I have a couple small high speed milling machines. They are not ever going to be able to handle a heavy cut with a 1/2 inch end mill, but being able to use one for some jobs pushing the work envelope of the machine would be very useful. "Stub" length are still 2-1/2 inches long which means they are heavy. I won't being using much of the flutes. No more than 0.015-0.020 DOC. A tool with a 1/4 inch flute and a total length of 1-1/2 to 2 would be more ideally suited to the application. Just long enough to fully engage the ER20 collet and leave 1/2 inch (+/-) stickout would be ideal. I've been looking and just not found anything.
Custom made is to expensive (for me) I think.
Cutting down the shank is possible. I have a diamond cut off wheel for my TC grinder, but these are high RPM machines. Typically I spin 24,000 rpm. For this operation I'm looking at testing at 8,000 to 10,000 rpm. I'll need to see where my spindle still has enough power to make the cut. Anyway, that's still pretty darn fast. I'm concerned about balance if I just shorten one.
I have a couple small high speed milling machines. They are not ever going to be able to handle a heavy cut with a 1/2 inch end mill, but being able to use one for some jobs pushing the work envelope of the machine would be very useful. "Stub" length are still 2-1/2 inches long which means they are heavy. I won't being using much of the flutes. No more than 0.015-0.020 DOC. A tool with a 1/4 inch flute and a total length of 1-1/2 to 2 would be more ideally suited to the application. Just long enough to fully engage the ER20 collet and leave 1/2 inch (+/-) stickout would be ideal. I've been looking and just not found anything.
Custom made is to expensive (for me) I think.
Cutting down the shank is possible. I have a diamond cut off wheel for my TC grinder, but these are high RPM machines. Typically I spin 24,000 rpm. For this operation I'm looking at testing at 8,000 to 10,000 rpm. I'll need to see where my spindle still has enough power to make the cut. Anyway, that's still pretty darn fast. I'm concerned about balance if I just shorten one.
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If the cut is square the balance shouldn't change. Can you rotate the endmill while cutting it, or afterwards, to square the end?
Oh, yeah. I would spin it in the 5C tool holder on the TC grinder and just slowly advance into the diamond wheel. I would probably grind a small chamfer on it as well the same way, but at a different angle. I just wasn't sure how good I could do it. At high RPMs even a small imbalance can be an issue. More so on a larger diameter tool. Most days I don't run anything larger than 1/4 inch in those spindles.
I have cut the chowdered tips off end mills before so I could still use them for side milling. It works decently, but I'm topping those out usually at 3000-5000 RPM. I can run a fly cutter at 3000 RPM, but the faster you spin the more affect there is from an imbalance.
Most of the tools I have made on the TC grinder are pretty simple single lip cutters run at modest RPM.
A lot of times I just try things like this and see, but these little quick change ISO20 spindles are a little more expensive than your average Chinese import high speed spindle. Worth it for the time they save me, but not super cheap.
Oh, yeah. I would spin it in the 5C tool holder on the TC grinder and just slowly advance into the diamond wheel. I would probably grind a small chamfer on it as well the same way, but at a different angle. I just wasn't sure how good I could do it. At high RPMs even a small imbalance can be an issue. More so on a larger diameter tool. Most days I don't run anything larger than 1/4 inch in those spindles.
I have cut the chowdered tips off end mills before so I could still use them for side milling. It works decently, but I'm topping those out usually at 3000-5000 RPM. I can run a fly cutter at 3000 RPM, but the faster you spin the more affect there is from an imbalance.
Most of the tools I have made on the TC grinder are pretty simple single lip cutters run at modest RPM.
A lot of times I just try things like this and see, but these little quick change ISO20 spindles are a little more expensive than your average Chinese import high speed spindle. Worth it for the time they save me, but not super cheap.
Bob La Londe CNC Molds N Stuff
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You could measure the squareness of the end after cutting, and maybe correct any runout.
I recently squared the spindle flange seating surface of a cast iron chuck backplate according to Tony Griffith's procedure on LATHES.CO.UK, using the tailstock, centers and a mandrel to remove any axial play in the spindle while taking the very light final cut.
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That could let you grind the outer portion of the end true, then true what's left in the center by running the endmill reversed in the mill against a diamond lap.
I came up with a different procedure to locate the mounting bolt holes. I removed the top jaws and extended the lower jaws beyond the chuck body to provide clamping surfaces. A tap screwed into one lathe chuck mounting hole centered it under the mill's drill chuck, then table clamps on the extended jaws locked the lathe chuck in position. Each backplate hole was drilled with minimum clearance (M8 cap screw, 5/16" stub drill) at that location, then bolted at another hole. Then the holes were counterbored for the heads the same way. I didn't have to increase the hole clearance.
