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  1. #21
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    Quote Originally Posted by cyanidekid View Post
    hey Kev, be careful, "parting between centers" is just not a thing. much like sawing off a limb sitting on the outside..first thing I thought ! there's a reason you didnt see it on line!!!

    making a grove for a saw to work in is WAY different than parting, and even so, I wouldn't consider taking say, a 2" dia held between centers down to 1/4, anywhere on a 13" piece, yikes. I dont know how far out you are parting, but imagine if it went bad down at the bottom of the cut and bound up, wrenching the part out of the chuck and jackknifing like a tractor trailer.

    THE THING THAT WOULD "CATCH THE PART" MIGHT BE YOUR FACE. (along with the flying shrapnel of the parting blade end going 120 MPH) and it wouldnt be in a predictable trajectory, could ricochet anywhere. a busted parting blade is one of the more dangerous things a lathe can spit at you.

    sorry if you already understood all this, but just to make it clear to anyone else looking, felt the need to get that out there.

    I've hand hacksawed off lots of parts spinning on a lathe, but much smaller stuff, and NEVER between centers. for 2" dia. that doesnt seem like such a great idea even well supported single side near the chuck. its better to start a grove 20% deep max if between centers, take it off the lathe and saw it, put it back on the lathe. cheers, and work safe!
    Copy, thanks for chiming in. I am glad I posted this! I checked and even turned around I can't get a steady rest in there to help so I am unsupported. I will make a groove with the parting tool and saw my way out of this mess. I have access to a target saw too so maybe I will use that but it's a messy affair to use that thing.

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    I'm gonna swim upstream here and tell you that you can part off the piece you want BUT you must be very careful and use a low cutting speed so you can avoid flying missiles if something goes off the rails. This is a back gear operation. Start with a sharp parting tool set exactly at the center height. The parting tool should be wider at the top than it is at the bottom. Extend the parting tool out of its holder maybe only 1/4". You need to do this to make sure you have a straight cut to start off. Advance the tool in its holder by small increments as required. Be very gentle with the feed into the material and use lots of cutting fluid--enough to keep the cutting surface wet. Be very attentive to watch/listen for any tendency for the parting tool to "want" to get sucked into the work.

    Make sure that the parting tool is exactly perpendicular to the workpiece. This is important. If you have continuing problems with the tool jamming in the cut, make another pass to widen the path to give some clearance relief for the tool and chips. If you do it right, the resulting chips should look like little clock springs coming off the work and there should not be any chatter.

    I wouldn't go down to a diameter of less than about 1/2 to 3/8 of an inch. Finish it off with a hacksaw. Be prepared for the operation to take quite a while but it can be done without damage to yourself or to your lathe.

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  5. #23
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    QT: [ except for the part off to 1" diameter then finish with a hacksaw.]

    With not knowing the size or quality of the machine or the OPs experience level it is not good to go anywhere near risky. The parting is just to make a guide parted to something that is logical. Cutting off an inch or so with a hack-saw is not that much. down to 3/8 would be dangerous with the out end on a tail.
    Even with finishing on a band saw the parting groove would be an asset. The stub could be finished with a file if not having a steady for the lathe.

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    Everything has been covered pretty well on this subject. Personally, Doberman says it best for me.
    Just a couple of notes. I purchased a "center-finding" level tool from Edge Technology many years
    ago and it allows me to find near dead center on the parting tool (as well as others). A pretty handy gadget.
    Pictures below.
    As a side note/discussion, it is my understanding that SB scribed a very fine "center" line on the
    operator side of the tailstock quill. Mine is barely visible these days. You might check to see if there
    is one on your tailstock. Otherwise, the tool from Edge works good for me. (I also recently purchased a 12" tailstock
    alignment bar from Edge, and new live and dead centers).
    You might also want to watch the edge of your tool the deeper you go; might want to hone the edge a bit
    after going through a lot of steel.
    Good luck, tho assume you've already done the deed!

    PMc

    pro_lathe_gage_for_setting_cutting_tools_on_spindle_axis_lathe_left__43583.1390617499.600.650.jpg tailstock_alignment_bar_lathe_cutting_tools_on_spindle_axis_southbend_angle__42705.1427686474.60.jpg

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  9. #25
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    Quote Originally Posted by mcload View Post
    Everything has been covered pretty well on this subject. Personally, Doberman says it best for me.
    Just a couple of notes. I purchased a "center-finding" level tool from Edge Technology many years
    ago and it allows me to find near dead center on the parting tool (as well as others). A pretty handy gadget.
    Pictures below.
    As a side note/discussion, it is my understanding that SB scribed a very fine "center" line on the
    operator side of the tailstock quill. Mine is barely visible these days. You might check to see if there
    is one on your tailstock. Otherwise, the tool from Edge works good for me. (I also recently purchased a 12" tailstock
    alignment bar from Edge, and new live and dead centers).
    You might also want to watch the edge of your tool the deeper you go; might want to hone the edge a bit
    after going through a lot of steel.
    Good luck, tho assume you've already done the deed!

