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Thread: Advice on drilling and tapping frames for optic mounts?

  1. #11
    I have to agree with those advising extreme caution. Long time machinist here (in my past occupation) and I'd likely not. At the absolute least buy your bits from a legit industrial supply like here. That drill press would work as long as it has a quality chuck like a Jacobs that runs true. You'll need a good ratcheting tap handle too. And possibly a bushing guide to start it and keep it straight while cutting the threads if your workpiece allows its use.

    Also you will save yourself a lot of heartache if you use the actual drill size for the tap. Standard sets very rarely have the proper size to work. Consult a tap/drill chart. And I'll double down on the TIN coated drills are not all equal. I got one from a big box store that was pure garbage. Wouldn't even drill mild steel and the drill was probably mild steel itself. Again...buy from a machine tool supply company.

  2. #12
    My question is why a frame mount? Slide mount technology has progressed to the point where frame mounts are obsolete. The lower bore axis of a slide mount makes them far superior.

    The only exception is mounting magnified optics.


    Sent from my iPhone using Tapatalk

  3. #13
    Quote Originally Posted by JCN View Post
    Would something like this help?
    Yes, even this one.

    Quote Originally Posted by JCN View Post
    Thanks! I like gaining skills and I don’t mind cost. ... an excuse to buy tools is like needing an excuse to buy guns…
    Well then, this is what you might actually aspire to:
    https://www.amazon.com/Klutch-Mini-M...s%2C210&sr=8-2

    There is a buttload of mini mill stuff out on YouTube.

  4. #14
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    Quote Originally Posted by john c View Post
    My question is why a frame mount? Slide mount technology has progressed to the point where frame mounts are obsolete. The lower bore axis of a slide mount makes them far superior.
    I guess it’s context and experience.

    I’m a USPSA Carry Optics GM and I find there’s a huge difference in how easy it is to track a frame mounted dot versus a slide mounted one when you’re talking about 0.15s splits and transitions.

    Like SO much difference. I would take a high bore access with a frame mounted dot over low bore axis on a reciprocating dot any day of the week. The dot tracking is also much simpler to accurately gauge and predict for follow up frame mounted optic shots when it’s not moving in multi-axis like a slide riding dot.

    But that might be just based on my personal use patterns of dots. YMMV.

  5. #15
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    Quote Originally Posted by Spartan1980 View Post
    I have to agree with those advising extreme caution. Long time machinist here (in my past occupation) and I'd likely not. At the absolute least buy your bits from a legit industrial supply like here. That drill press would work as long as it has a quality chuck like a Jacobs that runs true. You'll need a good ratcheting tap handle too. And possibly a bushing guide to start it and keep it straight while cutting the threads if your workpiece allows its use.

    Also you will save yourself a lot of heartache if you use the actual drill size for the tap. Standard sets very rarely have the proper size to work. Consult a tap/drill chart. And I'll double down on the TIN coated drills are not all equal. I got one from a big box store that was pure garbage. Wouldn't even drill mild steel and the drill was probably mild steel itself. Again...buy from a machine tool supply company.
    Thank you! Great advice!

  6. #16
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    Quote Originally Posted by MickAK View Post
    When teaching people to tap I prefer cobalt. They will work though. A lot of small Ti coated bits are garbage.

    Finding a piece of material to do practice holes in that is similar to a CZ slide in material would be a great idea. Practice extracting broken bits and taps in that. It's a lot of feel. Making a jig would be preferable to measuring. Pretty small tolerances for error here. Your punch can be a go/no go gauge in your jig hole and as long as it is clamped securely your divot will end up in the right place.
    I just ordered some cobalt bits. I have a few Shadow 2 frames that could get some sacrificial holes for practice.

  7. #17
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    This is what I’m working with

    The optic mount has two legs.

    One side uses existing holes
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    The other side needs two holes drilled.

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    Just short M4 screws a few threads deep.

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    I feel like this can’t be too crazy hard, right?

    With a drill press and clamp, I feel like this is something I should be able to do without bringing it into a Smith after a one month waiting period, right?

