Skip to Content.
Sympa Menu

machinist - [machinist] More Tramming

machinist@lists.ibiblio.org

Subject: Machinist

List archive

Chronological Thread  
  • From: Lawrence London <lfljvenaura@gmail.com>
  • To: machinist@lists.ibiblio.org
  • Subject: [machinist] More Tramming
  • Date: Thu, 13 Feb 2014 12:49:57 -0500

http://www.practicalmachinist.com/vb/general/more-tramming-280130/

Thread: More Tramming

  1. 02-13-2014, 11:43 AM #1
    Conrad Hoffman's Avatar
    Conrad Hoffman is online now Stainless
    Join Date
    May 2009
    Location
    Canandaigua, NY, USA
    Posts
    1,581

    Default More Tramming

    OK, yet another tramming question. For the things I make, flatness is important. Multiple passes of a small cutter can't leave slightly tilted parallel paths, not even tenths. When I use a fly cutter, a dished surface is a big no no. 1) Does it make sense to put a bar in the vise and make a cut in the X direction, and then tram off that surface? IMO, that surface is now parallel to the travel, which is what I want, not the table or vise surfaces, which may not be perfect. Then do same for Y. 2) I know I can measure this, but it would annoy people if I did, so how good or bad are those Kurt swivel bases under a 6" Kurt vise? In fact, how good are the vises.

    What I'm after is a surface that can be quickly lapped to flat, and the regular methods aren't quite good enough. Sure, any surface can be lapped, but I'm lazy. I want it closer to start with. I know a surface grinder would solve all, but the shop ain't got one.
  2. 02-13-2014, 11:46 AM #2
    jrmach is online now Stainless
    Join Date
    Jun 2012
    Location
    Boise,Idaho USA
    Posts
    1,036

    Default

    Sand it on a surface plate after milling as good as you can.
  3. 02-13-2014, 12:04 PM #3
    michiganbuck is online now Stainless
    Join Date
    Jun 2012
    Location
    Michigan
    Posts
    1,328

    Default

    I think getting dead tram is next to impossible on most mills. For a large circle like tree panning tool even though it may look good it is often not near flat. .0001 or .0002 per inch is much in 4 inches. Scallops with a 2 inch fly or cutter may look worse but may be actually better. Much like What you mention.

    We had lapping plates of cast iron with grove lines and with checking them for flatness every once and while, and careful hand held figure 8 and turning could make flat and finish. Using Clover compound. Steel plate should work OK.

    http://www.ebay.com/itm/Lapping-Mach...item1e86f02c68

    Any plate of iron grooved and then sent to a good Blanchard (or surface grinding) shop for dead flat might make one for lower price.
    I once made a power lapping table of a car flywheel that was Blanchard ground and then mounted on a vertical shaft geard to turn at about 200 rpm.
  4. 02-13-2014, 12:05 PM #4
    tay2daizzo8 is online now Plastic
    Join Date
    Nov 2013
    Location
    north of Bean town
    Posts
    22

    Default

    hold lightly in machined aluminum jaws try and take one pass if this isnt possible cut in one direction only rough it down to .004 above finish then finish cit....cant say more without knowing material/size etc. i consistently get .0005 over 8.00 before lapping.
  5. 02-13-2014, 12:22 PM #5
    Metalcutter's Avatar
    Metalcutter is online now Titanium
    Join Date
    Sep 2005
    Location
    San Diego
    Posts
    2,622

    Default

    The tram has to be to the Table Travel (X and Y).

    The larger the indicator circle the better the tram.

    If you decide to mill a surface, then check it with the indicator, by having the table travel the distance, and check for no needle movement. Both axes. If you lock the knee don't unlock it, or you wont know where you are. Don't know your mill.

    Actually you are headed in the right direction. I'm trying to give you additional info.

    Regards,

    Stan-
  6. 02-13-2014, 12:26 PM #6
    JRIowa's Avatar
    JRIowa is online now Diamond
    Join Date
    May 2003
    Location
    Marshalltown, Iowa, USA
    Posts
    7,138

    Default

    You can't mill flat
    You can't turn flat
    You can get close with grinding.
    If you want something really, really flat, you need to lap. We do the 2 helium light band stuff all the time. That's flat within 0.0000232" That's so flat and smooth that if a fly tries to land on the part, he skids off and crashes.
    JR
  7. 02-13-2014, 12:43 PM #7
    adama is online now Diamond
    Join Date
    Dec 2004
    Location
    uk
    Posts
    5,876

    Default

    Conventional milling is really not a reliable way of getting accuracy's in the sub thou range. Its were grinding and then lapping really come into there own. yes to a degree you can piss about and fight it and improve things. Then you can go by a cheap grinder and realise just how crappy at flat a milling machine really is. Chasing tenths on a grinder is as easy as chasing tenths of a inch on a milling machine if and only if you have the gear to measure at these levels.

    Above all you need to consider just how much surface finish really comes into play at these accuracy levels.



  • [machinist] More Tramming, Lawrence London, 02/13/2014

Archive powered by MHonArc 2.6.24.

Top of Page