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  • #16
    Derekg I agree with every thing that is being said, rigidity, square to work and cutting oil.

    As for tool height I find setting the tool a little below the centerline works better for me, because if it is anything above the CL when it flexes it will dig in. It is difficult to the tool exactly on CL, you will get a small cutoff burr but to me it is better than the tool digging in and snatching the part out of the chuck.


    Jim Connell, DeLand FL.
    Daytona Beach is near us.

    You haven’t begun learn until to learn until you learn how little you know.

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    • #17
      This is probably against all the rules but, my HHS cutter works best when I used a 6" grinding wheel about 1/32" deep to put a little back rake on the tool. Probably just dumb luck but the only trouble i had was in 6AL4V titainium. Wouldn't touch that stuff in fact I think it made it harder.

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      • #18
        Rake is your friend on a small lathe.

        This is what I use on a 7x10.



        Dan
        At the end of the project, there is a profound difference between spare parts and extra parts.

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        • #19
          On the Hardinge HLVH I use a P-2 size "T" style cutting blade"Empire" brand in colbalt HSS in the Aloris tool holder.
          Absolute 90 degrees perpendicular to the center line .
          A constant flood of cutting fluid.
          I use a product "Spray Tap" applied with a 1/2"acid brush
          On the top of the blade I grind a very small notch at the cutting edge to make the chip to form a curl... making...say about a 7 degree rake angle

          On the 20" Lodge & Shipley I use a P-3 size with the same method.
          Have parted off 3-1/2" diameter solid steel .
          Preventing chip weld on the parting tool is one of the secret and use a lot of cutting fluid.
          Robbie
          Robbie

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          • #20
            I wouldn't get scared away from using your HSS tool just yet. I've been using strictly HSS for parting for years without too much trouble. Like others have said, use plenty of lube. Also keep the tool biting into the work. If you have power crossfeed that'll work good if you have everything set up right and you're using the backgear. You need to use backgear with power crossfeed because it keeps the speed steady. Otherwise it can slow down and speed up causing breakage. If you're not using power crossfeed then you can get away without backgear because you modulate the feed by hand. I regularly part up 3" diameter using HSS.

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            • #21
              In addition to what everyone else has said I find that power feeding works much better for me. The lathe maintains constant cutting pressure and I get far less digging in and the swarf comes off in ribbons instead of dust.

              Jeff

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              • #22
                The carbide insert tools are wider at the tip than the shank, so there is side relief and therefore no rubbing.

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                • #23
                  Another vote for insert parting tools. I use one from Glanze and it parts off like a hot knife through butter. Superb finish as well. Lots of coolant and a pretty high speed.

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                  • #24
                    With HSS, a good dark cutting oil is a must. Just for fun I have tried ATF, hydraulic oil, gear oil and a semi synthetic water based coolant and by far the best results and finish were obtained with the sulfurized, chlorinated, cutting oil.
                    FYI, the Aloris tool holder adds 4 degrees of back rake.
                    Put the tool on center, if you put the tip below center you run the real risk of having the part roll over the bit, this breaks things.
                    Have fun with it, Mike
                    Last edited by mf205i; 05-05-2012, 06:04 AM.

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                    • #25
                      Originally posted by beanbag
                      The carbide insert tools are wider at the tip than the shank, so there is side relief and therefore no rubbing.
                      Just for the record, HSS tools are either T-style or tapered, therefore no rubbing. A slight amount of clearance along the top edge occurs through the cutting process if everything is aligned properly.
                      Last edited by Forestgnome; 05-05-2012, 10:28 AM.

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                      • #26
                        David.....

                        Not to put you on the spot...but...

                        I don't understand how what you suggested would prevent catching, could you please explain your rational?

                        On the topic of rigidity...I saw a short on U tube about changing the tool post over to a quick change on the shopfox 10" lathe. When he cranked down the toolpost I was amazed by the amount of flex there was in the compound slide assembly. One of the accessories I'm going to make for my lathe is a "chin rest" to go under the nose of the compound slide to support it. My thinking is that the flex I saw there may be a main contributor to chatter....comments?
                        Allans Rule: Anything worth doing is going to be a pain in the butt.

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                        • #27
                          I only have a 7x12 and 9x20, but I've found the flex in both cases is coming from the shifting of the gibs. virtually none comes from the bending of the tool, tool post or compound.

                          A dial indicator mounted on the cross slide shows the lift of the compound when the gibs are not tight enough. Mount the indicator on the ways and you can measure the movement iof the cross slide. I literally push on the tool post with all my weight to verify that I have them tight enough.

                          Of course, now I realize how much I need to fix my gibs.

                          Dan
                          At the end of the project, there is a profound difference between spare parts and extra parts.

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                          • #28
                            I didn't see this mentioned by anyone else, but perhaps I missed it. I realized I left something out of my first post that can make a difference.

                            Don't leave any more of the tool sticking out than necessary to complete the cut. Extra tool hanging out there hurts rigidity as well.

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                            • #29
                              Originally posted by Forestgnome
                              Just for the record, HSS tools are either T-style or tapered, therefore no rubbing. A slight amount of clearance along the top edge occurs through the cutting process if everything is aligned properly.
                              What I mean is not just clearance underneath the cutting edge, but all along the top edge, such that the parting tool doesn't have to be exactly perpendicular and there will still be no rubbing. Also, the parting inserts have a geometry that causes the chips to curl up with a little V cross section such that the chips are narrower than the groove.

                              With an insert parting tool and some coolant, I can get as good as a turned surface finish.

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                              • #30
                                When I first started out, I had the same experiences as many have expressed. I've tried all "remedies", and finally settled on a standard procedure in my shop any time I get a "new" lathe. I've only bought one new lathe, an Atlas 6", and it was this lathe and the solution to the cut-off problem that set the SOP, after I had purchased a 9" SB, and got me very interested in re-conditioning.
                                The procedure is to take the saddle, cross slide assembly, and compound rest assemblies apart and spot all the bearing surfaces with a straight edge and/or surface plate, and to make any corrections necessary. You will amazed at the results. Machine rigidity is very important. Also, getting rid of the lantern style tool post is very important, IMO.

                                My hat is off to those that can grind a cut-off tool, I've been trying for 35 years, with so-so results. I switched to inserts long ago, and never looked back. I also learned that slow speed doesn't get the job done, for me it's go as fast as possible, with-in reason, usually in the 700-1500 RPM range for stock up 2-1/2" D.

                                Machine weight will be important. The lighter the machine, the more troubles, the heavier the machine is, the fewer the problems. Keep the tool as close to the spindle bearings as possible for rigidity. Use coolant, and power feed where applicable.
                                Harry

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