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Thread: Installing threaded brass inserts in wood, hole size?

  1. #1
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    Installing threaded brass inserts in wood, hole size?

    I picked up some Hillman threaded inserts with a 5/16-18 internal thread and a 15/32, coarse external thread. The thread minor dia is .370, or just a smidge under 3/8.
    Should I use a 3/8 drill bit? They'll be going into maple burl, I don't want to crack it.
    Please help support the Creek.

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  2. #2
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    I'm not sure about the size but I'd think a quick test run on something weak like thin pine would let you know if 3/8 will blow it out or not. Can you back the insert out once installed? If not, I'm sure you could split the pine to retrieve it.

  3. #3
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    Are "Hillman" threaded inserts the brass ones with knife-thin external threads? If so, good. If not, you might look for them. Minimal thread material would mean less wood stress.

    In all the years I've used threaded inserts, I haven't ever split the lumber inserting them, using a bored diameter a little bigger than the minor diameter of the insert, just like you're thinking. However, I have chowdered up the surface of delicate wood. If you just crank the insert into the wood, those threads can try to excavate the wood instead of screwing into it. I'd imagine burl, with its crazy grain, might be specially sensitive to this. The cure is to put lots of pressure on the back of the wrench while you're starting the insertion -- kinda like what you do when you're trying to remove a screw whose drive slot has been damaged.

  4. #4
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    Try it in a scrap first...wax or soap helps...
    "All great work starts with love .... then it is no longer work"

  5. #5
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    Bruce,
    Using a drill press, turned off and rotated by hand, is a pretty good way to get a straight feed when doing the insertion. As to the thread/drill size issue, I have never found splitting to be a problem, but a test drive on scrap would be best.
    Alan Turner
    Philadelphia Furniture Workshop

  6. #6
    Bruce,
    That is downright scary. Try this, get a tap and thread the burl with a 15/32" thread. That tap should tell you what drill to use to prepare for the tap. I think the tap might be better at preparing the thread than the inserts. Also, when you have the threaded hle and are ready to install the insert, dab a drop of C glue ont he outside so it will stay in place.
    John Lucas
    woodshopdemos

  7. #7
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    Hi Bruce,

    In addition to Alan's suggestion for doing the insertion you could try what I have used. Put a 5/16-18 bolt with a suitable head on the insert and use a wrench to insert the coarse thread into the piece of wood.

    Regards,
    Bill

  8. #8
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    I do a lot of treaded inserts and brought some "treaded insert drivers" from McFeely's, 800-443-7937, www.mcfeelys.com. They have 5 different sizes including yours, run $14.95 each, part numbers 3603-PD to 2608-PD (yours 3607-PD). Of if you have their catalog, the show you how to make "shop-made threaded insert drivers" both with a power drill and wrench.

    I use brass inserts into mainly oak and walnut and they really strip easily. So as with most brass products, you want to pre-drill. I use 1/4-20 and have some steel inserts the same size I use for pre-drilling. And I try to remember to use lubricant as it helps things along.

    It sounds like you'll be inserting them into the flat part of the board so as Alan said, go with a drill press. If you can't use drill press, a power drill should work fine but best to use a square to make sure they go in straight (I've seen Norm do that many times even with all the equipment he has).

    On end or side grain, I use one of those self centering dowel jigs that works great (boy finally a use for that things now with biscuit and pocket holes).

    Regards, Joe
    Two weeks, your project will be done in two weeks!!! (From the Money Pit)

  9. #9
    I use brass insert a lot. What I have found is that you can't rely on the recommended pilot hole recommendation. I use a piece of scrap and drill until it threads nicely. I recently finished a loft bed and it had around 50+ threads. I used the drill press to not only drill the pilot hole but also to install the insert (turned by hand of course). It really worked well. Every insert was perpendicular and tight.
    If sawdust were gold, I'd be rich!

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  10. #10
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    When using the brass inserts I like to drive them in from the "bottom" side of the board whenever possible. This leaves the "show" side undisturbed and a lot cleaner looking. When doing this I will drill a hole size that is smaller than the outside diameter of the insert. Then from the back side drill the appropriate sized hole, but don't go all of the way through. This will form a shoulder that provides a very clean look when the insert is driven tight against it from the back side.

  11. #11
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    Thanks for the info everyone. The inserts have a screwdriver slot and are reusable. They will be going into a blind hole. Ill try them in some scrap first and see how it goes. Youd think the manufacture would provide the pilot hole size.
    Please help support the Creek.

    My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."

    - Steven Wright

  12. #12
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    Threaded Inserts Article

    Bruce, the current "Shop Notes", (Vol 15, Issue 85, Page 50) has an article titled "Success with Threaded Inserts". If you don't get this Mag, you could probably Peruse it at the Blue Big Box, to see if it gives you what you want. They even give Size holes to drill for the different size inserts, but NOTE: There seems to be a misprint on the hole sizes given for the 5/16 - 18 and 3/8 - 18 insert sizes. They show using a slightly larger size hole for hardwoods than for soft woods, but still recommend making a test run on some scrap. I think from looking at the hole sizes given for the smaller size inserts, they really meant to say, for a 5/16 - 18 size insert, to drill a hole 1/2" for softwoods, and 19/32" in hardwoods.

    Good Luck.

    PS; they show inserting them using a bolt threaded into the insert, and suggest inserting the insert with the screwdriver slots at the bottom for a neater, more finished look.

    One of the ww mags a short while back showed a shop made jig for installing the inserts that was real simple, but very effective, but I can't seem to recall which one offhand.
    "Some Mistakes provide Too many Learning Opportunities to Make only Once".

  13. #13
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    Quote Originally Posted by Bruce Page
    Thanks for the info everyone. The inserts have a screwdriver slot and are reusable. They will be going into a blind hole. Ill try them in some scrap first and see how it goes. Youd think the manufacture would provide the pilot hole size.
    Bruce, I bought some that did say what pilot hole size to use but it was too big. I always try them on scrap first and ise a homemade insert tool made from a bolt.

  14. #14
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    If those are the brass ones, those screwdriver slots are to be shied away from. It's real easy to snap the little piece of the cylinder wall off between the 2 slots even if your hole size isn't overly tight. Like others I've used a hand turned drill press to get the first few threads going in straight. I then switch to a bolt with 2 nuts threaded on the end and use a ratchet wrench to run it in the rest of the way. The right whole size for hardwoods vs soft will be quite a bit different. I've found what works for me is to get a piece of scrap (same species you're going to use) and put 4-5 holes in it with sequential size drill bits that are in the ballpark size-wise. Then see which one feels right turning the insert in by hand with the bolt and double-nut. You'll get a pretty quick read on which one feels like the best fit.
    Use the fence Luke

  15. #15
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    I also had this question months/years ago and found the answer on their web site

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