How to Countersink threaded hole?

[knucks]

The threads on my bike frame extend all the way. What do I need to counter sink them myself?

 

[Bigblue&Goldie]

The threads on my bike frame extend all the way. What do I need to counter sink them myself?

Without seeing how much taper you're dealing with, I'd think if you kiss the brake bosses with a countersink bit in a hand drill you'd probably get the clearance you need. You could drill a hole in a piece of metal the same size as the major dimension of the thread and test it before doing your actual frame.

https://www.amazon.com/dp/B07GBJBNLJ/?tag=atomicindus08-20

 

[ez-duzit]

The drawing shows a counterbore, not a countersink. However what the instructions are asking for is simply to countersink 6.2mm diameter to allow clearance for the radius under the bolt head. After doing this, test fit the bolt to insure that the head actually bottoms out against the end of the post.

 

[Bigblue&Goldie]

The drawing shows a counterbore, not a countersink. However what the instructions are asking for is simply to countersink 6.2mm diameter to allow clearance for the radius under the bolt head. After doing this, test fit the bolt to insure that the head actually bottoms out against the end of the post.

This.

 

[metlmunchr]

Use a zero flute countersink. The multiple flute ones like to chatter, and particularly so when used in a handheld drill.

 

[ez-duzit]

Actually a single flute countersink would be my first choice, if using a drill. However I would do this on my lathe using a 45-degree chamfering bit. But this simple job can be done with virtually any type of countersink.

 

[Bigblue&Goldie]

Coincidentally, this thread reminded me I needed to get a new set of posts ordered for my daughter's bike. This pic shows how much you'll likely need to relieve.

 

[knucks]

Ok so I can counterbore or countersink? Diagram shows a counterbore. I do own some countersinks

What size do I use ?

 

[PugetDude]

All you're doing is providing clearance for the radius between the shank of the bolt and the bolt head. I don't think it matters how you do it, but a countersink creates less of a stress riser than a flat-bottom counterbore.

 

[ez-duzit]

...I do own some countersinks

What size do I use ?

Come on. Use any size that is large enough to countersink the hole. 6.2 mm or larger.

 

[Monza Harry]

Or just resharpen a drill bit a little steeper and drill it out to as close as you can with your drill bits with out being undersized. 6.2mm is 0.244xx" a "D" drill is 0.246" a "C" is 0.242" Dia. "E" and 1/4" is 0.250" for your ease of information. [this is a pain to find on the internet for some reason, search, pick a pic, and try blowing it up or you have to download, Blah, Blah, Blah! I just happen to know these and about 20 or so letter and Number drills, used near daily. Harry

 

[ez-duzit]

Or just resharpen a drill bit a little steeper and drill it out to as close as you can...

If you use a drill there is a great likelihood of the bit catching and drilling out more of the threads than you'd care to.
Use a countersink.

 

[rjn2649]

If you use a drill there is a great likelihood of the bit catching and drilling out more of the threads than you'd care to.
Use a countersink.

Totally agree, AMHIK.

 

[joe49]

I get that you ask what to countersink with. But whats wrong with just following the washer recommendation.

 

[knucks]

I get that you ask what to countersink with. But whats wrong with just following the washer recommendation.

Saves me from buying a washer

Countersinks I have.

Done and done. Thanks and now I know the difference between countersink and counterbore is as well

 

[slowtwitch73]

Better just use a washer....