    PMc

    pro_lathe_gage_for_setting_cutting_tools_on_spindle_axis_lathe_left__43583.1390617499.600.650.jpg tailstock_alignment_bar_lathe_cutting_tools_on_spindle_axis_southbend_angle__42705.1427686474.60.jpg
    Good Stuff thanks. I haven't cut the groove yet. My work flow is something like this.

    1. Geek out of the order of operations
    2. Geek out on the set up
    3. Set up the machine and cuter(s)
    3a. wrestle with the chuck and/or the stock alignment
    3b. touch up cutter edges with oil stone(s)
    4. Perform the operation.
    4a. oil machine
    4b. remove the material
    4c. clean up machine

    I hardly ever get to complete more than two steps in any given day! So plenty of time for me to sense that I need to ask questions!

    Those tools in your link look interesting thanks a lot!

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    RE: Tailstock Quill Center Mark

    Looks like I have a scribe mark on the quill! Thanks for the tip Mcload!

    p1050496.jpg

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    Back from the lab...I had to give it a try with that parting tool if for nothing else than to have less material to saw through. I started out with a speed of 277 just to feel it out and it was...OK. Still I was telling myself that this wasn't ideal and I went until I started getting chatter. Then I widened the groove by plunging just a partial width of the bit, but chatter returned. Then I said well, lets try real slow and see what that is like. Back Gear engaged and RPM set to 35! Sweet chips were coming off that thing! Even made a bunch of nines as I hand fed it in with some tap magic. But then...

    The cutter caught and binded for a second before the smooth chuck jaws slipped. I had it shut down pretty quick but still I felt a little wreckless. I'm not sure I could have made to all the way and truth be told I wasn't going to. If it wasn't for the perfect chips coming off I might have stopped at about 1" dia remaining but as it was I got to .75. I had repositioned the cutter out once too.

    Some lessons learned there like start slow speed and move up of course I did it backwards!
    If I am compelled to do this again I may purposely use a smooth jaw chuck and not crank it super tight.

    p1050500.jpg

    p1050499.jpg

    p1050503.jpg

    Here's the hacksaw finish, couple minutes with a new blade.

    p1050504.jpg

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    Think ya did OK, I was taught to always part off at the slowest speed possible, regardless of anything. Works for me anyway. I don't think I've ever parted over 100 RPM in my life.

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    Quote Originally Posted by pavt View Post
    Think ya did OK, I was taught to always part off at the slowest speed possible, regardless of anything. Works for me anyway. I don't think I've ever parted over 100 RPM in my life.
    That's great advice! I should have re-read dobermans post too before I started.

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    My first observation is that you are not using enough oil on the cut.

    Parting used to give me fits, until I learned the "magic formula" (at least one that worked for me).

    My parting blade is a 1/16" wide, "P" type tool. With it, I can part off 1018 that is 1-3/4" in diameter. I use Cool Tool II as my lube, but almost anything that lubes will probably work. I part at the second highest speed on my Heavy 10 and I use power feed (with a fine feed-in rate). I also routinely part smaller diameter work with a center engaged in the work - I find that this just keeps the parted off part from dropping to the swarf tray. Before I start to part, I dip my lubing paint brush into my container of CT2 and start the feed. As the blade is cutting, I continually "paint" the groove with the lube. This is probably the MOST important step, because if my brush needs to be reloaded, I STOP THE IN-FEED AND RECHARGE THE BRUSH! Once reloaded, I re-engage the feed and continue to "paint".

    When parting, I always start with a freshly sharpened tool, which is not hard to do, just 2 or 3 seconds at the grinding wheel is all it takes. Also, I start with the tool advanced for only a depth of 1/2", even though the actual part is much deeper. Once I reach the 1/2" mark, I stop and reposition the tool for 1" depth, then continue. This goes on until I have parted as deep as I dare. Once I chicken out with the parting tool, I grab the hacksaw and finish the part.

    I also NEVER (at least very seldom) part manually. The power feed can feed-in far more consistently than I can by hand.

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    Quote Originally Posted by SLK001 View Post
    My first observation is that you are not using enough oil on the cut.

    Parting used to give me fits, until I learned the "magic formula" (at least one that worked for me).
    Yep, LUBE. I forgot to mention that. Probably the most important thing.

