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Thread: Learning to lathe [things]

  1. #1
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    Default Learning to lathe [things]

    The past two days have been spent working a fair bit on my lathe, trying to learn how to knurl.

    I have purchased a set of cutting knurls and their toolholder, that allow me to cut a 45-degree diamond pattern.

    When you haven't even seen one of these in action, it is hard to know if you've set the tool up properly, but suffice it to say that my first few attempts fell dismally short of being satisfactory. So off to the Practical Machinist website, where I asked for advice. The replies led me to another website, from a competing manufacturer to my tooling, where there was some very instructive material posted. See this.

    Armed with a little more knowledge than I had before, I managed to get something resembling what I was looking for, although it still isn't perfect. Of course, that will just mean a bit more lathe time.

    Two shots, both of the same piece, just one is darker than the other to cut down on the reflections:


    Last edited by PhotonFanatic; 12-19-2006 at 10:10 AM.
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    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    Knurling is an art. Also luck is involved.
    Cut knurling is very popular in Europe
    but it think it is now gaining popularity here.

    With soft materials like aluminium, you need to
    be able to get rid of the excess metal from being re ground into the pattern. Cut knurling is meant to alleviate this problem.

    Some people hate parting off. I hate knurling and am always on the look out for tips to improve.

    You seem to be on the right track.
    David............................................. "A few of my Home Built lights"

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    Flashaholic* Mirage_Man's Avatar
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    Default Re: Learning to lathe

    Guys how does this differ from other types of knurling? I have a knurling tool that came with my Phase II set. It has the two wheels that you push up against the work and give it a slow RPM and feed. With lots of lube of course.

    Just wondering what other options are out there as I hate to put that much pressure on my poor old 10L.

    I saw the post where Scott is using a "clamp" type knurling tool. Is that a better way to go?

    MM

  4. #4
    Flashaholic* will's Avatar
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    Default Re: Learning to lathe

    knurling is just pushing the metal in, and letting the peaks form. the knurling tool that is like a clamp only puts pressure on the work and the clamp itself. The other method puts pressure on the tool, pressure on the work, AND pressure on the bearings in the lathe.

  5. #5

    Default Re: Learning to lathe

    A much better way to knurl, and it's easier on the lathe too.

    TB

  6. #6
    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    For the sort of work we do, and the fact that most of our machines are on the 'light' side, the straddle/sissor style of knurling tool works well and is affordable.

    PhotonFanatic's new knurler does not squeeze the metal but rather cuts it. There is a little strain on the work piece,spindle bearings and cross slide nut and screw, and they say that the quality and consistency of the knurl produced is far better than any other.

    In my experience, Aluminium is the hardest metal to get a good knurl.

    Even the pros can set up their CNC machines for a 500 part run and get good knurl results.

    Repeat the same set up tomorrow and the knurl is wrong and they have to spend time tweaking things.
    Last edited by Anglepoise; 10-23-2006 at 08:45 AM.
    David............................................. "A few of my Home Built lights"

  7. #7

    Default Re: Learning to lathe

    I have two of the Eagle Rock/ Knurlcraft K1-201's, and they aren't inexpensive...I paid $250 each from McMaster, but it looks like they don't carry this knurling tool anymore. I've only been able to consistantly knurl stock that's .995" dead, and I only knurl solid stock.

    This method makes it much harder to produce a finished part, but it's all I've been able to do with good results.

    If the scissor pressure applied is too great, the knurler will move my tool post, everytime...and I'm sure you'ld cringe watching me tighten the tool post pre-knurling.

    TB
    Last edited by TranquillityBase; 10-23-2006 at 04:31 PM.

  8. #8
    Flashaholic* will's Avatar
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    Default Re: Learning to lathe

    there is a good write up over here

    http://flashlight-forums.com/index.php?topic=3740.0

    it shows the different tools

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    Default Re: Learning to lathe

    One night's work--meager as it was:



    Really spent most of the time switching tool holders and inserts to see how the new stuff from Sandvik worked.
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    *Flashaholic* wquiles's Avatar
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    Default Re: Learning to lathe

    Outstanding!!!

    You are certainly getting the job done

    Will
    Please no PM/Visitor Msg's. Email for questions/Paypal: wquiles [at] gmail {dot} com. Please visit my new website.

