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Drilling, Countersinking Kevlar?  
User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Posted (5 years 9 months 2 weeks 2 days 5 hours ago) and read 5371 times:

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...

12 replies: All unread, jump to last
 
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 1, posted (5 years 9 months 2 weeks 1 day 22 hours ago) and read 5308 times:

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.


User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 2, posted (5 years 9 months 2 weeks 1 day 21 hours ago) and read 5301 times:



Quoting Tdscanuck (Reply 1):

That is correct...thnxmuch....j


User currently offlineVikkyvik From United States of America, joined Jul 2003, 9787 posts, RR: 26
Reply 3, posted (5 years 9 months 2 weeks 1 day 19 hours ago) and read 5278 times:
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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.



"Two and a Half Men" was filmed in front of a live ostrich.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 4, posted (5 years 9 months 2 weeks 1 day 18 hours ago) and read 5269 times:



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.


User currently offlineVikkyvik From United States of America, joined Jul 2003, 9787 posts, RR: 26
Reply 5, posted (5 years 9 months 2 weeks 1 day 18 hours ago) and read 5265 times:
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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.



"Two and a Half Men" was filmed in front of a live ostrich.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 6, posted (5 years 9 months 2 weeks 1 day 9 hours ago) and read 5213 times:



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.


User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 7, posted (5 years 9 months 2 weeks 1 day 2 hours ago) and read 5180 times:



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.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 8, posted (5 years 9 months 2 weeks 1 day 1 hour ago) and read 5173 times:



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.


User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 9, posted (5 years 9 months 2 weeks 21 hours ago) and read 5147 times:



Quoting Tdscanuck (Reply 8):

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


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 10, posted (5 years 9 months 2 weeks 19 hours ago) and read 5141 times:



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.


User currently offlineVikkyvik From United States of America, joined Jul 2003, 9787 posts, RR: 26
Reply 11, posted (5 years 9 months 2 weeks 18 hours ago) and read 5131 times:
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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.



"Two and a Half Men" was filmed in front of a live ostrich.
User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 12, posted (5 years 9 months 1 week 6 days 21 hours ago) and read 5030 times:



Quoting Tdscanuck (Reply 4):

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


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