Models for grinding HSS Lathe Tools

[benmychree]

Be aware that aggressive grinding like that may cause microcracking of HSS, leading to breakdown of the cutting edge; if you see heat related color changes, it is not good.

 

[ttabbal]

OK, I'm still learning about making HSS tools, but have already learned that even with good grinding wheels (I have two dedicated grinders with various grits of Norton 38A and 32A wheels) that for some, there is a LOT of material to be removed. I've seen some YouTube guys making rough cuts with angle-grinders to get closer to the end shape with less grinding wheel time and wear and I happen to have a pretty decent old Ryobi 4" angle grinder sitting on the shelf collecting dust I could dedicate to this. So, my question, what is the ideal (might as well pick ideal(ish) since I'll be buying some wheels either way) type of wheel to use. Flat or dished/27? Grit? Material? I see some listed for Ferrous and Stainless. Is that good enough for HSS, or is there something better? Thanks in advance for any pointers.

This is where the belt grinders are really helpful. You can really hog material off with those things and a ceramic coarse belt. It's also easier to get a nice flat face. Other options can certainly work, but will likely be more time consuming for the larger material removal.

For an angle grinder, you could try a cuttoff disc for the larger chunk, then switch to the nicer grinding wheels. I've never done it, but I've seen people do it and it seems to work fine.

 

[Sailplane Driver]

HSS will turn dark blue at about 600F. No appreciable microcracking will occur even if quenched in water up to about 700F.

cooling hot tool while grinding [Archive] - Sawmill Creek Woodworking Community

Hi all!!! i'am new to this so if this is posted in the wrong place or whatever then PLEASE forgive me. Anyhow, I was reading some of the older post today, and one really interested me, it was regarding whether one should dip a high speed steel tool into water while grinding to cool it...

sawmillcreek.org

 

[devils4ever]

This is where the belt grinders are really helpful. You can really hog material off with those things and a ceramic coarse belt. It's also easier to get a nice flat face. Other options can certainly work, but will likely be more time consuming for the larger material removal.

YES. ^^^^this.

I was getting frustrated with bench grinders. I built a 2X72 belt grinder a few years back and it is amazing how fast I can remove HSS and get a flat surface. Definitely worth buying/building one.

 

[Janderso]

I have appreciated used pre-ground tool bits in batches from Ebay. Heck for $20 you have some very useable tooling and it saves a bunch of time.
This batch of 20 I got for about $15 plus postage.

 

[Downunder Bob]

I was taught during my apprenticeship to rough grind on a 32 grit wheel and finish on a 60 grit wheel, never felt the need to hone. This was in a toolroom so a good finish was expected, and HSS ground on a 60 grit wheel will give a good finish. The biggest proviso is that the wheel is properly dressed.

 

[roghmc]

Thanks for the comments guys. I have 36, 60, 100 and 120 on 2 grinders (and rarely touch the 120), so I suppose I'm OK there. I like the belt sander idea. I have an old belt/disc combo sitting mostly unused in my secondary workshop (old 10x20 shed) which at the moment has no belt anyway, so I'll look into this ceramic belt idea and see how it works. Any suggested belt grit, given that this, and maybe still the angle grinder idea, will be for very rough/big cuts?

Thanks

 

[ttabbal]

Thanks for the comments guys. I have 36, 60, 100 and 120 on 2 grinders (and rarely touch the 120), so I suppose I'm OK there. I like the belt sander idea. I have an old belt/disc combo sitting mostly unused in my secondary workshop (old 10x20 shed) which at the moment has no belt anyway, so I'll look into this ceramic belt idea and see how it works. Any suggested belt grit, given that this, and maybe still the angle grinder idea, will be for very rough/big cuts?

Thanks

Those combo machines are intended for wood sanding. They run too slow for great results on metal with a ceramic belt. I tried one anyway when I started, as my brother had the machine. It works, but isn't much better than a normal belt. There are various options to get the speed up I believe, but I just built one like the knife maker guys use. That is where it's at. Pre built machines are quite expensive, so I can understand not wanting to buy one. They can be built for a reasonable price, particularly if your scrap pile is pretty deep. I use 36 for most of my rough grinding on it.

Whatever you grind with, keep a little dish of water nearby to cool the bit. It goes from warm to blisters pretty quick. You have to get HSS crazy hot to mess with the temper, even quenching. You will hurt yourself before you hurt the metal.

 

[WobblyHand]

What do people use to grind specialized tooling? Where both a belt sander and standard grinding wheel can't get in? What kind of grinder and what kind of wheels? I want to make a tool to partially enlarge a bore. It needs to access something 12mm deep and relieve the bore 3mm radially. The relieved length is about 6mm long.

I find it tough to make tools like this. Any suggestions to make this easier?

 

[ttabbal]

My first thought for odd tool shapes is a die grinder/dremmel. I think I'd try to get the bulk of the material off with the belt grinder, then switch to the smaller tool. Probably hold on to the tool in a vise and cool with a squeeze bottle of water. I'm not sure what to suggest for grinding media though.

One alternative I have seen done on a Joe Pie video, cut in the mill with carbide tooling. It's probably tough on tooling, but it did work.

I'm interested in seeing what others suggest. I haven't made too many specialized tools.