Venturing into insert tooling

[Mcgyver]

My first experience with a truly sharp, well-ground HSS tool was a total eye-opener. I was able to cut deeper and more easily than I ever thought possible on my South Bend 10K. It is definitely the mainstay in my shop.

just for kicks, here's taking a 1.3125" DOC, .005 feed with a HSS bit. lots of rake via a big chip breaker. (admittedly, not a brilliant move pushing a machine to see what I can do, but the DSG didn't sound like it cared). Third pic....last weekend...cutting 57.6 x 3mm internal thread, lathe spindle back plate, which is a coarse thread by my standards. chipped two expensive crappy Criterion carbide internal thread tools before smartening up and grinding a proper hss bit.

on some forums the carbide/hss thing seems to be like guys rooting for their favourite team. I always thought that was wrong; they are just tools, understand the pros and cons of both and select the most appropriate for the job. As home shop guys, factoring in cost is also sensible - we're not hustling to cover overheads like a commercial shop

So what do you do when you get close and want to make a very light or few light cuts as you sneak up on a specific size? Do you switch to HSS?

SOP for most would be to not switch (100% for commercial shops). You're say 40 thou over, infeed 10 and measure. Then compensate on the last cut for how far off 20 thou targeted dim change you were. That's SOP. However, often I do switch when a lot of precision needed (say, fit for very expensive p4 AC bearings). I use a hss tool honed to fine edge and 10ths indicator on the infeed. btw, "creeping up on it" is I think frowned up by the commercial guys. It takes more time, but does work...the fineness of you DOC is function of the fineness of the tool edge; creeping works beautifully if you put the right edge on the tool. That works for carbide too...and 1/10 of thou DOC is not only doable, but a regular occurrence - just ask anyone who scrapes (but of course its a function of the edge which has to be there).

 

[DavidR8]

@ShawnR Something critical that I learned from the book I linked is that the minimum depth of cut with carbide is the the nose radius of the insert.

 

[ShawnR]

just for kicks, here's taking a 1.3125" DOC, .005 feed with a HSS bit. lots of rake via a big chip breaker.

on some forums the carbide/hss thing seems to be like guys rooting for their favourite team. I always thought that was wrong; they are just tools, understand the pros and cons of both and select the most appropriate for the job. As home shop guys, factoring in cost is also sensible - we're not hustling to cover overheads like a commercial shop

SOP for most would be to not switch (100% for commercial shops). You're say 40 thou over, infeed 10 and measure. Then compensate on the last cut for how far off 20 thou targeted dim change you were. That's SOP. However, often I do switch when a lot of precision needed (say, fit for very expensive p4 AC bearings). I use a hss tool honed to fine edge and 10ths indicator on the infeed. btw, "creeping up on it" is I think frowned up by the commercial guys. It takes more time, but does work...the fineness of you DOC is function of the fineness of the tool edge; creeping works beautifully if you put the right edge on the tool. That works for carbide too...and 1/10 of thou DOC is not only doable, but a regular occurrence - just ask anyone who scrapes (but of course its a function of the edge which has to be there).

Wow, that is some big cutting! Threads like this are great. I started talking about carbide inserts and am now appreciating my HSS more. I used both today, comparing them and getting to know the new set a bit. I also looked again at the belt sander and I think that will become my goto for sharpening the HSS.

I agree on the rooting for the team thing, but that might be a factor of member's backgrounds. As you indicate, industry looks at it differently than home hobbyists so have different perspective and comfort tools. As mentioned earlier, I have been hell bent on using and resharpening cemented carbides only because I have so many. I did peel the wax off of a brand new one last week and it cut very nice. Again, I look like the weak link in resharpening them.

Good info on the final cuts. I don't quite have the confidence to take a final cut that far out. But it can be frustrating to take, 6 "final cuts"! as I did on a project recently. But in the end, I was really happy with the slip fit I wanted and got.

Thanks for the input and photos.

 

[Former Member]

I have all three, inserts (love them except for the cost), carbide brazed also good (hard to sharpen or correct grind on cheap ones until now that I have a Deckel clone), HSS great for doing custom funky one of stuff that a special carbide & holder would kill you in cost (again Deckel grinder now just ups the game).

 

[Canadium]

I was a HSS fan until I tried to machine a cast iron disk brake. I found the CI cut my HSS faster than the HSS cut the CI! I tried one of my insert tools and that worked great. I concluded it all depends on the materials and job at hand. But then what do I know? I'm just a total hobbyist newb!