Slow Motion

[Blogwitch]

Jerry,

I can't explain where the extra lengths of chip has gone, but I might be able to explain why my chips were coming off spirally wound.

Looking at the cutting face on your tool, it has a lot less rake than mine. I use a lot of rake, about 10 to 15 degrees all round, and it is ground the same as I would a left hand cutting tool, with rake in three directions, top, front & back.

Also remember, I was taking a much shallower cut, so the metal being removed isn't as strong as the amount you are removing, yours would have a tendency not to twist as much.

When I get another chance, I will try to get some shots of mine taking larger cuts, and see if they match yours, and also see if I get the disappearing metal phenomenon.

BTW, with the way I grind mine, I always get a mirror finish, no matter what depth of cut I use (within reason), but I never go too fast a feed.

John

 

[Ken I]

Captain,
Material cuts in shear - imagine a deck of playing cards spread out to the length of the cut - then push the pack closed - its now thicker but narrower.

To some extent you can see this "stack of cards" effect on the dull side 0f the chip (the "up" side).

Measure the thickness of the chips - it will be much greater than your actual feed / cut rate.

Obviously chips can scroll closed and break at each closure or alternatively form long coils or ribbons. In your case the angular momentum of the chip is probably causing it to break at regular intervals along pre-existing shear lines.

Its also possible that is the entire chip - is "squashed down" by three or four times with a concommitant increase in thickness.

2c

Ken

P.S. The shaded area in the depth of cut zone goes into the shaded area in the chip volume.

 

[Captain Jerry]

John

I'll check the angle again and try it with a little more. I like the way this cuts but if I can improve it, I'll like it more. In this case I was going for stock removal over finish. I had more than .25" thickness to remove so I made a lot of chips. Maybe this is not the right tool for the job. Is there a better way?

I suspect that the rigidity of your mill makes for a better finish. The gearing in the head of my X2 is sounding a little rough and has a lot of backlash so I have decided to change it to a belt drive system. The bearings may also be rough but I'll wait to see what the difference is with belt drive.

Ken

That is exactly what the chip looks like on the inside of the curl. It looks crunched. Maybe a little more angle or slower feed would reduce the crunch effect. Its hard to believe that the whole width of that cut is compressed into that short chip but that seems to be the whats happened. Anything else would produce more random results.

Thanks for the responses.

Jerry

 

[Sshire]

John
Love the video. A few thoughts about focusing that may help.
Camera autofocus systems are based on contrast (passive autofocus) where higher contrast is assumed to be "in focus" or an IR beam reflecting off the subject (active autofocus). Most cameras use both.
The problem is that the contrast based system may like something with greater contrast and decide that this should be the point of focus. I find that on my mill, the the passive autofocus loves the accordion bellows covering the column front. My solution is to place a piece of black or dark gray paper between the part to be photographed and the bellows. Since this has, in effect, no contrast, the part becomes much more interesting to the autofocus system. On the lathe, the offending contrast grabber is swarf. Same dark paper laid across the bed if I'm shooting down.
Check your camera's manual in the macro section. They may have some additional suggestions.
One other issue with macro and high frame rates is that you need lots of light for two reasons. Depth of field at macro distances is tiny. The greater amount of light will result in the camera using a smaller diameter f/stop. Small aperture = greater depth of field.
Second plus for more light is the noise issue. Most non-SLR sensors are tiny. Most likely your sensor is 5.76mm x 4.29mm. The only way to make the millions of individual photosites(the actual light gathering part of the sensor) fit on a chip that small is to make each one tiny. They can't gather a great deal of light at that size. So, the light is amplified and as the light level is lower, the amplification must be greater. This comes with a higher signal to noise ratio. Low light = higher noise.
Hope this helps. When I was teaching, this usually caused lecture-induced sleep, so I'll skip the photon flux issue. ;D

Best
Stan