Drill bits/ Drilling speeds on a FRP/Al Assy

[tapirg]

Hi All;


I have to drill through a machined aluminium (7075-T7351) alloy ring slot and the carbon ring, which is slotted, into the Ali ring (please see picture attached for more references) and I am not sure which type of drills and “drilling speeds” should I use.

Final hole size is 6.35 mm Ø H7 ant this is achieved by using the following drill sequence: 2.5 mm Ø; 4.5 mm Ø; 6.00 mm Ø and a final reaming @ 6.35 mm Ø

Does this sound reasonable?

As is not only a carbon component, I am not sure if carbide drills are the best option to drill through the whole assembly.

Should I use variable speed as I drill through Ali first then carbon and then Ali again?

Any advice, guidance on this would be really appreciated.

Thank you all in advance

RGT

 

[tapirg]

Sorry, I will upload the drawing quite soon

 

[tapirg]

Hi All,

I have uploaded a pictorical representation showing a section of the the components I have to drill through.

Thanks

 

[RPstress]

Still no picture!

However, I can't help with the bit about changing speed when transitioning from Al to CFRP (or vice versa) anyway.

With regard to drill material you may get good life out of carbide rather than coated. We have seen DLC (diamond like carbon), diamond and TiN coatings give less life than the basic tungsten carbide. However, we've also seen PCD (polycrystalline diamond) give very good results (good is relative, here; carbon (and even glass) fibre composites eat cutting tools in large quantities compared to cutting metal).

The drill speed should probably be about 50 metres/minute (about 2500 rpm for a quarter inch drill).

Pilot, final size drill and then ream would be normal. I can't comment on your proposal to use three drill sizes. The carbon/polymer will shrink a bit after drilling.

 

[tapirg]

Thanks for your quick response RPstress.

Picture should be now attached