat because your spindle hole is too small to take the stock back into the head stock? and you do not want to lose that prize length? I can understand that being a cheap piker myself......
Seconds on the ginding of a "P type" blade, or a tapered cutoff blade. You probably have great luck until the ground part gets fully into the diameter of the work piece, then the unground part behind it starts to enter the workpiece. The "unground" back part, whih is higher in level then your cutting edge is actually wider than your ground part because th higher pat is wider, thus rubbing the sides and pushing the work into our steady rest. This explains bit further the correct comment above about these bits being tapered for a reason.
Try just a front relief grind on your blade, neutral rake on the top - do not grind the top at all. Slow feed,moderate to low speed. Lots of fluid - right at center or slight above or the part will continually try to kick up an re- center on its own. Use the .005 above suggested above.
If all heck is breaking loose, there is the "Craftsman hand mill method", also known as a hacksaw. Cut in your groove to finish cutting the part off, then reface the ratty looking side to your finished length. No the best or professionl method, but if it works, use it.
BTW, I tend to use "Way lube" when using my brass end stady to lube the brass ends ONLY. When using thin oils for cutting they tend to work back to the steady rest jaws, thus ctually causing gouging and scoring whre the brass contacts the stock, and also gums up the holding surface. Pam, WD40, and such tend to make cutting easier where Way lube actually inhibits cuting action and has mchanical pressure lube qualities that keep it from disipating or running out as fast from bearing surfaces. Went though a set to figure this out. Your brass on he softer aluminum actually beomes a cutter where you do not wan it. Use the oils recommended above (correctly) for the cuting area, but way lube up the brass to aluminmu surfaces
[This message has been edited by spope14 (edited 02-22-2005).]
[This message has been edited by spope14 (edited 02-22-2005).]
02-22-2005, 10:50 PM
In that picture it looks like there is not alot of lube being used at the actual cut, I may be seeing this wrong but when I part aluminum there is usually a puddle of lube under the cut on the cross slide or whatever, also you can hear when the parting tool needs more lube, it "calls" , also if you can, lock down your carriage, to eliminate any movement there and be sure that your steady is centered, if its a little out it will slowly pull the stock out of the chuck and cause a bind at your parting tool, when I have to make a part using a steady, I minimize the amount of overhang from the last point of support and where the cutter is working, it looks like a questionable amount of overhang in the picture, so in short use lots of an appropriate lube, lock down, and tighten up. I also would like to agree with the previous two posts keep at it your most of the way there I hope this helps,
02-22-2005, 11:02 PM
Maybe it is just the pic but it looks like you have a lot of top rake on the parting tool. This will be making you dig in problems worse IMHO.
You also look to be quite a way out from the steady. Maybe try getting a bit closer to the stesdy, Wind top slide out and lock it up if the saddle is keeping you away.
Maybe a squirt of wd40 will help the cutting action. I use crc same as wd40 pretty much and find it helps with aluminium. Make sure the tool is on centre hight.
I don't think there is anything wrong with your machine. Just need to tinker with the technique. I have seen posts b4 about parting. A lot of people seem to have troubles with it. Perhaps it doesn't work so well with smaller lighter machines.
[This message has been edited by zl1byz (edited 02-22-2005).]
02-22-2005, 11:28 PM
<font face="Verdana, Arial" size="2">Originally posted by Samuel:
I minimize the amount of overhang from the last point of support and where the cutter is working, it looks like a questionable amount of overhang in the picture, so in short use lots of an appropriate lube, lock down, and tighten up. </font>
<font face="Verdana, Arial" size="2">
You also look to be quite a way out from the steady. Maybe try getting a bit closer to the stesdy, Wind top slide out and lock it up if the saddle is keeping you away.
Agreed, in spades.
Looks to be two to three diameters out from the steady. I'd keep it at about 1/2 diameter from support in order to keep from chattering, springing, etc.
I managed to chase about 2 thous of spring out of the bearings on the Logan, and the difference was night and day, parting steel.
You've got I don't know how much spring from the overhang, PLUS the steady, which never holds as rigidly as a chuck or collet.
02-22-2005, 11:30 PM
To have a pleasant parting experience the following maybe of help.
