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Parting tool advise

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  • mf205i
    replied
    First off, use the "P" blades as they only require that 6-8 degrees of clearance be ground on the front. The "P" blades are the ones that are T shaped with the trough down the middle. The "T" blades have tapered sides and must be ground all over to use.
    The lantern has to go. At the very least, put a solid spacer in place of the rocker.
    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; 01-26-2015, 01:22 AM.

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  • darryl
    replied
    It has been mentioned a couple times now about play in the setup. As kev just suggested, taking out the play helps a lot. I've used his method, but better is to get the slides working well, with as little play as possible. There's already enough flex in the tool holding to allow for grab- then play just makes it worse.

    One problem I had with my lathe was that the rear of the carriage could lift off the rear way easily. Most of the weight is in front, so the front way stays in contact, but you could rock the carriage and make a small gap at the rear. There is a tab that prevents it from lifting right off, but unless there is full contact, there will be the potential for a cutter to either dig in, push back, or do a combination of both. I found that I couldn't make any adjustment there that would allow a free motion left and right for the length of the bed, without having some play in spots. I solved that for this lathe by making a spring-loaded bearing that keeps the rear way in contact without binding. Has been a significant improvement.

    I've also made a few holders that mount directly to the cross slide without using the compound. It's sometimes amazing how much better things work when you don't have that extra play and flex.

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  • kevkeller
    replied
    One thing I do that no one else has mentioned is to put inward pressure on the QCTP to take up any slop on the cross feed threads. This really helps keep the tool from digging in.

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  • Alistair Hosie
    replied
    I also ask is the tip of the cutting tool binding? it is imperative to back the tool out early on, into the cut,and return it back into the shallow groove, however set it a tad to the right or left of this groove to widen the path for the cutting tool to take.keep doing this so that binding does not occur during the process .I have actually laugh if you like , done this as I was taught by books videos etc on woodturning where this is also always done.In any case I don't accept you should part off with nervous intrepidation and be extremely anxious, as I have read about some people over the years. Alistair

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  • beckley23
    replied
    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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  • beanbag
    replied
    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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  • firbikrhd1
    replied
    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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  • danlb
    replied
    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

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  • Clevelander
    replied
    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?

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  • Forestgnome
    replied
    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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  • mf205i
    replied
    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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  • Stuart Br
    replied
    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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  • beanbag
    replied
    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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  • chriskat
    replied
    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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  • Forestgnome
    replied
    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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