What causing this "galling"? - Page 2
Close
Login to Your Account
Page 2 of 6 FirstFirst 1234 ... LastLast
Results 21 to 40 of 113
  1. #21
    Join Date
    Jan 2011
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    149
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    62

    Default

    Looks like a plunge cut straight in. Finish on both flanks is identical. Op needs to use the compound and come in at 29 degrees.

  2. #22
    Join Date
    Oct 2013
    Location
    netherlands Asten
    Posts
    1,159
    Post Thanks / Like
    Likes (Given)
    716
    Likes (Received)
    503

    Default

    take another piece of the same material chuck it in and start a thread LEFT HANDED at a different speeds
    no problem with stopping the lathe in time etc.
    find the ideal speed and try it on a right handed thread

  3. #23
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    18,345
    Post Thanks / Like
    Likes (Given)
    2022
    Likes (Received)
    3166

    Default

    Quote Originally Posted by FlyinChip View Post
    .......

    Confused though about coming in at 29.5 degrees or whatever. The tool is 60 degrees and going into a straight surface. It's gonna cut both sides of the point anyway, no?
    OK... there is a good reason.

    The half nuts are ALWAYS loose to a degree. So, if you come in straight cutting a thread, small differences in the metal can end up pushing the tool to one side or the other. That can cause a "drunken" thread, that wobbles, not a good helix.

    If you are cutting a 0-80 thread on anything the size of an SB9" or larger, that will not likely be an issue. But for that same SB, a 10 TPI thread might easily become drunken if the metal has any hard spots etc in it. Somewhere n between there is a point that the issue is not important anymore, and that depends on how sloppy the machine is, as well as how big and heavy the carriage etc is.

    Angling 29 deg puts the force back against the half nuts and leadscrew, so that the chance of drunken threads is much smaller, probably near zero. You DO want it less than the 30 deg half angle of the thread, so that it cleans up that face of the thread you are cutting.

    Naturally, yu feed in with the compound, and just come back to the same place with the crossfeed after each pass. That's why there are "threading stops", so you have a hard stop to come back to.

  4. Likes Bobw, Illinoyance, Hopefuldave liked this post
  5. #24
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    11,325
    Post Thanks / Like
    Likes (Given)
    3877
    Likes (Received)
    3995

    Default

    The side cutting edge at 10 to 15 degrees top rake angle positive off that edge.. That is the edge on the left side going toward the head stock. with that edge sharp enough to shave your finger nail, With the compound at about 29 to 30 degrees ( swing compound to the right off being straight). Cranking in with the compound hand wheel so the cutting is only at the left edge of the bit.

    The under the top clearance may be 10 to 12 at the left and 6 to 10 on the right...with the end flat clearance 6 to 8.
    Top rake and clearance are just ball park angles ... but one has to look at the way the tool holder holds the bit so the actual angle is off the horizontal as set in the lathe ..not how the bit looks at the grinder.

    The bit height should be set at about center of the part.
    A free down load of How To Run A Lathe is good but to order your own copy is better...a good lathe hand can thread at a couple hundred and more.

    I like to put a piece of tape in a chuck jaw and watch that to make my pull out exact on the spot.
    RPM at about 50 to 80 until you are comfortable threading.

  6. #25
    Join Date
    May 2009
    Location
    San Jose, CA
    Posts
    198
    Post Thanks / Like
    Likes (Given)
    270
    Likes (Received)
    236

    Default

    In case it is not clear, what people are referring to with the angle of the compound at, say, 29.5 degrees, is advancing the COMPOUND to cut the thread. NOT the cross slide. Thus the tool is entering the cut at an angle, not perpendicular. This makes the tool cut on the (left) side of the 60 degree tip, and the (right) side has a small bit of clearance. When you push the tool in at 90 degrees, you are cutting both sides of the tool, and it is a lot harder to get a smooth cut. It is also very important to set the tool up so that the centerline of the 60 degree tip is PERPENDICULAR to the axis of the part. This is regardless of whether or not you are cutting with the cross slide (90 degrees) or the compound (at 29.5 degrees). The tool MUST be perpendicular to the axis of the part. If you are advancing the tool with the compound, the depth of cut is reduced by the cosine of the angle (0.001" on the compound is 0.00087" in the radial direction for a 29.5 degree offset of the compound from perpendicular to the part axis). So you need to do a little thinking about what that means in your situation.

