Achievable tolerances on a hobby lathe - Page 2
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  1. #21
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    Of course you can, itís a one off, not a batch run, itís like pancakes the first is always a throw away, hitting H8 with a little shaft is just as hard with a bloody big pacemaker or monarch ( I ince saw a 1/2Ē shaft in a craven 72Ē swing lathe, Chuck in a Chuck in a Chuck in a Chuck it was funny seeing this bloody monster lathe with a tiny thing in it, done for a laugh btw) just take your time, HSS tool, stoned, ( oilstone not whacky baccy) donít bother with insert tools,
    Iíd certainly think of getting a better lathe but your pockets determine that, bout ml7 size or box Ford
    Mark

  2. #22
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    You can generally hit any tolerance you want with handwork (filing, polishing, honing, lapping etc.) if you know what you're doing. But turning/tooling directly to that tolerance with the cutting tool is a whole 'nother ballgame.

    For the purposes of the pin you've mentioned, I might be inclined to purchase something as suggested by thermite and modify it to suit.

    As regards the lathe, I think you should get one. It sounds like you have the right mindset to enjoy the machine and learning how to use it better. If you want to buy a cheap import as a first machine and learn to use it, that is up to you - if you begin to appreciate the work and machinery you will probably want to upgrade to something better later. The cheap machines can do that level of work IF you do the precision part using one of the "by hand" methods I mentioned earlier. A nicer machine ought to be able to cut the part right to that tolerance.

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  4. #23
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    Quote Originally Posted by thermite View Post
    Fear not. EVERYBODY on the planet surpasses ever' body else at SOMETHING.

    Even our wind-up-toy Pretezelbent knows better than the "geniuses" as advise him if he needs to check his watch to see if it is time to go pee?
    ....
    And your surpassing skill is....?

    Probably sticking your nose up the former guy's ass....

    And HIS surpassing skill, is whining and blubbering about unfair life is all of a sudden.

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  6. #24
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    If you have an access to purchasing a used industrial lathe made in the USSR, I highly recommend it instead of investing your money into the Chinese toy (to put it politely). I'm sure you can find a local machinist who will help you check a used lathe or even find one.

    I'm a strong believer in starting with better tools to learn right habits, enjoy the process and avoid bitter disappointment in the machining (or any other) field. Besides, you have to understand that tooling for any machinery will always be another sizable investment, and you don't want to waste money on something that you will DEFINITELY dislike shortly after trying.
    Last edited by MichaelP; 09-10-2021 at 07:37 PM.

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  8. #25
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    Quote Originally Posted by jim rozen View Post
    And your surpassing skill is....?

    Probably sticking your nose up the former guy's ass....

    And HIS surpassing skill, is whining and blubbering about unfair life is all of a sudden.
    WTF?

    Your OWN nose up you OWN sewercidal Bidenista a**.... in search of what? DJT's discarded condoms? Seems to be all you EVER needed, Oh perrenial whiner-blamer-hater proletarian limpet-mine.

  9. #26
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    Turning small shafts with a high L/D ratio doesn't have much to do with the lathe, which can be a piece of junk. The reason is that a moderately sane person would use a box tool of some sort, putting the burden of precision on the box tool, not the lathe. A completely sane person would just order centerless ground material of the correct size and not mess with it. The 6x12 hobby lathes vary, but most are going to drive you crazy. Drive? Probably more like a short walk.

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  11. #27
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    Quote Originally Posted by Arcadium View Post
    Hello,
    I want to buy a lathe with some parts in mind.
    I was looking at Holzman ED400 FD lathe.
    I need to turn a 8mm in diameter 40mm stickout brass shaft with h8 tolerance (+0; -0.022 mm)
    Also I need to ream a 8mm hole in a 10mm brass rod(same stickout), also with a H8 tolerances.

    My question is if you profesonals could adjust such level machine to achieve these results? The work amount to achieve the result is not that important, that kind of work is enjoyable for me
    "Its not the machine its the machine behind to machine".

    Roger

  12. #28
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    Quote Originally Posted by Arcadium View Post
    I think you seen a stipple art somewhere and there also a thing like wood burning (pyrography).
    So I want to stipple on wood. Just like wood engraving with laser. But I have found that laser can't produce high contrast on wood, i don't know if they just blast away coal particles or it's some kind of another phenomenal.

    I have made a simple CNC for tests and shows promise. The only problem is that it takes ages, so I want to increase the number of heads and reduce the dot size for better results.
    How about in English this time eh ?

    What parts doo you want to make on your hobby lathe ?

  13. #29
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    Arcadium: You are in Lithuania? Find your local makerspace/hackerpsace/technical college. See if they have a lathe (I did a quick google and there are several sprinkled around your country.) Talk to the people at the makerspace about your project and get some hands-on experience using a lathe. Your money will be MUCH better spent using their machines (some of them looked like some good old cold-war era Eastern European machines which were generally very well made.) You may find that for the cost of a few months membership you get the parts you need and the results you want. You may also find that some of the people at these places have a LOT of experience doing the kind of stuff you want to do... and they speak Lithuanian as their first language. Your English is excellent BTW (FAR better than my Lithuanian!)
    Good Luck.

