Thread: Milling or Drilling HSS with TCT

Hi .
Can HSS be milled or drilled with a TCT end mill or a solid tungsten end mill?
Im considering trying to put a 16mm hole or slot through some 8 or 10mm HSS bar.
Ive seen a 5/8 four flute end mill and also a 16 mm end mill with two fitted TC bits that can be replaced.
The 16mm two bit wold be the better size for me .

I did a bit of a search but only found one thing saying how careful he had to be with feed and speed . He was only using a 1/8 solid Tungsten bit though and it was on a CNC.

Thanks. Rob

I've never attempted milling HSS but drilling is no problem. Just a standard masonry bit with negative rake, high speed, coolant and with a bit of pressure. You need a backing piece to drill in to when going through the other side otherwise the drill will shatter.

About the hardest things I drill are chainsaw bars with the solid centre nose sprocket bearing material being easily as hard as HSS and I use the same method as Snapey's. A few years back while cleaning out deceased FIL's tools I came across a box of blunt masonry bits. A quick touch up on a diamond wheel and I have used these (and also shattered a few) ever since.

If you can get some unhardened HSS it should be possible.
To experiment with some small pieces, saw the soft chuck end off drill bits.

To re do my question a bit to get to what I want to understand .

Is HSS normally shaped drilled or milled with Tungsten ? That's the only option isn't it ?

I know its ground and cut with ceramic discs and stones but slots of 16mm wouldn't be done that way would they ?




Thanks for the answers . Masonry bits , Ive read that before. Will have to give it a try on a piece. I still may need a end mill though . I'm wanting to mount my own HSS knives on a spindle head that's on my tenoner . Ive got the proper old style square block head and the right dovetail nuts and bolts to hold them on . All of Wadkin manufacture.

Just drilling a hole for my knives means grinding the HSS knife to exact shape with equal projection for two blades per head. A milled slot means I have room for extra adjustment like was normally done . Either way will work.


Thinking more about the old knives Ive got or seen that were fitted to these heads from the 1950s or 1960s. They were not solid HSS, they are more like a hard tough steel body with either HSS silver soldered cutting edge or a hard tool steel soldered cutting edge of some type. Just because HSS was not available then in those sizes I think . These days the serrated heads handle the same size blades and projection from the head with HSS serrated back knives 8mm thick instead of the older 1/2 inch .

Rob

Carbide endmills come in many different grades, for different hardness of steels. Your general purpose off the shelf one will probably chew through HSS ok for a little while, but whether it finishes the cut is the question, only one way to find out. Depends on just how hard the HSS is, and the grade of carbide, and the runout in your spindle....

An indexable endmill using APKT or APMT inserts should get you there eventually, with some caution, but you might have to change the inserts a few times, depending on the length of cut. I have previously used a 2" facemill with normal inserts to true up some hardened vice jaws, it worked but was painful, and killed the tips.

If you have enough to do, might be worth buying a carbide endmill in a grade intended for 'hard milling'. Doubt you'll want to buy one at 16mm diameter though, 12mm is likely more affordable. They come in carbide, but you may now actually be able to get CBN based ones.

You can certainly get CBN inserts in many shapes - I have 5 Sumitomo CCMT inserts for the lathe I nabbed off eBay some years back for about $5 each. Absolute bargain, since unlike some CBN inserts they have two tips. Still on the first insert, one side I finally managed to break a chunk off, and the other side is a bit rounded off, but still absolutely rips off induction hardened and case hardened layers no worries, where regular CCMTs will only make it a short distance before completely losing their edge.

But whether CBN inserts are readily or affordably available in a milling insert for your regular Chinese indexable endmill, not so sure. Never looked.

Another option may be to drill holes at the end of the slots with a 16mm masonry drill as mentioned earlier (cheap and can be fairly easily sharpened), and join the 2 holes with the use of an air powered cutoff wheel, one of the 3" ones. Or AvE just did a video cutting through a bearing with a jewellers bandsaw that uses a diamond blade, might be some way to apply something like that?

I have tried to mill HSS with with good quality Garr solid carbide endmills a few times, but it wasn't hugely successful. Electric Discharge Machining (EDM) is normally used to machine features that cannot be ground in Hss.

OK , Thanks , seems its not the straight forward clear cut thing I was hoping for . At between roughly $70 to $150 a cutter its maybe not worth the risk . Trying the masonry bit out sounds good.

