Author Topic: Carbide milling cutters  (Read 697 times)

Offline AVTUR

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Carbide milling cutters
« on: August 17, 2019, 08:03:19 PM »
I am sure that the below has been asked and already answered but I cannot find any such posting.

I need to cut some slots in mild steel, 3/64” wide, 3/16” long and up to 1/4” deep (both slides of slot open). I have been told of and found firms that can supply suitable slot drills (both 3/64” and 1,2mm) but they are all carbide. I have no experience of carbide tools and what I have read fills me with some trepidation.

I know that carbide is harder and more brittle than HSS and is used at higher speeds. My milling machine has a top speed of 3,000 rpm. I have no idea if this is fast enough. What happens if it is not? What sort of table feed speed should I be using? Should I be using a cutting fluid? The only fluid I have is Morris’s CORA B neat cutting oil. Should I start the cut from a pre-drilled hole?

I realise that I should not take any answer as gospel and I must do some trials but any information would be useful.

There is no such thing as a stupid question.

Online sco

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Re: Carbide milling cutters
« Reply #1 on: August 17, 2019, 08:21:33 PM »
They are more brittle than HSS but stay sharp for much longer.  Probably most of what you have read is based on use in a production environment, I've found in a hobby shop they work just fine and don't need any particular extra care.

Ars longa, vita brevis.

Offline Admiral_dk

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Re: Carbide milling cutters
« Reply #2 on: August 17, 2019, 10:25:57 PM »
I have used both HSS and Carbide at max 2500-3000 RPM and around 20000-30000 RPM, and to me tha biggest difference is nicer holes and smaller risk of breaking the bit at higher speed. The more polished the surface before touching with the drill the smaller likelihood of wandering.

Offline Steamer5

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Re: Carbide milling cutters
« Reply #3 on: August 18, 2019, 02:56:22 AM »
Hi Avtur,
 On another forum, one of the guys uses carbide PCB milling cutters brought from EBay. He does great work with them, best of all they are cheep!

Cheers Kerrin
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Online kvom

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Re: Carbide milling cutters
« Reply #4 on: August 18, 2019, 04:07:53 AM »
With the data given, a DOC of .01 and 2 ipm feed is a safe place to start.  If more than 2 flutes, increase feed.

Offline Jasonb

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Re: Carbide milling cutters
« Reply #5 on: August 18, 2019, 07:18:13 AM »
For slots like that I tend to drill out most of the waste and then use a series of plunge cuts with the milling cutter stepping over say 0.2mm each time then do some final clean up passes along the slot as it puts a lot less side load on the delicate cutters.

Chip clearing will be more important that cooling/lubrication so if you have air use that instead of oil/coolant, this is another reason for drilling first as it reduces milling swarf and you have holes for any that is made to drop out of rather than sitting in a deep narrow slot. If you don't have air then duct tape a small tube to the end of a vacuum cleaner hose and use that to suck rather than blow.

Offline john mills

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Re: Carbide milling cutters
« Reply #6 on: August 18, 2019, 11:40:41 AM »
I agree  with jason plunge cuts take the side load off  and so are good to remove the bulk of the metal.
the use of air is good too  the oil or coolant requires lots of pressure to get the fluid to the cutting edge .
The cutters at the speeds you can use will be quite happy and won't get to hot if the chips clear.The carbide cutters give nice straight sides and good finish and last longer than his.