    -DU-

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    I once did the chuck in a chuck.....overspeeded the big chuck,which relaxed its grip on the 12" 3 j,which went for a turn around the shop at 2000 rpms when the spindle brake grabbed automatically .....for the mechanically challengd ,a Pratt 3j 12" weighs some 100lbs ,and makes a nifty jumping jack come spinning top.

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  17. #31
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    High thermal conductivity, low reactivity at high temperatures, easy to machine...

    Sounds like nickel plated copper might be a good bet for your application?

    For simple wood burning, nickel plated steel might work just as well. 12L14 since mechanical performance isn't really a concern? As long as the lead content isn't an issue.

    Otherwise if you need a truly high performance material that will last a long time you'd be looking at something like Monel or cupronickel.

    Also, when pricing your lathe... consider you will end up spending quite a bit in tooling and measuring instruments unless you can score someone's old hobby machine that's already been tooled up. Easily $1,000 if you're serious about the hobby and want quality tools. Hell, I spent that much on my quick change tool post + holders alone because I didn't want Chinesium garbage. Insert tooling extra on top of that, never mind calipers, micrometers, boring bars, precision level, yada yada...

    That's not to say you can't get *into* the hobby for less. As long as you have the patience to grind your own tools & keep them sharp, re-center your tools manually after every tool change unless you use a 4-position post and shim stock, etc. Price vs productivity you could say. You'll only get out of it what you're willing to put in. Whether by direct purchase or 'sweat equity'.

    +1 for obtaining a used quality machine vs a cheap new Chinese "lathe shaped object" as they're commonly referred to as around here. You'll be hard pressed to find a single person who will recommend a Chinese mini-lathe around here.

  18. #32
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    There are no tolerances on a part. For everyone to know.

  19. #33
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    The "Mini lathes" probably are just not good in general.

    What I am used to calling a "hobby" lathe is (in the USA) a Logan, or Southbend. In the UK, a Boxford, or Myford. Not sure what it would be in other places.

    But generally, that class of lathe is made to be able to work to about +- 0.001 inch, which is 0.025mm. A very good operator can, in limited circumstances, do better than that, but the basic construction and tolerances of the machine limit to around 0.025mm.

    A "Mini lathe" may not do that well, and the ones I have seen have other problems. The machines I named above were all made to be "light industrial", or school, machines. They were intended to work right, but not made (or priced) for extreme accuracy.

    The mini lathes are made to sell, not necessarily to work well.

  20. #34
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    Since I'm lazy and don't like to reinvent the wheel, if I were trying to build a "dot matrix wood-burner tip", I'd seriously look at stock or modified Metcal/Oki soldering tips and power-supplies. The Metcal/OKI soldering tips use the curie-point construction of the tip, and a high-frequency power supply, that supplies power as-needed to keep the tip at a constant temp; they do not require a large "thermal mass" to maintain the tip temp. The tips are available in a wide variety of styles, and several setpoint temperatures, and you could customize them if needed. You could also connect the power-supply input directly to the tip cartridge (without a handpiece), with the tip clamped in a (spring-loaded) bracket, for a compact, replaceable tip. The tip cartridges are about 5mm dia, and 100 mm long, with a coax looking connector on the end. There are lots of older Metcal power-supplies on Ebay, and tips, that work just fine. The "STTC" style tips are the best IMO (these are the ones with the coax-looking connector).

    Tip example:
    (1) OKI / Metcal STTC-031 Sharp Conical Replacement Cartridge Tip for MX series | eBay
    Power Supply (very old, built like tanks, I have three)
    Lot of 4 Metcal PS2E-01 Soldering Power Supply Hand Base Holder W/Power Cord. | eBay
    Cable and handpiece (note coax-looking (MX for STTC tips) plug versus pinned plug
    Metcal MX-RM3E Hand-Piece/Cable for MX Systems 696738209602 | eBay
    Metcal website, tips (again, the tips come in several different setpoint temperatures)
    https://store.metcal.com/en-us/shop/...ibute=name-asc

    One other comment on the lathe; a built-in collet-system and good quality collets are another feature useful for small precision work. Cheers

  21. #35
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    For less money and far better lathe you can get a sherl*ne. It will handle that size part *better* than 7x12 or 72x120. This will allow you to enjoy the process more - freeing your mind for the saurat-bot design and details.

    *better* = easier, It is designed for this size work.

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    Quote Originally Posted by rogertoolmaker View Post
    "Its not the machine its the machine behind to machine".

    Roger
    Correction- Its not the machine its the man behind the Machine

    Roger

  23. #37
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    A Sherline is slow and a pain in the butt for anybody used to a SB or Logan. It's good for light cuts only, but you can machine steel. Threading is annoying, but in spite of all that, it will hold reasonable tolerances and has enough accessories to do pretty much anything you'd want, up to its size limits. We have a few at work for specialized jobs and are reasonably happy with them.

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    I think I could make that part on such a lathe.
    A good sharp HSS tool bit. the compound swung for a small increment cross in feed. a few tries to see how close I could get with little worry of going under and expecting hand-finishing from there. A tool bit scalp to center the reamed hole. having a reamer .0002 smaller than my bores size target, knowing that I may need to use that tail center. not uncommon for watchmakers to make a close part on a small lathe when time was not an issue.

  25. #39
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    Longest mini lathe thread ever...

  26. #40
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    Quote Originally Posted by Mechanola View Post
    There are no tolerances on a part. For everyone to know.
    Yup, no print posted, who can comment yes or no ?


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