[CSW_Grinderman]

Im getting into sharpening end mills and iv been a tool grinder for several years now but im new at the air bar for grinding outside diameters and ends on these things. Is there anyone that knows alot about grinding these things on a KO Lee tool grinder? Or anyone who knows the angles for primary and secondary angles on all dif sizes of end mills???

[Boots]

They vary depending on material to be cut and dia. of tool. But you will need the air spindle to do this. Also remember that as you grind away the O.D. of the tool the edge falls below the centerline which makes it more difficult to cut.

[CSW_Grinderman]

my grandfather has been grinding ODs for a long time and has came up with a chart for different sizes and what the angles are the problem is that he is over 80 and has trouble remebering what the angles are and he thinks he needs to change his chart... instead of taking his word i was wondering if there is a chart from the factory a standered chart for these angles? I have the air bar and im grinding the ODs and matching whats on the bit but for the bits that he has already ground i dont know if the angles on it are ok or not...

[Boots]

Every tool manufacture uses "their own" geometry to do the primary and secondary angles of their tools and is usually calculated depending on the material to be cut and the forces to be encountered while cutting. I would do as you are doing and try to duplicate what is there already. But at any rate it will not cut as it once did when new because the cutting edge is now below centerline. When endmills are new they have what is called a Positive rake angle on the cutting edge. To get under the material to be removed. After sharpining, this edge begins to become negative and instead of Scooping off the material it does more of a Scraping effect but will still cut just NOT SO GOOD anymore, and the edge will not hold up, but it sure beats shelling out the $$$ for a new tool when a quick touch-up on the OD will get you by another job or two. In the Old Days tooling was more uniform but times have changed and tooling is becoming more Material Specific now a days.

[CSW_Grinderman]

Yeah i know what you mean by the edge being under center after i sharpen the od. Im also doin the ends on these end mills and im just putting them in a chuck a ragular tool grinding work head for grinding router bits and raised panel cutters, but Iv seen these fixtures that are set on a tool grinder that is suppose to do the primary and secondary on the ends have you heard of these or ever used one? It has a square base with a lip on one side im geussing it tilts for the secondary angle... any other tips for me on sharpining these things?

[handlewanker]

Hi CSW, about a year or so ago I bought a K.O.Lee cutter grinder on Ebay from the USA, complete with the air bearing head mentioned previously, cost me $2000 to get it to OZ, but there's nothing available on our 2nd hand markets like it for the price, especially with the air bearing head.

I had to shell out another $100 for a 240/110 volt transformer as the motor is 110volts.

Looking at your post #5 I take it you are supporting the edge on a "finger" or very thin hack saw blade in a holder to keep the cutter edge down below grinding wheel centre height a small but significent amount for the primary and secondary OD clearances, grinding wheel face rotating downwards?

There is a chart available for cutter grinding that gives you the cutter centre height below grinding wheel centre, in relation to ANY grinding wheel diametre, and it varies with the grinding wheel diam.

You should also have a gauge and setting place to set the cutter edges and finger on the grinding wheel centre, and you move the wheel head up or down to get the grinding wheel centre above cutter centre the required amount.

If you don't have this chart it is impossible to know by eye how much or little you are getting for the primary/secondary clearance angles on the OD.

For instance if you present the cutter edge down on it's centre line with the cutting edge on line with the grinding wheel centre line you get no clearance, but if you raise the grinding wheel centre line above the centre line of the cutter you get more clearance due to the curvature of the wheel, but by how much? It depends on the wheel diametre, and that is where the chart comes in.

I think the machinist's Bible The Machinery's Handbook will list all the settings relative to the wheel size, they list everything else.

BTW, the problem with regrinds is not in the change in cutting angle, it STAYS the same, (if you set it right), but in the reduced gullet behind the cutting edge, and after a number of grinds the diametre reduces and so does the gullet or chip clearance, and it's this reduction in gullet that makes the chips jam behind the cutting edge instead of flowing out.

Excessive regrinds do give a thick section to the secondary clearance and this can cause a problem too.

The end cutting clearance isn't a problem as it just requires setting the end up at the right amount about 3 degrees and 5 degrees for primary and secondary etc.

Side and face cutters are also done in the same manner as regards to the diam of the grinding wheel.

BTW, the cutting edge is ground down stream, with the cutting edge supported on the finger and the grinding wheel rotating downwards away from the edge, which does give you a slight grinding burr, but keeps the cutter pressed down on the support finger all the time as it slides along the helix of the cutter.

Also the cutter makes MINIMUM contact with the stone, probably just at the corner, tilted at a slight angle to the stone face, otherwise you get a peculiar grind on the OD if it grinds full face, as someone I know tried to do once.
Ian

[CSW_Grinderman]

yeah in that hand book it tells you what the clearence and drop is from the front of the primary to the back and for the secondary basically it just doesnt tell me what angle i should set it at to get that clearence. its hard to explain but yeah im using a finger and drawing it back with the wheel at center and the flute set on the finger at center on the center of the tool also i have everything set and ready to go i just am not 100% sure that im setting the angles right on the air bar to the get the right clearence angles. hey have you ever used one of those fixtures to grind the ends on end mills or do you use the KO Lee tool head for that? Im having some problems doin the ends just becuase in the tool head you have to eye ball that the tool is centered and adjust angles and what not. how do you do the ends if you dont mind me asking?

[handlewanker]

Hi CSW, the ends are the easy part and are usually the only bit most cutter would be sharpeners attempt at anyway.

