What size drill bit for 2-56 tap?

Anyone know, off the top of his head, what size drill bit I need for a 2-56 tap? I have the tap, but I don't know what size hole to drill.

Also, any tips or tricks for tapping FG tubes?

Thanks....

0.0700"

John, just out of curiosity, are you planning on tapping holes for shear pins?

I just used the 5/64ths bit (I think that's it, just 1/64 above 1/16) the other day for that same purpose.
-Ken

Worsaer said:

John, just out of curiosity, are you planning on tapping holes for shear pins?

Click to expand...

Yes.

#50 drill bit

Just my personal preference... I drill so they push in firmly, not thread in. They won't fall out...

my Apogee set came with a #51 drill bit


https://www.apogeerockets.com/Building_Supplies/Tools/2-56_Tap_and_Drill_Set

Nice drill chart here: https://shender4.com/thread_chart.htm

A #50 is pretty much half way between 1/16 and 5/64. When I taped the threads, I just used a 2-56 screw to form them. I figured it will make the shear pins easier to install and they should still pop out. The threaded fiberglass will wear out too sometime.
-Ken

When I was building my L3 rocket, I drilled and tapped the holes for shear pins.
After using them for a while; there is no need to cut threads into your rocket for them.
Just drill a 3/32" hole, press them in with you fingers then, apply tape over the heads so they don't fall out.


JD

While we're all posting our favorite tap and clearance drill charts...
https://littlemachineshop.com/reference/tapdrill.php

As always, Google is your friend.

I never look at a physical chart any more. If I don't remember a given tap or body drill size for a given bolt size, I google it on my phone faster than I could find the chart....

For carbon or fiberglass, I just use a 5/64" bit and then a different kind of tap (aka, a hammer) to insert them. If the holes are carefully aligned, they'll just tap right in. They can be difficult to remove, however, so tapping the holes might be an advantage if you often have to remove your shear pins.

Jim

JimJarvis50 said:

For carbon or fiberglass, I just use a 5/64" bit and then a different kind of tap (aka, a hammer) to insert them. If the holes are carefully aligned, they'll just tap right in. They can be difficult to remove, however, so tapping the holes might be an advantage if you often have to remove your shear pins.

Jim

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Confused ... don't you have to remove them after every launch?

Bat-mite said:

Confused ... don't you have to remove them after every launch?

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Yes, but I was thinking about getting them out without having to break the pin. If you break the pins (or after a flight) you can push them out more easily.

As it turns out, though, I gave you incorrect advice. The 5/64" bit works, and I used that for years, but it is tight. When I looked back at my bit case, I realized that I had identified a 45 or 46 bit as better for the #2 pins. They are held firm, but are easier to insert and remove if necessary. A #37 bit is what I use for #4 pins.

Jim

I ordered a #50 from Home Depot. Hopefully that will do the trick. I want to try threading just because I've never done it. I'll try to remember to reply when it's done so that folks know how it went.

Worsaer said:

Just my personal preference... I drill so they push in firmly, not thread in. They won't fall out...

Click to expand...

This. Screwing them in is pointless.

chadrog said:

This. Screwing them in is pointless.

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Yeah I tried that when I was a newbie. Screwdriver kept coming out of the tiny plastic head, scratching my paint-jobs.After second time, I enlisted a large screwdriver "handle" to just tap 'em in.

By the way Chad, flew some of those F-39's at the last launch & they worked just like new... surprising , considering they were made in '99. Thanks again.

Bat-mite said:

Anyone know, off the top of his head, what size drill bit I need for a 2-56 tap? I have the tap, but I don't know what size hole to drill.

Also, any tips or tricks for tapping FG tubes?

Thanks....

Click to expand...

Either wire gauge #50 or #51 drill bits for 2-56 threaded holes. #50 give a slightly better 62% thread.

blackjack2564 said:

Yeah I tried that when I was a newbie. Screwdriver kept coming out of the tiny plastic head, scratching my paint-jobs.After second time, I enlisted a large screwdriver "handle" to just tap 'em in.

Click to expand...

Now I feel challenged to make threaded holes work. :wink:

blackjack2564 said:

Yeah I tried that when I was a newbie. Screwdriver kept coming out of the tiny plastic head, scratching my paint-jobs.After second time, I enlisted a large screwdriver "handle" to just tap 'em in.

