picked up a running south bend 9" on a cabinet for 450.. ordered a tool holder and tried doing some light cuts on cast steel with hss bits I ground from a video explaining how to grind bits.. The belt is on the middle cog at the top and the middle on the bottom.. ive been trying to make light cuts. first the tool started glowing at some point, and the little bit of shavings too.. then the darn piece came loose! Then I ordered these chinese index carbide bits (yeah right?) thinking it would cut better. Nope! I noticed the motor laboring when i start even a very light cut.. the belt doesnt seem like its holding all that well.. only a light amount of the motors weight is on it, the adjuster inside for to pushed the motor down into belt and against spring is at its max and there is still a little slop in the belt.. hardly "firm" - as my first experience to say im lightly disappointed in my SEVERE lack of even mild success is an understatement. Add into that my first sandblasting attempt was a joke, as was my first polishing attempts - hey at least i can run a stick weld pretty good, 4 to 1!
Your tool cutting point needs to be about a 1/64 to 1/16 inch below center of the object your cutting. Also if your tool is glowing your turning to fast, that’s also why your motor may be laboring. Bones
Your tool should be a point with clearance ground into it, so it cuts, not rubs. At frist don’t use the automatic feed just move the tool with the wheel.take about a 10 to 20 thousandth cut. Try cutting a large diameter object first,nthey are easier. The smaller the diameter of your material the closer you need to be to center, at some point it will be almost exactly center. Bones
i have the southbend lathe handbook.. thanks, will check rpm - tool was about centered, i tried lowering it a little and raising.. i did also grind the tool to angle away from the forward direction .. i ground i think 2 cut aways from the one the tool came with.. all about the same angle, bottom, behind - they were square hss tools 5/16 with a single angle cut. i fed it by hand slowly in from the beginning.. hardly touching and then going in a tiny crank deeper -
Play with it, you get the hang of it! Speed and feed my friend! Don’t try grinding any of that fancy stuff yet, just grind a sharp point, give clearance, turn slow, get a tad below center and cut away! Ps. Are you trying to cut mild steel? Some metals are very hard and take special tooling. Bones
You could have many issues, really hard to say, rpm control is critical, if cutting a steel casting at too high rpm when first entering the rough casting the cutter dulls quickly. For machining cast iron we always used "K68" grade carbide, steel was "K21", these are uncoated. That was in the early 2000's so they may have changed the numbering system, I know throughout my 30 years in the machine industry they changed a couple of times. The Machinerys Handbook may look intimidating but it will have everything you need. You might try your local library for books on basic lathe operation.
i was experimenting with different rake angles and lowering the cutting point slightly to see - they were small adjustments, nothing too ridiculous.. 40 yrs old and 20 yrs shadetree mechanic exp - not a total dunce with things but obviously this lathe has teething issues.. for one the crossfeed rocks ever so slightly when the tool starts engaging.. its a little dirty and havent gotten to cleaning it yet in the last month.. for the most part ive been cutting pretty darn close to center tho - anyway i must be doing one or three things wrong, or the lathe/tooling has some serious issues, i cant imagine its that much of a black art to cut a straight line across a straight piece..
Here's another thought-- what are you trying to cut? If you are trying to use a cutter on hardened steel, you can get a red hot tool when you try to crank on the pressure after seeing the hard tool will not cut into hardened steel. There are quite a few hard steels that must be ground and not cut. Try making a hacksaw groove in it, then try a file. If they make hardly a dent, then you need to use a grinder not a cutting bit. Otherwise look very very closely at the tool contact... If you see the precise contact point at anywhere else but the exact sharp tip of the tool, then you do not have it aimed correctly. Look very close to see that the work does not contact at an area very slightly below the sharp cutting edge, or you will get a rubbing contact instead of a cutting contact. If your very sharp cutting edge is dulling with lots of heat, you are trying to cut something too hard. If it is not dulling your cutter edge quickly when it overheats, then your contact is in the wrong place such as very slightly barely below the sharp cutting edge. P.S. tool contact is supposed to be exactly on level with the centerline or very slightly above. If you use your tailstock center to judge tool height, you will not have a problem with misjudging the correct tool height. Try adjusting the tool height by the tailstock center-point, and youll be very accurate. WHY BE ORDINARY ?
