Which screws to use to fix Air con Frame to Aluminium Window?

[JJM1]

Hi all,

Just after some friendly advice on which screws to use to attach an Air conditioning Metal frame to an Aluminium Window. I have attached some photos displaying the opening after removing the existing Air Conditioner and surrounding frame (Arrows indicate where I want to screw the new metal frame into the aluminium). I have also attached a photo of the screws I removed which were holding the previous air conditioner frame in.

Can I please ask the following :

1.Can I ask the best screws to use and if I would drill through both the Metal Air Con frame and aluminium (if self tapping)? 

2.The new Metal frame is about 1 inch smaller in width and was looking to pack out the space with the below angle. Can I use the same screws suggested in Question 1 above for Aluminium to Aluminium ? (I assume so)

https://www.bunnings.com.au/metal-mate-40-x-20-x-1-6mm-1m-aluminium-unequal-angle-1m_p0427792

Any Help is appreciated.

 Window Opening - Arrows indicate screw location for new frameAir Conditioner External frameScrews used to attach old Air Con Frame 

Cheers

Jeff

[EricL]

Hello @JJM1 

The screws you have appear to be 8g x 20mm steel self-tapping screws. You can double check sizes when you get to the store, just make sure to bring one of the old ones for comparison. If you are installing a filler between the air con frame and the aluminium frame, please double check the size and add the appropriate length to the screw. For example, if the fill in gap is 20mm and you need to go 20mm into the aluminium window frame you will need at least a length of 40mm to make sure the screw goes through the aircon frame and through the aluminium filler and through the window frame.

Therefore, the side of the air con frame that is right next to the window frame can use the shorter screw which conservatively is 20mm++ an example would be the Zenith 10G x 25mm Galvanised Hex Head Metal Screws - 20 Pack and for the other side that has a long gap you can look at Buildex 12-14 x 50mm Climaseal Hex Head Hi-Grip With Seal Roofing Tek Screws - 50 Pack. Please make sure to double check your measurements.

If you need further assistance, please let us know.

Eric

[JJM1]

Hi Eric,

Thanks very much for your reply.

What size hole would you drill in the metal Air Con Frame/Aluminium frame for the screws mentioned above ?

Cheers

Jeff

[EricL]

Hello @JJM1 (Jeff)

The screws I've recommended are self-tapping screws there is no need for you to drill holes for them as they will self-drill through the steel. To keep the screw from wandering, I suggest using a steel punch to place a dimple on the steel surface to keep the screw in place.

Eric

[JJM1]

Hi Eric,

Many thanks for your help.

Cheers

Jeff

[EricL]

Hello @JJM1 

Please keep us updated with your progress, we look forward to seeing your air con frame installed and ready for use.

Eric

[R4addZ]

Hi @JJM1 

Just a quick note that any screws (other than good quality stainless steel ones) will react with the aluminium and corrode the aluminium. It is caused by moisture in the air and an electrical current created between the dissimilar metals. Its called Galvanic corrosion and examples shown here....

https://www.alumeco.com/aluminium/corrosion-of-aluminium/

[JJM1]

Hi Eric,

Thanks for the above, I've unexpectedly had a bit of luck with a tradie who I had to get to do something else and he gave me hand. The screws he used looked to be similar to the one you specified above 

All installed now.

Many thanks for your advice

Cheers

Jeff

[JJM1]

Hi R4addZ,

Thanks very much for the info above, something I will definitely consider moving forward.

Cheers

Jeff