If the mill is dull it is rubbing not cutting. Something will get too hot real quick. On one of my first milling jobs, cutting a 1/4'' slot 1/4'' deep with a 1/4'' mill (another no-no) in tool steel with manual feed, she started off great but soon started to complain so I just cranked harder. Then the fireworks started. What a show! It seems that I did something wrong. That's why I'm here listening.
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Using End Mill For Side Milling
- Thread starter HBilly1022
- Start date
- Joined
- Dec 22, 2015
- Messages
- 561
I'm glad you posted this. I haven't tried cutting a slot with the mill yet but what you describe would have been exactly the way I would have approached the task. Although I will be milling mild steel mot tool steel, if that makes a difference. I guess I better research slot cutting before starting that project. So much to learn.
I haven't cut hundreds of slots, but my experience has shown me that for some reason, cutting a round slot (with a ball end mill) I seem to be able to cut faster and deeper (and quieter) than when cutting a square slot. Just the other day I machined a 5/16" round slot 5/16" deep, and it just went through nice and quiet, then reverse the direction so as to polish it up, and it looked like a mirror inside. I checked the depth and width and they were right on. It seems to me also that rather than just poke along, get the machine up to speed and do as much as it will do comfortably and quietly.
The slot had to be square on the bottom although I can understand how a ball end cutter would do a better job in some situations. It was a bad idea to use a regular 4 flute mill the same size as the slot. It was cutting on 180 deg. i.e.both sides of the slot at once. No much room for chips to get out of there. Apparently a smaller mill with two or more passes would have been a better way. I am going to get some roughing mills ...they look real mean and a cooling/lube system....they look real cool.
- Joined
- Jun 7, 2013
- Messages
- 10,089
You don't say anything about cutting speed or lubricant, and in general too light of a cut will tend to dull any cutter, For soft steel, cutting speed should not exceed about 100 ft. per minute, and lubricant is a necessity.
Hi,
Just joined the forum. This is my first post. I've read this entire post and haven't seen mentioned anywhere something that's important to understand regarding end mills. Unless a plunge cut is being made, the end of the mill is not doing any cutting. Only the circumference (side) of the mill is cutting. This is true whether a skim cut is being made to true the top of a work piece, whether milling a .250" step along an edge, or using the entire cutter length to square up an edge. Likewise, only the end of the cutter is cutting when a plunge cut is being made. This may seem common knowledge to many, but those new to milling will progress more quickly if they understand concepts.
Regarding this OP's question, I believe others have touched on the probable cause. Cutters, especially those of lower quality, are highly susceptible rapid dulling when forced and/or run too fast. Heat develops and causes loss of temper, which dulls the cutter. A dull cuter rubs rather than cutting, which generates more heat and the cycle repeats until the cutter rapidly becomes useless. It is important that speed and feed not be exceeded based on the material being worked and the type of cutter. Speeds and feeds are something that are covered extensively in Machinery's Handbook and probably can also be found online. Use of good cutting fluids/coolants is also recommended for many operations..
All is not lost for the end mill in the OP's post, as it sounds as if it can still be used up to the point where it dulled.
Hope some will find this helpful.
Lee
Just joined the forum. This is my first post. I've read this entire post and haven't seen mentioned anywhere something that's important to understand regarding end mills. Unless a plunge cut is being made, the end of the mill is not doing any cutting. Only the circumference (side) of the mill is cutting. This is true whether a skim cut is being made to true the top of a work piece, whether milling a .250" step along an edge, or using the entire cutter length to square up an edge. Likewise, only the end of the cutter is cutting when a plunge cut is being made. This may seem common knowledge to many, but those new to milling will progress more quickly if they understand concepts.
Regarding this OP's question, I believe others have touched on the probable cause. Cutters, especially those of lower quality, are highly susceptible rapid dulling when forced and/or run too fast. Heat develops and causes loss of temper, which dulls the cutter. A dull cuter rubs rather than cutting, which generates more heat and the cycle repeats until the cutter rapidly becomes useless. It is important that speed and feed not be exceeded based on the material being worked and the type of cutter. Speeds and feeds are something that are covered extensively in Machinery's Handbook and probably can also be found online. Use of good cutting fluids/coolants is also recommended for many operations..
All is not lost for the end mill in the OP's post, as it sounds as if it can still be used up to the point where it dulled.
Hope some will find this helpful.
Lee
- Joined
- Nov 16, 2014
- Messages
- 27
One other thing to consider is the material being machined, you mentioned that you use scrap for your projects, so I assume that you don't know exactly what it is. I'm not an expert on steel but it is my understanding that most of the hot roll stuff that comes from across the water is a mixture of a little of everything, "hard, soft, various carbon and alloy contents" so you really don't know what you are getting. My experience with some of this stuff is that I will be merrily cutting along and suddenly everything goes to crap, like I just hit a ball bearing or something (usually ruins the cutter too). When considering the cost of quality cutters these days, might be penny wise and pound foolish to use good quality cutters on cheap scrap of undetermined content and quality, just a thought? Good luck and keep your enthusiasm.
- Joined
- Dec 22, 2015
- Messages
- 561
Good point Chuck. I'm not sure I want to use any good quality mill ends just yet. I'd rather screw up cheap ones while I'm learning, especially since I don't know of any sharpening services nearby. I get your point about the better ones being more resistant to wear and abuse though. I'm in the process of making an adapter to use my little air grinder for sharpening the ends of mill ends on the lathe. If it works then I should be ok with the cheap ones for a while. I tried using the 3" facing mill that came with the mill and really like it. The only thing is I chipped 2 of the 4 carbide tips and it doesn't cut well any more. I've tried sharpening them but no success yet. I replaced them with some HSS bits that I ground myself and they work fine for aluminum but so great for mild steel. I'll just keep at it until I figure it out or I'll be back here asking for more help.
It's good to know there is always help available from the forum members.
It's good to know there is always help available from the forum members.
- Joined
- Dec 22, 2015
- Messages
- 561
Sorry for the late reply, I must have skipped past your post. I haven't been using any lube up to now but in the last couple of days I have tried cutting fluid that I use on my bandsaw but didn't see any benefit from that on mild steel. Probably the wrong stuff.
My cutting speed is based on 90 fpm surface cutting speed for HSS on mild steel and 2 x that for carbide. I made up a spreadsheet for the various diameters and materials I plan on using and have it posted next to the mill.