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poor end mill life

Gard

Aluminum
Joined
Mar 18, 2016
I have a Clausing mill cutting what seems to be a fairly mild steel, it files and cuts with a hacksaw easily but I do not have a hardness tester. This is a simple one of a kind weldment, depth of cut was 0.1", 1/2" end mill at 600 RPM dry manual feed. The new end mill seemed to cut well until I got to the welded area then suddenly got dull about as the width of cut went from 1/8" to full 1/2". The end mill was brand new double ended 4 flute uncoated HSS Hertel. It seemed like a great price $18.99 for double ended end mil from MSC, WW41117607. I thought Hertel was a good name, these were made in Korea. The end mills seem to have a fairly sharp corner.

So what should I do differently?
Thanks

KIMG1228.jpg
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
Well...you're learning that cutting welds is often a miserable pursuit.

They are generally harder, less even, and show more variation in cut-ability.

The first thing to do would be buy a carbide end mill. Then, show it love and attention by giving it lube/coolant and not trying to take huge cuts. Then, accept you might chew up some end mills in the process, no matter what you do.
 

Gard

Aluminum
Joined
Mar 18, 2016
The weld area is soft enough that I can cut it with a file but I understand there could be inclusions that cause the problem. That was one of my thoughts.
I have read in some places that carbide end mills are not well suited to these older smaller milling machines but I do have one to try.
I have tried some oils as cutting fluids but seems to often get a lot of smoke which the wife complains about. Any suggestion of a type to try? Is cutting fluid more important for carbide?
 

Joe Gwinn

Stainless
Joined
Nov 22, 2009
Location
Boston, MA area
The weld area is soft enough that I can cut it with a file but I understand there could be inclusions that cause the problem. That was one of my thoughts.

The chilled (and thus hard) areas may be under the surface, near to the un-melted region.

One solution is to heat treat the entire article after welding.


I have read in some places that carbide end mills are not well suited to these older smaller milling machines but I do have one to try.

Carbide works fine on older machine tools, like my Millrite MVI. I run both HSS and Carbide as needed.

What model of Clausing mill are you using? I assume that it is of roughly the same technology level as my MVI.


I have tried some oils as cutting fluids but seems to often get a lot of smoke which the wife complains about. Any suggestion of a type to try? Is cutting fluid more important for carbide?

It sure sounds like you are spinning the mill too fast, taking too big a cut, and/or using too little coolant. Water soluble cutting oils, like Rustlick WS-5050 (which I use), yield far less odor even when the cutter is boiling the coolant. Probably because the temperature is far lower than with oil.


 
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Spruewell

Hot Rolled
Joined
Sep 8, 2015
Location
Northern California
The part appears to be pretty simple. You might consider abandoning the weldment and machining it from solid bar stock. You may find the trade-off in time and materials to be more cost effective. Not to mention it will result in a stronger, better looking product.
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
All good advice in the posts above.

One other help can be to chamfer the points of the endmill. Dead sharp points are very subject to chipping because they have little strength and, because they have practically no mass, overheating. I almost never run endmills without first using a fine diamond file and chamfering the corners establishing a perhaps 15 to 30 thou 45 degree land. It toughens the mill a good deal. You do not have to be super precise. I put on 5 diopter magnifier and put the mill in a vise cutting-end-up with good light. 5 strokes on each corner will pretty much do the trick.

I also run carbide rather than HSS. Cutting oil makes the job of the endmill a little easier. Experience will teach you what you can get away with.

Denis
 

Gordon Heaton

Stainless
Joined
Feb 19, 2007
Location
St. George, Utah
I use the WS-5050 mentioned by Joe Gwinn. The cooling properties are excellent, and if you apply it with an air mix (not a fine mist, but a coarse sputter) it will keep the tool cool, there will be no smoke (a bit of steam at worst) and your wife will probably not notice. Oil will smoke unless you flood it on and that makes a mell of a hess on a manual machine.
 

D Nelson

Stainless
Joined
Jan 7, 2015
Location
Missouri Ida
I’m out of town setting up a new job. When I get home I have a ton of hss Endmills I will get some pics they will be cheap and you can learn on them
Don


Sent from my iPhone using Tapatalk Pro
 

Gard

Aluminum
Joined
Mar 18, 2016
I have a clausing 8520, its 3/4 hp knee mill overall in pretty good shape, probably about 60 years old. Good to hear carbide is a good choice for this machine but they are sure pricey. I used up a box of old new stock HSS bits I got at a good price, now I need to start buying more. Always looking for a good deal, I use the 1/2 more than all others combined, any recommendations on what brand and style of carbide end mill for a small manual machine?


