Parting with cardide tools

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loply:
This is a small lathe, a 7x14 thing.

I have ordered a new replacement Glanze tip, which is the negative rake type.

Incidentally I also noted that the Glanze "blade" which goes in it's own tool holder and accepts the insert was 20mm, so I found and oredered an HSS 3/4" parting blade too. I checked the holder carefully and it will hold the 3/4" piece.

Once the new insert arrives I'll try again with a higher speed, and if it breaks I'll use the HSS :clap:

Incidentally the reason I ran such so speed was because of a video I found on YouTube wherein the author proclaimed the benefits of parting at slow speeds on small lathes. Alas I can't find the exact video now.

It did seem to work, a MUCH smoother cut than I've previously had, just with the obvious downfall at the end :hammer:

John Hill:
That style of parting blade is so expensive I have pretty much put mine aside. That was after having broken both ends of one blade and buying another blade which by then cost me more than the original blade and holder.

BTW, I ground the end of the broken blade to make a regular parting blade, it works so well it makes me wonder if I will ever buy any more chips! :coffee:

loply:
John, I did look at the end of the blade that I've broken and wonder about grinding it into a parting tool, it's almost the right shape already, and is probably decent steel.

Having read around a bit it seems the consensus is that carbide parting inserts are an expensive route, I'll see how the new insert goes when it arrives and if it ever breaks I'll just forget about it... Not worth the money for what it's worth!

mgj:
I don't know Loply. You buy a decent Eclipse blade and they cost a fortune. - plus you need grinding kit to sharpen - and to sharpen really well you need control too.

I bought 10 GTN tips, and I am still on my first (after I learned how to use them).

The problem is that most of us graduating onto indexable tips, are not used to this negative rake bit. They do cut (very) well, but the reason they don't dig in is because the negative rake creates an outward vector(unlike positive rake which is pulling the tool in). However that does place a premium on rigidity because one does have to push a bit harder than with a positive rake tool - as one would expect, they are designed to make one do that.

So, one has to learn how to do it right, rather than blame the tool, I reckon. Though, having said that and realised where I was going wrong, I did regrind all my HSS blades and dropped the rake angle right off to a couple of degrees or so, and all the dig ins, which is what made me go to indexable tips, just disappeared.

Got rather a lot of parting gear, me, and took quite along itme to get it all working right! (Like 20 years, mainly because IMO, the world of parting, with back toolposts etc is full of old wives tales)

loply:
mgj, interesting points, I think as much as anything as a casual hobby user I'm drawn towards the HSS route now because it makes me more independent. I'm fearful of depending on the indexable tool now because if it breaks again I will have to order a £30 blade to fix it, which is the opposite of what I want when I'm halfway through parting off an item on a Sunday afternoon! I can't justify keeping many spare inserts and blades because of the prohibitive cost.

With HSS I guess I would just regrind if it chips.

Having said that, I have one new insert coming in the post and will do my best to make it last!

How do you grind and sharpen your HSS blades? Roughly how much front clearance angle? Can you not run them with a totally neutral top rake?

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