Countersink bit for M10 bolt?

[gasket999]

Hi everyone. I need to fit some m10x70 countersunk Allen bolts into 5mm steel plate

like these: Here

but I’m really struggling to find the correct bit - I think a 20mm 90-degree bit is the correct size (unless anyone can correct me), but I’m confused about the shape/design of the countersink bit itself. Some have a toothed head, others are smooth with a cutting hole.

the countersunk hole would be eating into both the plate and the box section to give me head clearance.

can anyone recommend a design/model? I’m only drilling 12 holes but they have to be bang on so planning to spend £10-£20 on a reasonable quality bit.

thank you.

 

[grim_d]

Just different designs, zero flute work fine though I prefer 4 flute+ for actual countersinking and use zero flute for deburring.

A countersink bit from any reputable cutting tool manufacturer will do what you need...and honestly a set from eBay would do it too.

Biggest impact on countersink quality in my opinion would be hand cut Vs pillar drill (vanmar cages etc aside)

If it super critical that it's absolutely bang on (and I mean like aircraft sheet metal critical) then you will need a piloted bit.

 

[gasket999]

thank you - thats reassuring, I'll get onto eBay now