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Thread: Rookie lathe user needs some advice

  1. #11
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    Jan 2004
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    The 11" Logan is quite a nice machine. There were flat belt versions (900 series)and V belt versions (1900 series)

    Biggest problem is that flat belt for 900 series, which in some positions/speeds cannot transmit more than about a quarter HP.

    You want the belt going as fast as possible, and you want the belt tension high.

    More belt speed transmits the same HP with less torque, and torque is what slips the belt. A higher belt speed generally means a lower RPM, either through using a larger diameter part of the spindle pulley, or by using back gear. Using the largest pulley on the spindle means the most torque to the spindle for a given pull on the belt

    More belt tension allows more torque before slipping. Usually, the best belt to use is a canvas reinforced rubber belt, with a "sticky" type rubber. Harder rubber slips. With a good rubber or leather belt, the smoother the pulley, the better the grip and the more power transmitted. Leather needs treatment to make the surface softer, and the "hair side" goes to the pulley. This comment usually draws instant condemnation from folks who do not know, but it is true.

    Another issue is single phase motors, which tend to make the belt slip worse.

    If you are working the machine hard, closer to what the belt can transmit, you should start to hear the belt "talking", which is a sort of squeaking, heard more with rubber belts, perhaps, and has to do with the belt rubbing on the pulley as it goes around from the low tension side and stretches as it picks up tension.
    1601

    Keep eye on ball.
    Hashim Khan

  2. #12
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    Flint, Michigan
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    A lot of good advice so far. I would add from some considerable experience with the Armstrong holders, they almost always have the bit mounted at an angle so back relief is automatic. But when it is sitting on a rocker in a toolpost, adjusting the height of the cutting tip will change all the angles you carefully ground on the bit. I fixed the problem with a donut that replaced the rocker. I sized the donut to have the Armstrong horizontally clamped in the lantern, bit at a small projection from the holder, and on center. Easy peasy to repeat after tool changes too.

  3. #13
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    Jan 2003
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    Just a quick thought or two- an 11 inch Logan with a 1/2 hp motor, that seems underpowered to begin with. But as others have suggested the tool geometry is a big player. I would suggest that you get really comfortable with the idea of clearance angles, nose radius, and tool height. Start with tool height- do some facing cuts and see how setting the cutting edge height can almost eliminate the central nib. When you're there, the front clearance angle works properly. Side clearance is not affected by tool height as much, and back rake can be an experimental thing. I often don't use back rake, but it can reduce the power required to make a cut- and it can also allow a tool to 'dig in', which you really don't want. Some materials require a flat to negative back rake.

    As far as nose radius, I usually grind the side clearance angle, the front clearance angle, then carefully round over the front edge where the two angles meet with a diamond stick. That creates some nose radius and also refines the part of the tool that's leaving the actual finish behind. Don't rock the diamond stick up over the top- that will destroy your front clearance and back rake.

    Soon on in your lathe adventures you will want to know about spring passes, (taking another pass without advancing the cross slide) and how much material comes off with each successive pass. Call these finishing passes if you will, and note how close to diameter you can come with roughing passes before you take the finishing passes. It's all too easy to end up with a slightly smaller diameter than you were shooting for if you're unaware how much material is going to come off with a spring pass or two- or three, or four- ideally your second spring pass would only remove a bit of powder, perhaps reducing the turned diameter by no more than a half thou or so. Very measurable, and sometime very important. Proper tool angles and sharpness affect this quite a bit.

    Of course different materials machine differently. Some steels won't show a good finish however careful you are, and others machine beautifully. Differing alloys of aluminum also behave differently- it's always good to experiment a bit with any particular material if the end result has to be some exact size and finish. Sometimes I'll get within about 10 thou of a diameter I want, then do a finish pass and measure how much smaller the part gets, then do a spring pass and check again. From there I can gauge how much more to take off before I do the finish and spring pass again.

    There is a lot to learn, and if you're really engaged in the art of metalworking you'll always be learning. Takes time, and you'll get better and better.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  4. #14
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    Just as a counterpoint to the "1/2 HP is wimpy" idea:

    I have a 10" Logan, which actually swings near 10.5". Mine is powered by a 3 phase 1/3 HP or so motor, running from a phase converter. It is flat belt, same as the 900 series 11", and in fact shares parts with it.

    On some belt settings, the belt, which is a rubber belt with a fair bit of tension, will slip on clean pulleys without stalling the motor. In other words, the 1/3 HP motor exceeds the maximum power rest of the drive train can transmit to the spindle at that setting.

    I could put a 20 HP motor on, and it would make no difference at those settings.

