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View Full Version : Salvaging 25mm end mill



taydin
02-14-2010, 04:40 PM
I had recently bought a decent quality 25mm HSS end mill. My intention was to use this end mill for surface machining.

When I was working with the chinese vise on the milling machine, I noticed that the vise ways were not parallel to the vise bottom. The error was 0.15 millimeter. Being a newbie, I installed the 25 mm end mill into the milling machine and started machining the vise ways. I used about 1400 RPM and the slowest feed rate. The depth of cut was very little, maybe less than 0.1 mm.

But pretty soon, smoke started to emerge from the end mill. I stopped the machine and removed the end mill. The vise ways had a horribly marred surface and the cutting tips of the end mill were all dark. I later found out that the vise ways were hardened and only a surface grinder would be able to correct the out of parallel ways.

I found a surface grinder shop and had the ways and the jaws of the vise fixed. But what about the end mill? Can it somehow be salvaged? I paid about 50$ for it, so I really can't throw it out. The side cutters are still in good shape and very sharp, but the bottom cutters are busted.

beanbag
02-14-2010, 04:57 PM
end mills can be resharpened by a shop with the right jig. Around here, it would cost about $12 (SF bay area) but probably less elsewhere.

A carbide end mill would have been able to cut the vise

taydin
02-14-2010, 05:05 PM
end mills can be resharpened by a shop with the right jig. Around here, it would cost about $12 (SF bay area) but probably less elsewhere.

A carbide end mill would have been able to cut the vise

But I think the problem with the end cutters isn't just dullness. Because of the excess heat, wouldn't they have lost their temper? If this is the case, then it could be sharpened, but it would not be HSS anymore, but a weaker steel, no?

John Stevenson
02-14-2010, 05:09 PM
Somebody will be along shortly and tell you where to get it re-sharpened, it's well worth doing for a cutter of this size but it would help if you had your location in your profile.

No good me suggesting anywhere as I'm in the UK.

.

chrisfournier
02-14-2010, 05:11 PM
Your end mill will be fine once sharpened.

lane
02-14-2010, 05:13 PM
To bad you want let people know where you are. If you were to be next door I would say bring it over and I would sharpen it for you.

MrSleepy
02-14-2010, 05:18 PM
it should be okay once you have ground it back..
Even if you had wrecked the tip,broke tip end flutes etc...the end mill can be reclaimed by cutting off the damaged end and resharpening..

Rob

taydin
02-14-2010, 05:23 PM
Thanks guys. Now off to search for a sharpening shop :)

(PS: Just fixed my profile. I am located in Gebze, Turkey ...)

strokersix
02-14-2010, 05:27 PM
1400 rpm is a bit much for a 25mm HSS endmill. Should run it more like 200 rpm.

oldtiffie
02-14-2010, 05:32 PM
taydin.

If in doubt about the "cutability" of a job, try to file it (old files are OK). If its too hard for a file its too hard for a cutter. Its a job for the grinder then.

Does the shop that did your surface grinding work have a tool and cutter grinder service? If not ask them or a local shop where they get their end milling cutters sharpened and at what cost.

psomero
02-14-2010, 08:15 PM
yeah, i'd try asking the grinding shop that did your vise if they could do the endmill or had any suggestions on where to look...

Black_Moons
02-15-2010, 01:04 AM
taydin: Simple equasion that will save future cutters:
SFM = RPM * Diamiter * PI / 12
(the /12 is to bring the diamiter from inchs to feet)

HSS vs aluminum: Typical 200sfm max
HSS vs Mild steel: Typicaly 100sfm max
HSS vs Tool steels: Typicaly 40~60sfm max
HSS vs hardened steel ways: well ok your gonna lose reguardless sorry for wasting this post... :P

Less SFM is OK, but more will greatly reduce tool life.

25mm = 1", so SFM = 366 at 1" diamiter at 1400RPM. Really.. really high.

So, todays lesson is:
Your RPM was too high for the cutter to surive in anything much harder then plastic.

Your Material to be milled was too hard for the cutter to surive it period. (Other post about file test is A+, if a file won't dent it, neither will an endmill! Same for a center punch. Note things can be hard on one surface and soft on other surfaces, or hard just to the depth of a few mils.

Carbide may be able to do hard steels, but generaly things like ways are a job for a surface grinder and an experianced operator, theres a vise rebuild thread around here somewhere.. someone compleatly reground some chinese import to high precision... basicly had to grind every last surface of it as it had warped since its initial grinding.

Theres some really special inserts for doing REALLY hard steels, and these can withstand insane SFM (thousands!), but then you need a machine that can achive those speeds!

Mystery metal is not your friend. Identification and math are.

Scishopguy
02-15-2010, 02:42 PM
Several posters were asking Taydin where he was. His location appeared clearly in his profile as Gabese, Turkey. Is something wrong with the software or is my crystal ball just working overtime?!

wait...Someone from New York will have a smart ass answer in a minute I am sure.:D

Carld
02-15-2010, 03:04 PM
He updated his profile in the middle of the thread and when you do that it modifies all your past posts and threads to show the new profile. ;) Oh, and I am not from NY or NJ or anywhere East.

Scishopguy
02-15-2010, 03:28 PM
He updated his profile in the middle of the thread and when you do that it modifies all your past posts and threads to show the new profile. ;) Oh, and I am not from NY or NJ or anywhere East.

THanks Carl, I forgot that the software does not automatically update. No, wasn't you that I was poking fun at, it was Doozer. He generally has some coment that adds the "rectal intellectual" jab. :D