Best carbide insert shape/type?

[ukracer]

Well, thats it, i relent. I will get some 3/8" HSS blanks and grind some tools. I didnt want the fuss of grinding, thats why ive been so stubborn.
Everyones persistence has payed off. Thanks to everyone for their advice.
Be prepared for my next adventure.....trying to part off

It's funny as I posted that to show what could be done on lower powered large with carbide.

 

[HughF]

Seriously, just buy some positive rake inserts and give them a go. I'll never go back to hss tooling, for me, inserts are the way forward. Easy, consistent, handle hardened steel well...

 

[dobbslc]

Just to be sure, can you explain what a positive rake insert is compared to a negative one?

 

[HughF]

Basically, if you can turn the insert upside down and run the other side, it's negative rake - CNMG being the main one

 

[HughF]

Copied from a post on homeshopmachinist:

The negative rake insert vs. positive rake insert debate is really one on inclination angle. Fundamentally, if you screw the insert down with a screw down the middle and no top clamp, it's probably a positive rake. If you clamp the insert with a top clamp, no screw and sometimes a mechanical chip breaker (shim) on top, it's probably a neutral rake. (TPG's are most commonly used this way.) If you have an eccentric screw in the middle and a top clamp, it's probably a negative rake insert. (These have 0º sides and can be flipped over.)

Almost all inserts all types are actually positive rake because of the chipbreakers molded into the top surface. The correct term may be "top form geometry", but the term chipbreaker is the one used most. Without top form geometry, the holder's inclination angle determines positive, neutral or negative top rake. I have negative rake inserts with high-positive top form geometry that cut with less force and much better chip control (and life!) than a "positive" rake TPG insert.


The primary difference between positive and negative rake inserts is how sharp (and therefore, how fragile) the edge is. The sharper (more positive) the insert is, the less horsepower and rigidity it requires, but the edge breaks down much quickly. Great for home shop types, lousy for production work.

 

[dobbslc]

That's brilliant!
Pictures are always good to help understand these things.

 

[Member 66061]

I think I was a bit naive when i started this thread, I didnt think i would be opening such a can of worms.Theres some useful info about carbide inserts here now though. Heres a chart for translating the designations >CLICK FOR LINK<

 

[optima21]

Be prepared for my next adventure.....trying to part off

I use these parting tools (the 5/16" shank with 2mm x 10mm blade)

http://www.chronos.ltd.uk/acatalog/...ool-s-with-Chipbreaker-Blade--5--cobalt-.html

on my tiny hobbymat lathe (shown parting some 60mm dia steel bar)

ohh they are HSS steel though, not carbide

 

[roofman]

I can get a piece of HSS and put an edge on it to do general turning on a number of metal types...facing,inside,outside,up the speed alter the tool angle for fine surface cuts,slow it down for heavy cuts,plastics,alloys,even running very fast and a wooden dowl....All done with the same piece of HSS and enough to get me out of jail and get the job done. Now here,s the fuel on the fire bit,ide call all of the above "general turning"

 

[ukracer]

I think I was a bit naive when i started this thread, I didnt think i would be opening such a can of worms.Theres some useful info about carbide inserts here now though. Heres a chart for translating the designations >CLICK FOR LINK<

You are not on your own...I have a big one and I did not know all of what's being posted on here...

 

[ukracer]

I can get a piece of HSS and put an edge on it to do general turning on a number of metal types...facing,inside,outside,up the speed alter the tool angle for fine surface cuts,slow it down for heavy cuts,plastics,alloys,even running very fast and a wooden dowl....All done with the same piece of HSS and enough to get me out of jail and get the job done. Now here,s the fuel on the fire bit,ide call all of the above "general turning"

Oops. I guess it's good it's Xmas.

 

[Kram]

http://mmc-permanent.learnways.com/courses/75/index.html

 

[dobbslc]

I got 7 out of 10...

 

[Member 66061]

http://mmc-permanent.learnways.com/courses/75/index.html

I got 8/10 and im half cut

 

[GRUMPY1950]

I got 8/10 its 45year since I worked a machine tool in anger, the same things hold true today as then, Negative rake carbide tip need rigid machine loads of HP/KW. High speed steel tools half decent sharpened and away you go.
Parting off I thought was a black art until they put me on a Ward Capstan with collet chuck, you could part off 2" dia bar at 1000 rpm almost as fast as you could feed in. The Centre lathes we had were mostly machines supplied during world war two and were worn out, chucks slideways and headstock bearings. When parting off the work would jump on top of tool when you got to the centre and chip the tip.

 

[ukracer]

Watched this tonight.....best video yet I have seen on the subject...but then I think the guy is great anyway...

Oh and his next video is on carbide tips...

 

[Tinbasherdan]

Maybe too late, but for tip tools have a look at my el cheapo thread, half decent tools for what they cost, certainly as good as the rdg ones

 

[fixedfixer]

http://www.mig-welding.co.uk/forum/threads/el-cheapo-tip-tools.66499/. Thanks Tinbasher.Link in case people can't be bothered using the search.

 

[ukracer]

 

[DennisCA]

I decided to try out some carbide inserts as well, so I can see how it compares so I got a cheap chinese set with trigon inserts (WMNG0804). Will be interesting to see how it performs compared to my own HSS, I don't have high hopes for the chinese inserts but with the holder I can get some higher quality ones later. I got the impression the trigons were the most useful all rounders.