Somebody asked about machining blades with a surface grinder?

I've played with that concept a little bit.

The problem (as one guy points out on the BBF), is that two flat planes (i.e. the flat grinds that he is making) can never intersect to form a curve (i.e. the cutting edge). They can only intersect to form a straight line.

In other words, if you want a curved cutting edge (which we all do, for the most part), the grinds can't be flat. The only way to achieve that is rotation on at least one axis.

I have heard of people machining bevels with a sine plate AND a rotary table, and I suspect that is the concept.

Also, CNC grinders used to make production knives are not 3-axis (i.e. 3 linear motions, x,y,z) machines - they are 4, 5, or possibly 6-axis machines (i.e. 3 linear motions, and up to 3 rotational motions).

I don't think I'm really telling anyone new info, because we all know that there is a rotational motion involved in grinding from the plunge to the tip.
 
patriqq said:
Also, CNC grinders used to make production knives are not 3-axis (i.e. 3 linear motions, x,y,z) machines - they are 4, 5, or possibly 6-axis machines (i.e. 3 linear motions, and up to 3 rotational motions).
Click to expand...
Huh, I didn't think anybody MADE 6-axis machines... I thought you could get any direction at any point using only 5 axes.... :confused:
 
Robotic welders are frequently 6 axis. They articulate a lot like your arm. A Romer or Faro is a 6 axis CMM (I think).

The 9 axis machine JT is talking about probably has some redundant axis such as a U axis beside an X axis like in a split table or something like that. You know, JT - the tool carousel doesn't really count...

But yes, 5 axis would do the trick for a CNC grinder and is the industry standard for "far out" machining. That might be a standard three axis with a wheel that can also tilt and a table that can turn. A 5 axis generally has an A (or B?) and C in the head (for routers) or table (mills)

There are multi axis lathes too, with live tooling and subspindles.

These are all specialized machines that are not as far out capable as you might think. Unfortunately there are no magic bullets. They all have real downsides to them too.
 
That is a 4 axis mill, though what they're doing in that video could probably be done on a three axis. I do notice they mill the part free of the stock without restraining it. You'll go to machinist hell for that...

I did this on a much smaller three axis: http://i566.photobucket.com/albums/ss107/Nathan_the_Machinist/dagger/milled_dagger_project.jpg

I love how it is true to the medieval original. Right down to the salt pot HT and epoxyed on handle. Mine is also authentic, with CPM154 like they used during the dark ages. :D
 
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