Captive/insert/press-in nuts

[xtian]

Anyone tried installing these with a hammer?

http://www.mcmaster.com/#95185a176/=10cpix1

[img:196:198]http://images2.mcmaster.com/mvA/content ... gitall.png[/img]

[John_P_WI]

PEMs are generally set with a press. We use thousands of them and even the ones set by press can loosen and fall out. I love 'em for thin gauge stainless sheet metal but they truly are a pain in the ass.

[Phil_S]

No, but it looks to me like a hammer is the wrong tool for the job. I'm guessing you want a low cost alternative. They need to be pressed in. You could try a screw type C clamp. Depending which side you have the screw apparatus pressing on, you might need a metal plate as a helper. For that look in the bins hear the lumber where they have various fasteners. You'll find a small galvanized plate that I think will stand up to the task. $4 for a clamp if you don't have one and $0.50 for the metal plate. Cheap enough. Take the 20% off coupon to Harbor Freight, if you have one, and I bet you'll be in the $2 range.

[strelok]

Whenever I've had to install pems without a press, for instance say for the screws to mount on the bottom panel of an amp, i put the pem in place and then on the other side of the chassis start tightening it down. Just by installing the screw and getting it tight enough will press the pem in place. You just don't want to go too tight or it will break off. Fwiw I've only tried this with #4 and #6 pems not sure how well it will work with the bigger ones.

Edit: Also depending on the location of the pem sometimes its helpful to add a dab of superglue to hold in place while get the screw screwed in.

[xtian]

Good advice, guys. I'm not THAT much of a cheapskate...Harbor Freight has a $40, 1000 lb arbor press.

I have always liked the 1/4" pem nuts in the chassis I buy from Watts.

[dkochan]

Yep, press them in with red (bearing-type) Loctite, and/or stake them after they're pressed in.

You may find that 1/2 ton is surprisingly little force. Maybe buy a c-clamp as a backup.

You will need a reasonable accurate hole, in roundness and size, or they won't hold worth a damn. Or they just won't go in. You won't be doing that with a standard twist drill. Try a reamer.

[telentubes]

I've pressed them in, but occasionally they come loose. I've gotten in the habit of adding a dab of Bondo to help. Those with Bondo have stayed in place so far.

[davent]

Would these offer any advantage over Rivnuts? I've bought the tool and nuts but haven't had a reason to try it out yet.

dave

[Firestorm]

I've used the rivnuts. Some have a serrated mating surface, good to make them hold or establish a ground for a chassis lid.

[cbass]

I'm sure not much of a metal worker but would a nut and washer and bolt and a small piece of pipe or something work to press it in

[Bob S]

I settled on cage nuts. Had a couple of pems come loose.
The only drawback is making a square hole to fit them in.
Not a problem if you get the chassis water jetted before its folded.

[John_P_WI]

Rivnuts are larger in diameter and also longer in length. The pem fasteners are much lower profile, do not protrude through the sheet (allowing flush mounting opposite of the fastener) and are much smaller in diameter.

[telentubes]

I'm reminded that I use the technique that cbass described. You don't need the pipe though. Just the nut and washer. A little whack with a hammer will help seat them after tightening the bolt.

[The Ballzz]

Might I suggest to not reuse any screws you may use for setting the PEM's? It has been my experience that what knocks them loose is most often the process of forcing a screw in or out that has been cross-threaded or has otherwise buggered/stressed threads! Also, a dab of oil on the threads when setting will dramatically (by a factor up to 17 times) increase the clamping force for any given rotational torque.
Just My $.02 & Likely Worth Even Less,
Gene

[guitarmike2107]

I use cage nuts too, and have a 3/8" square hole punch which works a treat

They are easy to replace if you ever have to and they can be gripped easily if the screw ever seized in it.