If you draw a line horizontally through the center of the part you are cutting, you need to have the cutting tip just a little below that line to cut. How far below depends on the diameter of the pice you are machining. Above the center line, you will not cut but rub, to far below the center line you part will try to crawl up on top of the tool. Bones
WARNING about cutting below center -- cutting below center more often than not will pull the cutting tool into the workpiece and either make a deeper cut than planned or snag the work as the rotation pulls the tool into the work, or GRAB the cutter then release, grab, release, grab into the worse shudder you will ever see until it breaks the tool. Cutting below center except for the smallest amount if you do it at all is dangerous and harmful to the tools. You need to try to set it more neutral. The Machinist bible says on center or a tiny bit above. WHY BE ORDINARY ?
I was taught to put the tool a little below the center line. Dare says a little above. I guess it’s different, depending on who taught you. I never had any formal schooling in machining. Hired on at a machine shop back in the seventies, learned from the older machinists there. Made my living for a couple of years before moving on to Mechanic work. Been playing with them ever since. Just the way I do it. Can’t say if it’s right or wrong, but has worked for me. Bones
One thing you will find when buying remnants from steel surplus type places is you don't know EXACTLY what you're getting. If the color code is cut off the fresh end of the stock and not remarked ie 1020, 4140, etc. it's a crapshoot knowing what it is until you start cutting it. Look up the term "spark test" on identifying steel materials, not always dead accurate but its a starting point.
One more thing, if you are grinding your own bits from HSS, you need a 10 degree rake from your cutting, or contact, point. Keep that in mind if your tool holder holds your bit at an angle, you will have to compensate when grinding your tool. Speeds and feeds are of course vitally important, but are less of an issue with less aggressive cuts, and softer materials. If you are playing with 4xxx series material, I suggest you get some experience with something like 1020 first. Also here is another recommendation for a Machinery's Handbook. It will have you dreaming os spiral-bevel gears in no time.
Go to u-tube. There is a ton of videos explaining different how to's on performing different lathe operations. Look for Mr. pete 222. He is a retired school shop teacher & has a ton of videos on different shop equipment. Since he taught high school shop for like 30 something years, he explains how to so that its easy to follow. Bill
Do you have a small machinist ruler a thin little metal ruler take your tool post on your cross feed with your motor off. Roll your tool in with the ruler between the work piece and you cutter lower your tool until the ruler leans back to you that should.be the sweet spot it takes time but you will learn how to set up its all speed and feed !!
@Fstarocka what do you mean by " for one the crossfeed rocks ever so slightly when the tool starts engaging.. its a little dirty and havent gotten to cleaning it yet in the last month.. "? Is there slop, otherwise know as backlash, in the lead screw that it takes up as it contacts the piece being turned? Or do you mean that it continually rocks as you're cutting? Here's a great little video about taking up backlash: Obviously the lead and cross screws need to be properly oiled, but keeping everything else relatively clean is important. This really becomes paramount if you ever do any knurling.
Also, Try to cut aluminum first. As others have said, until you know what you have for steel, it can be a crap shoot. If the flat belt slips, you can shorten them. I know you said that you are doing the feeds by hand. But, if you want to try the power feeds, set them to the lowest settings to gain confidence. My dad taught me on a clapped out old clunker. He always said, "Just worry it a little. Don't try to take big cuts. When you get good, you can get creative and speed things up."
i always run my tool slightly below center the way terry said, also make sure the belt is tight. just like a air compressor that has a head of air on it and it labors to restart.
Cast steel can be problematic for any small lathe, especially if it's difficult to "get under the skin" when taking the initial cut. Once the tool bit has been red hot, it's likely lost its hardness. A new belt is probably in order. Can't do much of anything if it's slipping. some info worth perusing... http://www.americanmachinetools.com/how_to_use_a_lathe.htm Also agree with terry; the rule or thin stock should lean back towards the operator which means the tool tip is slightly below center. The Chinese bits look to have negative or zero back rake. They will work OK, but tip needs to be on center to slightly below. Another read; https://littlemachineshop.com/images/gallery/instructions/grindingtoolbits.pdf
That's the way I usually set them too. Just make sure the scale isn't leaning too far back towards you. I try to get it at the point where it is just barely noticeably leaning. Fine tune when you start cutting. Edit: Oh yeah, gotta make sure your speeds and feeds are correct for the material!
wow guys, thanks for the replies. I must say this site has the most knowledgeable folks around.. Ill read thru all the posts later, just wanted to say thanks, its really encouraging. So bummed yesterday.. anyways i never give up so will keep trying and post back. I think what ill do is clean up the bed and crossfeed and see if theres an adjustment there.. i could see the crossfeed rocking slightly like it was lifting off the bed a tiny bit..
Fyi the piece im trying to cut is a driveshaft yoke from a mercruiser inboard/outboard.. I presume its cast iron thats machined? One like this - im trying to cut the smooth area down where the seal rides, to fit either an oversize seal or put on a repair sleeve -
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