Re: holesaw on a lathe
Posted: Fri May 17, 2019 4:24 pm
Oddly the information about limiting the tool diameter with key less chucks seems to be not very well known by most of the people using them. Even the manufacturer's are pretty lax about pointing the problem out. I forgot to mention about using larger diameter taps in them as well. Those can create the exact same torque issues. I don't seem to have any problems up to roughly a 3/8ths tap. But tapping with them probably isn't the best idea anyway. Above 3/8ths in the mill I just use an ER collet.
A hole saw if it can do the job is likely the cheapest and most available method for most of us. Like most things related to machining it's not the only way to get the job done and hole saws have fixed diameter limits. Face cutting a groove or parting right through is called trepanning. Just for trivia purposes a gruesome detail is the name apparently comes from the early medical profession where they used a trepanning tool to bore large holes in peoples skulls. A trepanning tool can be made to do the same thing in a mill. It pretty much resembles an adjustable for diameter fly cutter with the cutting tools end pointing straight down. For tool post use in a lathe, http://www.penntoolco.com/trepanning-to ... olholders/ as one way over priced example. Everything I've picked about about trepanning mentions the tool grind is pretty critical to get them to work well. Plus the cutting tools radius has to be accounted for for both the O.D. & I.D. while grinding to get enough cutting tool relief. The one in my link clearly shows the radius used to help lift the chips up and out of the cut. Not getting those chips evacuated well enough can result in a quite spectacular crash if the tool binds up.
A hole saw if it can do the job is likely the cheapest and most available method for most of us. Like most things related to machining it's not the only way to get the job done and hole saws have fixed diameter limits. Face cutting a groove or parting right through is called trepanning. Just for trivia purposes a gruesome detail is the name apparently comes from the early medical profession where they used a trepanning tool to bore large holes in peoples skulls. A trepanning tool can be made to do the same thing in a mill. It pretty much resembles an adjustable for diameter fly cutter with the cutting tools end pointing straight down. For tool post use in a lathe, http://www.penntoolco.com/trepanning-to ... olholders/ as one way over priced example. Everything I've picked about about trepanning mentions the tool grind is pretty critical to get them to work well. Plus the cutting tools radius has to be accounted for for both the O.D. & I.D. while grinding to get enough cutting tool relief. The one in my link clearly shows the radius used to help lift the chips up and out of the cut. Not getting those chips evacuated well enough can result in a quite spectacular crash if the tool binds up.