my first part & insert-boring-tool question

Gary, stick around, most of us need what you have. common knowledge about inserts. I worked in industry for 25 years with carbide, had learned nothing of what you wrote above. (except the form of the groove tool)
 
G MORSCH said:
At a minimum, increase DOC and IPR to exceed the hone levels. When I do finesse work, I try to do it with "G" tolerance inserts. . . . I typically use Tap-Magic Protap for everything but aluminum and just apply a small amount with a toothbrush.
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Thank you Gary, that was tremendously informative and exactly the type of info I like. I recently learned the distinction between __M_ and __G_ inserts in this thread. I figured I could get some CCGT inserts in the appropriate size to use with these holders, to improve my results and allow finer cuts.

G MORSCH said:
There is a lot of tooling out there for cutting off parts. The best performers have a positive topography and a dimple in the middle. The dimple is designed to collapse the chip and make it smaller than the groove width and aid in chip control. The angular style can deflect the blade and affect flatness so stick with a cutoff insert with 5 degrees or less on long/deep cuts.
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Thanks, I'll keep this in mind as I look for an insert parting tool.
 
Jason:
CCGT and CPGT inserts do a great job! Think about the 100 degree corners that are typically discarded. There are tool holders and boring bars out there that will let you make use of the two unused corners. Rough with a 15 deg. lead tool holder or boring bar to squeeze every dollar out of your inserts. Here's a tip for everyone. Google/contact local scrap yards and ask if they recycle carbide cutting tools. If they do, ask them if you can buy some used tools from them. Most 80 deg. diamonds have unused corners on them and if they agree, you can do a lot of shopping in their 55 gal. drum full of inserts, drills, end mills, slitting saws, etc. At some accounts that I currently visit, they will allow me to search for usable carbide, and I offer to pay them double scrap price, which is currently around $7.50/lb. I pay them $15.00/lb. The photo below is mostly from one shop. I also check scrap yards. Bring a good light and a 10X magnifying glass, gloves, and a rag or too. Bring a lunch, once you start, it's hard to quit!

Boring Bars... Often, the insert is positioned at a negative rake and assigned a minimum bore size. This is built into the tool and determines the amount of radial relief required to deliver clearance at the bottom of the insert. I do see some folks grind away the bottom of the boring bar but that does nothing to add radial relief. "P" (11 deg.) and "D" (15 deg.) are also common on small diameter bars. Typically, "C" (7 deg.) requires the bar to be tilted, as in your case, to achieve clearance down to the specified minimum bore. Many of the P and D relief inserts are designed to cut in the neutral plane, 0 deg.

Good luck, Gary

Good Scrap.jpg
 
Jason, if your lathe is similar to my benchtop, the problem is probably not the toolpost, but the hold-down on the compound. If yours has two bolts holding it down, it will allow the compound to flex under load. If you want to make a real difference in how your lathe cuts and especially make parting easier, make you a four-bolt compound base. It made a world of difference on my lathe.

The plans and some instructions for the new base can be gotten here: http://bedair.org/clamp/9x20clamp.html

I used 5/8 cold-rolled flat bar for material. It's time well spent and will stiffen the compound noticeably, at least it did on my lathe.
 
vocatexas said:
I used 5/8 cold-rolled flat bar for material. It's time well spent and will stiffen the compound noticeably, at least it did on my lathe.
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Thanks; I do plan to make a new compound clamp. Though as I was sneaking up on my taper angle last night, I was thinking that it would be much more annoying if I had to deal with four or six clamping points instead of two. Obviously I wouldn't have to tighten all six, but I found it somewhat amusing. My plan was to wait until I have a mill (~8 weeks according to PM) to make the compound clamp.
 
G MORSCH said:
Jason:
CCGT and CPGT inserts do a great job! Think about the 100 degree corners that are typically discarded. There are tool holders and boring bars out there that will let you make use of the two unused corners. Rough with a 15 deg. lead tool holder or boring bar to squeeze every dollar out of your inserts. Here's a tip for everyone. Google/contact local scrap yards and ask if they recycle carbide cutting tools. If they do, ask them if you can buy some used tools from them. Most 80 deg. diamonds have unused corners on them and if they agree, you can do a lot of shopping in their 55 gal. drum full of inserts, drills, end mills, slitting saws, etc. At some accounts that I currently visit, they will allow me to search for usable carbide, and I offer to pay them double scrap price, which is currently around $7.50/lb. I pay them $15.00/lb. The photo below is mostly from one shop. I also check scrap yards. Bring a good light and a 10X magnifying glass, gloves, and a rag or too. Bring a lunch, once you start, it's hard to quit!

Boring Bars... Often, the insert is positioned at a negative rake and assigned a minimum bore size. This is built into the tool and determines the amount of radial relief required to deliver clearance at the bottom of the insert. I do see some folks grind away the bottom of the boring bar but that does nothing to add radial relief. "P" (11 deg.) and "D" (15 deg.) are also common on small diameter bars. Typically, "C" (7 deg.) requires the bar to be tilted, as in your case, to achieve clearance down to the specified minimum bore. Many of the P and D relief inserts are designed to cut in the neutral plane, 0 deg.

Good luck, Gary
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Thats alot of good carbide tools lol. I have a question for you though if its ok with @jwmelvin i got the 3/8 set of accusize inserts with tcmt21.51 inserts.im looking to make my own boring bar or two using this style insert and i was wondering if you could point me in the right direction for decently priced inserts that are all purpose but as you said above are sharp so that i can creep up on a number and take off a thou if needed to? I hope i see your around more id love to learn more about inserts. I can never tell which inserts go best for which material.
 
Jason,

I’ve been a hobby machinist for about 30 years and always used HSS tools. However, I recently bought some tooling that looks very similar to what you purchased. They actually work pretty darn well. My advise is to just try them out and see how they work. And, the angle of the boring bar looks right. You need it for clearance.

Tony
 
I got the grizzly set cause I didn't wanna have to make tiny lathe bits for the smaller bars
 
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