I managed to get the 2° angle on my end mill sharpening fixture wrong . I'd recut but the piece I used was just barely big enough to begin with . Oh well , looks like this one is going to cost me a few bucks instead of being made totally from stock on hand . I'll also be correcting a couple of things I thought were marginal - mostly due to the thickness of the piece . I'll also be keeping the first attempt just in case some day I have to sharpen a left hand twist end mill .
I managed to get the 2° angle on my end mill sharpening fixture wrong . I'd recut but the piece I used was just barely big enough to begin with . Oh well , looks like this one is going to cost me a few bucks instead of being made totally from stock on hand . I'll also be correcting a couple of things I thought were marginal - mostly due to the thickness of the piece . I'll also be keeping the first attempt just in case some day I have to sharpen a left hand twist end mill .
Snag
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How wrong?
I don't think the exact angle matters much as long as the cutting edges aren't straight across, the tips touch the work first. When I sharpen a 4 flute I may have to rotate the flute being ground somewhat to clear the next one, and that changes the 2 degree angle, but I don't notice a problem when milling with it.
If your end angle is large enough to show in the tool marks you could rotate the fixture base on the mag chuck to decrease it.
I've squared off and then reground a chipped brand-name endmill entirely by hand to rough it to shape before finishing it on the surface grinder. As a test it did cut smoothly with the one longest flute.
If the collet tilts the wrong way and you intend to grind on a vertical mill you can just reverse the spindle to grind into the edge of a right hand endmill.
No , he geometry is backwards . If I cut on the far side of the wheel , the center is longer than the corner . If I cut on the front , the angle on the cutting edge is backwards . It'll work perfect for an end mill that turns ccw ...
No , he geometry is backwards . If I cut on the far side of the wheel , the center is longer than the corner . If I cut on the front , the angle on the cutting edge is backwards . It'll work perfect for an end mill that turns ccw ... Snag
--------------------------- As long as the collet has enough tilt there has to be a rotation of the base that leans the collet a little to the left and more forward, viewed from the approaching grinding wheel. The combined collet tilt on my fixture appears to be about 6-7 degrees from vertical and rotated about 15 degrees to the left from that perspective. The base bevel is 25 degrees.
Can you cut down the base and attach it to a block that orients it correctly in the mill vise? Or maybe mark a reference line on the base parallel to the table and hold it there with tee slot clamps.
If I rotate the base of my fixture 30 degrees CCW it leans 2 degrees to the right, to grind a LH endmill. The correction for an accidentally left-handed base would be to rotate it 30 degrees CW.
And tomorrow I'll be out looking for the spring C clip that popped off the front axle of my truck and vanished where a magnetic sweeper couldn't find it. Although it also didn't find the clip, at night the thermal imager made everything lying on the ground including a sample tarp grommet stand out in high contrast to the warmer earth. It may be in a snow bank that I'll screen tomorrow.
And tomorrow I'll be out looking for the spring C clip that popped off the front axle of my truck and vanished where a magnetic sweeper couldn't find it. Although it also didn't find the clip, at night the thermal imager made everything lying on the ground including a sample tarp grommet stand out in high contrast to the warmer earth. It may be in a snow bank that I'll screen tomorrow.
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It was in a snowbank that I raked out to slowly melt. I don't normally let Jeezus clips get away like that.
Dad called 'em that too ... he also taught me that if possible put a plastic bag over the part so if it tries to escape it can't . Kinda hard to do often when working on a vehicle . I tried the rotating thing with my fixture , no joy . No matter which direction I oriented the fixture in the vice and rotated it I couldn't get the proper angles . I have another piece of aluminum on the way , looks like this project won't be all from stock on hand . I considered casting a block but decided to just buy it . I need to get all that money spent before MY bank crashes !
I tried the rotating thing with my fixture , no joy . No matter which direction I oriented the fixture in the vice and rotated it I couldn't get the proper angles . I have another piece of aluminum on the way , looks like this project won't be all from stock on hand . I considered casting a block but decided to just buy it . I need to get all that money spent before MY bank crashes ! Snag
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I didn't expect it to align in the vise. On mine the base rotation between RH and LH is about 30 degrees, not one or more quarter turns. The simple fix is to clamp it to the mill table in an orientation that gives you the grinding angles and then draw a line on the base parallel to the table slots so you can repeat that positioning. If you want you could attach it to a larger base that goes in the vise. You might have to grind the back relief by hand, which is faster anyway.
---------------------- It slipped past freezing fingers.
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Don't scare me like that. If my banks crash (I do spread it around for safety) I'm toast. I do almost 100% of all my sales on-line. Bob La Londe CNC Molds N Stuff
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Fear not, the Illuminati are in firm control.