How about a 16mm diamond a hole saw ? Would that be a more certain way to get it done ?

https://www.ebay.com.au/itm/DIAMOND-...frcectupt=true

Rob

Originally Posted by Jekyll and Hyde

Or AvE just did a video cutting through a bearing with a jewellers bandsaw that uses a diamond blade, might be some way to apply something like that?

That could be good. I just ordered two of these to try .

https://www.ebay.com.au/itm/1pcs-Dia...MAAMXQxKxSHKPt

May even be able to elongate and go sideways a little as I'm going through to get a slot if I'm lucky.

Rob

I don't see the attraction of machining hardened HSS, when unhardened is available.
M2 Tool Steel | 1.3343 | HS-6-5-2C| SKH51 - QiLu Special Steel

I need roughly 75 to 100 mm long x 35 or 45 mm wide x 8 or 10 mm thick matched pairs of knives made up .
Never knew there was un hardened HSS . Thanks . Not sure it comes in my sizes .

My stuff , which is the only source of HSS I know of in these sizes is conming from Hong Kong at $22 a 200 mm length inc postage .
That’s the Attraction . Instead of me paying the local bloke $225 a pair to cut them for me then add gst and postage . I’m wanting to drill them myself . The shaping of the cutting edge is no problem. I do that all the time . It’s just that hole or slot .

As well
Each time I do a profile change I need two pairs of blades . One pair for each head . It’s a 5 head machine and the second pair of heads are the ones I need these blades for . They are a upper and lower vertical running spindle direct mounted on its own motor shaft .

Rob

Originally Posted by nadroj

I don't see the attraction of machining hardened HSS, when unhardened is available.
M2 Tool Steel | 1.3343 | HS-6-5-2C| SKH51 - QiLu Special Steel

Can't speak for the OP, but personally, I have neither a heat treat oven nor a surface grinder to fix up any warpage after heat treating. So I can see the attraction. Or are you offering a heat treat and finish grind service?

Originally Posted by auscab

Thinking more about the old knives Ive got or seen that were fitted to these heads from the 1950s or 1960s. They were not solid HSS, they are more like a hard tough steel body with either HSS silver soldered cutting edge or a hard tool steel soldered cutting edge of some type. Just because HSS was not available then in those sizes I think . These days the serrated heads handle the same size blades and projection from the head with HSS serrated back knives 8mm thick instead of the older 1/2 inch .
Rob

HSS is quite brittle and breaks easily, the likely reason for putting a tip on steel as stated above.
How much overhang and what speed are these blades moving at?
Some pics would be helpful...

Originally Posted by shedhappens

HSS is quite brittle and breaks easily, the likely reason for putting a tip on steel as stated above.
How much overhang and what speed are these blades moving at?
Some pics would be helpful...

No I don't agree with HSS being brittle and breaking easily at all . Its the industry standard projecting out of heads and cutting wood on spindle moulders . Has been for a long time. Projections of 25mm sticking out of a 122mm diameter head and up to 9000 rpm are done .

I wouldn't like to be using anything running at 9000 but it happens . My particular spindle is running at 2830 . The standard motor speed of the 3 phase motor that the head sits on , could be 2840 ? I dint record it when I read it yesteday . Direct , no belts or pulleys . Its slow .

My other spindle moulders using the same heads and projections are doing from 3 to 4000 RPM

Rob

Here is an answer to your original question based on something I did recently.

I wanted a somewhat accurate radius tool for the lathe.
Bought a piece of M2 HSS and a 10mm 2 flute carbide endmill from the same supplier via eBay. Based on price I have no reason to believe either were anything other than imported from China.
I set the tool blank up for the angles I wanted and plunged the endmill through one side of it in a couple of passes Until I had it on my mark up. Closest I can liken it for a descriptor was it was like machining a 316 type stainless. You can use M2 without heat treatment, it will just dull quicker. If you’re doing a production run, that may not work so well for you.
For funsies, I decided to set up another blank that I know is Australian made (Sutton) cobalt impregnated M42 tool steel. The carbide slot drill turned to toast upon looking at the Sutton blank.

Nothing empirical about it, I just tried something, got a result in one instance and a burnt out cutter in the other. If I have to make another accurate radius tool again, I will buy a piece of M2 and a carbide slot drill and do the same thing, except without the last bit that nuked the cutter.