    Another confusing bit is what is meant by 29.5 degrees. Compounds are marked so that the degree marks are either from a normal (90 degrees) reference line relative to the axis of the part, OR on some lathes, measured from the axis of the part. In the first case, setting the compound to 29.5 degrees means that the motion of the compound will be along a line almost perpendicular to the (lefthand) face of the tool. in the other case, you need to set the compound to 90-29.5=60.5 degrees in order to feed the tool so that the (left) edge is cutting about the same across the (left) edge. I am getting old, and sometimes mix things like this up, so if I have it backwards, I hope someone will correct me.

    Cutting threads in other materials a LOT until you are very comfortable with all the required operations is very good advice. 12L14, brass, aluminum, etc. are all a lot easier to cut than 1018. I use carbide pretty exclusively on most materials on a Hardinge HLV lathe with good success. Which brings up another point. What is your stickout, and general rigidity? You mentioned a long part in 304 stainless. WATCH OUT!! I would recommend using a live center to support the work, especially if the part is skinny, sticks out more than say 2xDiameter (lots of personal preferences here- really depends on rigidity and accuracy of spindle). A non-rigid setup can allow nasty chattering, which also ruins the thread.

    In any case, hang in there, and DO NOT be in a hurry to work on the 304 stainless. 304 can be HORRIBLE to thread if your process is not really dialed in. You absolutely must use a good tapping fluid. Tapmagic, Anchor Lube are well known winners. I use Cool Tool also, and do ok. Seriously though, don't assume that because you can cut threads in 1018 you are ready for stainless. Eventually you will crush it, but it really is an unforgiving material in terms of tool geometry, sharpness, speed, DOC, tapping fluid, and so on. If you only need to do this once, and then you will retire to a nice Island in the Caribbean, you could consider roughing the thread most of the way, and then finishing by hand with a really sharp, new die with lots of lube to get the thread on spec and with a good finish.

    Listen to the advice people are giving you! It is priceless.

    All the best,
    Michael

  7. Likes theperfessor liked this post
  8. #26
    Join Date
    Dec 2003
    Location
    suburbs of Ann Arbor, MI, USA
    Posts
    13,150
    Post Thanks / Like
    Likes (Given)
    450
    Likes (Received)
    1077

    Default

    I really like turning and threading W1 drill rod in the soft state. A much better finish is possible. Cold rolled is terrible stuff if you need the inside of it. Outside with minimal machining is not that bad.

    The W1 drill rod also welds very well without cracking or brittleness and doesn't harden. Consequently I have a lot of it in stock in many sizes.

  9. #27
    Join Date
    May 2005
    Location
    Interior British Columbia
    Posts
    2,451
    Post Thanks / Like
    Likes (Given)
    255
    Likes (Received)
    783

    Default

    Dig around Amazon or ebay and find a used, not-current, copy of Technology of Machine Tools, by Krar. Expect to pay under $10.

    Senior High School/ Trades College Course manual. Small words, lots of pictures!

    Read the section on threading, look at the pictures. Follow the instructions. Much more happiness will result.

    The details matter, they make the difference between it coming out good, and what you got!

    Cutting oil or pipe threading oil, hell, even bacon fat from breakfast will go a long way towards making a better cut. If you put a random squirt of soluble cutting fluid in a soup tin, add water and stir with the same paint brush you use to apply it, it stinks less in your house and shop.
    The water will evaporate out if you don't use it all. In a week or so. Add water and stir, and you are back in business.

    Buy some known, easy to thread material. 12L14 is great. 303 if you want stainless. Cheap! No misery by mystery metal!

    Get a decent loupe or magnifier to really see what your cutting edges look like.

    I like the Eze-Lap diamond files. The medium one is great for knocking off a sharp tip or putting a radius on a cutting tool. The fine or extra fine is great for stoning the burr off the cutting edge.

