machining question / BIT

[Precision]

In my Sport, Buhurt

Armor weights a metric ton if you use steel, so many people (me included) upgrade to titanium. My brig went from 17# to 9# when I built the new one from titanium. So far so good.

I am beginning to make custom Brigandine (Back and chest) armor. I am using grade 5 titanium which is much stronger than the grade 2 and grade 4 the western Europeans use. This means I can use .040" where they must use .050" or thicker. I may also begin making splint leg and arm armor. The curves might make milling difficult. I could mill pre bend, but will likely cause ripped titanium. May not with a plate roller I plan to buy / build.

But even that could be lighter, gaming the system as it were. If you are wearing 80# of armor and I am wearing 70#, my speed will be faster, I will heat up slower and I will have greater stamina (all other things equal).

Towards that goal I am considering drilling out some of the plates in my armor to lighten them. I could probably lose at least 1# doing that. Moving to titanium arms and legs will save 3 and 5# respectively. Drilling them out might save another 1.5- 2#

This would only work (be legal to use) with brigandine / splinted armor as the cloth would cover the holes.

Questions
What percentage can I drill them without loosing much integrity
Assuming the metal is 0.050" and 0.040" thick sheet titanium, is there any value in milling down 75% and leaving the face of each hole closed.
For me that makes sense due to the cloth ( wool) covering the plates are riveted too. having the solid face makes it less likely to rip.

On a 4" x 8 " plate I am considering leaving a 1/2" or 3/4" undrilled edge, then 3/8" holes (or non through plunges) at 3/4" intervals with the layers being offset by 3/8".

so the pattern looks like this

o o o
o o
o o o

will something like this tragically weaken the plate or will it provide 80%-90% of the strength with a 20-30% weight savings?

[Netpackrat]

You know what they say about one test being worth more than a bunch of opinions. Also, consider investing in a Class "D" fire extinguisher.

[Cobar]

You know what they say about one test being worth more than a bunch of opinions. Also, consider investing in a Class "D" fire extinguisher.

+1

Skeletonizing like that keep strength in the material more perpendicular to the holes because they are essentially forming arches. Taking hits to the flat of the material would certainly be weaker than not drilled but like NPR said tests are in order.

I didn't see any pick-type weapons or pointed sword thrusts in those videos but chainmail has a tendency to blow apart links when taking thrusts because the weapon acts like a wedge when it goes in to a link. That could be a concern with holes in the titanium.

[Precision]

You know what they say about one test being worth more than a bunch of opinions. Also, consider investing in a Class "D" fire extinguisher.

+1

Skeletonizing like that keep strength in the material more perpendicular to the holes because they are essentially forming arches. Taking hits to the flat of the material would certainly be weaker than not drilled but like NPR said tests are in order.

I didn't see any pick-type weapons or pointed sword thrusts in those videos but chainmail has a tendency to blow apart links when taking thrusts because the weapon acts like a wedge when it goes in to a link. That could be a concern with holes in the titanium.

yes testing in valid and will be done

BUT

"Skeletonizing like that keep strength in the material more perpendicular to the holes because they are essentially forming arches"

this is the stuff I was looking for.

I seem to have read somewhere that moderate amounts of such drilling doesn't weaken much to impact / deflection

Also there is ZERO thrusting allowed. As in if you are in a position to thrust, you get two warning then forfeit the match on the third violation.
If you actually make contact with a thrust (intentional) the match is an immediate forfeit.

IIRC minimum radius on an axe head or sword is 15mm in some limited things. Most, it is 25mm, so nothing will fit in the 8ish mm hole I am suggesting. Minimum width on a blade is 3 or 4mm and a radius as well.

[Cobar]

The less material there is the less it will resist deforming from a blow. I can't say how much you can get away with removing and still perform the function of spreading the force of the blow over a larger area vs the titanium just giving and bending in to your body.

If you know any mechanical engineers they might be able to run a simulation to give you an idea of how much you can remove.

[HTRN]

Honestly, instead of bothering to drill holes, he's probably better off starting with perforated sheet instead.

[Cobar]

That would save a lot of drilling if it's available in the correct pattern. Only problem I can see with that is not having the option to leave extra material on the outer perimeter of the sheets to leave a little extra strength there.

[Precision]

Honestly, instead of bothering to drill holes, he's probably better off starting with perforated sheet instead.

That is a good idea, except grade 5 titanium is hugely expensive except from the place I get it. The reason it is much cheaper there is I am buying drops. No chance in getting it already perforated.

It may be a waste of time, but I am thinking about doing some testing to see if 10%, 20%, 30% - whatever is the fail point. if it is only 10%, no real point.
If 25% is still 90% as strong, then definitely a point

[BDK]

Just go ahead and jump to 3D sintered Ti designs

[Cobar]

In this video they are talking about arrow tests but you can see some results on the breaths of a helmet.

LINK

that part starts just after 40 minutes.