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  1. #1
    Join Date
    Mar 2012
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    Brisbane
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    72
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    8

    Question Help with Tuning RF-45 Mill

    Hi Guys

    I am seeking a little help with my old Hare & Forbes HM-45 mill.

    I was trying to flatten some bar in the mill using a 16 mm end mill, and noticed the back of the cutter making a cut, leaving a series of little depressions in the surface. So I made up a bit of a test jig out of a piece of scrap bar with some holes to mount a piece of round bar to go in the chuck at one end and my dial test indicator at the other end.

    This jig gave a difference of about 0.6 mm in the X direction over its swing of around 400 mm (nearly to each end of the table). So I managed to loosen the three big nuts on the head and gradually adjust that error down to about 0.05 mm.

    However, I found a similar error from front to back of about 0.3 mm across the table in the Y direction, and I am not sure how to adjust this out. Does anyone have experience of correcting this error?

    I did have the table locked down in both directions, the quill locked, and the gibs for the Z direction dovetails locked down.

    Thanks for any assistance.

    Cheers
    Al

  2. #2
    Join Date
    Aug 2007
    Location
    Saskatoon, Saskatchewan, Canada
    Posts
    253

    Default

    I think, and I'll sit corrected if wrong, you have to put shims at the bolts between the base and the column to correct the Y axis error.

    Pete

  3. #3
    Join Date
    Mar 2011
    Location
    Adelaide
    Posts
    894

    Default

    You can shim it between the base and the column, but... you may find it vibrates more when using bigger cutters because the column is no longer completely seated on the base.
    Stefan Gotteswinter did a video on shimming his 45 size mill with an epoxy made for that type of application, but unless you're making aerospace parts its probably not worth the effort.
    Try shimming it and run some test cuts at various depths of cut with different size cutters and see how it goes is my plan in a few weeks when I do mine that I've been putting off because I know I have to move the mill so the roller door can be replaced.

    Check your quill too. Turn an Angle plate so a flat stands parallel to the quill travel and run a dial down it using the quill feed. You'll be horrified if your machine is anything like mine...

  4. #4
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    8,802

    Default

    Did you check that the top of the table is parallel with the Y axis?

    Something that may* help you in the short term.

    If the mill is trammed on the X and not the Y(as it would seem yours currently is), then try doing your main feeding with the Y and step to the next cut with the X. It may also cut better in one direction. In theory this will turn a sawtooth step into something more like a wave of half the height.

    *I say may because if we assume your table it 200mm wide, my maths says a 16mm cutter should leave a 0.024mm step?

  5. #5
    Join Date
    Jul 2021
    Location
    Sydney
    Age
    51
    Posts
    16

    Default

    I had a similar problem.

    It could just be an easy fix. Firstly check the bolts that hold your column. See if they are torqued up. Sometimes backing them off and cleaning out the hole, cleaning the threads and re torque with some anti seize. You might just find the adjustment you require. Dont pull them all out at once as the head will fall. One at a time and then when you re install just snug up each one. Then crank them down in series.

    If you have to shim you can still add Araldite in the small gap created by means of a disposable syringe. Araldite is a strong epoxy and can be viscous enough to inject in this matter. It is also clear in colour and wont look like a mess. It will assist in bedding the column to the base to reduce vibration.

    How is your cutter being held? I once had a cutter slipping in the collet.

    Is this a new machine or you have owned it for some time and the problem recently occured?

    Check all the simple things first.

  6. #6
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,978

    Default

    Hi Guys,

    I had to put a couple of shims between the column and base under the top two bolts on my mill. I forget now how far the head nodded, but it only took a couple of thou of shim to correct the nod. I've not noticed any additional problems due to adding the shims. The bigger problem was keeping the head in tram ! But I've sorted that by fitting a pair of stops at the top of the head.

    23-02-2021-003.jpg 24-02-2021-010.jpg

    These are the stops that I fitted, one on each side of the head. You can see the left hand side one just in front of the DRO read head at the top left of the second picture.
    Best Regards:
    Baron J.

  7. #7
    Join Date
    Mar 2012
    Location
    Brisbane
    Age
    72
    Posts
    8

    Lightbulb

    Thanks for all those replies. It does seem I am not alone with the problem.

    I will try to measure the Y axis parallelism first, and then the change raising and lowering the head before taking it further. Will also check the quill and hope it's not too bad.

    Cutter is held in MT3 tollholder with ER25 collets. Didn't see any sign of slipping, and it was pretty tight in the quill, as I managed to shear off the drawbar nut pulling it up.

    Have had this mill for a few years, but not much use and it has been moved a couple of times. So it could have had the problem for a while.

    Thanks again

    Al

  8. #8
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,978

    Default

    Quote Originally Posted by Alh01 View Post
    Thanks for all those replies. It does seem I am not alone with the problem.

    I will try to measure the Y axis parallelism first, and then the change raising and lowering the head before taking it further. Will also check the quill and hope it's not too bad.

    Cutter is held in MT3 tollholder with ER25 collets. Didn't see any sign of slipping, and it was pretty tight in the quill, as I managed to shear off the drawbar nut pulling it up.

    Have had this mill for a few years, but not much use and it has been moved a couple of times. So it could have had the problem for a while.

    Thanks again

    Al
    Hi Al,

    I hope that you don't do any damage to the spindle bearings when you come to hammer the tool holder out of the taper ! There is no need to tighten a Morse taper up that tight. I only use hand tight on a three inch long tommy bar with a square socket on the end. Very occasionally I have to use a 5 inch length of alloy tube on the bar to loosen and crack the taper.

    31-07-2019x001.jpg 31-07-2019x003.JPG

    This is the tool that I use. You can gauge the size from the AAA battery that I used to tilt the wrench so that the writing could be seen.
    Best Regards:
    Baron J.

  9. #9
    Join Date
    Mar 2012
    Location
    Brisbane
    Age
    72
    Posts
    8

    Lightbulb

    Problem solved!

    Yes, check the simple things first.

    I did as suggested, and checked the table from one end of the Y direction to the other, all good and within the 0.08 mm spec I found. Then checked the Z direction with the angle plate. Winding the handle to check the column gave about 0.02 mm over 75 mm, so I felt a bit relieved that shimming the base was not likely to be needed. BUT, the quill was truly bad, about 0.40 mm over the 75 mm of the angle plate. So I left it that night and slept on the problem. Came back in the morning to try again, and in the daylight noticed a gap at the top of the head-to-column ring. I had loosened the big nuts to adjust the tram, and that had allowed the head to nod over.

    Duly chastened, I tightened the nuts and re-checked in all directions. All came in within the 0.08 mm spec over 200 mm, so I wasted no more time on it, and finished my milling easily.

    Thanks to all for the help, and I really like John's system of a pair of stops at the top to stop it wandering about again.
    And I am learning to be gentle with the drawbar.

    Cheers

    Al

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