By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Forum House Ad Zone

HSS and Carbide Milling mills

All Topics | Latest Posts

Search for:  in Thread Title in  
Alfie Peacock27/07/2017 02:42:43
55 forum posts
1 photos

I needed to cut a 25mm x 40mm x 12 thick rectangle in aluminium using a new 6mm 3 flute Carbide cutter. The noise it made was a screeching sound that came from the mill, I tried different directions and was only around 3mm depth, also at different speeds.

I then changed the milling cutter to a 6mm HSS 3 flute and it cut with no problem, both mills are sharp as they are new.

Why would a Carbide cut different to HSS on aluminium.

Also the collets and clamps where fixed so no play on the sx2p mill when cutting

russell27/07/2017 04:42:41
142 forum posts

is 'sharp' on HSS the same as 'sharp' on carbide? the load on the mill may be different.

I'd expect they have different co-efficient of friction, so the noise may well have been the swarf sliding (or not) over the clearance surfaces.

or not....

Jon Gibbs27/07/2017 09:11:12
750 forum posts

Hi Alfie,

What speed were you running the carbide end-mill compared to the HSS?

Carbide should be run faster (~3x) and worked harder than HSS.

HTH

Jon

SillyOldDuffer27/07/2017 11:02:07
10668 forum posts
2415 photos

Posted by Alfie Peacock on 27/07/2017 02:42:43:

...

Why would a Carbide cut different to HSS on aluminium.

...

I asked a related question recently about avoiding swarf ribbons. Andrew Johnston put me right by highlighting the importance of feed-rate. I'd twigged that carbide works best cutting 3 to 5 times faster than HSS, and that deep rather than shallow cuts are needed, but not that the rate of cut should be aggressive as well.

When you get carbide right, hot chips fly off. Reduce rpm, depth or cutting rate and you get ribbons. If you are too gentle, carbide rubs and chatters, which I think matches Alfie's description.

Alfie asked 'Why would a Carbide cut different to HSS on aluminium?'. I did some digging after Andrew's advice and found that the way metal is removed varies with speed.

  • Carbon tool steel cutters lose hardness at about 220C, which temperature is easily reached in a power tool. For that reason the maximum rate the Victorians were able to cut mild steel was about 35 feet per minute. At these very slow speeds, the tool's cutting action is that of a knife through wood, and the tool must be kept sharp.
  • Although HSS is mildly inferior to carbon steel in terms of edge and hardness, it stays hard up to about 650C. As such, HSS cutting rate is up to eight times better than carbon tool steel. At very high speed and deep cuts, a new cutting mechanism appears. Rather than the edge shearing at the point of contact, the tool acts as a wedge with the metal tearing just in front of the edge. This mode is said to need less energy than a cut, and it also means that more heat stays with the chip rather than overheating the tool. Unfortunately HSS isn't sufficiently heat resistant to cut in this way for long.
  • Carbide is much harder and temperature resistant than HSS. On the downside, it is comparatively brittle and it doesn't take a good edge. But, run hard and fast (3 to 5 times harder than HSS) it cuts using the wedging mechanism, where a blunt tool is an advantage, and this saves much time and energy, most important in a production environment.

So, Carbon Tool Steel, HSS, and Carbide aren't one-for-one replacements. They each have advantages and disadvantages. HSS is popular because it's a good compromise. It's sharp enough to get a good finish at slow speeds, and man enough to do serious work. Carbide has many advantages, but you have to use it right. Gently turning a small diameter on a slow lathe with a small motor isn't a sensible way to use carbide. Hacking into a large diameter spinning fast on a big motor, definitely is. There's room for experiment, for example, the sharp carbide inserts designed for Aluminium seem to work quite well on mild steel at slow speed.

I have Chinese tools. One advantage they have over older kit is high spindle speed. As a result a lot of the work I do sits on the border between 'HSS is best' and 'Carbide Today!' After much messing about I still find it hard to choose between them; this I think, is mostly down to inexperience. If forced to choose only one, I'd go for HSS. As it is I use Carbide more than half the time. That suits me, but proves nothing. So much depends on what you're doing.

Dave

 

Edited By SillyOldDuffer on 27/07/2017 11:04:03

Neil Lickfold27/07/2017 11:25:58
1025 forum posts
204 photos

Was your carbide cutter made for cutting Aluminium specifically, or is it a general carbide endmill? They are very different cutters and different geometries.

Neil

Alfie Peacock27/07/2017 12:50:44
55 forum posts
1 photos

Thanks for all these replies, as for the carbide cutter I have no idea what type it is. It seems that for me general use on a hobby mill its best to use HSS.

I.M. OUTAHERE28/07/2017 08:52:22
1468 forum posts
3 photos

Run it at double speed of,what you would with Hss and use WD-40 as a cutting fluid . Finish wont be great anyway so use the carbide as a rougher and switch to hss a better finish

WD40 is excellent for aluminium - one of its few usefull properties !

These days I only use carbide on cast iron or unknown materials as hss has a keener cutting edge and for home use it is better

Same goes for carbide lathe tools - run it fast and hard .

Bare in mind there are many varieties of aluminium and some are nice to machine some are not , try turning 6061 T6 after welding , it is like chewing gum !

Ian.

Neil Wyatt28/07/2017 09:53:13
avatar
19226 forum posts
749 photos
86 articles

I'll differ a bit, I have some 10mm carbide mills with very sharp edges designed for aluminium. Run at 1600 rpm they send swarf everywhere and leave a decent finish.

Neil

Danny M2Z28/07/2017 09:57:35
avatar
963 forum posts
2 photos

Why anybody would use carbide cutting tools on aluminium and its alloys in a home workshop with typical hobby equipment often makes me wonder what one is trying to achieve? Is this just convenience or just an easy way out from sharpening tools?

Maybe I am just a luddite, but a well honed HSS (or even carbon steel for a keener edge) tool is well suited to creating a fine finish on Al. work.

Easier to sharpen too!

* Danny M *

I.M. OUTAHERE28/07/2017 10:20:18
1468 forum posts
3 photos

Neil ,

I suspect you are talking about high helix cutters that some will not be aware of or experienced with - Now there is an article for MEW to discuss in the magazine in there somewhere !

Neil Lickfold28/07/2017 10:51:44
1025 forum posts
204 photos

Yeah, the carbide cutters for Aluminium and plastics , really are something quite new and fantastic. They work very well even at low speeds, and the surface finish is very good as well. They don't have to be run really fast , so can be run similar speeds to HSS with no ill effects. There are even some with fancy coatings that reduce the Al from welding or building up on the carbide edge. On soft steels like free machining MS, these cutters also work very well giving a great surface finish. Some companies that are specialising in this technology are DHF, A local company here in NZ https://www.carbidenz.co.nz/6mm-3-flute-carbide-aluminium-endmill.html have a great range. I like these 3 flute cutters, great as a compromise cutter, so can plunge, face and do sides. These work really well on plastics and copper as well.

Neil

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate