Thread: Carbide Turning Inserts, What flavour do you prefer?

Originally Posted by Anorak Bob

The triangular insert on the boring bar did a nice job initially on the toughish steel CTC use for their arbors but suffered from fine chatter when creeping up to the required finished size. Probably more to do with the bar extension and subsequent lack of rigidity than the insert.

Good point Bob - A friend of mine once told me that you only need one size boring bar for a lathe, but that is not 100% correct. While you might be able to get away with it, using the biggest boring bar you can with the shortest overhang will give the best finish. I now have 4 boring bars, ranging from one that will kick off from (I think) a 9mm starter hole to one that needs a 23mm starter hole. I also am much more particular these days about bar length - probably because I now have a set of tools next to the lathe kept there so I have no excuses about it being too hard to find the allen key...

Thats probably a worthwhile tip for someone new to metal turning in itself - have all the hand tools you need for changing tooling next to the lathe. Buy duplicates if necessary so you don't have to be put off because you can't find them in your main tool box and put them somewhere convenient so they are very accessible (don't leave them in that tacky tool box that came with the lathe) - a drawer directly under the lathe or a shadow board. You need to establish good habits/ routines with machines otherwise you will either do things in a less than optimum way or grow tolerant of slipshod (and possibly unsafe) practices.

Michael

Originally Posted by Steamwhisperer

Hi Ewan,
if it is that magical finishing cut you are after, have you tried a HSS shear tool?
The finish is most acceptable
Here is a video that shows it.
Metal Turning with Contrary Tool.mpeg - YouTube

Phil

Been meaning to reply to this for ages....
Good vid Phil, i have tried a few different shear tools on the lathe but never had success, but i have never ground one like that.
I got some WNMG 06T304 SF inserts in IC 907 last week, and took a few cuts. These inserts will leave a nice finish on the unknown bar i'm using to make collet chucks from (flavor of the month?) with a speed of 250 m/min (825 f/min) and a DOC from .1-.3mm, feed around .15mm/rev. The worst bit is the chips come off as continuous shavings.
I'm yet to put them to some free machining steel, 1020 or similar, i'm still waiting on grinding wheels so i can finish the collet chuck for the D/H and take the spindle off the lathe. Of course not much will happen now except a big re-arrange to make some space for the Blohm....

Cheers,
Ew

A collet chuck has been on my list of things to do for years now.....Where is the best spot to buy a D1-4 camlock blank?

re carbide - I bought some of those expensive high rake things from overseas. They are great when taking small cuts on ODs but I had absolutely no luck at all using them in my boring bar....they chattered, dug in, broke. Switched to HSS for boring and never looked back. The ones I bought (kennametal brand) were chrome like in finish and tended to break right through to the center hole when they let go meaning the whole insert was ruined, not just the tip. Dont think i'll buy more to replace the two I have left.

Besides that the only inserts I use are TCMT and DCMT inserts of varying brands. I find them to be tough and forgiving, they often come out when im doing stainless or cutting HSS. I find they will give a mirror finish on HSS and an excellent finish on stainless.

If im playing with mild steel I use HSS...I have really learnt to love the stuff after a rocky start.

Here are some photos of some of the Carbide tools that I use. The cheap set i have had for years, they are pretty spartan to say the least, but they work. Inserts are no name things bought from ebay. I mostly use these for roughing.

"Right" is my right hand turning tool (I think...cuts from right to left). Bought from CTC along with matching Iscar inserts. You can see damage on the tool holder where I crashed it once. I have a left one too, it is grey in colour...but couldnt find it last night.

Finish is just a quick shot of a cut I took last night with the RH tool pictured. 2000rpms, medium feed. I was playing with some HSS (that I now suspect to be a lesser grade of tool steel) and wasnt having much luck. Mounted the carbide tool, cranked the speed and got a nice finish first up....I am definitely a pro HSS guy....but you cant dispute the ease of using carbide. I just hate it how the chips come off burning hot.

Brendan

Peppermint mostly. If I could get chocolate I would go that way with the occasional mix of the two.

Dean