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Newbie needs help with mini-lathe

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  • Ringo
    replied
    Originally posted by devils4ever View Post
    I placed a dial indicator on the face of the chuck and I push and pulled in every direction possible and the needle didn't really move. Maybe, +/-1/4 thousandth (+/-0.00025").
    OK sounds good, now move the indicator to the outside diameter of chuck and look for play that direction.
    if it passes this test, then the next time you get chatter you know to look at your carriage/tool/post setup.

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  • David Powell
    replied
    Originally posted by devils4ever View Post
    I placed a dial indicator on the face of the chuck and I push and pulled in every direction possible and the needle didn't really move. Maybe, +/-1/4 thousandth (+/-0.00025").
    One point which has not yet been mentioned is that EVERY interface can bring the possibility of unwanted movement or play. If you have the ability and means to replace the compound( or maybe you call it the top slide as I do) with a plain block and mount your toolholder to that, then it might help you to do so. You really only need the second slide to turn tapers , with small lathes tool positioning can be done easily by moving the saddle. Hope this hint helps someone. Regards David Powell.

    Leave a comment:


  • devils4ever
    replied
    Originally posted by Ringo View Post
    My guess would be to put a dial indicator on the face of the chuck, and push/pull/jerk on the chuck looking for endplay.
    I had chatter problem with my Logan, and when I indicated the face of chuck I saw movement.
    I setup the head bearings properly and all is fine now.
    I placed a dial indicator on the face of the chuck and I push and pulled in every direction possible and the needle didn't really move. Maybe, +/-1/4 thousandth (+/-0.00025").

    Leave a comment:


  • markx
    replied
    Originally posted by dalee100 View Post
    Hi,

    Despite appearances, there are plenty of us that have benchtop lathes and mills. I have an 8x14 from the dreaded Harbor Freight, (and no QC gearbox heaven forbid!), and a G0704 mill from Grizzly. The truth is, even if you owned a 18"x144" 8000lbs lathe - the advice would be the same. The same principles apply no matter whatever country of origin or size. Some of us can just take heavier finish cuts............The talent to run the machines comes from the operator, not the color of paint.

    So pull up a chair and enjoy and learn from all who are here.
    Could not agree more ! A small machine actually let's you feel the process in much more finesse and forces one to be inventive and optimized. I feel that one can learn more quickly and more effectively this way. The only drawback of a smaller machine being that bigger workpieces simply can not be fitted into the machine.....but about all else can be bypassed with a little bit of inventiveness and "macgyvering".
    As a fact I used to work on a big 3 ton brute of a lathe in the early days of my career. To be honest the shear power and massive rigidity of the thing actually hid a lot of small important details from me. It would just plow through the metal without giving much feedback about the tuning being optimal or not. As a result I learned the basics, but a lot of the finer details escaped me. Only using a smaller machine would eventually reveal them and open up a totally new level of understanding and challenges.

    The safety acpect of a smaller unit can also not be underestimated. I recall that during the big lathe period I had the most deadly and stupid habit of wearing the lab door access card around my neck on a harness and though I tried to be meticulous about removing this noose before engaging in any machining I still managed to leave it there a few times. Only after being reminded by the clunk of the card tangling from my neck and hitting the toolpost was I woken up to the gravity of the situation. I was lucky, but make no mistake, that machine would not have hesitated taking my soul given the chance.

    Leave a comment:


  • mattthemuppet
    replied
    oh boy, my first lathe made the OPs look like an engine lathe It's a great way to learn good technique (unforgiving machine) in a safe-ish environment (machine isn't going to kill you).

    Leave a comment:


  • dalee100
    replied
    Hi,

    Despite appearances, there are plenty of us that have benchtop lathes and mills. I have an 8x14 from the dreaded Harbor Freight, (and no QC gearbox heaven forbid!), and a G0704 mill from Grizzly. The truth is, even if you owned a 18"x144" 8000lbs lathe - the advice would be the same. The same principles apply no matter whatever country of origin or size. Some of us can just take heavier finish cuts............The talent to run the machines comes from the operator, not the color of paint.

    So pull up a chair and enjoy and learn from all who are here.

    Leave a comment:


  • BCRider
    replied
    There is actually a good portion of the posters here with mini lathes and mills. And since it is a hobby there's no such thing as a "wrong size of machine". Just limits due to size that aim the user towards projects that are in scale with the machines. A lot of great projects can be done on small machines. So don't ever let yourself feel like you don't deserve to be here or that folks won't be interested in what you're doing on your smaller size machines.

    As you learn more and start making things on your mini lathe you might find that you want to upgrade at some point to a different size or nicer quality level. But a lot of folks have taken on the challenge of making their mini lathes into fine pieces of gear at a small size with improvements and upgrades of various sorts. YouTube is full of videos of what they have done.

    Leave a comment:


  • devils4ever
    replied
    lugnut: I agree. All you guys have been very helpful. However, I thought that there were a lot of "mini" machines here since it's a home shop forum. I guess I'm in the minority.

