Page 1 of 2 12 LastLast
Results 1 to 10 of 18

Thread: Setting up the magnetic chuck on a surface grinder

  1. #1
    Join Date
    Jan 2010
    Location
    Bismarck, ND
    Posts
    118

    Default Setting up the magnetic chuck on a surface grinder

    I finally finished refurbishing my Harig Super 612 surface grinder. It was initially in very good shape, just neglected with a longtime sitting idle and extremely dirty. In any event I have not setup the magnetic chuck mounted on its base. When I mounted the chuck I bolted it down with only a moderate amount of torque as I have read that too tight seating the chuck can either warp the slide table base or the chuck itself!! I set a dial indicator on the spindle housing and indicated the base and saw no real deviation (within .00005). Now I mounted the magnetic chuck (older Walker 6x12) and indicated about .0003 inch in total length and about .00025 across the 6" width. This indication is with the cross and slide table being operated. Is this enough deviation to justify dressing the top of the chuck? The existing surface of this chuck is not that clean anyway. If so, what type of stone is best for doing this and what is the correct procedure for grinding or dressing the top surface of the chuck? I have to admit that I have no previous experience with surface grinders with the exception of considerable reading (quite a lot from searching on this forum). I currently have a Carborundum AA46-J8-V40 wheel that came with the grinder. I would appreciate any advise on what other stones that I should have for mild steel, hardened steel and cast iron. I do not have any setup for flood cooling, and I am designing a vacuum dust collection system for the grinder. The grinder came with the original wheel shroud and a "Dust-Less wheel shroud. I plan to incorporate the Dust-Less shroud into my collection system. I understand the importance of safty in using this tool and I plan to utilize all the knowledge I have obtained to run this machine as safe as possible. I realize that dry grinding is much more susceptible to heating up the work and thus driving it into the stone with catastrophic results. I have also incorporated a VFD drive, locked out reverse, and made 60 cycles the maximum speed of the spindle motor. With the VFD I can start up the grinder at low speed and slowly bring it up to full speed.
    As a newbee I appreciate any and all advise relating to this subject.
    Thanks

    Skipd1

  2. #2
    Dr Stan Guest

    Default

    Quote Originally Posted by skipd1 View Post
    With the VFD I can start up the grinder at low speed and slowly bring it up to full speed.
    Skipd1,

    This is really not necessary as none of the surface grinders I ever ran used a soft start. You pushed the button and it went to full speed in a fraction of a second. With a 6 X 12 grinder your wheel is not even close enough in size to need the soft start.

    Your wheel is a general purpose surface grinding wheel and should be just fine. You need to dress the wheel with a diamond dresser prior to each use and it would also be a very good idea to balance the wheel on knife edges. Pay attention to your wheel rotation & the location of the dresser. Place the dresser on the magnet so that it would not be pulled though the wheel in case the dresser comes off the magnetic chuck. Balancing makes for much smoother finishes.

    I dress a mag chuck with it on in case it changes shape between the off and on states. Your last two or three passes should be with no additional down feed so it can spark out and produce the flattest surface possible.

    Enjoy your Harig, they're good machines.

  3. #3
    Join Date
    Jan 2006
    Location
    Rochester Hills Mi
    Posts
    1,337

    Default

    I have no ideas about which wheel to use, but your numbers, if I read them right, do not seem too bad. I would make sure everything on the mounting surfaces are clean with no dings before considering dressing the table. Bob.

  4. #4
    Join Date
    Jan 2010
    Location
    Kansas City area
    Posts
    5,442

    Default

    Hi skipd1-

    It sounds like you have a pretty good setup there. Your wheel is a 46 grit which is pretty coarse for grinding in the chuck. The best thing is to have a selection of wheels in 46, 60, 80 and 100 grit. For grinding the chuck I would choose 80 grit. The J is the hardness of the wheel. You want to stay in the H, I, J, K hardness range. H being softer and K being harder.
    To grind the chuck, remove any fence on the back or end so the chuck is clear of anything sticking up around the edges. Put on a good wheel, dress it with the diamond and grind the entire surface until it is ground all over. Only use 2 to 5 tenths depth of cut per pass. In your case I would stay around 1 or 2 tenths. When it's all cleaned up go back over it a time or 2 with no downfeed. Once this is done you should be able to make parts to 1/10 of a thou. at will.
    If you get scratches on the chuck, usually from removing a part, smooth them down with a coarse rubberized abrasive stick. These are available at McMaster-Carr and other industrial supply places.
    Also learn about the other things you can use a surface grinder for like spinning down taps and pins, sharpening tools, form grinding, etc. A surface grinder is the Bridgeport of grinders. They can do much more than just make things flat and parallel.

