Thread: Cuting High speed steel??

I have only ever had Chinese cut off disc'c fly to bits and that was 20 years ago, I solved the
problem by never using them again and only using Flexovit.

Just to add to what everyone else has said. First up, you won't change the temper of HSS by grinding, so there's no danger from using an angle grinder and cut off wheel. But as Stuart says if you can't clean up the cut and grind it square and parallel then it probably won't be much chop in the diamond tool holder.

If you have a surface grinder, then you should be able to square it up. Without a surface grinder, If it was me, I think I'd just buy some HSS of the right size.

Just for completeness, If you want to turn or mill HSS, then I believe you can use PCD or CBN tooling, or if it's complex profile shapes then EDM would be the way to go. It can also be forged, I played around last week forging HSS, not sure how successfull it was, I haven't done much more than bend it into shape just yet. ( It's an attempt to make a gooseneck cutting tool for a shaper).

Regards
Ray

Originally Posted by shedhappens

I have only ever had Chinese cut off disc'c fly to bits and that was 20 years ago, I solved the
problem by never using them again and only using Flexovit.

Interesting. I try to avoid Flexovit if I can due to problems with glazing of the edge and reduced cutting. My mate had this problem years ago with his Cutoff saw and I made a small cutoff saw from an old circular saw just after and sufferred the same problem. My cutoff saw has forward/reverse movement and this enables the cut to approach from a slightly different angle which clears the glazing but I have always felt that this involved wastage of wheel diameter. I hardly ever use it since I got the bandsaw. I use Smith&Arrow wheels in the angle grinders and have never had any break. At around $1.00 for125mm X 1mm wheels this is a good saving on the $4.00+ that the Fexovit wheels sell for. These are Chinese.

Originally Posted by lather

is there a reason they need to be 1.5 inch long ?
when first using the diamond tool holder i cut them short enough so the post can be turned 360 degrees, and sharpened both ends of the tool.
the drawback is the waste once the HSS gets too short.
now use HSS in the diamond holder at 2"/3" long, "basically cut the long hss in 1/ 2 and only sharpen the end furthermost from the grinder cut".
found that the post can still be turned to the positions needed, even with 2 tools in the post, when using the longer HSS bits.

Hello all, I apologize for not responding earlier, but it seems every time i try to respond using Internet Explorer, the site freezes up. I have just reverted to Firefox and can now reply on this website.
Firstly, yes the cut would have to be square to work in the diamond tool holder. Secondly, the pieces could be around 3" long, which means less wastage. I notice today that Eccentric engineering now offer the HSS and crobalt cutters at 3" lengths, which again means less wastage as the bits become shorter and unusable.

Soooooo, it looks like I might try slicing the HSS with an angle grinder with a thin (1mm?) cutoff wheel. If it works, then fine. If not, I just go buy some more 1/4" square tool steel.

A bit off topic, but I have tried their crobalt cutters on stainless, and find it chips the cutting face fairly easily, thus lots of re-sharpening, therefore reducing the life of the cutting bit.
My thanks to all who have contributed to this post.

Cheers,

Ned

Originally Posted by iron bark

A bit off topic, but I have tried their crobalt cutters on stainless, and find it chips the cutting face fairly easily, thus lots of re-sharpening, therefore reducing the life of the cutting bit.

I've had this happen to me too. After the 10th re-sharpen of the bit I chucked it in the scrap bin & swapped the job over to the Chipmaster with TCT tooling. No further problems.

Bit odd because I'd used the HSS bit previously to machine 316 pipe without dramas. The stainless it played up on was mystery grade from a friend of mine.

PDW

This is my third shot at posting this the other two disappeared into a black hole somewhere.
How have you found the diamond tool holders? Do they have anything to offer over American/English style holders and what are the positives and negatives.

"If not, I just go buy some more 1/4" square tool steel."
Yes, go buy some. Save the handy large piece for form tools, large HSS is rare and expensive compared to small stuff.
A.

Hi All

Just thought I'd chip in some thoughts on a couple of the topics raised.

Iron bark: With a piece of HSS that size (1/4" x 1:1/2" x 4:1/2") I'd try and keep it for a special purpose, not chop it in to small pieces. 1/4" square HSS is pretty cheap so it would be a shame to cut it up, it could be used to make a nice form tool one day if you have the power to drive it.
By the time you've roughed them down and surface ground them to size, that's a lot of work for a few tool bits.

Tool bits for the Diamond Tool Holders really need to be accurate and square, other wise the clamp and holder won't grip properly and the bit is likely to slip down on anything more than a light cut.
Also if the tool bit is a touch under or over sized the clamp will be sitting at an angle to the holder and the two "Vs" will not be square to each other, again this will lead to less clamping force.


