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Thread: Milling metal - need help

  1. #1
    Join Date
    Sep 2003
    Location
    Philadelphia, Pa
    Posts
    2,266

    Milling metal - need help

    I have in mind a dovetail marking gage which I would make, from steel or brass stock. My question relates to milling the metal tongue. I have no metal working equipment, but I do have a Griggio slot mortiser, in which I use solid carbide end mills. I have used this to date only to cut wood. The mills are normally used to cut metal.

    Can I cut a small groove in either 01 oil hardening steel flat stock, perhaps 1/16 or 3/32" thick, or in brass, by jigging up the mortiser, and using a 1/32" end mill, or perhpas a 1/16" end mill? The RPM on the mortiser is about 4000, I think, and is not adjustable.

    I know that the slot mortiser will not be the perfect tool for this operation, but I don't have a Bridgeport handy. I don't want to try this without some guidance from people knowledgable about milling metal. The required slot might be as long as two inches, and needs to be a very clean cut. The metal will not need to be hardened. I know that I will need to jig it carefully so that the metal stock to be milled will be held quite firmly, and you may assume that I will be able to accomplish this.

    Thnaks in advance to our metal working members.
    Alan Turner
    Philadelphia Furniture Workshop

  2. #2
    Join Date
    Sep 2004
    Location
    York Co, PA
    Posts
    398

    check these charts

    Alan, I'm not a machinist, but I found a couple of links to info that may help:
    http://www.lexcut.com/catalog/FEEDS-SPEEDS.PDF
    http://www.sherline.com/millinst.htm

    4000 might be a bit high from quickly glancing at these links...

    -Mike

  3. #3
    Join Date
    Feb 2005
    Location
    Easthampton, MA
    Posts
    986
    Glad to see you are using the Griggio. I'm a metalsmith as well as wood working machine repair tech and whatever else I need to be. Forget the Griggio for steel and if you go with brass you can cut and slot with a negative hook saw blade on a table saw and even use the Griggio for some operations with brass. The rpm is much to high for steel. I cut, notch and whaterver to brass and non-ferrous metals such as zinc, copper all the time. Negative hook blades are made to cut non-ferrous as well as giving a less aggressive cut on a radial arm saw. I've even used a router to work brass effectively vut it does tend to grab and you must use light passes. You should consider hooking up with a machine shop for this if you don't know much about milling metal. Far cheaper in the long run or consider posting on a metal working forum.

  4. #4
    Join Date
    Feb 2003
    Location
    South Windsor, CT
    Posts
    3,304
    Alan,

    A thin kerf, carbide blade on your table saw would cut the slot in brass. Lower the blade in the saw, clamp the brass plate down. Raise the blade and cut until the blade is about 1 3/4" through the plate. Lower the blade. Flip the plate, raise the blade to position the plate exactly on the blade, clamp the plate down and raise the blade, cutting just enough to trim off what the "roundness" of the blade left from the other side.

    You could clamp long, straight boards to the saw to act as guide fences to make sure you have the angle you want on the cut.

    Personally, for something like this - I'd buy a marking gauge. If you have an adjustable bevel gauge, all you need is a $5 plastic protractor and you're done.

    Rob

  5. #5
    Join Date
    May 2004
    Location
    Oakland, MI
    Posts
    494
    I don't know much about the mortiser you have and you are correct in wishing for a Bradgeport, but I disagree that 4000 rpm is too high. You would be at 65 FPM with a 1/16 endmill, we routinely mill at many times that speed. If you decide to try this, mill the brass first, or a piece of aluminum would be even better, to get a feel for the process. This will not be particularly dangerous as the endmill is small and will break well before anything really bad could happen, unless of course, you consider breaking the endmill really bad . If the groove you want to mill is for relieving the corner you will not need to go very deep. Take about .005 per pass in the 01 and, if you can, set up an air nozzle with a mild output to clear things away, including any heat in the tool. If you decide to do this, let us know how it worked. BTW, I just finished template milling several 13/32 diameter pockets 5/8 deep in 6061T aluminum extrusions with a 3/8 solid carbide endmill using my plunge router. I took my time and only went about .010 per orbit, but they came out perfect. You would have sworn they were done on a machining center.

    Greg

  6. #6
    Join Date
    Sep 2003
    Location
    Philadelphia, Pa
    Posts
    2,266
    Thanks for the guidance, guys. Rick, nice to see you over here. And yes, I love the Griggio. Can't imagine how I lived without it. Thanks for the initial help with understanding this tool. (BTW, I blew the motor in the first month, although I am sure it is nothing that I did. A 2 h.p. metric motor is sure spendy!)
    I am still thinking about this project. I can't use a sawblade for a variety of reasons, among them that it is a pocket cut I need, and the kerf is far too wide.
    I have several DT gages, and several sliding bevels, from Stanley 18's to a small and very handy Starrett, but this gage I am considering will have certain features that are different than the ones I have or have seen.
    We shall see . . . .
    Alan Turner
    Philadelphia Furniture Workshop

  7. #7
    Join Date
    Mar 2004
    Location
    Cockeysville, Md
    Posts
    1,805
    If you can post a drawing i might be able to knock out something in the mornings before the boss comes in....


    Brian
    The significant problems we encounter cannot be solved at the same level of thinking we were at when we created them.

    The penalty for inaccuracy is more work

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