I think I have a tendency to keep using the milling bits a little too long, I should throw them in the dull bit box sooner. I guess looking at them with a loupe and good light as well as judging temperature from color of the chips and amount of smoke? I will order some of the rustlick WS5050

From what I have read, 1 1/2" bit at 600 rpm should be about right for mild steel but I will run it slower if I am cutting thru welds again. I can see how welding can result in small areas that are much harder, probably depending u depending on the base metal, welding rod and technique. Heat treating after welding is a good idea. A lot of my repair work seems to involve machining weldments or areas of built up weld. Its a good idea to always be thinking about other options

I do use this mill more for aluminum than steel, I think these HSS bits will work well for that.

I had wondered if a slight radius or chamfer on the cutting tip would help with life, it certainty does with HSS bits on the lathe. In this case I can see that sides of the end mill have been dulled a little also. It is sort of visible in the photo. I will try the chamfer.
 

Gordon Heaton

Stainless
Joined
Feb 19, 2007
Location
St. George, Utah
. . .From what I have read, 1 1/2" bit at 600 rpm should be about right . . .

I'd not run a 1 1/2" endmill at 600rpm dry and expect it to last. I read your OP as a 1/2" cutter. Remember to dilute the Rustlik. I use a strong mix of 16 parts water to 1 part coolant. It will not work all that well if you intend to brush it on, at the least you need to be constantly spritzing with a spray bottle.
 

52 Ford

Stainless
Joined
May 20, 2021
Not 1-1/2" end mill. It's a 1/2" end mill (12.7mm). I looked up the part number.
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
Unless you are operating your mill in the bedroom, your wife has no business complaining about the smoke. Look her in the eye and simply say those four words every woman needs to hear from time to time - 'less bitchin', more kitchen...'
 

guythatbrews

Cast Iron
Joined
Dec 14, 2017
Location
MO, USA
Another issue is you might have slag pockets. Slag can be glass hard and destroy an end mill instantly.

If the weld looks nasty it likely is. May be nasty even if it looks good. Stick or flux core is suspect. Inclusions are bad. Carbide will help.

You can always slow down the HSS end mill. Try 30 sfm/230rpm. One part going a bit slower no big deal. Always a good idea if you are unsure of weld and material.

The weld/material may be fileable but still moderately hard. If the mystery metal is alloy steel the affected zone could be hard enough to work HSS endmill over at 80 sfm.

I find it hard to get an idea of hardness with the file test. Soft, medium, and file hard at best. Try using a center punch to estimate hardness. Compare a small punch mark between a known control piece and workpiece, obviously doing best you can to be consistent.

Cutting fluid always better. Sometimes stinky for sure. In a pinch you can use soapy water but it will rust stuff.

I save some junky endmills for this sort of thing. Finish with a good endmill.

Good luck and good milling.
 

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
Another issue is you might have slag pockets. Slag can be glass hard and destroy an end mill instantly.

I didn’t even think about slag as I TIG small parts 99% of the time. No end mill is going to do well in slag that is trapped in a weld. But, a chamfered one will do a lot better than one without a radius or chamfer. In my shop, for a welded part of that size that had slag, after removing slag as much as possible, I’d belt grind it close to size and finish with a generously chamfered older carbide end mill taking light passes at relatively slow RPM.

Denis
 

Gard

Aluminum
Joined
Mar 18, 2016
Unless you are operating your mill in the bedroom, your wife has no business complaining about the smoke. Look her in the eye and simply say those four words every woman needs to hear from time to time - 'less bitchin', more kitchen...'

LOL I do not think I will use those exact words. The shop is in the basement and the only time I get grief is when she comes down to get something out of the freezer or root cellar. To be honest there have been a couple of times when the smoke from the oil is probably not very healthy. In the future I will change the cutter, slow down the speed and get some of the rustlick WS 5050. Looks like the smallest amount I can buy is 1 gal, that will last me the rest of my life plus some. Sometimes I don't even notice the smoke in the room until I look up from what I am doing, I kind of like the smell.

Sorry about the typo, it is 0.5" cutter at 600 RPM, I would never try a 1.5" cutter on steel at that RPM.

In the original photo, I started the cut on the left side, about 1/8 thick steel. You can see a flux inclusion where that bar was welded to the shaft section. In hindsight, the bit worked very well on the first section then suddenly went dull about where it hit that inclusion it was also about where it went from cutting 1/8" wide to the full 1/2" wide so that seemed the cause at the time.

Most of what I do is one of a kind tools or repair work, speed is not a top priority.

I have often wondered about a way to measure hardness of steel, are there any small simple tools for this? I was also thinking of using a spring loaded center punch then trying to measure the diameter or depth of the divot and comparing that to some known samples. Perhaps a 0.0001" indicator with a pointed tip. I am sure there must be someplace I can get some known steel samples.
 








 
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