Counter sinking 4130 tabs

[SimonNicholson]

I am putting in nut plates for my floor boards and after one panel I have ruined on counter sink cutter already.

Any techniques I am missing when cutting into the 4130 tabs?

[jaredyates]

Spin them slower?
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[Cyco]

Yeah. I used an angle grinder at one point for access reason, but it spins too fast. Lesson learnt.

[Bdflies]

I think Jared's right. My countersinks were purchased in the 90's and are still in use.
4130 is pretty hard stuff. It'll eat HSS cutting tools if you run the tools too fast.

Bill

[S Lathrop]

I use a Bosh battery powered drill that has a slow speed setting for driving screws. You are going to want 500 rpm or less for the counter sinks to last.

[PaulSA]

And probably some lube..........?

[Bdflies]

For anything but aluminum, I use Mystic Metal Mover to drill and cut threads (especially threads!). Don't recall ever using any fluid with a countersink. Just slow speed and high pressure.

Bill

[S Lathrop]

And probably some lube..........?

Believe it or not, bacon grease works well as a cutting lubricant.

[Mark Goldberg]

I wonder why builders punish themselves installing nutplates on the tabs to hold down the floor. Tinnermans are so easy and are plenty adequate for the job. But everyone builds their planes as they want.

Turn the countersink very slow on on steel and use drilling/tapping lubricant. That is all I can think of. Mark

[JimParker256]

Dang, Mark... Couldn't you have poster that BEFORE I spent all that time installing the nutplates?!? 😂 I'm kidding, of course.

[Bcone1381]

Mark, Where else do you recommend Tinnermans where others use nut plates?

(I am installing nut plates right now for my floor boards as well.)

Simon, Do you know about the NAS1097AD3 rivet? They the identical 100 degree countersunk head, but one that is smaller than the standard AN426 rivet. The material one must remove to countersink the head is less....way less.... and its is suitable for this non structural application. Because the head is so small, and the countersunk so shallow, they don't require dimpling when used in thinner sheet metal. I have not applied them yet to aluminum, but I think I will be countersinking them into aluminum when deburring the hole.

FYI, there were some places I had to countersink these by hand, and about 12 turns of the countersink into the 4130 was all it took.

Spruce does not sell these, but Wicks has them. I learned about them from a popular RV builders site.

http://aircraftproducts.wicksaircraf...00-solid-rivet

[Battson]

I just used the hand-tool to countersink everything, still do today. If you spin the cutter fast on 4130 (or any steel), then you are doing it wrong. Aluminium wants a high cutting speed, steel needs a slow speed.

Go buy some RTD spray if you are cutting steel with a reamer or drill, and go slow. I never used any lube with the hand countersinker.

I am still on the same countersink tool, and it's as sharp as a tack. It's done the whole plane and then some. Avery Tools USA.

[SimonNicholson]

Thanks everyone. Patience in all aspects of building is my new mantra. I was joking with a friend the other day that by the time I am finished I will have made this plane twice.

[rv8bldr]

Mark, Where else do you recommend Tinnermans where others use nut plates?

(I am installing nut plates right now for my floor boards as well.)

Simon, Do you know about the NAS1097AD3 rivet? They the identical 100 degree countersunk head, but one that is smaller than the standard AN426 rivet. The material one must remove to countersink the head is less....way less.... and its is suitable for this non structural application. Because the head is so small, and the countersunk so shallow, they don't require dimpling when used in thinner sheet metal. I have not applied them yet to aluminum, but I think I will be countersinking them into aluminum when deburring the hole.

FYI, there were some places I had to countersink these by hand, and about 12 turns of the countersink into the 4130 was all it took.

Spruce does not sell these, but Wicks has them. I learned about them from a popular RV builders site.

http://aircraftproducts.wicksaircraf...00-solid-rivet

I used these everywhere on my RV-8 and have been using them on the Bearhawk. They are awesome to use on aluminum. Two or three turns with the hand swivel deburring tool (Like Jono Battson showed in his post) and away you go.

You can also get them from Vans Aircraft.

[PaulSA]

My experience so far is with aluminium, having built a RV-10. Despite the comments, I intend to use nutplates to secure the floor. Is it possible to #6 or #8 dimple the floor attach tabs?

[Mark Goldberg]

You will not be able to dimple the steel floor tabs. You could counter sink them. Mark

[Rollie]

I used tinnermans under the floor, but I did use nut plates on a few of the steel tabs and I dimpled those. Mark is right, of course. They dimpled partly, not completely flush, but ok for where I was using them and it messed up the dimple die eventually too. Maybe rivnuts would be a good in between solution if you really don't like tinnermans..