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Milling HSS

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Vic22/01/2016 12:09:14
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I took note on another thread that someone said they'd turned HSS on their Lathe with carbide tooling. As I don't have a surface grinder I'm wondering if you can mill HSS with carbide tools? Occasionally it would be nice to be able to mill some small pieces of HSS to size but I don't want to risk any of my carbide tooling if someone else has tried this without success!

David Clark 122/01/2016 12:13:25
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I would not try this.

Vic22/01/2016 12:45:37
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It does sound like an expensive mistake waiting to happen hence the question. I'm still surprised someone even managed to turn some HSS. Having said that I did see some diamond inserts the other day at £18 each!

Michael Gilligan22/01/2016 12:52:09
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Vic,

I can't find it on-line, but I have seen a video by P. Thornton, which I believe showed their HSS horological cutters being turned with a carbide form-tool. ... surprise

MichaelG.

JasonB22/01/2016 13:09:34
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I Turned a HSS csk bit about 10 days ago as I needed one to go inside a 9mm hole and teh 3/8" one I had was too big.

It was one of Andrew Johnson's post where he mentioned he used solid carbide bits to machine HSS

Edited By JasonB on 22/01/2016 13:18:46

David Clark 122/01/2016 13:16:56
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I expect Thorntons turn their cutters before hardening. Diamond is usually for non ferrous.

Ady122/01/2016 14:01:13
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There seem to be tons of solid carbide end mills on a well known site

Edited By Ady1 on 22/01/2016 14:03:09

Muzzer22/01/2016 14:02:29
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You'd need to ensure enough surface speed. Recommended 10-100m/min, so for a 10mm cutter cutting at the periphery, that would be between 300 and 3000 rpm. Ideally you'd also have the correct grade for intermittent cutting of hardened steel but if you don't mind sacrificing a couple of inserts you will probably get the job done with a normal grade in the interests of science.

If it's small pieces, couldn't you just use a bench grinder with a guide fence?

Edited By Muzzer on 22/01/2016 14:03:04

Andrew Johnston22/01/2016 14:50:49
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Posted by JasonB on 22/01/2016 13:09:34:

It was one of Andrew Johnson's post where he mentioned he used solid carbide bits to machine HSS

Dunno who that guy is wink 2, but I do mill HSS toolbits to get the basic shape I want before final grinding. I normally use a 10mm uncoated carbide cutter. I run hard and fast. Spindle speed is 2000+rpm, DOC about 1mm and fairly fast feed by hand; probably around 3-400mm/min. You want the metal at the interface to be glowing orange and the chips to be coming off red hot. I use my older cutters as the process is pretty hard on them, but they do survive to rough out another day.

Andrew

Vic22/01/2016 16:01:20
2208 forum posts
11 photos

Thanks very much for all the helpful replies. I remember now milling some hardened steel with carbide on my mill some years ago and that was tough going so I may shy of trying it with HSS!

MyrtleLake22/01/2016 16:10:19
12 forum posts

I've done it with a solid, micrograin carbide end mill with TiAlN coating. SFM is way up there. The exact figure escapes me at the moment. Feed should be lightning fast by hand. This is limited, though, by the rigidity of the set-up. Increase feed until surface finish goes way down. I was using 0.20 mm DOC. The chips are a fine, fuzzy dust.

I was making a small slotting tool and wanted the angle to be accurate while retaining the clearance and back rake angles. In such a small tool, this would have been a challenge by hand. After milling, the facets were finished with a fine India stone.

 photo 38b890ee-a6fa-4b20-a671-06b3ba247408_zps2hezdk96.jpg

The tool started as a larger diameter HSS, round bit. M2. I would be more skeptical of trying this on one of the tougher HSS grades (cobalt alloy, T-15, etc.). The shank was turned down initially using a ceramic insert. This left a larger diameter portion on the end. That was then milled into the shape shown.

Edited By MyrtleLake on 22/01/2016 16:11:30

Edited By MyrtleLake on 22/01/2016 16:12:47

Edited By MyrtleLake on 22/01/2016 16:13:31

chris stephens22/01/2016 17:09:33
1045 forum posts
1 photos

Hi DC1, Why ever not? It is easily done using solid carbide end mills, and they are cheap enough from JB to not matter much if things go wrong.

As an aside, one of your predecessors in the ME editors chair has been known to do it, once told it was indeed possible. Another advocate of the practice is Oxtool on youtube, and his opinion is very highly regarded by those in the know. Give it a go, it can be quicker than grinding, especially for roughing shapes.

chriStephens

Roger Head22/01/2016 23:54:23
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"cheap enough from JB"

JB??

Roger

chris stephens23/01/2016 02:18:35
1045 forum posts
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Hi Roger, Sorry, i thought everybody knew JB Cutting, they go to all the shows and sell carbide tooling at reasonable prices.

chriStephens

Roger Head23/01/2016 12:36:29
209 forum posts
7 photos

Thanks Chris, I've found http://www.jbcuttingtools.com, but no solid carbide end mills. Do they operate another site?

Roger

chris stephens23/01/2016 14:50:57
1045 forum posts
1 photos

Hi Roger, I would expect an Email to them inquiring about solid carbide end mills might help. I suspect the reason for not having them on the web is that they are "surplus" stock and as such supply is moderately random. I only buy in person from their stand at shows, never online. They do travel the country going to all sorts of shows that have an engineering bent, last weekend Ally-Pally, today Kempton Autojumble, and shortly at Brighton Modelworld. Again an Email might reveal if they are appearing at a venue near you, if they are unwilling to sell online for some reason. My person favourite endmills are their "ripper" ones, they remove stock at a phenomenal rate (in steel, not HSS!).

Hope this helps

c

Roger Head23/01/2016 23:55:37
209 forum posts
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Ok, thanks Chris

Roger

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