The above diagram shows the profile of a heat sink. At the center of the diagram are essentially two cylinders. The upper most is 3.5mm wide (the diameter of the screw may not exceed this) The 2nd, just below it is 7.5mm wide. A threaded nut slides from the end of the heat sink into the 7.5mm space. The heat sink is attached to the frame by a screw that passes through the frame and is screwed into the captive nut. The supplier of the heat sink says the nut is a M3 T slot nut. I looked through various online suppliers of nuts, fasteners etc.(Tnutz
, McMaster-Carr). On Tnutz I found a M3 x0.5 nut but no dimensional info is given. On McMaster I found a M3 square nut that is 5.5mm square. I think this may work because it diagonal measure is greater then 7.5mm (providing my geometry is correct). You need this to be case so you can securely tighten the screw / nut
I appreciate your help thanks
@beardless, Here is our Engineers response !
A square but would only be .05 mm larger (on a diagonal) than the slot opening. Even though mathematically it would work, I would be afraid of the extrusion flexing .05mm when torquing and the nut would then skip around. These are the closest nut I could find that would fit the dimensions given. They are made for a different extrusion type, but turn them upside down and i belive they would work, so long as the tolerances for the 4mm height are tight on both the extrusion and nut. Amazon.com: PillPack by Amazon Pharmacy
PillPack comes up
I’ll check amazon I think I know which one he is referring to.
If I have to use a square nut, I was planning on using a lot washer with it.
Thanks
Wow, nice fat buds @beardless. I am at day 46 on my auto WW and GSC. Still growing but one has just started to put on flowers. Hope mine look as good as yours do when they are done. Have a great day.
Thanks. You only post the nice ones. No, actually pleased with all that I have grown. Pretty new at this. Close to finishing the fourth grow of autoflowers. Started Northern Lights photos a few weeks ago. I’m doing a grow journal if you want to check it out. Northern Lights First Photo Grow
You are at a good place if you have questions or need help.
I will definitely go and keep up with you @beardless. Love seeing others grow, and learning their different approaches to producing a great harvest. Have learned so much I didn’t any idea of. Thanks for the reply and have a great evening.
Okay at least her tried I got PillPack also
Nuts for nuts - good grief. Have a good weekend.
You do the same, I’m a Accountant by Trade 
that is to funny. I put in 40 plus years in public practice, certified and everything. Small practice. The usual, tax, financial statements, consulting, tax and succession planning, gave up audits 6-7 years before retiring. I am one happy MFr not having to deal professionally with the mess we are dealing with now.
Tried the CPA test servera; times and got 3 of the 4 parts and gave up !!! Family was more important at that time ! 
Please find attached pictures of the Girls this morning and pictures of the Trichomes from last night. Some clear some milky but no Amber
Please give you opinion on the “Airport”
Thanks
Don’t know airpots. Girls are looking good. How did you stabilize the USB?
So I need to keep circling for awhile ???
I bought your suggested Tripod and still learning how to use it.
Much better thou 
Yes sir. Pistils white and standing up.
The tripod didn’t take long to arrive. If you put the plastic around the lens against the bud, then you can zoom in. It will blur out, keep turning the focus then it will come back into focus.
Thank you, What a great Hobby and goods friends to enjoy it all with.
I like this picture too! Very frosty !
The hobbyy that nevers keeps wanting more ! LOL
Now am looking for a tool to traxk tthe humidity in my Jars during the curing proess. 