Author Topic: End mill grinding fixture  (Read 16002 times)

Offline grinder

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End mill grinding fixture
« on: September 13, 2010, 12:59:47 PM »
Hi Guys,

Here are a few pics of my latest project, an end mill grinding fixture. I have a bunch of old end mills that are in pretty sad shape. I would really like to put them into service again, so I thought I'd try to sharpen them myself. Years ago, I spent some time in a machine shop and saw a fixture that could be used on a mill to sharpen these things. I found out as much as I could about the cutting angles and such and came up with this. It kind of resembles a commercial fixture, but is smaller, since all my mills are about 2-3 inches in length. Anyway, see what you think. I need to find a better grinding wheel though....Any thoughts?? I tried using a small grinding wheel (actually, a heavy duty cutoff wheel) froma Dremel set, but these things are not very strong and break very easily.





I feel like a 22-year old, but my wife won't let me have one.

Offline Bogstandard

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Re: End mill grinding fixture
« Reply #1 on: September 13, 2010, 01:10:40 PM »
It is not just a matter of grinding across the face, it has to come from the right direction, otherwise you will find that the cutter will either go dull very quickly or in fact chip along the cutting edge.

Really, you require a much heavier wheel, and preferably in an upright position, so you are using the periperal of the wheel rather than the side face.


Bogs
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Offline winklmj

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Re: End mill grinding fixture
« Reply #2 on: September 13, 2010, 01:15:55 PM »
I've come across a couple of places showing the small diamond disks (Harbor Freight variety) being used. They back them up with an metal backing plate to eliminate the flex.
Mike

Offline Trion

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Re: End mill grinding fixture
« Reply #3 on: September 13, 2010, 01:37:25 PM »
Funny you should ask just now, as I was just searching for the same stuff, and found these threads showing a very simliar fixture to yours. It got even better when i saw that bogs had replied :thumbup:

http://madmodder.net/index.php?topic=1428.0
http://madmodder.net/index.php?topic=1434.0

Here's also a guy who has built his own grinder, quite a bit of usefull info on end mill grinding
http://www.gadgetbuilder.com/Brooks%20Grinder.html

Offline Bernd

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Re: End mill grinding fixture
« Reply #4 on: September 13, 2010, 01:51:27 PM »
 :offtopic:

Hey Bog's welcome back.  :thumbup:

Bernd
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Offline John Rudd

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Re: End mill grinding fixture
« Reply #5 on: September 13, 2010, 03:14:13 PM »
:offtopic:

Hey Bog's welcome back.  :thumbup:

Bernd

Ditto,

Nice to see a familiar face again... :)

Hope you and yours are keeping ok...oh and Bandit too.. :thumbup:
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Offline Bogstandard

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Re: End mill grinding fixture
« Reply #6 on: September 13, 2010, 03:57:57 PM »
Thanks gents,

Looks like the worst is over, everything is stable and the only way now is up.


Bogs
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Offline dsquire

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Re: End mill grinding fixture
« Reply #7 on: September 13, 2010, 04:17:30 PM »
John

Glad to hear that things are all on the upswing and glad to see you back in here.  :ddb: :ddb:

Cheers   :D

Don
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Offline Bogstandard

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Re: End mill grinding fixture
« Reply #8 on: September 13, 2010, 05:15:47 PM »
Just to put things back on track for Grinder.

What you have made looks great, and I am sure with the correct grinding technique, it will work fine.

Just a suggestion now.

If you want to continue to use the grinder you have been using, you just need to change your method slightly.

The grinding 'grooves' should lay at 90o to the cutting edge, the way you are doing it now, your 'grooves' will in fact lay sort of parallel to the cutting edge.

The way to get them laying correctly, feed the cutting edge in the Y axis rather than the X axis as you are doing now.

Line up the cutting edge in the Y axis in line with the grinder spindle, then just feed in on the Y until you have cut the whole cutting edge, retract, rotate to the next edge and repeat. Do not move in the X axis.

I hope this explains it OK.


Bogs
If you don't try it, you will never know if you can do it.

