# Proof load for screwing into aluminium plate

I have a required clamping force for fastening two pieces of metal together, and am trying to work out if an m4 bolt will be sufficient. The pieces will be fastened without a nut, just a hole through one piece and a threaded hole in the aluminium block it needs clamping to.
The clamping force that the fastener must be able to withstand is 3400N, so I have found that an m4 bolt should be suitable at grade 8.8 or higher (with an allowance for 75% of proof strength) https://www.engineeringtoolbox.com/metric-bolts-minimum-ultimate-tensile-proof-loads-d_2026.html.
However, how can I verify that the thread in the aluminium plate will be able to withstand this force, or does the size of the hole not effect this (eg. if it can withstand it for an m6 bolt it will be fine with an m4)?
Diagram to show hole placement and depth in aluminium.

• You interchange the words block and plate where you say the thread will be, so state the thickness of this part as the number of threads will be crucial to the strength needed. Aug 2 '19 at 8:54
• The threaded hole in the aluminium can be up to 10mm deep, the aluminium itself is 140mm deep. The width of the plate where the hole will be needs to be as narrow as possible, which is why I would like to use a smaller size bolt. I was thinking of 8mm wide plate if an m4 bolt can be used. Aug 2 '19 at 9:44
• Add a diagram with the detail you have just explained to your original question. Aug 2 '19 at 9:48
• Be sure to lubricate the threads as aluminum is prone to galling. Sep 1 '19 at 14:38
• There are two failure mechanisms on the aluminum plate - thread and plate. For checking the threads of the aluminum you need to compare the tensile strength of the bolt and the plate. Yes, the hole size matters. It will affect the tensile capacity of the aluminum plate as the available thickness to resist the load is reduced for larger holes.
– r13
Aug 21 at 16:07