If it lifting the bed, the point of your tool is too high. There is a shim adjustment on your crossslide. Be careful adjusting it as it may have a wore spot and if adjusted too tight your crosslide may bind when moved into the none wore spot. Most all old lathes have some wear. You will get used to it and learn to compensate for it. As stated in an earlier post, use the point of the live / dead center on your tailstock. That should be exact center at its point. Once you get the tool at center, measure with a scale the exact distance from a point of reference, such as the ways or something that won’t change. Also practice with a large piece in your lathe to learn, maybe something 1 1/2 or so diameter. Small stuff is harder to work with and tool location is more critical. U I is right, that’s a tough job with a tool. Might try spinning it in the lathe, and using a length of emery cloth to smooth it up. But! Be careful, lathes have a tendency to grab hands, fingers, clothes.. anything! Also!!! Remove any rings or jewelry you have on while operating the lathe! Don’t get discouraged, we found your problem. Play with soft stuff first. Bones
Yep. You could call this one 'the school of hard yokes'... Seriously, any splined shaft will have been hardened, or the teeth would shear off. As mentioned earlier, try and scratch the surface with a file, or hacksaw. If to no avail, it would have to be precision ground, NOT lathe-cut.
Yeah, I didn't think about the hardening factor. That makes it damn near impossible to cut on a lathe, grinding is the way to do it.
i have read this a few times, tried moving the punctuation, adding a few letters, drawing it out on paper and i am still not smart enough to learn this good trick. can i get a picture, or a simpler explanation?
With tool just snug and eyeballed on center of material, run the tool up to within a 1/8" of the part, hold the scale between tool point and part, advance tool until scale is "JUST" sandwiched lightly between tool point and part then from the side see if scale is straight up and down, adjust height accordingly.
We always made a gage to check tool heighth or center on all the lathes where I worked, established from either tailstock center or a center point turned from stock in chuck. Weld a piece of 3/8" stock with the upper section curved and flattened and reasonably pointed to a plate that spans the two ways of the lathe between tool point and chuck (headstock), bend and/or grind to center height of chosen center. Depending on wear in the ways, there could be a slight difference between headstock and tailstock center heights, generally not by much. Edit Always make sure there are no metal chips on ways or botton of gage plate, also lightly file any burrs from gage getting bumped, use a hone stone on any nicks on the ways too.
Take a look here for a couple of pix showing the procedure... https://www.instructables.com/id/Correct-Lathe-Cutter-Setup/
Here's a video showing how to use a scale for centering. Skip to 3:43 for using the scale, but the video has some good info if you're new to all of this.
First off, there's way too many cooks in this soup, and some of them are way out in left field with the advice to set the tool below center. And this comes from over 50 years as a machinist, including a stint at instructor in a tech school, and 24 years as an aircraft machinist for a major airline, working to tolerances as tight as +\- .0002". That yoke is likely harder than hell's hinges and not something you can machine in any lathe much less a worn out old South Bend. I have a great big 6000# Monarch that is a real tough and rigid machine and I wouldn't even attempt to machine that yoke on it. That's a job requiring at least a tool post grinder, or even better a cylindrical grinder such as a Landis or Studer. You need to get on a site strictly for machinists, as well as get a good textbook. Some good info on "Home Shop Machinist" and "Home Machinist" and more advanced stuff on "Practical Machinist". Some videoes on You Tube are good, but some you need to take with a grain of salt, regardless of the subject.
Fstar, there are guys on here that have book learning, there are guys that have ojt , learning while doing, and we have guys that have both.... You want to listen to the last group. Those guys opinions can be considered “ expert” and more often than not they are right. Unfortunately I’m in the right side of the middle one. Lol You never too old to learn. Looks like I’m going to have to raise my tool, in the future..... unfortunately that’s not alway easy at my age! Lol Bones
I still agree with the 50yr machinist. You dont want a tool below center unless its on a very large diam workpiece, and even then only a tiny bit below may be acceptable, but never on small diam pieces. Now that I know its a hardened yoke with even harder welds (I guessed it was something like that), I will repeat myself and agree with others who say to first practice on something much softer because you have tried to tackle something extremely hard to cut correctly if at all. WHY BE ORDINARY ?
