soon7x7
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Drilling, Countersinking Kevlar?

Fri Oct 17, 2008 7:25 pm

I'm looking for a supplier that has counter sink bits that are used on Kevlar panels. Tooling for this material is different than most others...any help...is appreciated...
 
tdscanuck
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 2:31 am

These guys seem to make them (put "kevlar" in the search field):
https://www.onsrud.com/

Solid carbide with a major cutting tip at the front, I assume to cut the Kevlar fibers before they turn into a string ball around the drill shaft.

Tom.
 
soon7x7
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 3:29 am



Quoting Tdscanuck (Reply 1):

That is correct...thnxmuch....j
 
vikkyvik
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 5:28 am

Interesting, Onsrud is the only company I ran across when I just searched.

I haven't worked with Kevlar before. What, specifically, makes it difficult to machine?

For reference, I work mostly with aluminum, PVC, expanded PVC, delrin, and occasionally steel.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
tdscanuck
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 6:13 am



Quoting Vikkyvik (Reply 3):
I haven't worked with Kevlar before. What, specifically, makes it difficult to machine?

Kevlar has an extremely high toughness, unlike glass or carbon. As a result, you effectively can't pull it or bend it apart, you have to shear it. If your cutter damages the matrix to the point that the fiber is "free", it'll just flop around forever and never get cut. Imagine trying to cut limp fishing line with a knife...you need to get the fiber in tension to stabilize it before you can cut it.

Dupont has a nice guide on this:
http://www2.dupont.com/Kevlar/en_US/...Cutting_Drilling_Sawing_KEVLAR.pdf

Tom.
 
vikkyvik
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 6:34 am



Quoting Tdscanuck (Reply 4):
Kevlar has an extremely high toughness, unlike glass or carbon. As a result, you effectively can't pull it or bend it apart, you have to shear it. If your cutter damages the matrix to the point that the fiber is "free", it'll just flop around forever and never get cut. Imagine trying to cut limp fishing line with a knife...you need to get the fiber in tension to stabilize it before you can cut it.

Interesting, thanks.

I'd imagine Kevlar is much tougher, but I wonder if it's conceptually similar to machining FR-4, which I had to do a fair amount of at my last job. Although, even though FR-4 has woven fibers, they are encased in an epoxy or whatever. But many times, you'd end up with tons of little strings hanging off of a machined edge.

Not to mention, I had to use end mills with the titanium-nitride coating - they could resist higher temperatures, and that FR-4 got HOT if you machined too deep at once (not to mention, the machine I was using didn't have coolant). I ended up machining in depth cuts, probably 0.02" at a time or so.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
tdscanuck
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 4:11 pm



Quoting Vikkyvik (Reply 5):
I'd imagine Kevlar is much tougher, but I wonder if it's conceptually similar to machining FR-4, which I had to do a fair amount of at my last job. Although, even though FR-4 has woven fibers, they are encased in an epoxy or whatever. But many times, you'd end up with tons of little strings hanging off of a machined edge.

Same deal. I think the Kevlar guys call it "fuzz out" or something like that.

Tom.
 
soon7x7
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 10:23 pm



Quoting Vikkyvik (Reply 3):

When Kevlar is layed up in the manufacturing process, it pretty much acts like carbon fibre and fibre glass. After the component is cured...it has outstanding strength, just like all the others...the difference I have found is that once cured...the epoxy resins encapsulate the fabric weave and the components seem welded together. That way, due to the resulting stiffness and brittle qualities...the component can be drilled, machined and countersunk with clean results. Just like it is a solid core of a substrate...however Kevlar seems to defy the "we are one" philosophy...the Kevlar fabricated panel, though extremely strong...once disturbed mechanically by virtue of tooling, (drill, scissors, countersinking bits, that sort of thing). The Kevlar wants no part of it unless you use very sharp, specially designed tools, to deal with the stuff. Basically the fibre is encased in the resin till you tool it and it becomes a very tough fabric pain in the a__!, It does not like to be cut, drilled etc...so it frays, it seems to want to just be a layer of fabric sandwiched in some epoxy where as the other fabrics like to become one with the epoxy. The result of tool missuse w/ Kevlar is a sandy colored furry look around the drilled out hole or a sanded edge will reveal sandy color fur or weave. I'm not sure about this but I would not be surprised if it is no longer used on Boeings.
 
tdscanuck
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RE: Drilling, Countersinking Kevlar?

Sat Oct 18, 2008 11:27 pm



Quoting Soon7x7 (Reply 7):
I'm not sure about this but I would not be surprised if it is no longer used on Boeings.

Still used.

Tom.
 
soon7x7
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RE: Drilling, Countersinking Kevlar?

Sun Oct 19, 2008 3:56 am



Quoting Tdscanuck (Reply 8):

I suppose if any one could or should perfect techniques dealling with the stuff...it should be Boeing...Thnx...J
 
tdscanuck
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RE: Drilling, Countersinking Kevlar?

Sun Oct 19, 2008 5:15 am



Quoting Soon7x7 (Reply 9):

I suppose if any one could or should perfect techniques dealling with the stuff...it should be
Boeing...Thnx...J

No problem. I know it's not used that much...only places where the oddball properties of Kevlar really pay off. Glass and carbon show up a lot more often. It's pretty easy to go off the deep end with aerospace materials if you just look at performance and raw material cost and don't look at manufacturing cost.

Tom.
 
vikkyvik
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RE: Drilling, Countersinking Kevlar?

Sun Oct 19, 2008 6:55 am



Quoting Soon7x7 (Reply 7):



Quoting Tdscanuck (Reply 6):
Same deal. I think the Kevlar guys call it "fuzz out" or something like that.

Interesting, thanks for the explanations.

I think I would pull out my hair if I had to machine Kevlar at work. Lord knows I get frustrated enough with delrin and PVC, and those are cake to machine by comparison.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
soon7x7
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Joined: Thu May 04, 2006 10:51 am

RE: Drilling, Countersinking Kevlar?

Mon Oct 20, 2008 3:30 am



Quoting Tdscanuck (Reply 4):

Tom,,,thnx on the Dupont listing...it is good info!...J

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