HSS for grinding

Which do you use for your tooling . I have a few bits ,some work better than others .Unfortunately there's no name on any of them .I guess what I'm asking is ,any recommendations on what to get . I'm nearly running out of my freebie carbide inserts lol... cnmg 432 are way too expensive!! for my playing about on the Fortis.

Sean

I use a combination of cutters, including HSS, brazed on carbide and cutters with replacable inserts.

There are varying prices for CNMG 432 inserts. Depends where you buy them from. A quick search on *-bay have a packet of 10 Kyocera inserts for $28. ($2.80 each is not expensive)

Paul

Found these as well,my kinda price , I still need to learn how to put a nice grind on a piece of HSS ,I'm getting there ...slowly .

http://www.ebay.co.uk/itm/10Pcs-17-Types-Carbide-Tips-Inserts-Blade-Cutter-External-Turning-Tool-With-Box-/132048087689?var=&hash=item1ebeadea89:m:mUzTvGO176d6vZ1BQP4yjGg

Thanks for your help Paul ..

Sean

I only ever use hss tooling, £2.80 would buy a 3" hss blank which would last a lot longer than tips will do, grinding is not complicated and is satisfying to do. It is possible to get hung up on lots of different angles for this or that I only use about 3 angles for all my tools

Mick

Diamond tool holder, HSS blank. Does most turning and facing, easy to sharpen of even grind up a new "insert".

I don't buy any bits, just square and round blanks of HSS. I grind my own lathe tools. This is not rocket science. It is not even difficult. Just try it.

I have no idea what I would do with an insert, HSS, carbide or any other material. (Inserts are what you use to repair threads).

The biggest problem with HSS blanks is cutting them to size. If you want to shorten a 5" blank to 3" notch it at the chosen break point using your grinding wheel, put it in the vice so that the notch is just above the jaws, put a cloth over it and hit it hard with a hammer. It should break at the notch. If you don't use a cloth the loose end will fly across the workshop at great speed and if you are lucky you will never see it again.

However I do fully understand why inserts are popular within our fraternity.

JA

i agree with JA... i cut mine to shape with a plasma type 1mm disk then grind. I use inserts onlt for milling (they are brilliant) and high speed turning.

Like John, I use HSS for cutting threads and a diamond toolholder (well I have two) with HSS toolbits for finish turning. Since I often use black steel I tend to use crbide inserts for the roughing cuts.

Thor

As above, rough cuts with carbide and finish with the Diamond tooholder from Eccentric Engineering. A bit pricey but well worth the money and dead simple to sharpen with the included jig on a standard grinding wheel.

Paul.

I keep a fair bit of HSS for lathe tools but only a "Knife" tool is mounted up in a holder. All my other tooling is indexable or brazed on carbide. You do need a lathe that is happy at the higher end of speed range to get the best out of carbide though. I recently bought some DCGT tips for aluminium and light finishing on steel, they give excellent results and are not expensive.

I found a way of breaking 1/4" x 3" HSS. Notch the bar, then put it in the 4 way tool post with a bit of packing under each end, bring the screws down,front and back to hold the bar, then the middle one, just ease it down until it goes click, job done without things flying around.

Ian S C

+1 for homemade tangential toolholders.

I also have a homemade Wimberley toolholder which is great for roughing and is even easier to regrind than the tangential because the toolbit is ground in the holder and QCTP holder. See **LINK**

I also grind my own HSS tools but am not too proud to use preformed HSS tools like these... **LINK**

I started with righthand, lefthand and chamfer versions of these which have preformed chipbreakers and can often be resharpened by simply grinding off just the front face to expose a new part of the chipbreaker face and rehoning the face below the chipbreaker.

HTH

Jon

I was apprenticed in the early sixties and introduced to HSS grinding then and always found it an easy process and so simple to produce what ever tool style one needs. No concerns about whether i have got the correct insert for this or that material. However this always requires the use/access to an offhand grinder and I do get the impression from various posters on here, that maybe a lot don't have and hence a lot of favouritism directed towards inserts.

Any thoughts/comments?

Phil

I think Philip may be correct. Grind your own. I use angle grinder with 1mm disc for cutting and a newish grinding disc for rough shaping, finish on bench grinder. Angles not very important, shallow for steel etc. and sharper for aluminium. I do have a carbide tool for the first cut in cast iron and sometimes black steel.

I too grind my own HSS tools from square (8mm) stock ,cutting the rough shape with an angle grinder using a 1mm disc and finishing on an off-hand bench grinder. I have a water dip ready at all times to cool the tool. Silver steel is very useful for making small boring bars. I only use carbide for cast iron and to speed up the job on very tough steel. I also always go for much more than textbook recommended side and top rake on my tools to make them cut faster with a decent finish . Colin

Thanks everyone for your input ,I have ground HSS tools with some success .My biggest problem is that i have quite a bit of steel round stock in various diameters i just don't know what kind of steel they are. Up to now a lot of it seems quite hard (a lot of the material was sourced from a distillery and was used for making shafts for elevator rollers and the like, so I'm assuming that's why it appears to be tough stuff .) I have trouble sometimes with HSS in that the cutting edge flattens ,gets a tad frustrating and that's when i turn to carbide inserts . Hss does give the better finish on both steel and aluminium IMO .