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    Default Re: Learning to lathe

    Tonight's experiment: I have a tube of 6AL4V Titanium that I wanted to play with--turn it down and cut it off into less than 2" lengths for future anodizing experiments.

    Now I don't have any inserts or tools specifically for Ti, but taking Anglepoise's suggestions to heart, I decided to give it a try using what I do have.

    I used some Sandvik inserts designed for Al. They are brand new, and therefore very sharp. Cranked down the RPMs and went to work. This is after some sanding and polishing, but nothing close to what the Kenster can do. I'll poll him for his techniques later.




    Overall, I was pleased with how easy it was to machine, but then again, I haven't tried knurling it, nor have I tried to thread it yet.
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    *Flashaholic* wquiles's Avatar
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    Default Re: Learning to lathe

    Good going Fred!. You are already more brave than I am by using Ti. I am sticking to Al for now, even if TranquillityBase is hounding me to try Ti already

    Will
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    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    Fred,
    You should not have any problems threading Ti. Knurling.....well that's another matter<g>.

    As far as getting the best finish on Ti. This is the one time you can ramp up the speed safely. I am still learning Ti secrets, but found that the best surface finish was with a round nose tool, .002>.005 thou cut at approx 780 rpm, (200sfpm)

    This was the only time I was able to get away with some speed and I was delighted with the finish.

    Just carry on experimenting and it will all drop into place.
    David............................................. "A few of my Home Built lights"

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    Flashaholic* KC2IXE's Avatar
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    Default Re: Learning to lathe

    you know, with the right inserts, Ti can be cut at around 1400 sfm - crank up the speed for surface finish

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    Default Re: Learning to lathe

    you know, with the right inserts, Ti can be cut at around 1400 sfm - crank up the speed for surface finish


    I'm all eyes and ears! What would your insert material recommendation be, please?
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    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    Quote Originally Posted by KC2IXE
    you know, with the right inserts, Ti can be cut at around 1400 sfm - crank up the speed for surface finish
    Is that a typo? Do you mean 1400sfm or rpm?

    I have never seen any recommendation any where near that high figure ( 1400 sfm translates to approx 6000rpm on an 1" diameter) and would like to have more info even though my poor lathe can not get past 1000 rpm and thats on a good day.
    David............................................. "A few of my Home Built lights"

  17. #17
    Flashaholic* KC2IXE's Avatar
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    Default Re: Learning to lathe

    Quote Originally Posted by Anglepoise
    Is that a typo? Do you mean 1400sfm or rpm?

    I have never seen any recommendation any where near that high figure ( 1400 sfm translates to approx 6000rpm on an 1" diameter) and would like to have more info even though my poor lathe can not get past 1000 rpm and thats on a good day.
    Nope guys - NOT a typo!!! 1400 sfm!!

    Go to the Sandvik site

    Go to the insert guide
    I picked (at semi random)
    Turning, External - Longitudinal, C-shape insert 80° - Lead angle -5°, T-MAX M, screw and top clamp, Square shank

    ISO Area "S" insert grades
    S= Heat resistant and titanium all,

    - enter the material ASTM B348 (one of the specs for 6al4v)


    and the one I grabbed this AM came out to 1400sfm - the one I JUST picked came out a bit over 900 -

    CNMG 09 03 04-PF 1525
    CNMG 321-PF 1525

    ap = 0.4 mm ( 0.25-1.5 )
    0.016 in ( 0.01-0.059 )
    fn = 0.15 mm/r ( 0.07-0.3 )
    0.006 in/r ( 0.003-0.012 )
    Vc = 280 m/min ( 350-215 )
    925 sfm ( 1150-705 )

    (wish I had written down the one from this AM)

    When I figures a .005 DOC and the like - came out to 1400sfm.

    CNC in industry - the speeds can get CRAZY if you have the HP and rigidity

    A couple of years back, I got some high end inserts - I found I can wind my Craftsman 12 out most of the time, and it's got a 2K+ spindle speed

  18. #18
    Flashaholic* KC2IXE's Avatar
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    Default Re: Learning to lathe

    forgot to mention - boy was I scared the first time I turned a piece of 3.5" diameter 6061 at 2K RPM - but BOY it came out like a mirror

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    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    Well something is wrong because on page A82 of the Sanvik 'Metal cutting
    Technical Guide' they recommend a high of 670 sfm using there H10 carbide insert at a .004 feed and that is for Ti low grade( Commercially pure soft stuff)
    The rating for ASTM B, Grade 5: Ti-6AL-4V drops the SFM down to 260.

