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  1. #1
    Join Date
    Sep 2012
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    Yorkshire UK
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    733

    Default Two thou bigger at one end !

    Hi Guys,
    A little background. I recently made a mill tramming tool simply because I was having difficulty ensuring that the head of my mill was truly at 90 degrees to the table. Anyway I learnt a lot about my mills behaviour and I suspect many other similar mills as well.

    Having spent a lot of time tramming my mill and getting to understand why it varied as it did I decided to check that my mill vice jaws were truly parallel to the table. So by placing a 0.0005" dial gauge spindle into the mill chuck I proceeded to sweep it along the top of the fixed jaw of the vice. Fine I got around 4.5 thou from one edge to the other. So I re-checked by opening the vice fully and doing a sweep at the base of the jaws. OK I get less than one dial division from one edge to the other (0.00025") the gauge is marked in half divisions. I closed the jaws and made sure that they were firmly closed.

    So I put a fly cutter into the chuck and took a 5 thou skim off the top of both jaws. Lovely finish. The cutter just skimming on the trailing edge. Definitely took more off at one end. I decided that was it and then put the dial gauge back in the chuck. Now I've got two thou higher at what was the higher end before. I put the fly cutter back in and did another skim, but only a couple of thou. The cutter seemed to cut evenly from one side to the other. Re-checking and I've still got a two thou difference.

    I'm perplexed ! I can't for the life of me understand why I have this tiny difference in hight.

    If any of you can throw any light on this behaviour, please do. Thinking further I am going to find a suitable length of MS and see if I get the same behaviour when I skim it.

    Thanks for reading.
    Best Regards:
    BaronJ.

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  3. #2
    Join Date
    Oct 2011
    Location
    Adelaide
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    Default

    If the jaws are hardened what you may have done is taken some material off at the beginning of the cut but rapidly blunted the cutters so that at the end of the pass the cutter had been rubbed down/ blunted to an extent that nothing was taken off.

    It's a working theory...

    Michael

  4. #3
    Join Date
    Oct 2010
    Location
    melbourne, laverton
    Posts
    1,469

    Default mill set up

    hi mate. what sort of mill are you useing?
    what do you mean " you put the fly cutter in the chuck?"
    do you have any photos?
    aaron

  5. #4
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    Jun 2012
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    SA
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    Default

    Sounds like the mill table is not perpendicular to the spindle on at least one plane.

    Mount a test indicator in the spindle (on an extension) and sweep the table surface.

    If that measures OK then it is probably flex in the mill.

    Rob
    The worst that can happen is you will fail.
    But at least you tried.



  6. #5
    Join Date
    Sep 2012
    Location
    Yorkshire UK
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    733

    Default

    Quote Originally Posted by azzrock View Post
    hi mate. what sort of mill are you useing?
    what do you mean " you put the fly cutter in the chuck?"
    do you have any photos?
    aaron
    Hi Guys,

    Its a Chinese mini mill. Similar if not identical to a Warco WM16. But a longer wider table. I used the fly cutter in the drill chuck.

    Just to clarify the mill vice is a cast iron "Record" brand vice from about 1970/1975 ish. I've machined it before on my last/first mill, a Denford. Basically a Bridgeport clone but smaller. If I can find a suitable piece of material tomorrow, I will set it up and see if I get the same issue. I'm starting to suspect that there is something wrong with the table travel.

    Photos I can take tomorrow.
    Thanks:
    Best Regards:
    BaronJ.

  7. #6
    Join Date
    Jun 2007
    Location
    sydney
    Age
    60
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    3,566

    Default

    Quote Originally Posted by azzrock View Post
    hi mate. what sort of mill are you useing?
    what do you mean " you put the fly cutter in the chuck?"
    do you have any photos?
    aaron
    Would think he was referring to using either a drill chuck or collet chuck to hold the fly cutter.

  8. #7
    Join Date
    Sep 2012
    Location
    Yorkshire UK
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    Default

    Quote Originally Posted by nearnexus View Post
    Sounds like the mill table is not perpendicular to the spindle on at least one plane.

    Mount a test indicator in the spindle (on an extension) and sweep the table surface.

    If that measures OK then it is probably flex in the mill.

    Rob
    Hi Rob,
    Good idea. I only ran the dial gauge across the base of the vice jaws and that was essentially spot on. The vice jaws are 100mm/4" wide. I'll check that tomorrow as well.