Since the drill bit stopped short of the chuck body a little flash was left at the end of the holes, but a hand held drill bit and countersink easily removed it. On other jobs I've used a step drill as a piloted countersink. jsw
Well, when I accidentally spun a Sharpie marker up to 24,000 rpm I knew there was a problem seconds before it exploded, but I still wasn't able to hit the e-stop button until after I felt bits of ink and marker hit me in the face.
Ok, I have an approximation of one lower speed power limit now for the spindles. I tested the 1/2 inch 2 flute mill at 10600 RPM and was able to slot almost as fast as I could turn the pendant knob. Around 100-120 IPM. At .05 inches deep it ripped through like it was nothing in
6061-T6511. At .13 it bogged down. This gives me a feel now of available horsepower at lower RPMs with these high speed 2 pole motors. I've always been afraid of running these spindles at the lower end of their RPM range. That's either 8000 or 6000 depending on which reseller you believe.
If I have the math right that tells me I still have safely over half horsepower available down as low as 10K. That's a lot more than I expected.
These are 1.8KW (nominally about 2.25-2.4 HP depending on which guesstimate you use) spindles, but I only ever figured they could produce it at RPMs where I couldn't use it anyway. I do spin them at
1500 RPM with edge finders, but that is virtually zero horsepower to spin a wiggler.
To test I ran it with the doors open and no coolant so I could see and hear the cut. These chips come off fast and hot. Pretty darn hot for aluminum anyway.
I'd still like to find a mill that's a half inch shorter with a half inch shorter flutes, but I'm comfortable running these now for the job they are intended.
The nice thing about aluminum is if you run coolant you can get away with all kinds of less than perfect speeds and feeds so this is as good as I need to dial it in for now. (Actually you can get away with a lot with some steels too, if you run a quality end mill with a quality coating, and an air blast.)
Ok, I have an approximation of one lower speed power limit now for the spindles. I tested the 1/2 inch 2 flute mill at 10600 RPM and was able to slot almost as fast as I could turn the pendant knob. Around 100-120 IPM. At .05 inches deep it ripped through like it was nothing in
6061-T6511. At .13 it bogged down. This gives me a feel now of available horsepower at lower RPMs with these high speed 2 pole motors. I've always been afraid of running these spindles at the lower end of their RPM range. That's either 8000 or 6000 depending on which reseller you believe.
If I have the math right that tells me I still have safely over half horsepower available down as low as 10K. That's a lot more than I expected.
These are 1.8KW (nominally about 2.25-2.4 HP depending on which guesstimate you use) spindles, but I only ever figured they could produce it at RPMs where I couldn't use it anyway. I do spin them at
1500 RPM with edge finders, but that is virtually zero horsepower to spin a wiggler.
To test I ran it with the doors open and no coolant so I could see and hear the cut. These chips come off fast and hot. Pretty darn hot for aluminum anyway.
I'd still like to find a mill that's a half inch shorter with a half inch shorter flutes, but I'm comfortable running these now for the job they are intended.
The nice thing about aluminum is if you run coolant you can get away with all kinds of less than perfect speeds and feeds so this is as good as I need to dial it in for now. (Actually you can get away with a lot with some steels too, if you run a quality end mill with a quality coating, and an air blast.)
Bob La Londe CNC Molds N Stuff
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We are exploring nearly the same question under very different conditions. After regrinding the HSS bit I worked up to 0.100" depth of cut at ~0.2 IPM manual feed (axially) in a cast iron backplate for a 5" chuck. Might as well get all the CI projects done before thoroughly cleaning the lathe.
https://shane.engineer/blog/measuring-mill-power-speed-and-torqueI like the Wattmeter idea, not so much the brake. The $16 PZEM-061 Wattmeter with a 100A current transformer can be added to the line side of a power supply to show instantaneous and totaled power consumption. 1 HP = 0.7457 KW. jsw
If I'm bragging I use 750 as a quick tool. If I am really pushing limits I use 800 to make sure I am accounting for overhead inefficiency and slippage. If I am using a low price multi label Chinese motor I assume they calculated watts using peak current at stall without accounting for voltage drop and divided by 700 for horsepower.
If I'm bragging I use 750 as a quick tool. If I am really pushing limits I use 800 to make sure I am accounting for overhead inefficiency and slippage. If I am using a low price multi label Chinese motor I assume they calculated watts using peak current at stall without accounting for voltage drop and divided by 700 for horsepower.
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I just keep an eye on the voltage/current/temperature/pressure/RPM meter to establish a normal value for when the equipment is happy, and a don't-go-there-again limit and recovery procedure based on when it wasn't.
For instance last spring the transmission in my car stopped locking up the torque converter when cruising. The subtle indication that it wasn't a transmission problem was the slightly low and variable needle position of the temperature gauge; a rubber seal on the thermostat had deteriorated and wasn't letting the coolant temp rise quite high enough to trip the at-operating-temperature switch that enabled lockup, etc. I could have wasted a lot of money at the dealership if I hadn't figured it out.
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