Grinding, honing and lapping that "bowl" should definitely produce interesting results. Unnecessary and unacceptable results but that's what will be interesting. "Pretty" isn't "performance".

Are you sure you don't need the dried wing membranes from cadaver flies mixed in with choice single malt alcohol that to make it work? Always good to hear from you Forrest. All the best, Tom

oxtoolco The spring tool was the main message but I failed to emphasize. Another minute on the ass-kicking machine for me. Actually gin works pretty good.

I never see form tools with any positive top rake, is there a reason besides keeping the grind as simple as possible? Or, even, negative top rake form tools?

Zero top rake makes it easy to grind a relieved cutting profile. Add rake and interacting tool and work geometry gets far more complicated if profile accuracy is a major factor. If a positive rake is desired you can always grind in a chip breaker with a formed wheel or a mounted point in a die grinder. Very delicate work if done by hand but not that difficult on a Monoset or equivalent. My career shop of 600+ machinists had a fine tool grinding department up on the mezzanine. They routinely ground chip breakers on single point radius tools that worked very well especially if you had spring or gooseneck toolholders to mount them in. Tinsel chips on the final stages of form cutting seemed to be the gold standard for attaining satiny finishes in difficult materials. My approach was to select a somewhat larger radius tool (for external radii) and, with with travel indicators to track X and Y, hand circular interpolate a small radius tool path. This resulted in a far narrower chip, proportionately lower cutting forces, and a finished radius that was very slightly bumpy. A distinct advantage when forming a 2" radius on a deep drawing die. Bear in mind this is Stone Age manual machining. CNC can buzz out finely finished radii tangent to surfaces in a single tool path, the spoiled bastards.

Usually one surface is the optically flat surface. In some cases both are optically flat and in further cases both surfaces are parallel. The Russian ones are one surface that is indicated with a mark or line.

Single point boring? Honing improves hole roundness and diameter but not position. Single point boring locates holes in position best. Hope this explains your question. Cheers, Tom

Saar Tal check out the engineers black book. Has a great breakdown of all insert tooling nomenclature

Precision ground flat stone. Cleans the surfaces and knocks off hangers and embedded metal. Not the same animal as regular stones. These are lapped flat to better than 50 millionths. Check out Professional instruments precision ground flat stones for a better explanation.

Thanks , checked them out - now i get it .

Then all my scratches will show more prominently. Deep scratches and high polish is my middle name. Best, Tom

The N in WNMG means negative. Negative inserts have straight sides and can be molded as opposed to ground.

Hey Jim. The grinding is the fun part for me and will make great video. I could insert small hardened feet but I decided to make it monolithic and permanent.

I could insert small hardened feet -- " That's a Great Idea." Monolithic and Permanent. -- Wow what big words -- What are you smoking ??? I've heard of "Legal Ease" -- is this called "Machining Ease" I think that California smog has effected your thinking . That is one tall unit -- It must be dead square with the surface plate. If it's off .0001-.0002 At the bottom -- It will be a mile off at the top Hold the round hardened feet in with flat head screws . If it is out of square you can remove the hardened feet and lap them accordingly . I'm talking about function -- your talking aesthetics / pretty. What good is Pretty Hooker without a Vagina -- Pretty but not functional. Useless as Tits on a Bull. --- Kisses and Hugs from your adoring fan ,

Easier to lap four feet for perpendicularity with the vertical post. Nothing wrong with slots at all.

oxtoolco Thank you Tom. I really learn so much from your videos (and old blog posts). Thanks for your time producing them, truly.

Hi Matt. I wanted the through holes in the block so I could put the holdown studs all the way through. Needed room underneath for the nuts.

Easier to lap for perpendicularity with four feet. A rim is nice but a lot of surface area to lap and correct for squareness errors.

Harder to lap the entire base for correcting perpendicularity to the post.

The idea behind the device is its not adjustable therefore not subject to random twiddling or getting out of adjustment. Otherwise you need to qualify it every time you want to use it. Cheers, Tom

They'll cut others, but they're fragile. I use CCMT for general purpose.

nevermind

John Miller, but with four feet you can feel when something is under a foot or the surface it's on isn't flat

Turn on the audio and listen to his explanation.

Hey Boss. Brand new drill. Sorry. Previous hole runout, sure I'll buy that.

Where were you on Sunday? You could have saved me a minute or two. You are totally right.

Why are they better than 1 feets? (lap the entire base coplanar).

Big drill was brand new with a factory grind. Most likely the pilot hole was not centered well which will start a wobble. 99% of tailstocks are low on anything but a brand new lathe. I agree theoretically a proper grind should act like a boring bar but in my limited experience its just not the case and you can't count on it.

It looked to me that the magnitude of the drill "movement" was more of a camera artifact from the vibration, than actual movement. Same as it goes with airplane propellers, etc.

I had to think the same, a "jell-o" product of image stabilization or rolling shutter. It looked like the pilot hole was a little off center, but I can't believe that drill would look like spring steel.

Yep; drill for the hole, bore for concentricity, and ream for size. (This last is, of course, not practical for large holes in most shops; careful boring and perhaps lapping/sanding must suffice.)

Hey Deer in the headlights, Not following your comment here. My comment was 8620 specifically grinds easily and I will specify case hardening .080 deep. Didn't think it was that hard to follow. I apologize if you were confused. Cheers, Tom