    At work, I used to flood the work with the old-school sufurized dark cutting oil. They bought that stuff by the gallon, and it works. And if I forgot to turn the oil on, tool tips would break right off, every time..

    LUBE. Very important.

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    Quote Originally Posted by SLK001 View Post
    My first observation is that you are not using enough oil on the cut.

    Parting used to give me fits, until I learned the "magic formula" (at least one that worked for me).

    My parting blade is a 1/16" wide, "P" type tool. With it, I can part off 1018 that is 1-3/4" in diameter. I use Cool Tool II as my lube, but almost anything that lubes will probably work. I part at the second highest speed on my Heavy 10 and I use power feed (with a fine feed-in rate). I also routinely part smaller diameter work with a center engaged in the work - I find that this just keeps the parted off part from dropping to the swarf tray. Before I start to part, I dip my lubing paint brush into my container of CT2 and start the feed. As the blade is cutting, I continually "paint" the groove with the lube. This is probably the MOST important step, because if my brush needs to be reloaded, I STOP THE IN-FEED AND RECHARGE THE BRUSH! Once reloaded, I re-engage the feed and continue to "paint".

    When parting, I always start with a freshly sharpened tool, which is not hard to do, just 2 or 3 seconds at the grinding wheel is all it takes. Also, I start with the tool advanced for only a depth of 1/2", even though the actual part is much deeper. Once I reach the 1/2" mark, I stop and reposition the tool for 1" depth, then continue. This goes on until I have parted as deep as I dare. Once I chicken out with the parting tool, I grab the hacksaw and finish the part.

    I also NEVER (at least very seldom) part manually. The power feed can feed-in far more consistently than I can by hand.

    Is this what you are calling "P" type?

    p1050512.jpg

    Mine is 1/8 x 7/8.

    p1050518.jpg

    Looks like the tip of the cutter failed, could be from heat yeah? It had a nice chip breaker relief on when I started.

    p1050515.jpg

    p1050519.jpg

    Since it was my first attempt at parting a good hunk of steel I was not comfortable using the autofeed. Of course once I got the speed down where it shoud have been I got a lot more confidence but still kept feeding manually. So i needed an extra hand! I like this 1018 steel, if I do enough projects with it I'll get there. I wasnt doing constant lube more like a squirt and then a few revolutions of the feed and then repeat.

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    Quote Originally Posted by pavt View Post
    Yep, LUBE. I forgot to mention that. Probably the most important thing.

    At work, I used to flood the work with the old-school sufurized dark cutting oil. They bought that stuff by the gallon, and it works. And if I forgot to turn the oil on, tool tips would break right off, every time..

    LUBE. Very important.
    Ahhh, your post is spot on! Thank you for offering some of your experience to my efforts! I really appreciate you guys offering all the advice.

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    Home Depot has the dark cutting oil in quart bottles with the squirt top. Look in the plumbing dept. by the black pipe. I would use one of those and let a continuous small stream on the cut. Same stuff plumbers use in the pipe threading machines. Keep a catch pan underneath the lathe, drain it out and re-use the oil next time.

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    Quote Originally Posted by Kevin T View Post
    Is this what you are calling "P" type?
    This is a type P parting tool. It is 1/16" wide and 1/2" high.


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    Default The Best Parting Tool!

    Quote Originally Posted by SLK001 View Post
    This is a type P parting tool. It is 1/16" wide and 1/2" high
    Far too many professionals with vast experience on this site for me to comment on "how to", but just a couple
    of thoughts. First, I do like the profile of the type P parting tool from SLK001. I've always just ground my own
    side relief on my blades; guess I should get a few and try them out. Are they a better/tougher metal than HSS?
    Has been a long time since I've tried to fully part a hunk of round stock steel. I always had to go back-gear dead slow; manually advance the tool (which I prefer anyway); sharpen the tool several times; and literally fill the workshop with smoke from cutting oil! I've also widened the tool gap on several occasions. Nothing like little blue-hot smoking missiles flying everywhere!
    Also, the reason why I like belt drive: get a tool stuck in the work and the belts will slip. Get a tool stuck in a geared lathe and all kinds of shite can happen, let alone a busted tool!
    After cutting about .25 or .5 into the piece, I will usually turn to my best parting tool...the horizontal bandsaw. And you bet it cuts square! Yeah, I know it's a cop-out, but sure saves time. And I'm gonna have to face that side anyway.
    Parting a chunk of steel although possible, can really show you how weak those Armstrong tools really are in the lantern tool holder...lots of flex, or so it seems. Need to tighten gibs and saddle to remove all lost movement. Stretches a 9" to its limits; I'd prefer a 10K lathe myself.

