quest about the strength of MDF - I'm thinking about routing a keyhole to adjust the light. Do you think the MDF would be able to handle it? the keyhole and slot would be ruffly 1/8" wide and 1/8" to 1/4" deep depending on the bolts I use.

suggestions? advice? free pizza?

thanks guys.

I wasn't able to find much on the LL site about this, but doing a regulat Google search shows that a lot of people are doing this - usually to hang pictures and such.

Google: +keyhole +mdf

Not knowing exactly what you are trying to achieve then it is hard to advise but it really depends on the thickness of the MDF and the weight of the object being supported and its bearing surface.

You can always 'help' the MDF by putting washers on the inside/outside to give better bearing surface support these can be sunk into the surface if it is aesthetically better.. You could also 'inlay' a small piece of aluminium or a 'key hole' plate obtained from the hardware store.

MDF is surprisingly strong as long as you are realistic about the weight being supported and the method used to support an object.

What are you going to be using the keyhole slot for?

ok -

Haas enclosure > from the back - right side > LL T15 bulb + mogul - mounted horizontally

The 2 threaded holes will be bolted to a plate of 1/4" ply that allows a 1/8" lip around the base. like THIS

difference is I'm recessing the plate fully into the mdf plus 1/8" for the mogul to bring the bulb center in my build.

that pic is in a pine enclosure. I need to recess it do to my enclosure being a bit thin, and the table saw I had access to is shot so no recuts till I can afford one.

You might see if they have any scrap MDF at the lumber store that you can experiment on. Heck, they might even just give it to you.

You might want to take a look at this "Adjustability, First step: Adjustable bulb mount" thread for alternate solutions.
In that first picture, you could cut a slot for the bulb and metal mount to fit in, instead of cutting a keyhole slot.

I have it in acad but not sure it would translate in a pic, so here it goes:

I'm thinking of taking that overall design, and sinking it into the mdf about 3/8" total. the base is 2" dia. so I'll need a 2.25 x 4.25 box thats 3/8" deep. still working out the kinks in acad. Thanks for that link - going to read it now.

PS - The reason is that the center (arc) of the bulb is 1/8" to far past the center of the pj. so to keep it all centered I have to sink the base in, and then everything else to keep it centered.

I understood you correctly. I'm glad you understood me.

Philw ran into a similar problem when he switched from one of those "football" style bulbs to his 250w replacement. He ended up using a tuna can (of all things) as an extension on his enclosure.

I also noted that the arc position is different with different brands of lamps, even with the same wattage. That creates problems as well.

MDF is nice and strong in the way you want to use it but there may be a few ways to make the cutout less deep.

The plate on the bottom of the mogul could be made of thin steel which would give slightly more room.

You don't have to use the two screws on the bottom of the mogel. A large round 3/4" thick donut MDF shaped mount that went on the outside of the mogel like a clamp with a slot cut into it and a flat spot for a clamping screw would alow you to mount the socket almost flush.

You did not say how thick your MDF is.

You don't have to be perfect with the lamp center as long as you can move the triplet center hole mark before you cut it. The PJ would then shoot slightly crooked but you would never see it.

DOH!! sorry about that - would be good to know eh? Its 3/4"

now that I have the router I've pretty much decided to test drive the keyhole slot idea. There was still some scrap mdf where I cut the side pannels so I'll practice on those and see if my idea pans out - a prototype if you will.

This whole PJ is a prototype enclosure wise. The router gives me a few more options now. I just have to learn about the bits and which does what.

Thanks for the replies,

From my experience with MDF you should be totally fine with a keyhole rout, as long as you're not bearing any heavy loads in the channel, which it doesn't sound like you are. If you were using 1/2" or less, I'd advise you to watch out for crumbling, which MDF does (it's just sawdust, after all) but a nice thick slab like yours will do perfect. And like was said before, you can reinforce it, with a piece of steel or (easier to machine) thin aluminum.

If you do run into strength issues, you could always use plywood for the one section in question, plywood has the huge advantage of having the directional grain strength of wood, rather than MDF which is just a homogeneous sawdust/wood mixture. But MDF is cheap so just hack up a prototype and work from there!

I foudn some scrap mdf form my stash at my grapms ( was his ANCIENT table saw I used) and made a test cut witht he specs I wanted and the resaults:

The router did fine, the 1/4" ply leaved 1/8" for the mogul to sink into as planed. The keyhole actually goes all the way through the restr of the mdf - however it does hold the ply pretty well as I used a drill to tighten it and it did great. I need to tweek the design howver the prototype was working as planed - so not bad. I was actually shocked at howwell the little shelf of mdf in the keyhole held.

though will it hold the weight of the mogul+t15 bulb I havnt figured out a way to test that - though they are not that heavy.

anyone know the shank / thread size int he bottom of the LL mogul?

The holes in the mogul are not threaded. It's intended that screws go from inside the mogul to the mounting surface, not the other way around.

I used 1/8" screws to mount mine.

hmmm... my mogul was "threaded". I don't know what it's called, but it's one of those "single thread" type things, it doesn't look like the threads in a nut or anything, but it certainly does a fine job when using a screw from the outside... just be sure the screw isn't too long, otherwise it'll interfer with the lamp base. I believe it's a 6-32 that I used.

gs

edit... hmmm maybe it's actually 8-32...

A tinnut? A piece of metal that has a keyhole shaped opening in it, with the hole bent to form a thread?

Hmmm... It's possible that mine had them, and I pulled them out.

6-32, 8-32? Maybe even bigger IIRC. Check this.

Mine (from Lumenlab) held machine screws very well.

YMMV.

Yea. This is the little guy...

10-32... hmm.. maybe... I think these are somewhat "universal" as the little tabs will bend to various sizes/threads... maybe ?

Click to view attachment

I love that . . . "universal"!!! It's true really.

What's with the rust? Damp basement? Or has the ice FINALLY melted?