Last weekend I finally had a chance to to something with my lathe. During the last 3 months I have collected a variety of carbide inserts and now I finally had a chance to test them. I noticed that my lathe is actually quite rigid being a chinese import.
One warning about the cheap chinese parting tools. Especially the one that comes with 10 inserts. That tool is meant for very soft materials like wood, plastics and maybe aluminium. Bronze is already out of the limits of that tool. I tried to part a 30mm hot rolled steel with it. No chatter, everything was just fine until suddenly .... the tool went into a banana. It just bent. I would assume that a carbide tool bit holder should be made of some rather tough material. This one was as soft as some soft steel. For those interested the
ebay link is here.
While testing diverse carbide bits there was a few that were seemingly better than the rest of the collection. I now have my favourite carbide inserts.
For some reason I actually do not like aluminium. I prefer using steel or some yellow metals whenever possible. In order to create something useful while fiddling with the inserts, I did a hammer with plastic hitting surfaces for aligning the work.
Especially when machining that thin arm (10mm) out of silver steel one specific insert stood out. The insert was eating the steel for breakfast and left very nice finish behind. Today I went to the Frankfurt flea market and bough rest of these inserts from the guy who sells them. The type of this insert is TPGH110304TLF1 T15. These are made by NTK.
Another item that I started with was a thing that can be put in the backhole of the lathe and then be equipped with indexing plates in order to index the spindle. I might also equip it with a crank for hand turning. And Yes, there will be a microswitch that disables the power when this thing is stuck into there. As it happens I have a few quite hard 2mm thick aluminium disks with a 40 mm center hole and with large enough diameter in order to set up the indexing accurately enough. These have very accurate dimensions. Some old-timers might know the origin of those disks.
That thing on the right is machined from some mystery material which has always been troublesome to get a good finish into. It might be cold rolled steel. In addition to that quite a lot of material had to be removed from that one. It was originally 50mm in diameter and now mostly 38 mm. I now know why chip-control is actually quite an important thing. With suitable cut depth, speed and bit I succeeded to remove that excess material without filling my bin too much. That bit could do 1mm cut withoyut whining too much. On my lathe that is a lot especially with that material. I now have another favourite carbide bit. The type of this bit is N20TCGT110202RS and the maker is NTK.
The last thing I tried was an intermittent cut. The material is construction steel (100 x 100 x 20 mm) and that piece succeeded in breaking quite a lot of different bits. Apparently that kind of machining is kryptonite for carbide bits. However - one survived. This is now my most favourable insert as it can do decent finish on cold rolled steel, does not break up on intermittent cuts and can do hard materials as well. There is one thing this bit does not tolerate at all. Turning the spindle on wrong direction will break the bit no matter how delicate the touch is.
So what is Your favourite carbide bit and why so ?
