Threaded insert-best practice?

[LuncHwagon]

I'm building some mini statements, and due to my construction, I dont have good access to the inside of the baffle. I'm thinking that for the speaker mounting, I'm going to use threaded inserts rather than any kind of T-nut/hurricane nut, etc. I'm taking feedback on both:

1. Anyone have stong feelings AGAINST the use of threaded inserts?
2. When using inserts, whats the best method of securing them? ive heard of epoxy on outside threads etc.I want to make sure I get the best possible outcome.

Thanks
LW

[Bill Schneider]

I've used them occasionally, and they work fine. Give them a fair amount of space next to an edge because they could expand the MDF enough to split it. For example, when inserting them into the edge of 3/4" MDF, there's a very good chance that they'll split it (at least the large 1/4-20 inserts did).

I use a c-clamp when inserting them to apply a little pressure to the sides of the MDF to prevent splitting. It seems to work fine.

BTW, I use Gorilla Glue as the adhesive and drive them in with t-handled tools available from Woodcraft.

[sawdust]

I used threaded inserts with epoxy on the outside threads and it worked fine. Word of caution though - make sure they thread straight into the baffle. They can get started off a little and then your holding screws may bind going in and it will break the epoxy loose. I know this from experience! I've used T-nuts as well on other projects and think they are superior, but take more space on the inside of the baffle. I used the T-nuts that have a circular base and small holes in them for using small screws or nails to hold them from turning.

[LuncHwagon]

with the use of epoxy or GG, do those inserts come loose when small amounts of tightening torque are applied to the screws?

Looks like I'll be doing a few test holes to amke sure we get situated. Thanks for the great pics and input.

[Bill Schneider]

I haven't had any come loose yet. I use them to hold baffles in some designs, and in one case, to assemble the top and bottom plates to upright slabs of MDF for speaker stands.

The machine screws going into brass don't produce as much torque as it takes to budge these once they are fitted. Threaded inserts are often used in furniture assembly, so if they fell out, they wouldn't be as popular as they are.

If you need a little more torque resistance, you could always take a small triangular file and make a series of small notches in the outside threads. The notches would make driving them in more difficult of course, but would also improve resistance to backing out.

[mikela]

sawdust,

Where did you get those?

Mike

[Space]

There's a huge difference between zinc inserts and the brass or steel inserts. The zinc type has gaps between the threads and very limited holding power. The brass type holds much better, with continuous threads, although the threads are pretty fine. Also the brass type have a slot drive, which you definitely don't want to drive with just a slot screwdriver. Much better to either get the special tool (called a power driver), or install these with a cordless drill and a machine screw inserted inside the insert, with a couple of washers as bond breakers. The washers allow the screw to back out from the insert without binding and backing the insert out as well. I've installed brass inserts (sometimes called Roseannes) in MDF without using any glue, and they work very well. The washer also lets you install the insert to a consistent depth, because it puts the brakes on the driver. But you need a tough washer to survive more than a few hits this way. There's no substitute for case hardened steel for situations like these.






The best type is probably the steel insert, which has coarser threads than the brass. These use an allen drive, which is user friendly.

[sawdust]

with the use of epoxy or GG, do those inserts come loose when small amounts of tightening torque are applied to the screws?

Looks like I'll be doing a few test holes to amke sure we get situated. Thanks for the great pics and input.

Not with a small amount of torque, but I tried forcing a screw into a misaligned insert and it bound and spun the insert loose. If properly aligned the results are great.

[sawdust]

sawdust,

Where did you get those?

Mike

I purchased mine locally at a hardware store, but they should be available online. I'll do a search when I get a moment.

[sawdust]

I purchased mine locally at a hardware store, but they should be available online. I'll do a search when I get a moment.

Here's one place:

http://www.lowes.com:80/SearchCatalogDisplay?storeId=10151&langId=-1&catalogId=10051&N=0&newSearch=true&Ntt=tee+nut&x=0&y=0

[Not2Evil]

One of the best sources I have ever found for all types of woodworking issues is shopnotes magazine. Lots of how to do its, techniques and shop built fixtures and jigs. Including experte reviews on tools, fastners, glues, etc.

They specifically covered the topic in question. I could look up the issue if anybody wants to order a back issue. It wouldn't be instant gratification, but it would be made in the USA!

I'm not affiliated whatsoever, but I am a fan. Just put a www. at the beginning and a shopnotes in the middle and a .com at the end.

[kingpin]

:t :t :t

the best type is probably the steel insert, which has coarser threads than the brass. These use an allen drive, which is user friendly.