    I have never bothered with rake on HSS for threading. Still got good results. Cutting edge MUST be dead frikken sharp, with the relief under the edge, all the way up to that edge. Get a little angle protractor, both to check angles, and to sight along the cutting tool edge to see if it is ground straight.

  10. #28
    Join Date
    Apr 2018
    Country
    UNITED STATES MINOR OUTLYING ISLANDS
    Posts
    3,973
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    1794

    Default

    Quote Originally Posted by Conrad Hoffman View Post
    ... the proper way is to use the compound so the cutter mostly cuts one side of the thread and just skims the other. Thus the 29.5 or similar angles they tell you to set the compound to.
    That is the "proper" way and even the control makers' threading cycles normally use a 30* infeed but my Sandvik guy, who was sharp, recommended straight-in with inserts. The chips were not as nice but tool life was much better and the threads (full form inserts) were also better.

    But that's at speed on an nc machine. I'm too cheap to do that on an engine lathe when a properly-sharpened $2 HSS tool works the same as a $10 insert in a $100 holder. No idea why people are in love with inserts for that kind of work.

    And brazed carbide takes forever to sharpen and you really need one of those slow-speed diamond wheels to finish it off properly. There's probably a good reason that sharpening tools is the first thing you learn when you start machining.

  11. Likes AD Design, Hopefuldave liked this post
  12. #29
    Join Date
    Jul 2007
    Location
    Missoula Mt
    Posts
    285
    Post Thanks / Like
    Likes (Given)
    7
    Likes (Received)
    101

    Default

    Try hhs and a faster spindle speed, cut a relief at the end so you dont have to disengage fast, set the compound at 29d and light finish cuts, life should improve...Phil

  13. Likes Hopefuldave liked this post
  14. #30
    Join Date
    Jun 2012
    Location
    Eastern PA
    Posts
    1,026
    Post Thanks / Like
    Likes (Given)
    298
    Likes (Received)
    465

    Default

    Quote Originally Posted by ferretlegger View Post
    ... the tool is entering the cut at an angle, not perpendicular. This makes the tool cut on the (left) side of the 60 degree tip, and the (right) side has a small bit of clearance. ...
    Close, but no cigar. The right side has no clearance, but takes a very small cut. If there was clearance on the right side, you'd end up with steps in that flank of the thread.

  15. Likes ferretlegger liked this post
  16. #31
    Join Date
    Dec 2017
    Country
    UNITED STATES
    State/Province
    Rhode Island
    Posts
    204
    Post Thanks / Like
    Likes (Given)
    3
    Likes (Received)
    8

    Default

    thanks for the tips. I do get the feed at 29.5 degrees now.

    as to tooling, where's the best place to buy those square HSS blanks either 3/8" or 1/2"?

  17. #32
    Join Date
    Aug 2015
    Country
    UNITED STATES
    State/Province
    Illinois
    Posts
    1,489
    Post Thanks / Like
    Likes (Given)
    1092
    Likes (Received)
    635

    Default

    I think your decision to flank feed the tool will pay off. Also consider the dark cutting oil used for threading pipe which is even gummier than 1018.

  18. Likes Hopefuldave liked this post
  19. #33
    Join Date
    Jun 2012
    Location
    Michigan
    Posts
    5,100
    Post Thanks / Like
    Likes (Given)
    4657
    Likes (Received)
    3076

    Default

    The problem isn't because it's 1018. I've been cutting 1018 for 30 years and the only time I had a part that even remotely resembled the OP picture is when I was first learning this trade.

  20. #34
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    11,325
    Post Thanks / Like
    Likes (Given)
    3877
    Likes (Received)
    3995

    Default

    Some such galling can come from the tool top rake being negative on the right side of the bit and feeding straight in on the part. The cutting pressure builds up until the part material can let lose with being rubbed off not cut off.. Then a sudden chatter causes the galling.
    If a lathe is sound enough to turn an OD with no galling it should also be sound enough to turn a thread with no galling.
    The compound at 29/30* and compound in-feed allows only the positive (left) edge to do the cutting.

