What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Countersink fiberglass!

JeremyL

Well Known Member
I don’t know who needs to see this, but if you are trying to decide how to countersink fiberglass and don’t want to destroy your metal countersinks, then this little tool is just the ticket. The perma-grit tungsten carbide stone is worth every penny (about $32 US with shipping from the UK). I purchased the 100 degree with no nipple, but they have nipples of various sizes. Makes quick work and a nice neat countersink. Perfect for tinnerman washers and the countersink needed for the flush rivets in the zip tip inspection panel. The “no nipple” allows me to countersink any hole size.
 

Attachments

  • F8708B93-B850-4CC0-B5E7-0ED8D265A91B.jpg
    F8708B93-B850-4CC0-B5E7-0ED8D265A91B.jpg
    475 KB · Views: 288
  • 8F975212-15CD-4796-B091-F5BB0834B02D.jpg
    8F975212-15CD-4796-B091-F5BB0834B02D.jpg
    145.1 KB · Views: 305
I don’t know who needs to see this, but if you are trying to decide how to countersink fiberglass and don’t want to destroy your metal countersinks, then this little tool is just the ticket. The perma-grit tungsten carbide stone is worth every penny (about $32 US with shipping from the UK). I purchased the 100 degree with no nipple, but they have nipples of various sizes. Makes quick work and a nice neat countersink. Perfect for tinnerman washers and the countersink needed for the flush rivets in the zip tip inspection panel. The “no nipple” allows me to countersink any hole size.

Brilliant! 100° angle is the key for getting all the aviation grade stuff (tinnerman, AN507/MS24693, etc. ) to fit well & proper.
 
I have a couple with different size guide pins and they're great for fiberglass. I do prefer the ones with a "nipple", e.g., a steel guide pin (drill hole for screw, guide pin fits into hole and keeps the countersink from wandering.)
I can't recall where I bought it but it was domestic US, somewhere.

Edit: Avery tools used to carry them.
 
Last edited:
I bought them from the UK site about 2 years ago . It was fast delivery.

It revolutionized my ability to make repeatable countersinks first time every time.
 
They are only 100 miles from me and I just ordered. I will get a US dealer link for you all later in the day.
 
Gents,

Spoke with Ian at Perma-Grit

The countersinks were originally produced for L*ncair - plastic.....spit child, spit !

However, they look very useful for lots of stuff on the vastly superior RV series ;)

Sadly, these are produced as short run things and the US dealers won't take them.

Ian has suggested that you deal direct - I would suggest that a few of you get together and do a group buy and distribute. He despatches via USPS, fully tracked and there are deals for no duty import to the US.

Mine are inbound as we speak and should arrive tomorrow. He reckons that despatch to the Colonies would be around $15 and take a week.
 
I searched long and hard for them domestically with no joy. But the delivery from the UK was pretty darn fast without any issue. I’m at about 100 or so holes countersunk in just 3 days and the bit is still going strong without a single issue. As a note, I haven’t had any issue whatsoever with the bit wondering without a nipple. I Chuck it up in my air drill and vary the speed to get the desired countersink. *finished inspection panel below.
 

Attachments

  • 0DFDE5AC-B7BF-4FBB-B127-37C860DFE57D.jpg
    0DFDE5AC-B7BF-4FBB-B127-37C860DFE57D.jpg
    168.1 KB · Views: 179
Perma Grit

These are really cool. Wish they had 120 degree piloted with a small shank.
I bought a dremel stone and shaped it on a grinding wheel. I get close then make them perfect with a standard bit on a hand tool.
 
For what it's worth, I ordered a set of countersinks from the Perma-Grit website on May 9th when I saw this thread, and it arrived at my house in the US two weeks later. A timely purchase since I have a bunch of fiberglass countersinking coming up - thanks to the OP for the tip.
 
Perfect tool

The Permagrit stuff is great. You can make even easier using the stone in a Dremel. Makes a very clean countersink with the higher RPM.
 
Ya'll think about where you countersink glass/epoxy. Flush screws are beautiful in the right place, but the holes wear poorly if vibrated or loaded in shear, a matter of bearing strength. Long term, those applications are better served with AN526's and nylon washers.
 
Ya'll think about where you countersink glass/epoxy. Flush screws are beautiful in the right place, but the holes wear poorly if vibrated or loaded in shear, a matter of bearing strength. Long term, those applications are better served with AN526's and nylon washers.

I think that the bit will will be handy for the work necessary here, and could be for other 12 builders as well.
 

Attachments

  • Screen Shot 2022-05-24 at 10.20.34 AM.png
    Screen Shot 2022-05-24 at 10.20.34 AM.png
    967.3 KB · Views: 103
Back
Top