Threaded inserts for mdf

[Chuck Pickering]

Looking for fastener system for project built with either mdf or plywood, 3/4" thick.
Looking at the threaded inserts like these from Lowes.

https://www.lowes.com/pd/The-Hillman-Group-12-Count-8-x-0-39-in-Zinc-Plated-Standard-SAE-Screw-In-Insert-Nuts/4316644

Do these need a special tool to install?

[Adam Herman]

i'm not sure how well they will hold in MDF.

usually just use a hex key to insert them.

[Bruce Page]

A 3-Prong Tee Nut would be much stronger but is not always a design option.

[Yonak Hawkins]

With regard to an MDF project, it will hold as well as you should need (as long it is inserted in the face and not the edge, of course). In a plywood face, it should hold as well as solid wood.

[glenn bradley]

I find the ones you show to be too soft for my applications. Several malformed on insertion with a hex key and had to be replaced. I stick to these (https://www.amazon.com/E-Z-Threaded-Insert-Internal-Threads/dp/B002WC8TPW/ref=pd_sim_328_10?_encoding=UTF8&pd_rd_i=B002WC8TPW&pd_rd_r=MZPR09TSY20NVP2QVS04&pd_rd_w=puQYG&pd_rd_wg=d0H3o&psc=1&refRID=MZPR09TSY20NVP2QVS04) (or something similar) for the most part now. I have used them in ash and pecan so MDF should be no problem.

[Edwin Santos]

I have had good success with them. I prefer the tapered, hex driven kind to the brass ones because they tend to go in straighter if you're driving them by hand. Also, if your design will allow for it, you might be well served by the flanged version of the one you posted, installed where the flange is opposing the pull (like a tee nut would do). Here is a link for what I'm talking about - https://www.amazon.com/E-Z-Threaded-Hex-Flanged-Internal-Threads/dp/B002KT43MU/ref=pd_sbs_328_1?_encoding=UTF8&pd_rd_i=B002KT43MU&pd_rd_r=YTPT43MQ452WS2SW7EDF&pd_rd_w=8Fe38&pd_rd_wg=OqsOv&psc=1&refRID=YTPT43MQ452WS2SW7EDF

Regardless, the knife threads hold with a lot of strength. I've never had one pull out.

I'm not sure if what you are building is something that needs to knock down and disassemble. If not, another alternative for fasteners in mdf is Confirmat screws. They excel with mdf and particle board core. You need a special step drill bit to use them, but they are fast, efficient and strong and might be an option if you need to drive a lot of fasteners into your mdf.

[Lee Schierer]

I find the ones you show to be too soft for my applications. Several malformed on insertion with a hex key and had to be replaced. I stick to these (https://www.amazon.com/E-Z-Threaded-Insert-Internal-Threads/dp/B002WC8TPW/ref=pd_sim_328_10?_encoding=UTF8&pd_rd_i=B002WC8TPW&pd_rd_r=MZPR09TSY20NVP2QVS04&pd_rd_w=puQYG&pd_rd_wg=d0H3o&psc=1&refRID=MZPR09TSY20NVP2QVS04) (or something similar) for the most part now. I have used them in ash and pecan so MDF should be no problem.

I've used the same brass inserts recommended above with great success. They are also available in steel. The key to insert them is to have the correct size pilot hole. I use a hex head bolt with a stop nut instead of the screw driver slot to drive the insert flush. It you want the insert slightly recessed you can then turn it using the screw driver slot.

[Art Moore]

With MDF I try to use tee nuts. If the insert is going to be sandwiched between pieces I'll use a Forstner bit to cut the recess (sized to the flange of the nut and then drill for the body of the tee nut. I install them either with a bolt/washer combo or with a small arbor press.

[Curt Harms]

Not a fan of MDF so no experience there but I've used them in ply. Don't drill the hole too undersized or the wood will raise/distort and I bet MDF would be worse. I've heard of people putting a little epoxy in the outside threads of the insert for better hold.

[Mac McQuinn]

I've used the HD brass items sold by Lee Valley. They were used on a reloading bench to hold a press and top was 3/4" MDO.
Using the correct sized hole is the trick. Very happy with the result.
Mac

[Chuck Pickering]

The project in mind will probably be assembled and disassembled many times during the build, so strength is a factor. Final assembly might be permanent. I like the idea of adding epoxy to increase strength.
Thanks for all input.

Chuck

[Chuck Pickering]

BTW, there will be edge connections in this project. Any advice there? I don't want to split the mdf. MDF thickness will be 3/4 in. I do want to be able to disassemble during build in case of design changes. The project, BTW, is a low budget CNC router.

Chuck

[Grant Wilkinson]

I've used the Lee Valley brass ones in MDF successfully. As others have said, the pilot hole size is key. In MDF, I go a bit bigger than the recommended size and use epoxy to make up for the shallowness of the threads. When putting them into edges (rather than faces), I was getting split out. I started using a C clamp on the face "squeezing" the hole a bit while I screwed in the insert and the problem was solved.

[Joel Wesseling]

I will never use threaded inserts in MDF anymore. Right now I'm constructing a basement pantry style cupboard with MDF doors and I'm using Hillman posts, with through hole in the doors, to secure hinges.

On the edge connections, I would plan the project to have plywood blocks bolted to the Face of MDF, and screw or bolt through the plywood - or angle brackets.

[Dan Cameron]

For the edge connections, barrel nuts work well.

[Doug Garson]

Have a look at this method for installation, I could never get them to go in straight until I used this method.

http://www.popularwoodworking.com/techniques/q-installing-threaded-inserts

[Andrew Pitonyak]

I rarely use MDF. Last time I used it on a project, I was creating a router table top that because part of my table saw top.... As part of the process, I screwed some things into the MDF.



I drilled a hole.
I tapped the hole
I used some of that very runny glue (cyanoacrylate???) and dropped it into the hole. The glue soaked into the MDF both stabilizing and strengthening.
I don't remember if I ran the tap through it a second time after the glue hardened or if I just used a screw, I think I used the tap.


I would not use the other to cut the threads until I had tried it in a few sample boards to test for things such as tear out and strength. of course, you do it once and then you have confidence.

[Chuck Pickering]

Thanks, Doug. Saved that for future reference.

Chuck

[Chuck Pickering]

Tank you, Andrew. Another good idea.
I wonder what the thread on the outside of the insert is, and can I find or make a tap for them? I like the super glue idea, to!

Chuck

[William Shelley]

Tap threads into the MDF directly, using an undersized pilot hole. Put epoxy into the tapped hole, thinned enough so that it soaks deeply in to the MDF. Chase the hole with the tap and now you should have very strong threads without any extra hardware.

Metal hardware in MDF tends to cause the MDF to fail quickly because neither material have any "give", but the MDF is weaker.

I've found that this method works great with 5/16-18 or larger fasteners. 1/4-20 is do-able but smaller doesn't work well. 1/2-13 will be large enough that each thread will have a fair amount of "meat" to it.

EDIT: whoops didn't see that Andrew posted almost the same thing.

[Greg Hines, MD]

One technique I have seen is to make an installation jig, with a piece of 2x4 scrap, with a cut out on one end, and a hole drilled through above it, with a bolt/nut so you can insert it square. I think that was on the Woodsmith TV show a while back.

Another technique I have read about but not tried was to insert a Domino or large dowel in the area you want to place your insert, glued in, so that it has some actual wood to bite into.

Doc