Sharpening Milling cutters

Additional to my post :- Sharpening Milling cutters...

Just a note of safety...

The Dremel resin bonded grinding wheels are easily damaged and bits of wheel can fly off at high velocities...PLEASE WEAR EYE & FACE PROTECTION .

Bob -.- -.- -.-

Hi Bob,

I would like to ask how you measure the helix of the cutters for sharpening.

I have tried all manner of devices (mechanical ) but have failed miserably . The area I am trying to address is that of

sharpening the sides of small end mills when the usual mechanical guide does not work.

your use of an electronic solution looks to the answer but the helix variation has me stumped.

thanks

paul

Hi Paul...

Most cutters needing sharpening will only have part of the helix available, if they are anything like the ones I have! which were used in a machine shop and thrown out when they became worn on the edges.

In order to find what the pitch of the helix is, you can put the cutter in the lathe 4 jaw chuck and set the end of one of the cutting edges horizontal with a rule or straight piece of steel set in the toolpost holder, if you have an electronic Wixey angle gauge this is set on the chuck and zeroed, this could be magnetically fixed to one of the jaws, or you could use the jaws themselves as indicators of the spindle angle ... this is always 90deg or 180deg.

The chuck is then hand rotated 1/4 of a turn or 1/2 a turn (if you have that much left on the helix) and the rule is moved along using the leadscrew handle so that it lines up with helix cutting edge, the x distance is now 1/4 or 1/2 the pitch .... for example if the distance moved to line up with edge at the new position is 20mm and you have rotated the chuck 1/4 of a turn then the helix pitch is 4x20 = 80mm.

I have only used this method on 2 flute cutters and for the grinding operation will be making a fitting something along the lines of Harold Halls grinder cutter tool holder so I can rotate the cutter for grinding the other flutes without disturbing the electronic setup which indicates where the spindle will be when the leadscrew is started up.

I don't see why this method couldn't be used on a normal screwcutting lathe if large pitches are available which would provide the same pitch as the cutter helix, the only problem might be that the spindle speed is too great, I am using a spindle speed of 1 rotation every 8 seconds which gives the grinding wheel some time on the work.

Hope that helps....Bob -.- -.- -.-

Hello Bob,

Thanks for your prompt response

I have an excellent ELS but it is fitted to a lathe. My hope is to make a small simple as possible item to use on the T&C grinder. As previously mentioned I have tried mechanical systems but the prospect of a variable pitch in the region of 1-2 TPI on up to 3" is still to be found.

was your Arduino program from a library, and was it simple.

thanks

paul

Hi Paul...

I wrote an article for MEW in November 2015, No 235. The design uses 2 Arduino's which were coupled together so as to provide synchronism in providing pulses for the stepper motors, however it is not necessary to electrically couple them and I am assured that if the Arduino's have proper Xtal signal sources you can use them as they are.

The program could not be simpler for the Ard's ... it uses the Blink program and the article describes how to find the correct pulse times, there is also a circuit and explanations, someone with a small knowledge of Arduino programs could easily set it up. I can give you the progs no problems.

There is a Spindle speed program which just runs the Blink sketch continuously and there is a Leadscrew motor program which has an interrupt control to start the Leadscrew motor at a specific point in the spindle rotation.

I have used this lathe many times for making screw threads of various pitches, some quite peculiar for telescope eyepieces and suchlike, but the beauty of the system is that you can adjust the parameters for virtually any pitch you want, the only drawback is that my spindle motor is not as powerful as I would like, you could even vary the pitch within a pitch ... there is absolute full control over this.

The system however does not have any feedback and relies on the start pulse to set it running, if there is too much load for the motors there will be problems so light cuts are needed, in the case of a grinder for milling cutters there would be no problem.

Bob.. -.- -.- -.-

Posted by Paul White 3 30/06/2019 13:22:09

I would like to ask how you measure the helix of the cutters for sharpening.
I have tried all manner of devices (mechanical ) but have failed miserably .
The area I am trying to address is that of sharpening the sides of small end
mills when the usual mechanical guide does not work.
your use of an electronic solution looks to the answer but the helix variation
has me stumped.

An article that was in MEW 143 through to 147 "A cnc cutter grinder "
may be worth a look,it describes the construction of a machine and its use.
The photo here shows a 3/4 inch long endmill and a 3 mm 3 flute carbide
endmill alongside ,both have been sharpened on this machine.

It is important that the cutter should follow the original lead of the cutter, as
can be seen the lands on the large cutter form a parallel edge along the length
of the cutter,any deviation from this would mean the clearance angle would
change or the cutter would become tapered.
Some cutters have the lead engraved on the shank ,as can just be seen
the imperial cutter is marked 5.440 inch and the metric has 56 next to the
small triangle indicating the lead is 56 mm.

Much more sophisticated machine seen here...

www.youtube.com/watch?v=qxU0K-TmEvI

They use the same method as i do to measure the cutter but their
system is much easier to use.

John

Bob.

Thanks for your helpful comment, I will try to

get a copy of your article .

John,

Thank You for your helpful input . More to source and read.

Paul