Indexable tooling or HSS ground to shape?

[raynerd]

Hi, just a quick one as I have done a few searches on this one and can`t find any answers.

Basically, I have only ever used HSS tool steel ground to shape for my cutting tools. I find it a slight pain having to re-grind the tool every so often to sharpen it up. I`m just wondering what indexable tooling will offer as an advantage? Obviously the tips/inserts are replacable but what advantage does this give? Also is the finish better?

I`m considering purchasing a profile tool as this shape blunts in HSS quickest, primarily because I use it most often but I`m just curious to know what I`ll gain for the significant price.

Chris

[jim]

i only have one indexable tool, you really have to have the right inserts. most indexable inserts are designed to cut under pressure, and hence don't have a sharpe edge ( most wouldn't cut you if you really pushed into you skin).


as well as HSS square section, i use old taps etc ground as cutting tools, i also use the carbide shanks from solid carbide endmills, all you need is a "vee" in your tool post or half round channel in a bit of scrap flat/square section to make a seat for them.

[spuddevans]

Hi Chris, I started off turning with only carbide insert type tools but now I also use Hss a lot. It's kinda like horses for courses, if you know what I mean. I have a round profile insert tool which gives an amazing almost-mirror finish to brass and Ali, but obviously cannot turn to a sharp edge. In fact all my insert-type carbide tools will not give me a good sharp edge into a shoulder.

Another difference I have found with Hss vs carbide tools is that Hss will allow you to shave off a whisper of a cut, like 0.001-0.002mm if you needed, but on my C2 ( which, lets face it, is made out of a 50-50 mix of industrial grade pasta and used post office elastic bands, so this may not be true of better, or better tuned, machines ) using indexable tooling is a little less precise, ie you can wind on a cut of 0.02mm and it doesnt cut to that depth, as far as I understand it, the carbide does not have as sharp an edge on it and cuts by brute force rather than by sharpness.

That's fine for roughing out, but when you take finer cuts, I've found on my lathe when winding on 0.02mm per pass, the carbide will take virtually nothing on the 1st pass (probably partly due to the flexing of the rubber machine) , then will take more than the 0.04 ( 0.02 1st pass + 0.02 2nd pass ) on the 2nd pass. This makes fine finishing cuts very unpredictable for me, so I tend to use Hss for the final finishing cuts.

For roughing out and heavy cutting though, indexable tooling is great, it'll hog out a deeper cut and leave a better finish while doing it (in my very limited experience) I've found on some mystery steel I have that indexable tooling gives a better finish on when taking a heavier cut (0.12-0.14mm) than lighter cuts (0.06mm)

So I guess what I'm trying to say is that indexable tooling does have a useful place in my workshop, if looked after it can last well, but the tips can be expensive. But they wont replace Hss tooling, both have their uses and places.

I'd reccommend getting the 6mm round profile tool, it has been the most used and most useful out of the indexable tools I have, and I am only on my 2nd tip. ( it's great, when it gets a bit blunt or damaged, just rotate the tip around a bit to expose a fresh cutting edge  )


Hope this rambling tome is of some help.

Tim

EDIT:

I forgot to mention that if you dont have a QCTP, you can get some indexable tooling that has the cutting tip the same height on each tool, handy for reducing setup time. My 6mm round profile tool and my standard LH turning tools can be swapped without adjusting the height setting at all. I got them both from RDG, they are both 6mm shank.

[raynerd]

Thank you for your reply both of you.

Tim - I am actually making a QCTP in the next few weeks. I have all the materials, plans and Darrens thread, I just need to finish my X axis power feed on the mill and then I`ll make a start. Once this is made, I can spend time setting up all my HSS tools to correct height and then I`m sorted! With the indexable tools being quite pricey and HSS doing a good job for me at present, I just feel I have other things to put my money into.

Do you use your round 6mm profiling tool for roughing then? My concern is that I very very rarely use a round tool because I`m 8/10 working up to a shoulder! - I see lots of project log pictures with people using a round profiling tool and it concerns me that I am doing something wrong with not using these enough!! I tend to use a LH tool like this by far the most:

[spuddevans]

Do you use your round 6mm profiling tool for roughing then? My concern is that I very very rarely use a round tool because I`m 8/10 working up to a shoulder!

I do use it for both roughing and finishing of brass and ali, and then I often switch to Hss to finish off any sharp shoulders that are needed.

I see lots of project log pictures with people using a round profiling tool and it concerns me that I am doing something wrong with not using these enough!!

Dont be concerned, if it works for you then it must be all right. There is more than one way to skin a cat, so if it works for you and you are happy with it, go on with what you have.

Having said that, if you have the spare cash, get the round profile indexable tool, it really does give an excellent finish, not that you couldn't achieve that finish with Hss, but it can be more consistent with the indexable tool ( just because you dont have to grind it to shape, the shape is always the same, unless the tip's chipped, therefore the finish is more predictable.)

Tim

[jim]

theres nothing wrong with your lathe!!

when we size cuts at work, you always try to leave about 0.010" for a sizing pass, otherwise you end up taking a couple of passes with nothing coming off and and then the tip will cut and under/oversize you go

the above even applies to ally!