As to losing temper: as a couple of the posters have mentioned, you will not lose any hardness through grinding or cutting.
You would have to keep the tool bits red hot for several hours to lose the temper. M42 HSS can be silver soldered on to a mild steel shank if required without losing hardness.

With regards to the Crobalt; did you put a radius down the front corner of the tool bit ? all lathe tools tend to work better with a small radius on the front corner, it increases the life of the cutting edge and gives a better surface finish. With a dead sharp corner you will also tend to get lines in the workpiece, in effect a very fine screw thread.
I use one of those diamond sharpeners to put a radius on both HSS and Crobalt tool bits. Putting a radius on the front corner of the Crobalt bits is especially beneficial, as cast alloys are more brittle than HSS.
I did a lot of experimenting with the Crobalt on 304, 316, and 431 stainless, and SG and grey cast iron, but I can't say I had any issues with the tip chipping even on interrupted cuts.
Some of the stainless steels can be pigs to machine though, any idea what type it was ?

Incidentally, I found the Crobalt isn't suitable for thread cutting in the Diamond Tool Holder as the smaller point is too fragile and chips easily, HSS is better in this instance.

Cheers
Gary
Eccentric Engineering

Gary,
thanks for the tips on the crobalt.
is it better to use crobalt on cast iron, does it need to be ground to a different angle ?

Originally Posted by Gary S

I did a lot of experimenting with the Crobalt on 304, 316, and 431 stainless, and SG and grey cast iron, but I can't say I had any issues with the tip chipping even on interrupted cuts.
Some of the stainless steels can be pigs to machine though, any idea what type it was ?

No. I asked a friend of mine if he had an offcut of 50mm dia as I didn't want to buy a 1m length when all I needed was less than 100mm. So no idea.

Don't know what the tool bit was either - I have a lot of HSS and other stuff. I'd been using it successfully on 316 pipe previously but could not get it to hold an edge on this stuff - and I played with the DOC, feed rate, relief angles etc quite a bit before giving up & swapping to the other lathe with TCT tooling.

Wasn't a rigidity issue either - the Monarch masses 5X what the baby Colchester does.

I just put it down to one of those oddities of machining, tried a different way and moved on. First time I've ever had a tool bit edge chip away like that though.

PDW

finally tested crobalt on mild steel.
seems quicker to sharpen compared to HSS.

the finish on a face cut was better than using m42 HSS.
not sure why, but the feel when cutting is smoother compared to using hss

tried it on broken cuts, on a rough plasma cut 7" diameter disk, which wears out HSS,
no chips on the tool, the finish is fine and ran it at a much higher speed.

"i'm hooked" mainly due to the increase in cutting speed

Is it o.k. to run crobalt at speeds in which the swarf turns brown or blue ?

No the Crobalt works fine with approximately the same angles as HSS.
With the tool holders the 10 degree front and side clearances are built in of course, and I usually use the recommended angle on the top face which comes out at about 12 degrees back and 12 degrees side rake.
If you ever want to increase the angle for materials such as plastics or copper you can just put a bit of flat strip under the jig so that the top face of the tool bit contacts the wheel higher up.

The normal top rake for general purpose use is pretty good for cast iron, you could reduce it a few degrees to increase the strength of the cutting edge, but don't go too far or you'll increase the 80 degree angle and will have trouble cutting into a square corner.
If you sharpen the tool bit on the low side of the grinding jig instead of the normal high side you will find that will reduce the top rake a few degrees, it's quicker than lowering the grinder tool rest.

Lather: Good to hear the Crobalt worked okay on the plasma cut disk. Cast alloys are about the same hardness as HSS but they retain their hardness for longer when they get hot. It should still be fine when the chips are coming off brown or blue.
When I did the video of it cutting some stainless steel the chips where damn hot, but stainless swarf doesn't change colour so hard to say what temp it was.

Gary
Eccentric Engineering
( I have no affiliation with this company other than being a satisfied owner

Forgot to mention, yes the Crobalt does work much better than HSS on cast iron.

Hmm was supposed to be a smiley at the end of the last post not a rofl, that'll teach me to preview before submitting a post.

Gary,
tried it out on a face plate today, as the dam thing didn't fit the spindle.
all went well.

ran some tests using crobalt and sutton M42 HSS on mild steel
keep getting a build up which fuses to the tip of the hss tool, which is probably why there's a big difference when machining with crobalt, as it doesn't get a build up.
both tools were sharpened to the same angle, as well as a radius and honed with a diamond stone.

can't work out whats causing it, couldn't find any info on the web..