1st. A good griping chuck is required, tired 3 jaw chucks will give you trouble because of bell mouthing of the jaws. Your work must be held firmly, this is done using a 4 jaw chuck. If your work is thin wall such as pipe, a short plug is machined and tapped into the end held in the chuck, this keeps the thin wall from collapsing and wriggling free from the chuck jaws.
One note here is that the gib of the compound slide is snuged up, so that it is fairly hard to move the handle, left too loose, it will allow the top of the slide to travel. Once you have set the carrage to the required parting length, tighten the carrage lock bolt. The only slide that you want to move is the cross slide, this slide should have it’s gib adjusted so there is a slight drag when turning the hand wheel.
2nd. Keep the area where your parting close to the chuck jaws, trying to part 1" dia stock 6" from the chuck will fill your shorts. If you must part some distance from the chuck use a steady rest for support, keeping the steady as close to the parting action as possible. The steady must be set to hold the end of the work on center, if not, the work will walk out of the chuck. If the O.D. is rough or out of round it is advisable to turn a small area down for the steady jaws to run on.
3rd. Parting blades are normally held horizonal in their holder, not tipped up. Many parting blade holders don't hold the blade firmly, this is from the extreme pressure of the blade on the holder when it grabs and breaks.
To check your holder insert your blade in it's holder and tighten the clamp, now using a feeler gage try to insert the feeler blade between the bottom of the parting blade and the front of the holder. If the feeler blade goes between the holder and parting blade, where the blade sits in the holder, the holder is worn (bent), or damaged the only thing to do is replace the holder.
What happens is, you set the parting blade on centre, now you feed in to the work. The blade enters the work, pressure wants to push the blade down, and the worn holder allows this to happen.
The rest happens very quickly, the blade is tiped down and the work wants to climb over the blade faster than your feeding, a loud bang is heard and your blade is broken, and the holder is damaged further.
4th. Sharpening the blade, look at the end of the blade, you will see that it is tapered, wider at the top than the bottom. What you want to do is reduce the width of the blade at the top surface just behind the cutting edge. This is done by turning the blade upside down and holding it on the OD of a 8" or larger grind stone, the blade should touch the stone around 1" back from the cutting edge. What you are trying to do is form a gentle concave (hollow) on the top of the parting blade. This narrows the parting blade a few thou just behind the cutting edge, this top grind also gives your blade a little top rake (a must have when parting gummy 1018,aluminum or stainless steel). Next you need just a "little end" clearance on the cutting end of the blade, 2° to 3° is sufficient, "too much" will allow the parting blade to feed too fast and pull itself into the work. The cutting end of the blade should be square to the blade.
5th. Mounting the blade, install the blade in the holder leave only a 1/4" more sticking out from the holder than you need and tighten clamp. Now you want to set the cutting edge on centre, take a thin 6" flexable scale, hold it between the work and the blade in a vertical position. Gently bring the parting blade to just touch the scale holding it against the work, you move to right of the cross slide, look at the scale. If the scale above the tool bit is leaning towards the centre of the lathe , it's too high, if the scale is leaning away from the work it's to low, adjust parting blade height so the scale is held straight up and down (90° to the bed).
Now the last thing to check, is to see that the parting blade is parallel with the cross slide travel. This is checked by using a mag base dial indicator, attached to the carrage or lathe bed, the dial's tip on the side of the parting blade, now move the cross slide back and forth, 1/3 length of the parting blade. If the dial pointer doesn't move "you got lucky"!, If the dial pointer moves, loosen the tool block nut and tap the block to make the dial read 0 the length of the parting blade travel, tighten the tool block nut, check one more time to be sure it hasn't twisted with the tighting of nut.
6th. Your ready to begin parting off, run the lathe at half the normal cutting speed, if you have water base coolant let the nozzle aim over the parting area, lacking coolant use sulfer base cutting oil for steel, penitrating oil/ WD40 for aluminum. Power feed in at a rate of .002 to .004.
The chip should be curling (like rolling up a tape measure) in the concave of the parting blade (where you ground). What you want is to keep the heat down, water base coolant works for me, but I have noticed the sharp cutting edge lasts longer with sulfer base oil on steel.
Some people recommend using bacon fat for lubricant, I haven't tried the bacon fat as of yet, so I can't comment on it's performance.
