Drill bit size for 1/4 x 20 Heli coil?

[1982fxr]

Pretty sure it's 17/64 but want to be sure.

Thought this would be easy to Google but can't find it, maybe my phone just has the biggest ************* search engine ever.

 

[NDJ]

Ya its generally 1/64 over any nominal thread size.

 

[MoonRise]

Letter H (0.266"), 17/64" should be close enough.

Tap for a 1/4-20 helicoil, with drill dia info https://www.mcmaster.com/91709A105/

 

[darkzero]

Thought this would be easy to Google but can't find it

For future reference, search "STI tap drill size" & you'll find references & charts pretty easily. STI stands for screw thread insert.

 

[saltwater4life]

I’m partial to metric where is nominal diameter minus pitch. When I saw 1/4-20 I didn’t even know where to begin other than looking for a chart on Google images

 

[RoninB4]

maybe my phone just has the biggest ************* search engine ever.

-Not being critical of the OP but if the phone can't pull this up then I'd have to agree. What words/phrase did you use in your search?

 

[vssjim]

it is usually printed on the Heli Coil package

 

[1982fxr]

-Not being critical of the OP but if the phone can't pull this up then I'd have to agree. What words/phrase did you use in your search?

Drill bit size for 1/4 x 20 helicoil

And 17/64 drill bit for 1/4 x 20 helicoil

Seems like the most basic **** is getting harder and harder to pull up.

 

[NORTON'S SHOP]

Drill bit size for 1/4 x 20 helicoil

And 17/64 drill bit for 1/4 x 20 helicoil

Seems like the most basic **** is getting harder and harder to pull up.

The drill bit size for a 1/4-20 helicoil is stated in the instructions directly following the sentence that says DO NOT EAT THE HELICOIL.

 

[dutchgray]

I’m partial to metric where is nominal diameter minus pitch. When I saw 1/4-20 I didn’t even know where to begin other than looking for a chart on Google images

You can do the same for imperial screw threads, you just have to do a bit more maths.

1/4" is 0.250
20 tpi is 0.050 pitch

0.250-0.050= 0.200

Which would be a No 7 drill or a 5.1mm.

It's quicker to use a charts whereas for metric it isn't.

None of this is revenant to the OP's question as you need to know what the specific thread insert calls for.

 

[RoninB4]

Drill bit size for 1/4 x 20 helicoil

And 17/64 drill bit for 1/4 x 20 helicoil

Seems like the most basic **** is getting harder and harder to pull up.

-"Helicoil drill chart" pulled up multiple links. Odd how selective words produce results and others don't. At least one site triggered my anti-virus (noblefix dot com). Sometimes I can't find shyte either and have to ask the GF to look, the Google Fu is strong with this one.