    And that rating is full flood coolant with their recommended for Ti, H10 insert
    and a 15 minute life expectancy of the cutting edge.

    So who knows. All I know for sure is that my little lathe can just hit 1000rpm with the bearings warmed up.
    David............................................. "A few of my Home Built lights"

  20. #20
    Flashaholic* KC2IXE's Avatar
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    Default Re: Learning to lathe

    Quote Originally Posted by Anglepoise
    Well something is wrong because on page A82 of the Sanvik 'Metal cutting
    Technical Guide' they recommend a high of 670 sfm using there H10 carbide insert at a .004 feed and that is for Ti low grade...snip...
    Yeah - I have not checked all the various grades, but I know there can be HUGE differences in speeds between grades

    Believe it or not, I HAD/HAVE flood cooling on my little Atlas. Makes a mess, but when you need it, you need it. I say had/have because I hvae not NEEDED it since I moved 5 years ago!! Recently, I've been working mostly in brass, and I'm actually speed limited by a counterboring operation, so turning and the like have not needed flood cooling

    I hope my one paying client doesn't get TOO shocked at the price jump next time he orders. Hvae you looked at the price of brass lately? GASP

  21. #21
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    Default Re: Learning to lathe

    Speaking of surface finishes, take a look at this:



    Unfortunately, I don't know the magnification involved in these photos, but suffice it to say, I want the tooling that did the machining on the left.

    Of course all you bright guys will have this figured out in a heartbeat.
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    Flashaholic* Carpe Diem's Avatar
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    Default Re: Learning to lathe

    Hi PhotonFanatic...

    You and I are now kindred spirits!

    Here are my credentials in the wide world of lathes:
    http://candlepowerforums.com/vb/show...38&postcount=8


    (SORRY...I just couldn`t resist!)

    Proud custodian of Tvodrd`s works of art; Peter`s Arc`s and Brass Arc AAA; Mike Jordan`s gems; some really great lights from Enrique, Fred and Tain ....and *several* of Don`s mods, Ti`s and McLux masterpieces.

  23. #23
    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    As far as a good finish is concerned, I will pass on what I know.
    Now if we use a regular nice and sharp carbide or HSS tipped tool
    and we make a finish cut, it will most probably come out like a very very very fine male thread. Think about it for a minute. Sharp pointy tool being traversed
    along the part. A thread effect will be clearly seen under low power magnification.

    Now what we need to do is blend in the hills and valleys and this is done with a tool with a rounded nose. Now I am not talking about a blunt tool, just a very sharp tool with a round tip.

    Now we do another finishing traverse, same speed , same depth and same feed.
    Now in theory the finish will be much much better. You can actually test this out with a parting off tool with a gentle radius. You can get an amazing finish.

    Now I said above 'in theory' as for this to work, the lathe must be rigid with no play in bearings , slides etc. Otherwise the thread effect will just be swapped for a 'chatter' effect as the round nose tool has more area in contact with the part.

    Upping the speed also helps to flow the hills and valleys but also can be limited by
    the rigidity of setup and work piece.

    On our small, inexpensive machines, we will always be somewhat compromised.

    Hope this helps a bit.
    Last edited by Anglepoise; 11-02-2006 at 11:11 PM.
    David............................................. "A few of my Home Built lights"

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    Default Re: Learning to lathe

    Hi PhotonFanatic...

    You and I are now kindred spirits!

    Here are my credentials in the wide world of lathes:
    http://candlepowerforums.com/vb/showpost.php?p=1504538&postcount=8


    (SORRY...I just couldn`t resist!)




    But at least I bought a lathe, rather than talking about buying one!
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  25. #25
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    Default Re: Learning to lathe

    Anglepoise wrote:

    As far as a good finish is concerned, I will pass on what I know.

    Now if we use a regular nice and sharp carbide or HSS tipped tool and we make a finish cut, it will most probably come out like a very very very fine male thread. Think about it for a minute. Sharp pointy tool being traversed
    along the part. A thread effect will be clearly seen under low power magnification.

    Now what we need to do is blend in the hills and valleys and this is done with a tool with a rounded nose. Now I am not talking about a blunt tool, just a very sharp tool with a round tip.