    Thanks:
    Best Regards:
    BaronJ.

  9. #8
    Join Date
    Jun 2013
    Location
    Tasmania
    Posts
    92

    Default

    Ah, Baron.

    I've got a BF20L (same mill) that I'm having a hell of a time with too. I haven't got time to write a full reply here at the moment because I have to go out.

    But basically I'm currently fighting with the people I bought the mill off because like you I just could not get it trammed - they blame my inexperience and inability to measure accurately. I thought it was an undersize gib strip on the Z-axis causing the head to deflect in varying amount depending on how tight you clamp the gib locks. However, upon more examination I've realised that the actual dovetail isn't parallel. If I measure the width of the dovetail using dowel pins, the dovetail is 0.2mm narrower in the middle. So I can't get my gib properly adjusted because of the curved dovetail and the head deflects varying amounts up and down the column when you snib up the gib locks.

    I'll come back and expand but basically I can't tram this head in properly.

    Try putting a DTI on the side of the lower part of the head and see what happens when you tighten the gib locks (particularly the lower one). I'm going to guess that like me your head will tilt a varying amount depending on how tight you snib that gib. Mine will kick out up to 0.014", which at the end of the tool equates to about 0.020" deflection - even worse on a long drill bit as it amplifies the misalignment.

    Your 0.002" could easily be due to how much you tighten the gib locks. Measure the width of your dovetail in 50mm steps up the column and tell me what you see.

    I'm trying to claim warranty on a faulty column but its falling on deaf ears.

  10. #9
    Join Date
    Sep 2012
    Location
    Yorkshire UK
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    733

    Default

    Quote Originally Posted by Hornetb View Post
    Ah, Baron.

    I've got a BF20L (same mill) that I'm having a hell of a time with too. I haven't got time to write a full reply here at the moment because I have to go out.

    But basically I'm currently fighting with the people I bought the mill off because like you I just could not get it trammed - they blame my inexperience and inability to measure accurately. I thought it was an undersize gib strip on the Z-axis causing the head to deflect in varying amount depending on how tight you clamp the gib locks. However, upon more examination I've realised that the actual dovetail isn't parallel. If I measure the width of the dovetail using dowel pins, the dovetail is 0.2mm narrower in the middle. So I can't get my gib properly adjusted because of the curved dovetail and the head deflects varying amounts up and down the column when you snib up the gib locks.
    I'm glad that you posted about this ! Because this is exactly what I found when I started to try and tram mine. On my machine the gib strips on all axis are tapered gibbs. As near as I can measure I only have about 0.07 measured on the side of the spindle sleeve.

    I'll come back and expand but basically I can't tram this head in properly.

    Try putting a DTI on the side of the lower part of the head and see what happens when you tighten the gib locks (particularly the lower one). I'm going to guess that like me your head will tilt a varying amount depending on how tight you snib that gib. Mine will kick out up to 0.014", which at the end of the tool equates to about 0.020" deflection - even worse on a long drill bit as it amplifies the misalignment.

    Your 0.002" could easily be due to how much you tighten the gib locks. Measure the width of your dovetail in 50mm steps up the column and tell me what you see.

    I'm trying to claim warranty on a faulty column but its falling on deaf ears.
    Yes mine moves as well. To account for that I made sure that I locked up the gib locks whilst I trammed the head. I also found the the spindle lock would cause a very tiny but varied amount of movement. So I locked that as well ! The hardest part of tramming my machine was the amount the thing moved when trying to tighten the two nuts to lock the head in place. I used the nip tap nip tap technique and whilst I know that its not perfect its a darn sight better than it was. See the pictures in the next post.
    Best Regards:
    BaronJ.

  11. #10
    Join Date
    Sep 2012
    Location
    Yorkshire UK
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    733

    Thumbs up

    Hi Guys,

    As promised some pictures. There are two of the mill. Then there are some of the vice and the gauge readings. I also machined a test piece. Its a 6" long chunk of hard aluminium bar. I put it in the vice and took a 0.1mm cut across the top to clean it up, then to avoid any possible deflection a second cut 0.05mm. The photos show the test piece and the fly cutter. The same one that I used on the top of the vice jaws. The photos of the gauge readings at both ends of the bar as well. The two smaller pictures of the gauges are the ones from the top of the vice after machining.

    I'm pleased to say that the test machining shows that there is very little difference in measurement between the ends.

