Accurate Counterbores on 7x16 Lathe

[MaverickNH]

I completed my first project - a Hemingway Machinist’s Hammer. It turned out pretty well. The finish on the tapered steel handle had a few visible grooves that I didn’t fully sand/buff out and some are visible on the aluminum/bronze hammer faces too. Straight Z-axis cuts turn out well with the feed but manual facing cuts are a bit iffy, even when I keep DOC low. I have a manual carriage lock but there’s some likely some play in the cross slide/compound slide.

My biggest challenge was counterboring the 7/16” through hole in the hammer head with a 1/2” drill. The hammer head was clamped in my 4-jaw lathe chuck. I used a 1/2” end mill in my tail stock drill chuck to counterbore and I think the first flute to engage pulled it off-center on the convex hammer head surface. I’m not sure if I would have seen the same problem counterboring a flat surface.

How might I approach that next time for better counterbore precision?

BRET

 

[GrifterGuru]

Personally, I have stuck to using boring bars due to the "flex" or "slop" prevelant in a 7x. That said, I have resolved much of that through adjustment.

Also, try to avoid using the tailstock unless you have aligned it and definitely do not use an endmill in a tailstock chuck.

If it was me and I stress, if it was me, I would bore to a shade under size with a boring bar, then ream it to finish size. I appreciate not everybody has reamers and we all have our own methods.

one method is to put a small 45 degree chamfer on the inside edge to help guide the end mill to center, another is to use a low spindle speed whilst the endmill starts the cut. Deflection (which is what you describe) is a problem but one that can be overcome with patience and time.

There are very many ways to reach the number ten, none of them wrong. In other words, find an approach that works for YOU.

Practice will gain knowledge, as will seeking out examples of others carrying out similar work (specific bore diameter and getting to that finish diameter with different methods.

Blondihacks (Quin Dunkley) (<<< Link) is a great source of information

This is a particularly intersting video.