Sunday, October 12, 2014

Sunday Toolfoolery- Installing Threaded Brass Inserts By Hand

Some time ago I posted a video demonstrating how to use a drill press to install brass inserts into wood.  While you don't actually fire up the machine, you do take advantage of the steady, perfectly aligned down pressure provided by the tool.  That system works well with pieces that can be easily brought to the machine, but larger slabs require you to install them by hand.  And without the precision and heft of the drill press it is easy to get less than satisfactory results.

I also noticed, as I was ordering new hardware, that there are lots of general questions about these particular inserts.  I don't claim to be a world-class expert on these things, but I have come up with a couple of tricks that take the stress out of installing brass inserts by hand.

1.  Question Authority
The only instructions that come with inserts is a recommended diameter for the pre-drilled hole.  I don't know if it is result of sloppy manufacturing, or if there is some industrial process by which these get installed in a factory setting, but in my experience this number is often wrong.  I drill a couple of test holes in similar material with gradually increasing diameters.  I start with the recommended number and then another 1/32" larger and then another 1/16" larger.  Test the fit in each (the first will be very tight) and drill the appropriate hole in the actual project. 

This insert was installed using the recommended 3/8" diameter hole.  Even with the jig, it distorts the wood and looks botched.
For me, the right size is the hole that provides clearance for the body of the insert and enough purchase for the threads.  Oh, and do your self a favor and skip the screwdriver . .

I increased the diameter by a full 1/16".  The threads have plenty of grip and the insert does not distort the wood.

2.  Spend a Few Bucks on the Right Tool
For five dollars you can buy a purpose-built T-handle that screws into the insert and lets you bypass the chipped tops.  Again, this is just my experience, but the flat head screw grooves are better for removal - less so for insertion.  Armed with the new toy, a registration block (with a hole the diameter of the T-handle, drilled at 90 degrees to the workpiece) guides the insert.  I have a couple of holes drilled to deal with any tight spaces and I affixed sandpaper to the bottom to keep it still in use.

This seems like a lot of words on a simple task (akin to instructions on a bar of soap) but hopefully it will help you avoid unsightly mishaps on one of the last steps of a project.


  1. Thank you for this post Christopher! I've had all the same problems you described but you provide a better solution. I've had to drill holes several sizes up from the recommended sizes and I still get nicked edges in the face of the brass insert.

  2. Happy to help! BTW, to demonstrate how tight the recommended diameter is for the insert, I tried to remove and salvage it but the screwdriver broke the top even just trying to retract it.

  3. These insert nuts are SO much better: The flanged hex head allows for straight insertion and eliminates the problem of slipping/breaking. Just countersink a little to accommodate the flange.

    1. I am going to have to check this provider out, thanks for sharing.

      I am currently using

      Great post Christopher, keep up the good work!

  4. Thanks for the tip, J.Rusten! I've often wondered if counter sinking would solve most of the issues, but a better widget also seems to be in order. BTW I love your work and I think that the Palo Alto chair video is one of the coolest, most interesting ways to demonstrate the vibe of custom furniture.

  5. You're very kind Christopher! And, I hope my comment didn't seem condescending at all. I just have so many horrible memories trying to install those brass, slotted insert nuts... having them break on me and then having to file them down and leave an ugly mess...and, I hate to think of anyone else struggling with them. I'm angry that woodworking suppliers would even carry them. Here's a photo of the flanged inserts installed:
    I use them all time for all kinds of applications. Great blog btw... always keen to see what you have on the bench. Cheers!

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