Location - Crewe, Cheshire

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Offline Ned Ludd

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Re: End mill grinding fixture
« Reply #9 on: September 13, 2010, 08:58:36 PM »
Something is very wrong when Bogs is described as a "newbie" :bugeye: I cannot think of a less appropriate adjective.
Ned
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Offline dsquire

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Re: End mill grinding fixture
« Reply #10 on: September 13, 2010, 09:15:31 PM »
Something is very wrong when Bogs is described as a "newbie" :bugeye: I cannot think of a less appropriate adjective.
Ned

Ned

It might say Newbie but just wait till some real newbie or stranger comes along and tries to pull the wool over Bogs eyes. They will be in for a real surprise.  :doh:

Cheers  :beer:

Don

Good, better, best.
Never let it rest,
'til your good is better,
and your better best

Offline Lew_Merrick_PE

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Re: End mill grinding fixture
« Reply #11 on: September 14, 2010, 11:45:03 AM »
Grinder,

Cup-type wheels are most commonly used for this type of sharpening operation.  Diamond coated (Borazon) wheels are used for the greatest precision -- and also cost like crazy ($280 US for a 3-1/2 cup wheel).  The problem is that you spindle is unlikely to reach a really good grinding speed (usually in the 5000-8000 rpm range) which "suggests" (at least it did to me) that an alternate spindle set-up mounted off you mill head would be a valuable project.  Also, be very careful about getting grinding dust into your ways.  You really do not want abrasives getting in there.  I have a set of leather (suede) "drapes" that cover things and I use a vacuum dust collector when doing such grinding.

One of these days I really need to learn how to post pictures here.  I just haven't had the time to dig into the instructions for that of late.  I made a "spindle adapter" some years ago that is a plate with a .750 round bar (to mount in a collet) index and a split collet that clamps over the (3.500 -- as I recall) OD of my spindle to provide a "platform" to attach other tools to my mill's spindle.  It started out as a mount for a die grinder so I could use small burrs when doing detail milling.  That gets me a 15,000 to 20,000 rpm spindle that is firmly attached to my mill head.  I have been thinking about (but have yet to do anything about it) mounting an angle grinder on that "adapter."  That would get me an 8000 rpm spindle with reasonable power.

I hope this helps.

Rob.Wilson

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Re: End mill grinding fixture
« Reply #12 on: September 14, 2010, 12:04:47 PM »
Hi Grinder

That  a well made bit of kit  :dremel:  :clap: :clap: :clap:   ,it will save you a good few dollars  :med: ,,,,,,,,, thanks for showing  :thumbup:  ,,,,,,,,, another tool to add to the build list  :D

What are the two grinding  angles you decided upon for the base ?


Cheers Rob


Offline grinder

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Re: End mill grinding fixture
« Reply #13 on: September 14, 2010, 12:16:25 PM »
I've come across a couple of places showing the small diamond disks (Harbor Freight variety) being used. They back them up with an metal backing plate to eliminate the flex.
Hi wink,

I tried that, but all it did was stiffen the wheel up to the edge of the washer. The very edge of the wheel that projected past the washer did most of the cutting but still was too flexible. Insted of breaking in half, the wheel broke around the periphery.  Bogs suggested that the wheel should rotate so that the periphery of the wheel did the cutting. I thought about this at the time, but had no way to turn the grinding wheel through 90 deg. I think I have to find a way to mount my Dremel tool horizontally  :nrocks:
I feel like a 22-year old, but my wife won't let me have one.

Offline grinder

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Re: End mill grinding fixture
« Reply #14 on: September 14, 2010, 12:41:23 PM »
Just to put things back on track for Grinder.

What you have made looks great, and I am sure with the correct grinding technique, it will work fine.

Just a suggestion now.

If you want to continue to use the grinder you have been using, you just need to change your method slightly.

The grinding 'grooves' should lay at 90o to the cutting edge, the way you are doing it now, your 'grooves' will in fact lay sort of parallel to the cutting edge.

The way to get them laying correctly, feed the cutting edge in the Y axis rather than the X axis as you are doing now.

Line up the cutting edge in the Y axis in line with the grinder spindle, then just feed in on the Y until you have cut the whole cutting edge, retract, rotate to the next edge and repeat. Do not move in the X axis.

I hope this explains it OK.


Bogs
Hi Bogs,

Thanks for the encouragement. You must be an old hand at this stuff, seems like everyone has a lot of respect for you, well earned I'm sure. :clap:
Anyway, thanks for the suggestions. The way I was grinding the mill is this: I had the setup pretty much as your sketch indicates, but I was using the X handwheel to move the fixture under the grinding wheel. Any grooves cut into the face of the cutter would then be smoothed out by the varying angle of attack of the grinding wheel as the mill passed under. My biggest problem was the fragile wheels I was using.
I feel like a 22-year old, but my wife won't let me have one.