    The 1/2 HP motor will be fine.
    1601

    Keep eye on ball.
    Hashim Khan

  5. #15
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    Apr 2012
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    NE Thailand
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    Quote Originally Posted by RWO View Post
    For small lathes using HSS, a Diamond toolholder is a big improvement compared to the old style Armstrong set-up. https://eccentricengineering.com.au/...=32&Itemid=297 Sharpening is simplified and much faster. https://www.youtube.com/watch?v=xUAPrkC7Q-Q

    RWO
    I'd say sharpening is simple & faster - concur.
    But better?
    If the rocker is binned and a suitable base washer remade, an Armstrong holder in a Lantern toolpost can be an effective cutting method. as someone else mentioned above.

  6. #16
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    Dec 2015
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    Quote Originally Posted by thaiguzzi View Post
    I'd say sharpening is simple & faster - concur.
    But better?
    If the rocker is binned and a suitable base washer remade, an Armstrong holder in a Lantern toolpost can be an effective cutting method. as someone else mentioned above.
    If a suitable size base washer was made given how the Armstrong holders tend to angle all the cutting teeth the tips could be set for length such that they all hit the same tip height with a single packing washer. And in that form it would be not far off of a quick change tool post option. And for some of the other holders like the snail shell threading cutters and parting tool holders it would not take a whole lot to have other packing washers so the user does not need to fuss with the rocking shoes.

    So yeah, I like this suggestion. I think it's got some merit for those with an older lathe that came with a bucket full of Armstrong tooling of this sort.

  7. #17
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    Oct 2002
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    Saskatoon, Saskatchewan
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    Quote Originally Posted by RWO View Post
    For small lathes using HSS, a Diamond toolholder is a big improvement compared to the old style Armstrong set-up. https://eccentricengineering.com.au/...=32&Itemid=297 Sharpening is simplified and much faster. https://www.youtube.com/watch?v=xUAPrkC7Q-Q

    RWO
    I agree. When I got my 9" SB it had the lantern style tool holder and Armstrong tool holders but what a PITA to swap tools and have to fool around getting the center height correct again. Then I saw an ad for a Diamond toolholder in a HSM magazine and bought one. I made a steel monobloc to fit the shank and hold it at the right height; it provided a great deal more rigidity than the the lantern style did and sharpening the tool bit was a snap.

  8. #18
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    Oct 2014
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    One thing to do to the tool is to hand stone it with a smooth stone until the marks from the grinder are gone. You want to see it look smooth and almost shiny. Looking at the edge with a 10x loupe will show t he need for the hand finishing and show you when you have it sharp. A small radius a(even 1/64 or 1/32")on the point will make it last longer than a sharp point. A sharp point will to some extent break off and start to become dull as soon as you touch it to the work. A good sharp tool will produce a nice surface with the feed rate you are using and a small radius on the point. A radius too large can contribute towards chatter, keep it small. Try and find the How To Run A Lathe book by Southbend. If you are new to lathes it will tell you about tool shape and a whole lot more of interest to you and a Logan is close enough to a SB.

  9. #19
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    Mar 2002
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    Kirkland, Washington
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    Years ago I bought a Diamond toolholder from Rudy Kouhoupt at a Gears show in Oregon. I use it on my SB9 and it works well. When I switched to quick change tooling I machined a tool block to fit the Diamond tool.

    Because the leather flat belt was worn, I cut and alternator multi-V belt to length and glued the skived joint with Shoe Goo. The tapered joint was skived/cut with a band saw and a quick fixture. The new belt does not slip. On a SB9 there is a V-belt that transmits power from the motor to the flat belts. The new flat belt caused the V-belt to slip. A close examination of the V-belt showed the belt was worn but the motor sheave was in good shape. A new V-belt to complement the new flat belt and I had a "new lathe".

  10. #20
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    Quote Originally Posted by Stepside View Post
    Years ago I bought a Diamond toolholder from Rudy Kouhoupt at a Gears show in Oregon. I use it on my SB9 and it works well. When I switched to quick change tooling I machined a tool block to fit the Diamond tool.

    Because the leather flat belt was worn, I cut and alternator multi-V belt to length and glued the skived joint with Shoe Goo. The tapered joint was skived/cut with a band saw and a quick fixture. The new belt does not slip. On a SB9 there is a V-belt that transmits power from the motor to the flat belts. The new flat belt caused the V-belt to slip. A close examination of the V-belt showed the belt was worn but the motor sheave was in good shape. A new V-belt to complement the new flat belt and I had a "new lathe".
    Interesting.

    Which side of the multi-V do you have toward the pulley?

    How smooth is the pulley?

    That type belt has been recommended enough that it was on my list to use when the existing belt wears out.
    1601

    Keep eye on ball.
    Hashim Khan

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