    Ringo: Yes, I'll try that with a dial indicator.

    BCRider: Thanks for your extensive reply. It's all starting to make sense now.

    Leave a comment:


  • BCRider
    replied
    Originally posted by Ringo View Post
    My guess would be to put a dial indicator on the face of the chuck, and push/pull/jerk on the chuck looking for endplay.
    I had chatter problem with my Logan, and when I indicated the face of chuck I saw movement.
    I setup the head bearings properly and all is fine now.
    Yep, that's the trick. But using a lever and fulcrum to do the lifting and pushing so the movement is positive.

    What to look for in the dial gauge is a sudden initial step or jump of the needle. THAT is the free play in the bearings being telegraphed through the structure to the dial gauge. After that further pressure will result in a smooth motion of the needle which is the head shaft flexing like a spring from the pressure. After all when we're working down to thousandths or even fractions of a thou (or hundredths of a mm) EVERYTHING is a spring of some sort. But any play in the bearings will show as a sudden jump of the needle even if you can't feel an associated "click" in the lever or hear a click when things shift.

    Lugnut, happy to help. And thanks for the vote of confidence. I've picked up enough hints from the others here that have helped a lot in my own shop or even just made me think more about what I've done. It's nice when I can pay it back here and there.

    Leave a comment:


  • Ringo
    replied
    My guess would be to put a dial indicator on the face of the chuck, and push/pull/jerk on the chuck looking for endplay.
    I had chatter problem with my Logan, and when I indicated the face of chuck I saw movement.
    I setup the head bearings properly and all is fine now.

    Leave a comment:


  • lugnut
    replied
    WOW, you guys that contributed to this post need a pat on the back. You took your time to help the OP with his problem. I think BCRider"s post was great, actually they was all great, but I think I learned the most from BCRiders the most.
    It's refreshing to see a post like this where the OP gets the help he was asking for without ridicule of his small lathe and his admittance of his lack of the proper technique. Not one photo of corndogs or pizza in the replies. Welcome to the forum Devils4ever.

    Leave a comment:


  • mikey553
    replied
    I do not think the tool stickout is too big to cause the chatter at .005" depth of cut. But spindle bearings are under suspicion - I agree with BCRider here. The design of this little lathe is already deficient. If you divide the distance from the chuck jaws to the front of the bearing by the spindle diameter inside the bearing, you will most likely get a ratio grater than 3. If you ball spindle bearings (2 single bearings in front and back), it will not help either. Such design is very flexible, it lacks rigidity.

    But your lathe should be able to take .005" cuts. Therefore I think the bearings are loose or not preloaded properly. In a lathe spindle the rigidity is very important. You preload the bearings to increase the rigidity even so you sacrifice the bearings life by doing so.

    You can easily test my theory. Take a light cut on a piece of scrap material held just in a chuck. Use the same tool and same stickout as on your picture. If you feel chatter, try to support the part with a tailstock. If you see better results now, you have a spindle problem. Try it and let us know.

    Leave a comment:


  • devils4ever
    replied
    I had great success! I ground a 3/8" tool blank without touching the top surface. It's not pretty, but it works. I reduced the overhang to a minimum, rotated the cross-slide and centered it to give maximum support. I increased speed a little and raised the bit to slightly above the center-line.

    The cut was smooth and has a nice finish. Thanks to all! You guys are great!





    Leave a comment:


  • PStechPaul
    replied
    When I tried knurling on my lathe, I found that the QCTP would rotate when pressure was applied. It appeared that the top of the compound, and/or the bottom of the toolpost, were not quite flat, so I added a piece of drywall sanding screen to provide better grip.




    And, yes, my 200 series (BXA) QCTP set is larger than recommended for my 9x20 lathe, but it works OK. I got a good deal on the set at the LMS booth at Cabin Fever a few years ago - I think I paid about $150 and now the list price is $300.

    Leave a comment:


  • dalee100
    replied
    Hi,

    I use "stickout" to refer to the amount of tool over hanging your tool holder. You have at least 2x's more than needed. A good rule of thumb is only have as much tool sticking out of your tool holder as you really need to do the job. Less stickout = less chatter and better finish. More stickout means more chatter and worse finish.

    Yes turning your tool to the face of your part will give you a much better chance at an improved finish. And stoning a radius on your cutting tool will help to minimize that "threaded" look of a rough finish.

    Most carbide inserts have a radius of some size molded into them. This is done to increase edge strength to make it harder to chip or break the cutting edge. It will also increase surface finish. The drawback to choosing a radius on inserts is the power often required to use them - a larger nose radius tends to need more power to use. Not an issue with large machines, but can be an issue with small lower powered benchtop machines. Brazed carbide tooling can be ordered with a variety nose radii, from sharp like HSS to radii as big as can be ground on them. Brazed carbide has lost a lot of popularity because of the ease of making inserts and convenience of use.

    Leave a comment:

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