Offline 75Plus

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Re: End mill grinding fixture
« Reply #15 on: September 15, 2010, 08:44:01 PM »
It appears that your mill is an X-2. This addition will allow you to grind the tooling at a much higher speed.

http://littlemachineshop.com/products/product_view.php?view=classic&ProductID=2892

Joe

Offline stovebolt

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Re: End mill grinding fixture
« Reply #16 on: September 16, 2010, 04:18:23 PM »
 A few years ago I bought one of those fixtures from Enco along with the 5C collets, unfortunately the indexing system is crude but I have sharpened a lot of end mills with it.   I too started out using those cut off wheels, then I went to  a  standard cup wheel,  now I use a diamond cup wheel.  I hope I don't start anything here but my understanding is diamond wheels should be used a low speeds, I run mine at about 500 rpm. 

 CDCO has these diamond cup wheels for $43.00, usual disclaimer/ no connection just a satisfied customer.
 
 The web site won't let me post a direct link,  but if you enter "diamond" in the search box it'll take you to the right page, near the bottom. 

http://www.cdcotools.com/

         

Offline ScroungerLee

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Re: End mill grinding fixture
« Reply #17 on: September 18, 2010, 08:13:39 PM »
I've come across a couple of places showing the small diamond disks (Harbor Freight variety) being used. They back them up with an metal backing plate to eliminate the flex.
Hi wink,

I tried that, but all it did was stiffen the wheel up to the edge of the washer. The very edge of the wheel that projected past the washer did most of the cutting but still was too flexible. Insted of breaking in half, the wheel broke around the periphery.  Bogs suggested that the wheel should rotate so that the periphery of the wheel did the cutting. I thought about this at the time, but had no way to turn the grinding wheel through 90 deg. I think I have to find a way to mount my Dremel tool horizontally  :nrocks:

The diamond wheels are made of metal with diamond coating.  Are you sure you are thinking of the right thing?

Lee

Offline Bogstandard

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Re: End mill grinding fixture
« Reply #18 on: September 19, 2010, 02:00:17 AM »
Grinder,

All you really need is a standard cupped wheel on your spindle, and the quill speed as fast as you can get it. For dressing the wheel, just clamp your diamond in the vice and dress in the Y axis.

Use the method I said, feed in the Y axis only, and you should end up with good enough ground cutters.

For sharpening tungsten cutters, use a green grit cup wheel.


Bogs
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Offline ScroungerLee

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Re: End mill grinding fixture
« Reply #19 on: September 19, 2010, 07:43:14 PM »
Hey Grinder, it looks like you will get this working nicely.  What angles did you use when you made your fixture? 

Rob.Wilson

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Re: End mill grinding fixture
« Reply #20 on: September 20, 2010, 05:09:02 AM »
  What angles did you use when you made your fixture? 

I asked that very  question  ::)

Rob

Offline grinder

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Re: End mill grinding fixture
« Reply #21 on: September 20, 2010, 12:35:22 PM »
Hi Rob and scrounger,

The angles I used are 2 degrees, 5 degrees and 30 degrees. The cutting tip to the center of rotation of the mill is 2 deg, so that only the tip of the cutter is doing any work. The clearance from the cutting edge to the heel is 5 deg. and the back clearance from the rear of the cutting edge is 30 deg. In my next post, I'll try to get some ACAD drawings in to show details. The numbers are from a website http://getmachinetools.com/pro1113095.html I found while researching this project. My selection of mills are short (dimensionally speaking) and mostly 3/8" shank, so I didn't see the need for a support column found in commercial designs. This kept assembly simple. Now that I know it will work with the right grinding wheel, I need to make some more tool holders for my 1/4" mills.
I feel like a 22-year old, but my wife won't let me have one.

Offline Bogstandard

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Re: End mill grinding fixture
« Reply #22 on: September 20, 2010, 03:16:24 PM »
I did these a while back, and actually shows the original sharpener.


Bogs
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Location - Crewe, Cheshire

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Offline ScroungerLee

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Re: End mill grinding fixture
« Reply #23 on: September 20, 2010, 08:06:05 PM »
Thank you Grinder and John. 

I think I will put this on the "I am bored" list.  Not to be confused with the act of boring which can refer to metal working operations or, at certain times, conversation.

Lee


Offline Bogstandard

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Re: End mill grinding fixture
« Reply #24 on: September 20, 2010, 08:15:00 PM »
Quote
Thank you Grinder and John.

I think I will put this on the "I am bored" list.  Not to be confused with the act of boring which can refer to metal working operations or, at certain times, conversation.

Lee

Could you please explain.

Bogs
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Location - Crewe, Cheshire

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