If all the above is followed, you should be parting like a pro.
If you are "still having trouble" (usually on older worn lathes with loose gibs) part off from the back side of the work with the parting blade upside down and on centre.
To all owners of threaded spindle lathes,
Your lathe can do something that a cam lock can't! On most of these older style lathes the cross slide can travel past centre, unlike the more modern lathes. "This is a good thing"...
This fact doesn't seem to be useful on the surface, but..... let’s look at a couple of machining operations.
Parting off, "the normal way", lathe spindle rotation normal, parting tool, between you and the work, parting tool on centre, at right angle to the work.
You start to feed by hand, something moves, the parting blade is drawn into the work, you hear the lathe bear down, growl, and "bang". You look,.... the blade is broken, the work is damaged, maybe even scrap %%&@#*.
Is there a way to prevent this from happening? "Yes", "if your cross slide can travel past centre". By mounting the parting blade holder upside down, with the cutting edge on centre, spindle rotation normal, come from behind (back side) the work with the parting blade. The blade contacts the work on centre, if you watch the blade closely you will see it lift, ever so slightly, and this action lifts the tool up just a little and "away" from the work, "just the opposite" of the normal way, chatter is gone, grabing of the work gone. No more suprizes when parting off.
This same procedure can be used another way!...
You have a piece of plate, you want a circle, or a ring. Chuck the plate in a 4 jaw leaving room, behind the plate, for the tool bit to break through (1/8”). Next, and "this is the only time I use a tool holder that angles to the left,and holds the tool bit at a 20°", mount on the compound. Don't use the rocker just the post, turn the plate upside down, use spacers, now grind up a tool bit to form a parting or grooving tool, making sure you grind the side clearance back enough to penetrate the plate.
Don't grind the chip breaker just yet.... Mount the tool bit up side down in the angled holder, with the cutting edge at the bottom, the compound mounted on the cross slide is past centre of the chuck. Now bend down to look at the bottom of the bit, grind a chip breaker that is at 90° to the surface of the plate, parallel with the lathe axis. Re-install the tool bit, you will notice you now have too much end clearance on the bit, you can reduce it, but you can wait until it becomes dull.
With the compound past centre, spindle rotating in it's normal direction, bring the carrage up to the work, as the cut begins again you will see the tool lift ever so little, it's lifting away from the work, not grabing and digging into the work. If your making a ring, cut the id first then the O.D. You may have to grind a little more side clearance on the far side of the bit to be clear of rubbing the outer edge of the groove.
These two methods come in handy when you can't change the spindle rotation or motor rotation because of a threaded spindle. And, "you won't have to worry about the chuck unscrewing".
On a lathe with a cam lock and reverse spindle rotation the same tool setup is used but, your bit is on the normal side of centre.
I have cut up to 1" thick plate (for large flanges) held in the chuck using this procedure, the tool lifts up and away from the work, no messy shorts, ever...........!
[This message has been edited by vmil3 (edited 02-23-2005).]
02-22-2005, 11:44 PM
Never had much luck parting with anything but the bandsaw until I went to insert-type parting tool. Center height of .003"-.005" above center works best. Steady doesn't have to be tight to the workpiece as the parting tool provides one point of support -- my steady is not snug, not loose, just a few thou clearance. The parting tool will push the stock back into the steady. RPM (SFM) is the hardest thing for me to figure out. Never can go by the charts in the book, usually have to go slower than shown. Make sure the compound is dead 90* to the cut. IMO.
02-22-2005, 11:54 PM
<font face="Verdana, Arial" size="2">Originally posted by precisionworks:
Steady doesn't have to be tight to the workpiece as the parting tool provides one point of support -- my steady is not snug, not loose, just a few thou clearance. The parting tool will push the stock back into the steady.
Maybe.....and maybe not. I had figured that loading via the cut would take up the bearing slop I had. So did a bunch of folks who suggested not to worry about it. No such luck, in reality.
But taking out the slop via a preload scheme made parting work. Prior to that it had never worked worth a hoot, no matter what was tried.
Maybe the two other points of support will help. The bearing didn't have "two" other supports, so it's a little different.