  21. Likes ratbldr427 liked this post
  22. #35
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    11,325
    Post Thanks / Like
    Likes (Given)
    3877
    Likes (Received)
    3995

    Default

    Q:[as to tooling, where's the best place to buy those square HSS blanks either 3/8" or 1/2"?]

    I think it is good for a new guy to turning to buy a used bunch of bits so one can have a good look at how different bits are ground....and used.

    One can hold them on a parked grinder wheel and get feel how to sharpen.

    Lot of 13 HSS and Carbide Tipped Lathe Tool Bit's 1/2" | eBay

  23. Likes Bobw liked this post
  24. #36
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    11,325
    Post Thanks / Like
    Likes (Given)
    3877
    Likes (Received)
    3995

    Default

    Chip breaker carbide inserts can be/act positive on both right and left edge so may be used straight in, but flat inserts not.
    I still thread only at 29-30 and compound in-feed.

    *The shoulder cut at going near the head looks very poor so likely your bit is not sharp or does nor have any top positive rake angle....or there is not enough clearance under the cutting edge.

    Good to file test parts to know they are HSS compatible...1018 is soft in its normal state..

    McMaster-Carr

  25. #37
    Join Date
    Apr 2018
    Country
    UNITED STATES MINOR OUTLYING ISLANDS
    Posts
    3,973
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    1794

    Default

    Quote Originally Posted by michiganbuck View Post
    Chip breaker carbide inserts can be/act positive on both right and left edge so may be used straight in, but flat inserts not.
    The sandvik fullform inserts I was using were flat on top, relief on both sides. Made a funny chip but better tool life going straight in.

    But again, that was nc. I would not try that on an engine lathe.

  26. #38
    Join Date
    Mar 2006
    Location
    jacksonville,fl.
    Posts
    1,258
    Post Thanks / Like
    Likes (Given)
    1100
    Likes (Received)
    420

    Default

    If your lathe /set up were rigid enough any angle less than 30deg would leave steps on the back side.That is why it is a good idea on the last few passes to feed straight in a few thou.
    As michigan buck said it is the extreme negative rake due to the helix on the back side of the thread that causes the tool to be unbalanced;the back side tends to push the tool to the front free cutting side and most set ups are not rigid enough to control it.

    You would not expect to cut any material with a tool angled to the work the same as the back side of a thread is.

    To add it is the load on the lead edge that forces the back edge(spring effect) to take up the 1/2deg clearance and skim that surface in a 29 1/2deg setting.

  27. Likes michiganbuck liked this post
  28. #39
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    11,325
    Post Thanks / Like
    Likes (Given)
    3877
    Likes (Received)
    3995

    Default

    Quote Originally Posted by ratbldr427 View Post
    If your lathe /set up were rigid enough any angle less than 30deg would leave steps on the back side.That is why it is a good idea on the last few passes to feed straight in a few thou.
    As michigan buck said it is the extreme negative rake due to the helix on the back side of the thread that causes the tool to be unbalanced;the back side tends to push the tool to the front free cutting side and most set ups are not rigid enough to control it.

    You would not expect to cut any material with a tool angled to the work the same as the back side of a thread is.

    To add it is the load on the lead edge that forces the back edge(spring effect) to take up the 1/2deg clearance and skim that surface in a 29 1/2deg setting.
    and very often there may be a build up at the OD making the OD a little larger.. so a touch of a hone or fine file maybe needed at near the last passes.

  29. Likes leeko liked this post
  30. #40
    Join Date
    Mar 2009
    Country
    UNITED STATES
    State/Province
    California
    Posts
    5,586
    Post Thanks / Like
    Likes (Given)
    103
    Likes (Received)
    1079

    Default

    What is you depth of cut routine look like. That would be the number of passes with the depth of cut on each pass. Such as:

    1. .010
    2. .007
    3. .005
    4. .005
    5.
    6.
    .
    .
    .
    last pass something like .002.

    When I look at your picture it reminds me of threads that I cut in some 304SS which was probably imported for Vietnam or China.
    The scale of the tearing is much smaller but it can be seen at 5x or 10x.

    The one book I like the best on threading is Machine Shop Practice Vol 1 by K. H. Moltrecht.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •