What brand is your mill? Can you post pictures? I recommend you find out why your spindle is getting hot and fix it. It could be just a bearing preload adjustment or worst case the bearings need replacing. My 2 cents.
Tom S.
-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
Best Practice: Roughing Bits
- Thread starter Metal
- Start date
What brand is your mill? Can you post pictures? I recommend you find out why your spindle is getting hot and fix it. It could be just a bearing preload adjustment or worst case the bearings need replacing. My 2 cents.
Tom S.
It is one of these guys: http://freemansgarage.com/blog/wp-content/uploads/2010/02/mill311.jpg
The motor is not original (the mill is 50+ years old!) and is from a tablesaw apparently, I have found the manual, and the highest rpm setting is 2100, which it performs fine at. (IIRC when I got my tachometer to work I was right around 2k at the pulley setting i'm currently working at)
At the highest setting the tachometer no longer wants to work at all, but it sure sounds quite a bit faster.
The motor is not original (the mill is 50+ years old!) and is from a tablesaw apparently, I have found the manual, and the highest rpm setting is 2100, which it performs fine at. (IIRC when I got my tachometer to work I was right around 2k at the pulley setting i'm currently working at)
At the highest setting the tachometer no longer wants to work at all, but it sure sounds quite a bit faster.
Running at the fastest rated speed your bearings do not run hot but when you go above 2100 rpm they get hot. Am I understanding correctly?
Getting back to your original post and having a better understanding of your mill you will be limited on the size of cutter you can effectively use. Again, it's experimenting and practicing that will lead you to a logical conclusion.
Tom S.
- Joined
- Dec 20, 2012
- Messages
- 9,422
I would go with a fine pitch HSS roughing end mill as large and as short as is appropriate for your job. It will perform well at the speeds your mill can attain. I suggest the fine pitch tool to keep down chatter in aluminum and WD-40 will do fine for a cutting fluid. Roughers usually create a lot of chips and clearing them periodically helps so the vacuum suggested above works well.
I normally take a full depth of cut with this tool and slow the speed appropriately. You will have to sort out what feeds to use and listening to and feeling your machine will tell you when its right.
I normally take a full depth of cut with this tool and slow the speed appropriately. You will have to sort out what feeds to use and listening to and feeling your machine will tell you when its right.
Sorry yeah
In the manual it states the highest speed is 2100, obviously the motor I have is faster than that since I clocked it in at ~2000 at about half way through the pulley range, any higher than 2k and it heats up.
when I say the spindle heats up, I mean just the spindle, the bit seems okay, the collet is hot but not burning, the drawbar is much warmer than normal, the area where the collet interacts is too hot to touch after a few minutes, ect. It appears the heat is coming from the lower spindle bearing just above the collet holder since the upper portion of the spindle is "fine" not really hot at all. the bearing could be overloaded but I am a little timid in taking a hammer to the spindle to try and get the shaft out of those bearings since when I was refurbing the mill to begin with I wrecked those seals and had to replace them. (its been plenty of hours and they are obviously broken in)
Also one other question: when using cutting oil (I occasionally use some cutting oil if a particular part of a cut causes more vibration than i'd like due to the backlash in the table) is ot normal for it to burn off when cutting? on youtube I generally dont see slightly smoking chips go flying but it would be hard to detect anyway. I could also be using inappropriate cutting fluid.
Also new part!
http://img.photobucket.com/albums/v684/GRSL/2_zpscmbvtaow.jpg
I like the new part! What is it?
The bottom bearing carries the most load so will get hotter than the top bearing. If your spindle doesn't get too hot at the max rated speed then I wouldn't worry about it. Unless of course you want to run at a higher speed.
Cutting oil will smoke if the chips are hot. That's a normal reaction between the oil and induced heat from the chips. You can try different cutting oils or fluids to see which one gives off less smoke. Or you can look up "No Fog Mister" on this forum. I built one for my manual mill drill. It doesn't cost a lot to make and works great.
Tom S.
Its part of the frame of a robot I'm building. http://img.photobucket.com/albums/v684/GRSL/ruin2cad2_zpsixgboamc.jpg
I might have gotten a little carried away with this whole milling thing
I might have gotten a little carried away with this whole milling thing
- Joined
- Oct 3, 2015
- Messages
- 983
I have a bench top mill similar to yours, and notice the same problem at top speeds. I replaced the spindle bearings about 8 years ago and found they are the angular roller type and are only rated at those lower speeds, so there's not much you can do to them to eliminate the heat. On extended jobs when running at top speed, I directed a jet of compressed air to the spindle to help with the heat. It still got a little warm, but not as much as it did before.
Using a solid carbide end mill will lead to less chatter because of the stiffer shank. Rigging up a solid mount for a shop vac nozzle close to the cutter will create constant airflow and pick up chips. A periodic shot of WD40 will keep the cutter clean and prevent chip weld.
Using a solid carbide end mill will lead to less chatter because of the stiffer shank. Rigging up a solid mount for a shop vac nozzle close to the cutter will create constant airflow and pick up chips. A periodic shot of WD40 will keep the cutter clean and prevent chip weld.