Lathe tool brass forming tool grind

redvan22 said:
This is right in my wheel house, so to speak. You do some really fine work. You have a new follower.
I too am using more than one tool bit.
I initially looked at the width of my tool blank which was 3/8 and I wanted my knob to be 3/8 so I tried doing the entire knob with just one and that was a disaster, to say the least. No matter what I did to improve the cut and eliminate issues, nothing helped. So, changed my thinking to use two, one for the front and another for the back. The back TB cuts a slight shoulder and the back end of the teardrop. The second does the rounding of the front and defines the cutoff point. (you'll see from my photo's when I post them)
I notice that you have quite a bit of tool and stock stick-out. Many have suggested minimal stick-out for both. Doesn't that alone cause you issues?
I'm not familiar with a Sherline lathe and it's rigidity. My mini lathe needed quite a bit of work to eliminate the majority of the slop in the carriage, cross-slide and compound-slide. When I first acquired it, the first time I experienced a dig-in, I thought the entire carriage was going to come apart - everything suffered, even bent the compound slide shaft.
I cannot attach photos at this time but will attach photos of my tooling and setup as soon as I can.
Thank you very much - this was an inspiration to not give up and simply expand the tooling used to make each TB do less work.
Click to expand...
The amount of stock I have sticking out and the tools positions were determined by trial. I have a bit more stock because I polished the parts before cutting them off and I don't like my hands that close to the spinning chuck.

The Sherline lathe is small but is quite rigid when working close to the headstock. If setup using their regular tool holders attached to the carriage the cutting load is carried down through the solid metal cross slide and saddle to the bed. The key is still light cuts and a small contact area. It does the job for me.

The tendency of brass to grab a tool has to be addressed by the shape of the tool cutting edge. If the tool has any positive rake it will want to hog in. I've broken some end mills and damaged my lathe tail stock because of it. I hope I've learned my lesson.
 
I have found when turning brass that zero top rake is important. Side rake required but angle not important.
Speed as high as possible and razor sharp fine diamond honed tools.
Obviously a rigid setup, I use a solid plinth and no top slide.
A shield to protect you from the spray of ultra fine needles.
 
One other thing I have found woodworking router bits work brilliant on brass and there are a plethora of shapes to choose from.
Roman ogee are cool, you dont have to use the full width of the cutter just the part that has the profile you want.
 
I watched a few of ClickSprings videos and he truly is a master craftsman.
 
redvan22 said:
I watched a few of ClickSprings videos and he truly is a master craftsman.
Click to expand...
He is amazing but, his videos don't really portray how tiny everything is. For the longest time I couldn't understand why he sawed so far from the line.
 
redvan22 said:
I'm trying to make a run of small brass knobs from 1/2" brass rod and I am having a lot of trouble eliminating chatter and sudden dig-in.
The tool bit I have designed is an elongated tear drop with the point shortened for drilling and tapping for the screw and the round end flattened.
I make the profile with two bits, one for the back end and back side of the knob and another for the front round and flat. Both give me trouble.
Zero side rake
Zero back rake
Front relief should be 8 degrees, as suggested but that caused issues so I have reduced it gradually to 3-4 degree.
Still get chatter and dig-in which makes a mess and in most cases ruins the piece.

Any suggestions?

Michael
Click to expand...
Part overall length is 3/8 ? Thread is ?.
 
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