Ok guys thanks, makes alot of sense! I did get some alu stock from the geezer who sold it to me (he has about 20 GIANT lathes doing all kinds of insane stuff).. Apologies for my ignorance - I ha dno idea the yoke would be hardened steel.. little bummed as I was looking fwd to repairing the 90 dollar parts for customers.. ill try all the advice given here on some alu and report back.. Ha di known that stuff was hardened id never have tried. Are crankshafts hardened too? Just curious (no im not planning on machining any crank soon!) Dave - is it possible to put a grinding stone attachment onto a lathe? like a single disc stone grinder mounted on the cross feed / compound? Just thinking outside the box here -
Bones you do have a good point. I grew up in a family owned shop and have over 43 years on lathes and mills. I have some very unorthodox ways on some of the jobs i do. Are they right, maybe not but i get the job done. Change may never happen with me. That is the main reason when my grandson ask me questions about what he is doing in the shop, my answer is ask your teacher he is the one teaching you. Oh by the way i do adjust my tool according to what i'm doing.
RE: grinder on lathe: yes that's a tool post grinder,most popular of which are DoAll brand. They mount where there lathe tool is normally mounted on a lathe. They will usually do a passable job, but only if the lathe is in a good condition and the operator is skilled in it's use. I don't like them and won't put one on my lathe because the grit created from this grinding will eat up the ways on a lathe in short order. I would rather find a grinder shop to do that job on a proper machine.
Most driveline parts like the one shown are cast from medium carbon steel. Splines and seal surfaces are induction hardened for increased strength and wear resistance while the rest of the part is left as-cast so it has greater toughness than a fully hardened part. The seal surface could be turned for adding a sleeve by hard turning with a ceramic insert, or, depending on the actual hardness, with a cermet insert. Of the two, the cermet would be a better choice for a not-too-rigid South Bend since the cermet can work with a sharp edge while the ceramic cannot. Since he's cutting it to add a Speedi-sleeve or something similar, the surface finish isn't so critical as to require a ground surface. I'd hope there's a center hole on both ends of the part from the original machining because that part needs to be turned between centers to maintain the concentricity of the original machined diameters and to avoid excess tool overhang which would cause chatter on any attempt to hard turn. And I agree 100% with DOM that a toolpost grinder will ruin a good lathe in short order.
There are two things to keep in mind at our age: 1. Never pass up an opportunity to raise your tool. 2. Never trust a fart!
Go to you tube and look for a series by Tubalcain. They are really good. They cover just about all the basics in machine shop
You need 3 angles when you grind your cutting tool, I was taught all 12's...you pick your flavor. Cutting speed is calculated off a few things, mainly the material and diameter of it and cutting tool you're using. I'd have to look it up (and do now for as often as I use mine these days)... But center the damned tool on the work...simple way is to take a 6 inch slide rule...and run your tip to it, while the rule is between the cut tip and the work, it should (rule) be 90*'s from the lather bed, adjust as needed. Now next thing is if you're cutting a right hand tool or left hand, and then your direction of travel for the cut. I know it's been said before, but at the minimum, get a "how to run a lathe" book
I learned to run a lathe from an old high school textbook from the 40s. Also, if you can find a Machinery handbook you will use it for the rest of your life. It doesn't have to be new, mine is from the 40s, but they give you feeds and speeds and a lot of tables on threading, how to grind tools for a particular job, and much more.
Before blaming the lathe I'd chuck up a one inch or so piece of hot rolled steel rod (or aluminum) that you know can be turned and experiment with that. We have several lathes ranging from a little Acme to a large Monarch with a middle sized LeBlond being my favorite but one of the most useful is a Rockwell with the infinite speed adjustment. One can touch off on the work and slowly bring the speed up to where it goes from not cutting to making a continuous tailing. It's very surprising sometimes at what the right cutting speed is.
Find a vocational school , I took two years tool and die but reality was the first semester was where I learned what I needed to know
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