Does anybody know how to make a straight flute drill bit (in the most foolproof way possible)?
Posted by Undertow619@reddit | GunnitRust | View on Reddit | 5 comments
BoredCop@reddit
Can you use a simple D bit? It won't clear chips, so you would have to peck drill and use compressed air or something to get chips out of the hole.
Undertow619@reddit (OP)
What shape is a D bit? I type it into search engines and I can't find it.
BoredCop@reddit
Start with a round bar of tool steel. Grind or mill away exactly half to make a D shaped, or half circle, nose form. Don't grind further back than about one diameter length, or it won't be rigid enough and won't stay centered. D bits can cut very straight holes to a precise diameter because they only have the one cutting edge and the shank bears against the sides of the hole so it stays aligned, but they are slow and get packed with chips very quickly since there is nowhere for the chips to go except for that small cavity where you ground away some material.
Depending on what material you are drilling into, you may or may not need to put a slight relief angle on the nose by angling the flat face of the D slightly.
A gun drill, used for making gun barrels, is a specialized and more advanced form of D bit with an opening for chips to evacuate and with a channel for high pressure coolant to flush the chips out.
No idea of this helps, since I don't know what you are trying to accomplish. But it's one of the simplest ways to DIY an effective metal cutting drill for precision work.
Undertow619@reddit (OP)
Should I step up to the diameter of my D bit or should I just drill it from the full bore
BoredCop@reddit
Not sure I follow what you are trying to say.
The whole point of a D bit is that it is as rigid and straight as a drill bit can be, and that it stays aligned in the hole it is drilling. This only really works if it's one straight diameter the whole way, or at least for long enough to be self guiding.