  8. #18
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    Quote Originally Posted by JCN View Post
    Thanks! I like gaining skills and I don’t mind cost.
    Would something like this help?
    https://smile.amazon.com/gp/aw/d/B09...KIKX0DER&psc=1
    An excuse to buy tools is like needing an excuse to buy guns…
    A small drill press beats a drill motor in a fixture, but for that price you can buy a used table top/mini mill, if you're patient. Sometimes they are free if you are willing to haul it away.

    Quote Originally Posted by mmc45414 View Post
    Sort of a hijack, but which one did you get?

    I am also getting more realistic about quantifying the risk. The first thing I drilled into myself was a 870 to mount a Trak-Lock sight. I was nervous and apprehensive and had some fear of failure, then I reminded myself I was working on a cheap-ass 870 Express like could be bought (at the time) at Wal-Mart for $350 and I charged ahead. It wasn't perfect, but it was perfectly fine.
    It was my Dad's, and I think it was either free for hauling it away, or $100. Either way, for work like this the cross slide mechanism is nice, as it allows one to use an indicator to check alignment. It was imported by "Central Machine", but I think it was made by Rong-Fu. They have probably gone out of business and been reincarnated three or four times since then. This type of machine is a joke compared to a real Bridgeport, but they are fine for drilling and tapping holes. If you look closely at the picture there's an AR barrel/front sight in the middle of the redneck collection of gage blocks, clamps, and indicators. And the rear sight is dead center after zeroing at 100 meters.

    Yes, it doesn't take too many successful jobs to cover the replacement cost of what you are working on, when compared to the price and hassle of shipping firearms. That being said, I do have a small assortment of parts I have ruined through the years, but that's minor compared to the satisfaction of doing it myself. There is not a gunsmith out there who hasn't ruined a pile of parts, usually their own, in the learning stage.
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    Quote Originally Posted by mmc45414 View Post
    Well then, this is what you might actually aspire to:
    https://www.amazon.com/Klutch-Mini-M...s%2C210&sr=8-2
    If you're going to buy a new mini combo machine, I would trust someplace like Grizzly over Amazon. I've done no research on that, just a gut feeling. But it's always good to get out of the bottom of the barrel. You will recoup the cost differential between the drill press you proposed and a mini combo mill by not screwing up the first pistol.

  9. #19
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    Quote Originally Posted by JCN View Post

    I feel like this can’t be too crazy hard, right?
    Snapping a tap off in a partially tapped hole is one of the most awful feelings in the world. It cuts straight to the soul. I recommend you doing some practice runs before jumping into the real thing. You have to be able to feel the right resistance clock wise cutting the thread chip, stop, turn back counter until you feel clear and the chip being shucked then repeat. Lots of compressed air to keep it clean and tap magic to keep it lubed. The margin of error isn't much especially if one gets over enthusiastic. I'm not saying you can't do it. Just practice a couple of times to get the feel for it before you dive into the real thing.

  10. #20
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    Quote Originally Posted by medmo View Post
    Snapping a tap off in a partially tapped hole is one of the most awful feelings in the world. It cuts straight to the soul. I recommend you doing some practice runs before jumping into the real thing. You have to be able to feel the right resistance clock wise cutting the thread chip, stop, turn back counter until you feel clear and the chip being shucked then repeat. Lots of compressed air to keep it clean and tap magic to keep it lubed. The margin of error isn't much especially if one gets over enthusiastic. I'm not saying you can't do it. Just practice a couple of times to get the feel for it before you dive into the real thing.
    Thanks for humoring my noobness!

    When drilling, I caliper measure the drill bit and the tap to make sure the drill bit is appropriate size, correct?

    I don’t need a lot of thread engagement (the other side of the mount is structural, the side I’m tapping just kind of has to fit somewhat) and I thought slightly larger hole would make tapping easier.

    Any general advice for drilling a hole for an M4x0.7 that would make tapping easier?
    Am I using an M4 or M3.5 drill bit depending on how it caliper measures?

    I debated doing trial tap and die runs on the frame with smaller hole and tap, then drilling larger and tapping for additional practice and work upwards but I understand the resistance feel of chip cutting would be different with different diameter and pitches.

    Thanks in advance!

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