Hollow ground end mills?
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Thread: Hollow ground end mills?

  1. #1
    Gunsmith Fritz's Avatar
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    Default Hollow ground end mills?

    When I was installing my Badger Ordnance tactical bolt knob on my 700 project, I did it using an adjustable offset mill attachment that used a lathe-like bit rotating around the center axis. It took forever, but it did get the job done well. In the directions provided with my tactical bolt knob, it spoke of using a 5/16" hollow ground end mill to take the factory handle down to the major diameter before threading. I haven't had any luck in locating one of these at this time and I am hoping somebody will be kind enough to point me in the right direction, or let me know if they go by any other name.

    Having one of these should decrease the time needed to do an install, and after I did mine, I had several requests to install them onto friends weapons. So now, I am going to be trying to do these in a more timely fashion. One of these specialized end mills should do just that.

    Thanks ahead of time gents.

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    Gunco Good ole boy kernelkrink's Avatar
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    M-42 Cobalt 2-Flute Single End Mill at Wholesale Tool Company | Industrial Machinery + Tool Supply


    Hollow Ground is just the profile of the flutes, a standard end mill would probably be adequate if you use coolant.

    Sounds like you used a flycutter on yours?

    LittleMachineShop.com - Fly Cutter Set

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    Gunsmith Fritz's Avatar
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    Okay, the terminology I am using is just what was on the directions. I may be using it improperly. The diagram however illustrates the end mill itself as being hollow, with a recess inside of the end mill exactly 5/16". The diagram shows the end mill coming over the end of the factory bolt knob, and trimming away the outside material and leaving a 5/16" stud in the middle. If hollow ground is not the correct term, or a more generic term than what I am looking for, it may be the reason I am having trouble locating the tool I am trying to find.

    Maybe it is just a hollow mill. I am finding adjustable hollow mills via google that work upon the same principle, but the one I am trying to locate is fixed. Here is a picture of the adjustable type.

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    Gunco Member Crankfire Systems's Avatar
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    Three possibilities come to mind.

    Endmills are available in both center cutting and non center cutting end configurations. If you make a plunge cut with the non center cutting type, you get a cylindrical shaft left in the center of the hole. I've not seen many that had a very deep hollow though and no idea what size cutter would have a 5/16" diameter.

    The generic term is Rotobroach or Sluggers. These cutters are used for producing large diameter holes with low horsepower/rigidity machines like magnetic base drills etc. Made by Hougen and Jancey among others. They are a mltiple tooth end mill type cutter that works like a hole saw. They only cut on the periphery and leave a cylindrical center post in the slug they produce. Again, no idea what the I.D. sizes might be, since that is strictly a clearance bore.

    And a regular counterbore that uses removable pilots, might do the job nicely. They are multiple flute, end cutting tools with a precision hole full length in the center for the pilot shaft. 5/16" is a standard pilot shaft diameter for the larger counterbores. Only hitch will be getting the cut started on a round knob, may try to walk a bit until the inner shaft starts to form.

    Those are the only "Expedient" get bys that come to mind. Beyond that would be to have one of the cutter manufacturer make a special for you, but that does get pretty pricey.

    HTH
    Emory Jones
    Crankfire Systems Home/Index Page

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    Gunsmith Fritz's Avatar
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    Thanks for the input gents. Maybe making up my own lathe jig is the route to go here. I just thought the mill answer was going to be the simple route.

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    gunco irregular moleman's Avatar
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    Theres a set of hollow mills on ebay right now item # 180234263352 and one of them is a 5/16". They are made differently than the one you showed, but maybe they'ed work.

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    Gunsmith Fritz's Avatar
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    Moleman,

    You sir nailed it. That is exactly what I was looking for. Now I guess I'll have to figure out what I am going to use the rest of them for if I win. I'll be keeping my eyes on that auction for sure.

    Thank you for looking out.
    -Fritz

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    gunco irregular moleman's Avatar
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    Glad to be of help. I was looking at milling machines and thought I'd give it a shot and got lucky.

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