Hi all I am very new to the machining world so be gentle on me. I searched for counterbore and counterboring but didn't really come up with the answers I needed. Anyways I am trying to machine some flat steps in round aluminum stock, I am making a scale wheel rim, on the lathe. I am not CNC'd as of yet so I wanted to make multiples of this rim and doing it by hand with a boring bar is time consuming. I learned about counterbore drills and came across many, many different systems (drill bits, indexable tools, etc) My question is what does everyone use to counterbore with, is there an easy way to counterbore, does it have disadvantages over using a boring bar? The diameters I am working with are 16.6mm and 15mm. Thanks for reading and helping.
CB's are nomally used in a mill or drill press for SHCS clearance to recess a bolt head. Where in, minimal precision is expected as to concentricity or diameter, but depth can be controlled. Then there is risk of doing some damage to the pilot hole with the stock size pilot if that was intended as a press fit. A wayward chip in the pilot can score it up too. I have had to grind the pilot to use them, but the counterbore itself was not critical.
Using them in the lathe may be fine for roughing. Best to finish off with a boring bar to have better control of concentric bores to size and depth where required.
Not all lathe tailstocks are repeatably precision depth controlled. Although, with some ingenuity, you can create a paddle clamp that attaches to its quill barrel so that you can use a magnetic back travel indicator on the body and indicate quill movement off the paddle.
Either that or put the CB in a tool holder on the compound/carriage. But, then you must know where center is each time that operation comes about in your process.
Last, but not least is that they tend to be a low RPM cutting operation. What they make up for in convenience does not always replace efficiency. 2-4 more passes with a boring bar that is already in position can be less futz'n than changing, setting and running another tool.
What it really comes down to is personal preference and being able to live with the results you get.
Learn cause and effect through experience. Mastering those relationships is the "Common Sense" ability within the art of any trade.
Thanks guys. Great info, now I am a little more informed, I am always looking for the easy way out. Guess I'll look into a little nicer boring bar.