But I bet you need to keep the feed on continuously, because if you let up, the part will spring out a bit and then it will have room to climb and do other bad stuff.
02-23-2005, 12:00 AM
Is that a tube or solid stock?
If it's solid, go ahead and support the bar with the tailstock until you only have about 1/2" diameter left, then pull the tailstock away to finish it off with just the steady.
02-23-2005, 01:54 AM
Perhaps fiddle with speed. With **** bearings speed must be a LOT slower. Lots of coolant. Good tool geonmetry. Polish the partoff tool with a abrasive dremel polishing point on the top of the cutting face this will help reduce the gooey aluminumn booger stick syndrome. I have run some bizarre low speeds to part off stuff dont be afraid to experiment every lathe is differant. Good Luck and NEVER SURRENDER remember death before dishonour. A canadian motto.
02-23-2005, 03:02 AM
The late and most lamented George H Thomas wrote in Model Engineer and later in the Model Engineers Workshop Manual- edited by Bill Bennett a complete chapter to parting off.
Trying to reduce the chapter into a few lines, George designed a rear toolholder with a 7degree tilt. The top( upside down) bit, was vee'd at 140 degrees and the front was also veed.
Probably, the Hemingway website will give the details more clearly.
02-23-2005, 04:14 AM
I will add my two cents worth. I have found that oil is completely inadequate for lubing steady rests. Use grease. Then it is much more forgiving to snug things up the way they should be. Good luck to you!
02-23-2005, 08:50 AM
Wow, what a flood of great advice. Thanks everyone for the input. Here are some answers to the questions.
King lathe: http://www.kingcanada.com/Products.htm?CD=116&ID=2369
The aluminum is a solid bar, too large to go through my headstock. Spope14 is right, I am trying to conserve my precious (expensive!) metal supply. I wanted to cut several pieces off and end up as close to the steady as I could, so I set it up to allow the cuts I needed without having to move the steady. This left the first cuts a fair ways away from the steady.
I am using WD-40. I started a thread a while ago about lubs and aluminum. The school says cut dry, some of my responses to the thread said lube or don't, but do not use intermittant lube that allows heat to build up and then a sudden dose of lube.
I would rather not grind on the parting blade, but my problem with the 4-way tool post is that I have no height adjustment. The "side-shooter" blade holder brings the top of the blade down much further than a regular holder, but I still have to grind the top of the blade down to get to centre height. I do have a smidge of back rake. Maybe I should stop reading Sparrey.
I have heard of the upside down cutting idea. I don't have the height adjustment in my tool holder to try it, but it sounds neat. I hope to build a tool holder with height adjustment in future. And some bearing tips for the steady rest.
I am scrupulous about the setup, parallel travel to the work and so on. Everything goes swimingly until the blade tip digs in and it all stops with a big screech. I will try centre height or a bit above. I am below a bit at present. The descriptions of the "work trying to climb up the blade" is exactly what seems to be happening.
Thanks again for all the advice.
02-23-2005, 10:43 AM
Here is a tip for your steadyrest. I take a piece of cloth backed sandpaper,emerycloth, and put it between the work piece and your steady rest tip.(sanding side away from the work piece!) and snug up,add a bunch of oil. The cloth becomes oil soaked and acts like a wick help keeping everything sliding nice. But if you have a choice, bearings are the way to go!
02-23-2005, 11:54 AM
Most all my parting woes went away when I mounted the cutter upside down and reversed the direction. (Be nice to yourself and get a Quick Change tool post).
Some approach the work from the back side with an upside down cutter. This is to prevent unscrewing of the chuck.
Keep the parting tool sharp, sharp, sharp.
Also... In Aluminum I'll cut about 1/4" deep and then widen the slot on each side about 0.050" and repeat. Slower, but, much easier on the Heart.
02-24-2005, 02:04 PM
One other item-that lathe looks like the typical 9x20 lathe. The plate with two bolts holding the compound to the cross slide isn't stiff enough; most people make a 4-bolt plate to replace it. Google up Steve Bedair's 9x20 site to see an example.