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"In the case of the SVB collapse, I believe the banks listed above are set to receive large inflows of deposits as businesses around the nation rethink banking relationships."
Besides, the FDIC insures you for up to $250,000 per bank.
The vise isn't bolted down , I rotated the whole thing . Even used one of my new angle plates to set it at 30° .
Snag
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Without seeing / examining it I can only guess, so I assumed you made a mirror image of the correct geometry.
Can you find and measure the maximum collet holder tilt and mark its direction?
On mine it's tilted about 6 or 7 degrees, and rotated about 15 degrees clockwise from the center of the beveled end so that about 2 degrees of the tilt dishes the cutting edges in toward the center and about 5 degrees of it is back relief. Those are rough visual estimates of mine because my vernier protractor doesn't fit against the angles.
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Eagle Rock ones are shown from the perspective I've used. I took the 2 and 5 degree angles from the note, my fixture has the base bevel at 25 instead of 30 degrees.
Looking at the "thick" end , the 2° bevel leans the end mill to the left instead of the right . So if cutting on the front side of the grinding wheel , the center will be longer than the perimeter . And if cutting on the back side of the wheel the center will be cupped , but you will be grinding the cutting edge backwards . When the new piece of stock arrives I'll cut a new tilted wedge and start over . I'll be changing the order of operations too , the hole will be the first thing machined , it's a lot easier to hold a square block than a tapered one .
Snag "You can lead a dummy to facts but you can't make him think."
Looking at the "thick" end , the 2° bevel leans the end mill to the left instead of the right . So if cutting on the front side of the grinding wheel , the center will be longer than the perimeter . And if cutting on the back side of the wheel the center will be cupped , but you will be grinding the cutting edge backwards .
{{{{{{{{{{{{{{{{{{{{{{ That's what I took from your description, that it's an opposite-handed mirror image. I suggested how you might be able to salvage it with a rotation and different way to hold it on the mill, at least to better understand and prove your intended fix, but it's your project.
Now you have a physical sample to compare to, the spatial translations between how a part is used and how it needs to be machined can be confusing to visualize. You could double check by putting the existing block in the new fixture to confirm that the cut will be at the correct opposite angle.
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I acquired some practice understanding and mentally modeling symmetry, reflections and rotations in 7th grade drafting class. The teacher had a set of difficult models we had to draw correctly. Handling and looking at them from different directions helped a lot. That's why I machined samples of my suggestions to show the project engineers, instead of trying to describe them. Mechanical engineers didn't really need help but electrical engineers lacked that sort of training.
A friend in the drafting class was the son of an architect, and determined to prove he was the best draftsman. I wouldn't let him get off easily and thus learned a lot myself. I also learned how manipulate someone's competitive and egotistic nature, and recognize those tactics from sales people.
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}}}}}}}}}}}}}}}}}}}}}} When the new piece of stock arrives I'll cut a new tilted wedge and start over . I'll be changing the order of operations too , the hole will be the first thing machined , it's a lot easier to hold a square block than a tapered one . Snag
------------------------- And you will have become a better machinist from the problem-solving experience.
If a check of the tram on my milling machine shows that it's gone off I might tilt and swivel the head for a job like this before squaring it up again.
Jim - you are a polymath for sure, and you shine lots of useful additional illumination on a topic.
I was once presented with a problematic weld
problematic in that we had a suspicion it had defects
problematic in that its geometry defeated all volumetric NDT/NDE I had a good colleague who is as well as an engineer a qualified UT (Ultrasonic Testing) technician. We could see a potential way - but it conjecture only. Procrastination would have been endless - and angry. So I got my colleague to "request" the subcontractor provide the equipment. Left in a bind - everyone was - the box was there with the kit we asked for. Something like an hour passes and we are making progress, prepping and trying, and people come closer and closer. Before long we have a deep semicircle of welders and engineers and the idea is "in play", all scratching their heads and making suggestions. Had we asked anyone and not kept our mouths shut and simply prototyped it, we would have got nowhere.
My Doctorate "flew" because I tried many techniques - "finite" concept tests. "Dead-certs" fell by the wayside never working at all and "outliers" "far out in the long grass" performed even though for them to work must mean there is some law-of-the-universe we don't know about (yet).
This - crashing straight through all the reasoned objections and holding-up working completely unexpected solutions in unexpectedly short timescales, upsetting a lot of people, is why I have to work as a welder "incognito" rather than having my name with title on a door indicating I am a leading "linking it all together" person.
"Prototyping"... You recognise "prototyping" as everyone getting together and trying ideas, seeing which ones work and if so how well?
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