By the way Chad, flew some of those F-39's at the last launch & they worked just like new... surprising , considering they were made in '99. Thanks again.

Click to expand...

Cool beans. Strange how some propellants age more gracefully than others. Probably not strange at all, I just don't know the reason...

kenstarr said:

I just used the 5/64ths bit (I think that's it, just 1/64 above 1/16) the other day for that same purpose.
-Ken

Click to expand...

Years late, I know, but just did this through paper tube and styrene nose cone, and this bit works great for 2-56 nylon screws used as shear pins, without tapping these materials.

It. depends on how engineeringyyyy you want to get. The Machinery Handbook has all the details. Buy a copy. Engineering data doesn't really go out of date.....Mine's the 24th edition....
If you want a really good rule of thumb....... Take the screw pitch off the outside diameter of the screw. In metric this is really easy M4 x 0.7 pitch tap is 3.3mm So a 1/8" drill is close enough. 3.175mm
1/4-24 take 1/24 th of an inch off 1/4 and you've got your tapping size.
For your 2-56 measure the outside diameter of your bolt or tap with verniers and remove 1/56th of an inch.
You could just ask google, but there's no real easy explanation like mine..... which is correct enough.....
For my method, it gives a tap drill size of 0.068" Google gives 0.069" 1 thou difference. close enough.....

Google answer. https://www.machiningdoctor.com/threadinfo/?tid=4

OzHybrid said:

It. depends on how engineeringyyyy you want to get. The Machinery Handbook has all the details. Buy a copy. Engineering data doesn't really go out of date.....Mine's the 24th edition....
If you want a really good rule of thumb....... Take the screw pitch off the outside diameter of the screw. In metric this is really easy M4 x 0.7 pitch tap is 3.3mm So a 1/8" drill is close enough. 3.175mm
1/4-24 take 1/24 th of an inch off 1/4 and you've got your tapping size.
For your 2-56 measure the outside diameter of your bolt or tap with verniers and remove 1/56th of an inch.
You could just ask google, but there's no real easy explanation like mine..... which is correct enough.....
For my method, it gives a tap drill size of 0.068" Google gives 0.069" 1 thou difference. close enough.....

Google answer. https://www.machiningdoctor.com/threadinfo/?tid=4

Click to expand...

Oh I’ve never thought about calculating minor diameter like that but it makes so much sense!

pathtouch said:

Oh I’ve never thought about calculating minor diameter like that but it makes so much sense!

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And you can thank the metric system for making it that easy to figure out. Only took me 20 years....
As we're figuring things out.... Here's another. Lithium batteries. Last 2 digits are thickness in 0.1 mm increments. First ones are diamater. CR 2032 is wait dor it... 20mm dia. 3.2 mm thick...., OMG the code is unlocked .....Try it.... The good thing is that if you can fit a slightly thicker battery in, you can get a massive increase in capacity/ battery life.

OzHybrid said:

For my method, it gives a tap drill size of 0.068" Google gives 0.069" 1 thou difference. close enough.....

Click to expand...

Especially when you measure the actual hole you drilled using gage pins and find out what size it came out to be.

Bat-mite said:

Anyone know, off the top of his head, what size drill bit I need for a 2-56 tap? I have the tap, but I don't know what size hole to drill.

Also, any tips or tricks for tapping FG tubes?

Thanks....

Click to expand...

I buy the Dubro kit. It contains both.

Total tangent, but if you are buying drill bits to make holes in composites, I highly recommend spending the money on purpose-built drill bits. They are more expensive, but they pretty much eliminate the tear out on the other side of the hole. And they last a very long time. I bought one in each of the sizes I tend to use in rocketry for drilling into FG/CF tubes, etc.

Composite bits: https://www.mcmaster.com/catalog/129/2777

I should caveat this recommendation with the fact that these kinds of drill bits are very brittle. If you are hand drilling (as opposed to using a drill press or mill), you need to make sure you are super steady and only drill relatively thin products (like a rocket tube). Trying to hand drill a thick composite sheet (like you would use for fins on a big rocket) would most likely end up with a drill bit snapped in half.