02-24-2005, 09:02 PM
Arghhh, no. This lathe is about 3 times heavier than those 9X20's everyone sells. I looked at one and it is much too light and poorly built. You have to do lots of mods to the cross slide and carriage. The 10X20 is a very different lathe. Still needs some work (mostly, a good DRO!) but a much heavier lathe. I originally wanted an Emco 7X12 for miniature engine work. I might still try and pick one up. This lathe can do small and large, and is about all you would want to try and get down your basement stairs (me and 3 other guys from Harry's Moving will swear to that. A very high pucker event, this baby weighs!). Only has the feedscrew for both threading and feed, but, you get what you pay for. My experience with this lathe so far is very good. I am comparing it to the expensive 14X40's at the school. For the dollar difference, it comes out pretty good.
02-25-2005, 06:09 AM
It may help to skim the stock true where the steady is running. Looks pretty rough from here.
I use steam oil for steadyrests.
Those open front steadys aren't as good as a bolted closed job.
When parting, I cut .25 deep (depending on material), as mentioned and take another cut .030 to the side to give chip clearance to the tool.
Can you run the live center in the stock until you get close to the breakthru point?
Your compound is on some kind of angle. I would either bottom it out, or set it square, or in line with the parting tool.
They can creep under pressure when set on an angle.
[This message has been edited by kap pullen (edited 02-25-2005).]
As was said, a live center if you have room may help.
If no room, machining up a simple adapter center drilled on the live center side and a shallow cone on the workpiece side would work.
Using a hand held hacksaw works fairly well although you'll have to face off the bushing after it parts.
I've done this one by cutting a shallow groove with the cut-off blade for a guide.
With the lathe running, use a hand held hacksaw with a somewhat coarse blade to cut the bushing off.
The hacksaw bit works especially well on aluminum pieces with a small hole.
Seems once the cutter gets down to the smaller diameters it's more prone to dig in.
Granted, not a particularly classy or machinist like way to do it, but it works and is as safe as using a file on a spinning workpiece.
02-25-2005, 02:35 PM
The school says cut dry? Many schools will say this for the reasons of saving oils, oils disposal issues, or coolant dis[posal issues - including not using coolant on a daily basis and tramp oil / coolant rancidity.
Using carbide on ferrous and brass, I cut dry. Using HSS on anything, I use black cutting oils. On aluminum I like to use a product (solid bar of soap type)called edge lube, and in cutoff either black oil, which is not the best thing on ASL, or very light kerosene treatment in the groove.
I also use the edge lube lightly on facing and turning in alum. with both carbide and HSS. Prevents (BUE) - mentioned below.
Aluminum is a very sticky metal, so cutting dry with any cutters eventually leads to a "Built Up Edge" (BUE) which destroys finish, and in cut off actually adds rake to the cutter very quickly and at a very high angle. In a sense builds up the cutting edge with very lightly work hardened aluminum (yes, aluminum work hardens to a very slight degree - this is the big issue with pocket milling in aluminum and chip build up as the chips will destroy a cutter), but then after a short while, the BUE tends to just plain inhibit cutting and cause "rub" as the center of the cutting edge has built up far beyond the center in height.
WD 40 works good on aluminum, but for less expense and a better cut, you may want to look at kerosene or edge lube.
Your Old Dog
02-25-2005, 02:56 PM
When I've had the same problem on thicker aluminum I always blamed it on heat. It may be coincidence but the most problems happen when the aluminum heats up and starts to expand thereby pinching my cutter. I use Kerosene applied with a 1 inch paint brush and set the cutter absolutly square to the work so there is minimal side interferance and centered up on the stock. I also use (and it takes a quantum leap of faith) the automatic feeder to prevent gouging in!
02-25-2005, 04:29 PM
[QUOTE]"...my problem with the 4-way tool post is that I have no height adjustment."
I had the same problem. Ground a bit off the bottoms of the holders and now use shims when necessary. I'm a no-nothin newbie but it works for me!
02-25-2005, 09:14 PM
I have had really great luck with A-9 Aluminum cutting fluid. I use it for cutting, drilling, and machining. A few drops does a great job at preventing drills amd mills from loading up. I found it worked pretty well on the parting tool as well.
I know that a normal lathe bit requires a fairly steep back rake for aluminum. Is the same true for the parting tool? Something in my mind says a zero rake so it doesn't dig in, but the other part says lots of rake to clear the chips.