Sean

I've been trying different styles of grind on HSS with some success which is persuading me to stick with HSS more than inserts for two reasons ...better finish and cheaper ,I'll still use inserts for any large removal of material .

Is it true that you can make HSS too sharp on the cutting edge ?.... I've tried straight off the grinder and then ground and honed and I have to say that for me straight off the grinder (no honing ) seems to last longer ,not as nice of a finish though .

Sean

Yes it is true, in the sense that if the included angle between the top surface and the front side surface is too acute, the edge is very sharp but lacks support behind the cutting edge so bits can break off it easier. Sharpening a lathe tool bit therefore is a compromise between a blunter angle that will wear longer and a more acute angle that will cut better but wear quicker. For small hobby lathes with small tool bits that are quickly and easily reground it is best to go for a good sharp tool, say a 20 degree rake on top and 10 degree clearance on the front side. This gives an included angle of 60 degrees, easily checked with your thread tool grinding gauge, aka fishtail gauge in the USA. It cuts well without chatter in a small lathe and lasts reasonably well.

I don't know why honing would make your tools go blunt faster. Maybe you are leaving too much of a point on the tool. A tiny radius on between the two vertical sides of the tool (the side and the front really,) helps longevity.

If your HSS tool is "going flat" while turning tough steel, slow down the spindle. Use lower rpm. You can still shift metal by upping the depth of cut or feed rate. But too high RPM will melt the edge off the tool every time. For this reason I got to the stage where I stopped using scrap metal of unknown provenance and grade and started paying the money to buy new bright mild steel bar from the steel merchant so I know what I am working with. It machines nicely every time, no battling lost tool tips to work hardened high tensile alloy steel etc.

Your question has to be answered within context Sean and whilst I am no expert, I'll try to explain from my experience and practice (and it's context).

"Can you make the cutting edge too sharp" - well the answer is yes - the cutting edge has to be sharp enough to cut well but if the tool angle is too acute, then the cutting edge has less support under it and it will be more fragile. So basically you need enough clearance to clear the work (without rubbing) and sufficient rake to cut the specific work material. The machine in use can also effect these considerations - my shaper tools have less clearance than my lathe tools because they need the extra strength (a shaper always effectively takes an interrupted cut).

So for roughing down (especially a harder material) you need the strongest 'edge' that will actually take the cut (the tool shape also helps), whereas for 'finishing' a sharper edge will obviously be better and the edge can be weaker because it will not take the same battering when making a lighter cut.

As for honing, this came up recently I think. I've seen folk who swear by it and others who say it's pointless but again it depends on the context. I hone some of my HSS tooling but not all. There are two general reasons I do this.

The first is that by sharpening in a two stage process (grinding - then honing) I can effectively create the main clearance angle and then a secondary (honed) smaller angle that not only gives a very sharp edge but is also much easier to quickly restore (e.g. re-sharpen or touch up) because not much HSS has to be removed. So this form of honing can be very useful for larger HSS tooling where grinding can be very slow and tedious. However, much of my HSS tools are (deliberately) small section (I've generally standardised on 3/16th) - simply because I don't need heavy section tools most of the time and also because it is very much quicker to shape and sharpen smaller tools.

Secondly, there are some small tools where I hone the 'whole' cutting edge (e.g. not two facets) because it's either just easier/simpler to do so - or there is no choice given the tool shape/size - but these are very small tools for small work I occasionally do mainly in brass. A fine finish on very small wok requires a very sharp edge (e.g. a hones one) but this is "my" context - not yours.

So for 'roughing' you may well find that honing is not helping at all, although the "two" angle approach can still make it easier to get a couple of quick 'tool refreshes' out of the HSS before you need to really grind it back - but this may not be "honing" per-se but simply a two facet grind. I don't do this on my shaper tooling as the angles tend to be smaller and on my larger lathe (S7) I use a Diamond tangential tool quite lot and never bother honing that - as it is obviously quite easy to sharpen but then it's not suitable for everything.

So my general advice to you would be - no need to hone a roughing tool but do try different clearances/rakes to learn which holds up best (and when). However, do experiment with honing your finishing tools, especially with the two facet method - it makes it quicker (and easier) to keep a tool sharp and you will therefore be more inclined to do so and keep it that way.

Regards,

IanT

Edited By IanT on 05/02/2017 11:39:11

I don't always you HSS bought as blanks, but sometimes I'v converted other tools like this one inch HSS flat bit, left behind by a railway maintenance gang, all it needed was a major attack with an angle grinder, and it became a lathe tool.

Ian S C