Parting tool chatter fix

[dahui]

Hi all,

I've been having major problems with the OEM parting tool and chatter on 6061 aluminum with a 3/32 blade clamped as short as possible. I tried playing with all the mechanical stuff like fluids, tool height, speed, work holding and feed but nothing seemed to work. I found a thread where people suggested cutting a groove in the tool blade or buying an indexed one, but no one said if the groove worked. I didn't really want to buy a new tool and holders, I already bought several widths to fit this holder, so I wanted to try and groove the blade.

As a new machinist I wasn't really sure how to do it and I don't have a grinding wheel, but I discovered a really easy 10 minute mod to cut the groove. You can check out some photos at: http://www.the-alchemist.com/partingtool.html I suppose an endmill might have worked, but the abrasive felt like a better option for some reason.

I've cut about 10 grooves with it so far, about to do six more, but it seems to improve the performance by magnitudes. Let me know if you have any additional questions or suggestions.

thanks,

DaHui

[WhiteTiger]

Top rake makes a big difference, but the usual way of getting it is to grind more end relief on the blade and then set the cutting surface above center.

Mostly just a matter of economy, I suppose. Once you've sharpened away all upward curving end of the blade, you have to throw away (by grinding) all the rest of your notch length before you can sharpen again. If you grind the end relief and set above center, you never have to discard any length, just regrind the end of the blade.

It's also much simpler to do the end relief. I always just did mine by hand on an 8" bench grinder (the wheel arc is handy, as it leaves more support material closer to the cutting face).


Tiger

[smallblock]

Originally Posted by WhiteTiger Top rake makes a big difference, but the usual way of getting it is to grind more end relief on the blade and then set the cutting surface above center. Mostly just a matter of economy, I suppose. Once you've sharpened away all upward curving end of the blade, you have to throw away (by grinding) all the rest of your notch length before you can sharpen again. If you grind the end relief and set above center, you never have to discard any length, just regrind the end of the blade. It's also much simpler to do the end relief. I always just did mine by hand on an 8" bench grinder (the wheel arc is handy, as it leaves more support material closer to the cutting face). Tiger

Shoptask used to offer a backside parting tool. It was built by one of the Shoptask owners. I was also having some trouble parting off solid stock with the stock toolpost. This parting tool sat on the backside of the part and the blade mounted upside down. That allowed the spindle to rotate in the normal direction and also allowed me to use my standard toolpost on the front side and then come in from the back to part off. For some reason, cutting from the back made a much easier and chatter free cut- I never really figured out why, but I'm sure it has something to do with the direction of the forces generated against the spindle .