    Kevin, I wanted to ask what part are you saving and what part is excess? I always cut off (on bandsaw) what the part needs plus 1 inch for the chuck jaws and another inch for room to work. Only reason I ask is because it looks like you turned down the the piece in the chuck first...probably a good idea tho.
    Looks like you've done good.

    PMc

    img_0908.jpg

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    Quote Originally Posted by mcload View Post
    Kevin, I wanted to ask what part are you saving and what part is excess? I always cut off (on bandsaw) what the part needs plus 1 inch for the chuck jaws and another inch for room to work. Only reason I ask is because it looks like you turned down the the piece in the chuck first...probably a good idea tho.
    Looks like you've done good.

    PMc

    img_0908.jpg
    Nice saw!

    The part I am working on is for a collet closer drawbar concept. I haven't figured out all the mating conditions yet but out of that round bar I am making the Blue part in this assembly. I am sort of ahead of myself since I don"t have it all the way thought out but it looked like the most fun part to make outside what I choose for a handle and I have enough material to make a couple of them if I screw it up. So it's the blue part below I started on. I am calling it the indexing shoulder for lack of a better term.

    concept.jpg

    I am not sure I am ready to make threads of any quality so I might be looking at grooves and keeper pins to keep parts together and maybe steel rivets or small screws to keep the green and yellow attached to each other.

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    Very much a newly. I use a 1/16th x1/2 p style blade in china piston type tool holder. I usually have pretty good luck on 1018 cold roll at normal turning speeds, as long as I keep the parting groove wet with lube. Gummy hot rolled, if I blink and runout of cutting oil, tool will bite in and jam. Now here is the question? What thickness of a blade on my 10l works best. I really don’t like inserts. HHS suits my needs and budget.
    Thanks

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    Quote Originally Posted by drsorey View Post
    Very much a newly. I use a 1/16th x1/2 p style blade in china piston type tool holder. I usually have pretty good luck on 1018 cold roll at normal turning speeds, as long as I keep the parting groove wet with lube. Gummy hot rolled, if I blink and runout of cutting oil, tool will bite in and jam. Now here is the question? What thickness of a blade on my 10l works best. I really don’t like inserts. HHS suits my needs and budget.
    Thanks
    Well, you seem to have discovered the secret to parting - the use of CONTINUOUS LUBRICATION - not a lot, but just enough to keep the groove wet. If you have flood and recover and reuse the fluid, then I imagine that would be the ultimate method.

    Your 1/16" tool seems to do the trick. The upside is that parting forces are lowest and the material lost is minimal. The downside is that the tool is the weakest and most likely to break.

    A 3/16" tool will require 3 times the cutting force as a 1/16" and the material lost is 3 times. The upside is that this tool will be the strongest and LEAST likely to break.

    For a H10, I would use what I found to be the easiest and most reliable one to use for my machine and my technique. You seem to be having good success with the 1/16" blade, so I would stick with that. As insurance, I would have on hand some thicker blades to use with problematic materials.

    When I part, I always use power feed. That way, I am assured that the feed will be constant and not herky-jerky. It is these variations in in-feed speeds that cause the most problems for newcomers to parting. I also use higher speeds, so that the momentum of the work helps smooth out the tendency of the work to climb onto the parting tool.

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    Quote Originally Posted by Kevin T View Post
    Of course once I got the speed down where it shoud have been I got a lot more confidence but still kept feeding manually. So i needed an extra hand! I like this 1018 steel, if I do enough projects with it I'll get there. I wasnt doing constant lube more like a squirt and then a few revolutions of the feed and then repeat.
    For no more lube than this needs?
    Yah don't HAVE to have a "coolant pump". Nor a third hand and arm.

    Gravity works.

    Rig you a dark-oil "IV bag". Or workalike.

    W/R Power feed: The PROBLEM is that - as with facing - your RPM is constant but the surface feet per minute is rapidy diminishing as yah move toward center.

    CNC critters part-off really well compared to all-manual lathes. They make it look so easy yah might think all yah need to do to replicate that is to buy the same tooling.

    Not so easy.

    Among other advantages? They are not limited to a single rate of RPM nor of tool advance, can ramp to constant surface speed / rate of removal - rather than constant feed and RPM.

    And a few more tricks, yet!

    Some have to do with back-finishing the off-part and prepping the next.

    The CONCEPTS yah might see in a CNC You-Tube can be portable to an older all-manual lathe.

    The actual doin' of 'em gets harder.

    "Patience, clodhopper."



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