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ERBenoit
05-04-2008, 06:35 PM
I have an application where a device will be mounted on a plate, the plate will then be installed over MDF as a substrate. I would like to use a machine thread (1/4-20) in the MDF if it can be done sucessfully. Has anyone tried tapping MDF, and if so, how were your results? Will a machine thread hold, or should I ditch the idea and use a sheetmetal or wood screw?

I have seen here that some have used MDF for fixturing purposes, though not sure what types of screws were used, so.....

I'm thinking tapping sucesfully is possible as MDF composite appears to be a solid, more or less.

Ries
05-04-2008, 06:53 PM
MDF will crumble if you try to tap it.
Not a good idea.
However, there are inserts you can buy that are machine threads inside, and a coarse, wood thread outside, that will do what you want.
They use them for knockdown MDF furniture.

http://www.woodcraft.com/family.aspx?familyid=1048

Mark Hockett
05-04-2008, 07:24 PM
ERBenoit, Ries,
There is a way to tap MDF and it works very well. First drill and tap the hole, then pour a cyanoacrylate (Krazy glue) glue in the hole, and then re-tap the hole. This make a very strong thread. This is how the MDF pulley is made on the Rose Engine lathe that I posted about here a while back, http://bbs.homeshopmachinist.net/showthread.php?t=24226&highlight=rose+engine+lathe

http://www.ornamentalturners.org/assets/content/RoseEngine.pdf

We have sold over 100 of the kits and have not had one complaint about the strength of the threads. The thread holds the rosettes (cams) which are changed frequently so it sees many cycles.

ERBenoit
05-04-2008, 07:44 PM
However, there are inserts you can buy that are machine threads inside, and a coarse, wood thread outside, that will do what you want.

http://www.woodcraft.com/family.aspx?familyid=1048

I had thought of, and forgot about those. I will be working cramped inside of a cast acrylic box, so the inserts seem to be my best option, as I only want to visit this once.

I'll file Mark's method for when circumstances will be easier to give that method a try.

Thanks

Bill Pace
05-04-2008, 07:51 PM
I've tapped MDF with pretty good results.... Nothing as small as 1/4", did a good many in 3/8" for application in woodworking, like for positioning/hanging, never anything with any stress to speak of. It makes a pretty thread, ---never tried the super glue trick but I bet that would make for a pretty decent thread.

I'm presently pondering a situation to use a piece of 3/4" MDF as back up on a complicated milling procedure in some thin sheet, maybe 3/32 aluminum or steel... will probably give it a try

john hobdeclipe
05-05-2008, 08:52 AM
Can you drill through and insert a T-nut from the back?

Evan
05-05-2008, 09:08 AM
Use what are called here "euroscrews". These are specifically designed for secure holding in MDF.

http://www.ovisonline.com/store/detail.asp?product_id=MFPE05300R2N

Duffy
05-05-2008, 09:23 AM
Euroscrews are also sold by Lee Valley Tools in smaller packs, (100s.) They also produced a technical report on using bolts instead of wood screws for wood assemblies. In essence it proved that tapped holes and bolts beat wood screws hands down for holding power in hardwoods. They made no mention of hardening the threads with cyanoacrylate, but with it, the logic would extend to soft woods like pine, spruce, and plywoods.

Evan
05-05-2008, 09:30 AM
We can buy euroscrews in blister packs at Canadian Tire and other hardware stores. I don't know how available they are in the US.