    Thanks again. You Guys give me the confidence to do more.
    Attached Images Attached Images
    Best Regards:
    BaronJ.

  12. #11
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    Sep 2012
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    Default

    Quote Originally Posted by BaronJ View Post
    Hi Guys,

    As promised some pictures. There are two of the mill. Then there are some of the vice and the gauge readings. I also machined a test piece. Its a 6" long chunk of hard aluminium bar. I put it in the vice and took a 0.1mm cut across the top to clean it up, then to avoid any possible deflection a second cut 0.05mm. The photos show the test piece and the fly cutter. The same one that I used on the top of the vice jaws. The photos of the gauge readings at both ends of the bar as well. The two smaller pictures of the gauges are the ones from the top of the vice after machining.

    I'm pleased to say that the test machining shows that there is very little difference in measurement between the ends.

    Thanks again. You Guys give me the confidence to do more.
    Hi Guys,

    I think my problem is solved ! Or at least a way to prove the explanation that a friend has suggested. Someone here suggested flex in the mill column but flex in the cutting tool is much more likely. It was also pointed out to me that the grind on the tool tip was far too weak to cut properly and would be more inclined to rub.

    The explanation given is that the cast iron is harder or more dense at one end than the other causing the tool to deflect and rub rather than cut. The suggestion made is that the vice top be skimmed again with a heavier tool and see if the same effect occurs. I will be borrowing a 50mm carbide face mill tomorrow to try.

    Looking at the cutting marks in the top of the vice jaws also point to this explanation. See photo.

    Having spent some time machining a piece of aluminium and finding that its the same at both ends suggests that he might well be right !
    Attached Images Attached Images
    Best Regards:
    BaronJ.

  13. #12
    Join Date
    Jun 2004
    Location
    Kyabram. Vic
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    822

    Default

    I see two problems with the set up shown.

    1, The mdf between the vice and the table. It will compress with the hold down bolts and is not manufactured to engineering standards;
    2, The vice itself. It is only a drill vice, made to hold things on the drill press. A proper milling vice is engineered for accurate milling conditions. Their quality is another matter.


    Ken

  14. #13
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    Quote Originally Posted by Toggy View Post
    I see two problems with the set up shown.

    1, The mdf between the vice and the table. It will compress with the hold down bolts and is not manufactured to engineering standards;
    2, The vice itself. It is only a drill vice, made to hold things on the drill press. A proper milling vice is engineered for accurate milling conditions. Their quality is another matter.


    Ken
    Hi Ken,

    There isn't any MDF between the vice and the table. The vice is securely clamped down by the hex head bolts at either side. The alan socket screws are holding the alignment rib that is underneath and setting the vice square with the table, making it easy to remove and replace in the same position. I think that the MDF that you are referring to is a pair of hardboard covers that I use to keep the table clean and rest tools on.

    I agree about the vice. Its a very old "Record 414" machine vice that I bought to replace an even older drill vice that I still use but on the "Forbco" drill.
    A good vice is one of those things that I want to make as and when I get the time.

    Thankyou for your concern.
    Attached Images Attached Images
    Best Regards:
    BaronJ.

  15. #14
    Join Date
    Mar 2011
    Location
    Dural NSW
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    1,120

    Default Tool Grinding

    Baron J
    The first thing I noticed, before even reading in detail, was the tool grinding, shown in the photo.
    The tool would probably be partially rubbing along the horizontal face, of the workpiece, & causing deflection when hard sections are encountered.
    I believe with these small mills, High Speed Steel toolbits are adequate, if ground correctly.
    A small radii at the flycutter toolpoint also reduces load & chatter & deflection.
    Spent a fair amount of time with my Hercus End Mill Head & came to the conclusion that it did not have the torque, power or speed to effectively use Carbide.
    After a bit of experimenting, found HSS works very well. Its also low priced !!!
    These were my findings.
    Agree with the comments on the Drill Vice, a mill needs a strong accurate vice.
    regards
    Bruce

  16. #15
    Join Date
    Aug 2011
    Location
    Melbourne
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    2,951

    Default

    Hi Baron,

    Another observation is that because you are not using a "dedicated" milling vice, you may find that the jaws of the vice may slightly lift when tightened. This would also give rise to unrepeatable results. While it may not be relevant with the test you are conducting since you are measuring with the jaws still tight after cutting, if you were to loosen and re-tighten you may well find a different result yet again.

    Just a thought.

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

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