    Now we do another finishing traverse, same speed , same depth and same feed.

    Now in theory the finish will be much much better. You can actually test this out with a parting off tool with a gentle radius. You can get an amazing finish.

    [snipped]

    Hope this helps a bit.

    David,

    Yes, your explanation is quite helpful, and that technique is one that I am aware of.

    There is also the use of Wiper inserts, from the likes of Sandvik:

    The wiper technology incorporates five radii to "build" the nose radius of the insert. The main cutting radius is situated at the point of the insert. Behind this radius on either side is the wiper radius itself. It is blended into the main cutting radius by using a blending radius. This reduces tool pressure by eliminating the need to use a flat as the wiper.

    As the insert enters the material, its main cutting radius cuts in the same manner as a standard nose radius. The cutting action produces feed lines that are equal to the feed rate being programmed. These feed lines have peaks and valleys (also called "scallops") that can be measured using a profilometer. The trailing wiper radius removes the scallops as it passes. As a result, improved surface finishes and high feed rates are possible.

    I hope to try this on my lathe at some point in time, but wipers are primarily designed for the larger, more rigid CNC machines, so I have no idea if they will work on my manual lathe. But it will be fun trying.
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  26. #26
    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    Quote Originally Posted by PhotonFanatic

    I hope to try this on my lathe at some point in time, but wipers are primarily designed for the larger, more rigid CNC machines, so I have no idea if they will work on my manual lathe.
    You have hit the nail on the head. 90% of what is written on tooling tech is for production, very rigid machines. Sandvik has nice stuff but all set up for industrial use. Min order quantity on inserts is 10.Can get expensive and is not necessary for us hobbyists.
    David............................................. "A few of my Home Built lights"

  27. #27
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    Default Re: Learning to lathe

    Sometimes this lathe work is much, much tougher that one might expect. Most lathes do not present any problems when it come to cutting threads, but my lathe is basically a metric lathe, and uses changegears to cut Unified National threads. Problem is that the manual doesn't give enough info to be able to determine which gears exactly to use for the standard U.S. tpi's. Nor did it provide any insight into how to operate the machine for threadcutting.

    My first attempts were terrible. I just couldn't get the second pass, or the third, etc., pass of the tool to align with the first cut. I wasn't disengaging the half-nut, but I was unconnecting the gearbox mechanism that drove the leadscrew. Mistake. The real solution was to reverse the spindle! Thanks to a chapter in Machine Shop Essentials for that tidbit!

    Here's a thread I'm almost proud of, except that it isn't quite 24 tpi, but real close:


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  28. #28
    Flashaholic* Anglepoise's Avatar
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    Default Re: Learning to lathe

    Looks good. Very good.
    Now you will have to get the change gears sorted.
    Sadly " isn't quite 24 tpi, but real close:" is not going to work.

    Practical Machinist website or 'Homeshopmachinist.net" will help on that.

    A tip that was passed on to me you might want to put away. When you get it all sorted and you are about to commence internal threading, coat the area to be threaded with a black 'Sharpie' ink pen. Now you can see how the depth is going and when the thread has been completely formed.
    Without this, it all looks shiny and is difficult to see the hills and valleys.
    Good luck.

    PS. Will you be offering good Crees in the future.
    David............................................. "A few of my Home Built lights"

  29. #29
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    Default Re: Learning to lathe

    David,

    All your tips are great--thanks for sharing them.

    No, I am not about to jump on the Cree bandwagon, for a couple of reasons: 1) the Cree is a PITA if it is an unmounted LED (I would only order one on a board), and 2) Philips-Lumileds will soon have something to kick Cree's butt. Think thin film technology, think a K2 with 300 lumens at 1A by the end of 2007, lower outputs before then.
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  30. #30
    Flashaholic* yclo's Avatar
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    Default Re: Learning to lathe

    Always find interesting threads in this part of the forum, here's my first attempt at knurling using a scissor type knurler on a Taig:



    I didn't turn on the lathe at all, just spun the spindle by hand and tightened the knurler progressively. For some reason I couldn't get the knurler to move along the work, possibily due to the setup not being rigid enough? There's also the problem of the top knurling wheel not lining up with the bottom wheel.



    The Taig can't do threads..

    -YC

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