  5. #5
    Join Date
    Dec 2010
    Location
    Finland
    Posts
    3,256

    Default

    If you do add the flood coolant, put a T-section in the line after the pump and put a length of pressurised air hose to it and one of those 5 dollar air pistols on the other end. Hang it near the front of the grinder, so it is easy to use for flushing debris down from the table and for cleaning the just ground part

    Also, your best tool is a window cleaner/wiper, buy one and shorten the blade of it to fit your table width. Makes it very easy to clean the table surface, just flood the coolant on it from the hose you created and wipe the table clean with the window wiper
    Amount of experience is in direct proportion to the value of broken equipment.

  6. #6
    Join Date
    Mar 2005
    Location
    Oroville, WA
    Posts
    12,033

    Default

    Don't know if it is the case here, but I don't think I'd make my magnetic chuck the first project for a newly restored grinder. I'd start with something cheaper.

  7. #7
    Join Date
    Jun 2010
    Location
    St. Louis
    Posts
    1,147

    Default

    Quote Originally Posted by Jaakko Fagerlund View Post
    If you do add the flood coolant, put a T-section in the line after the pump and put a length of pressurised air hose to it and one of those 5 dollar air pistols on the other end. Hang it near the front of the grinder, so it is easy to use for flushing debris down from the table and for cleaning the just ground part

    Also, your best tool is a window cleaner/wiper, buy one and shorten the blade of it to fit your table width. Makes it very easy to clean the table surface, just flood the coolant on it from the hose you created and wipe the table clean with the window wiper
    I like your ideas Jaako. Is the take off hose "pressure air hose " or "pressurised air hose"?
    i.e. are you applying any air pressure or just using high pressure hose for the take off from the tee.
    Last edited by jep24601; 07-28-2013 at 04:50 PM.

  8. #8
    Join Date
    Jan 2010
    Location
    Kansas City area
    Posts
    5,442

    Default

    If you use coolant, always turn off the coolant and let the wheel run for another 30 to 60 seconds to get the coolant out of it by centrifugal force.
    If you just turn off the coolant and wheel at the same time the coolant in the wheel will all collect in the bottom half of the wheel and dry out. Then it will be out of balance the next time you turn it on. It will stay out of balance until more coolant can get it rewetted enough to move through the wheel. Sometimes it can be off balance enough to break the wheel, usually it just makes it vibrate.

  9. #9
    Join Date
    Dec 2010
    Location
    Finland
    Posts
    3,256

    Default

    Quote Originally Posted by jep24601 View Post
    I like your ideas Jaako. Is the take off hose "pressure air hose " or "pressurised air hose"?
    i.e. are you applying any air pressure or just using high pressure hose for the take off from the tee.
    No pressure, it is just a good hose as it is usually flexible, quite cheap and withstands water

    Oh and one thing about installing a magnetic chuck. Dial it in straight, as this helps in setting up various work pieces on the table that need to be aligned to the movement.
    Amount of experience is in direct proportion to the value of broken equipment.

  10. #10
    Join Date
    Jan 2005
    Location
    Buffalo NY
    Posts
    3,955

    Default

    If you have never ground a chuck before, learn some about grinding first.
    Use the machine and get a feel for grinding and what does and what does
    not work. Only then attempt to grind your chuck. Wheels like to load up
    and burn the work, especially taking only a few tenths on a soft steel chuck.
    Walker chucks grind pretty well. Brown and Shapre chucks can be problematic.
    B&S used solder or babbit between the stay poles and the magnetic poles.
    This tends to clog the wheel easily, and causes the wheel to burn a streak in
    your surface. Same can happen with a chuck constructed with brass in the
    laminations. It can load the wheel before you finish one complete pass.
    Sometimes rubbing the chick with paraffin wax and no coolant works better than
    using with coolant. Don't make grinding the chuck the first thing you do in your
    learning curve with the surface grinder. Wait a year and get some experience.

    --Doozer

Posting Permissions

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