You mount the slotdrill/end mill in a collet or Autolock adaptor in the head, or any holder that allows you to rotate the cutter to give you two/four or more divisionals whatever the cutter is, and this applies to shell end mills which can have a lot more teeth than the regular 4 tooth end mill.

Whatever you want to grind you MUST first set the teeth on opposite sides exactly horizontal across the centre line, be it for slot drills with 2 teeth or end mills with a lot more.

Old hands eye the cutter to a steel block at cutter centre height across the two end edges, the centre height will always be the same for the head no matter what the cutter size.

Set the index on the head to zero, peg in the hole.

The head is now swung across the table pointing end on to the wheel face, and about 1/2 a degree off the table longways.

The wheel is usually a cup stone with the face slightly angle inwards, achieved by hand dressing with a dressing stick.

With all end work the teeth MUST be angled in to the centre of the cutter by about a 1/2 degree, so that the middle of the cutter is clear when you mill a slot or face etc.

Next set the cutter up 3 degrees for the primary angle and when all edges are finished, cut the secondary angle to leave you with a 1mm wide primary face.

The stone rotates clockwise using the back spindle of the grinding head, so the cutter is ground with the left cutting edge upwards, (sparks going down) on the right hand edge of the stone, table moving right to left.

The k.O.Lee cutter grinder I have has a motorised head with a spindle having one end with a short stub for 1/2" X 6" disc type wheels and the other end with an extended spindle for cup stones etc to allow reaching over the table.

Again you are working on the corner edge of the stone and traversing it with table movement longways, just enough to grind to the centre of the cutter.

Two tooth slot drills have one tooth ground just a bit beyond centre so that when they drill into the work they don't produce a "pip" in the centre.

End mills, on the other hand being side cutting, aren't used to drill due to the middle part being recessed and non cutting, but still have their end teeth faces angled inwards.

You also set the cutter at 1/2 degree to the table travel and set a table stop to make sure you don't run the corner of the stone past the cutter centre and into the other side of the cutter face.

The primary clearance is from memory about 3 degrees, and the secondary about 7 to 10 degrees, but I'll have to look up the exact recomendations if you can't find them.

One other thing, always mark the end where you intend to grind with a RED or GREEN marker, (felt tip pen) not a blue or black marker, otherwise if you get a bit ambitious in the grind with a dull stone and blue the metal you won't be able to see the difference in grind progress.

The exception to the angled face of the cutter to the stone is with side and face cutters that are mounted on a mandrell between centres and are traversed across the full face of the stone, which is rotating toward you.

It's easier done than written, and becomes clear if you just hold a cutter in your hand and go through the motions.

BTW, don't be afraid to redress the stone, (with a diamond dresser) as required or you'll just burn the metal instead of cutting it, and the white alluminium oxide stones wear down pretty quickly as they'r very free cutting.

I always give the cup stone a quick touch up with the hand dresser for the final cut.
Ian.

[handlewanker]

BTW, the air bearing head is a luxury, practically friction free, and I never previously used one in my life, just using the indexable head with collet and cutter edge on the finger for the cutter side grinding, and table movement longways, but now I have the air bearing head so life will be much easier.

The Cincinnatti tool and cutter grinder has ball rollers in the table and a wire drive to the table movement so it's pretty sensitive to feel, but does not come anywhere near the smoothness of the air bearing head for sensitivity and feel.

I think on Ebay the KO Lee air head went for $1000 by itself, and I was lucky to get it as part of my grinder.

I would still use the normal indexing head to grind the ends though, more control, but that's for later when I get a round tuit and investigate the air head further. LOL.
Ian.

[CSW_Grinderman]

Right on thats nice to know thats kinda how I do them here and Im all about consistancy do you gash the end mills by hand or do you grind the gashes on the tool head when you do the primary and secondary or what? i dont like grinding them by hand and if you have any more helpful tips that, that would be awsome.

[handlewanker]

Hi, the slot drills get gashed with a thin cut off wheel, sometimes by hand when you get lazy and only have to do one or two, but it gets more precise if'n you have a cut off wheel set up, maybe on a second smaller machine, and just nick the slot, but if you're doing a number of cutters, you have to re-set each cutter anyway at the right angle in a locked head so that the cut off wheel doesn't touch the newly sharpened ends, and this gets done at the end of the job.

The air bar needs a calibrated index ring to stop it from turning and also index the cutter faces if you want to grind end faces on slot drills etc, and also to stop it from moving in and out.

I wouldn't like to use the air bar to plunge a cutter straight into the stone, which is the only way you could do the end face in that mode, too iffy, but it could be used as a head with an index collar, while the cutter is mounted, if it is prevented from in/out movement with a stop collar both ends, and using the table movement to move the cutter across the stone.

Someone who's more familiar might add their experience too in that set-up.

It's hard enough getting the exact position of the cutter and head to each other for a good grind when you do the OD, without having to move the set-up just to do the end faces or slot the end mid-way.
Ian.

[CSW_Grinderman]

yeah thats how i do them also by hand. thanks alot!!! If anyone else has a dif way of doin end mills besides using a cutter master I would like to hear the dif ways.

[handlewanker]

Wow CSW, if'n you've got access to a CutterMaster you certainly are a lucky one.
I tried to give my nuts for a Cuttermaster, twice on Ebay from the USA, but got outbid both times, in the end I bid on the K.O. Lee model (bench type) from the seller Reliable Tools and finally got it.

A friend of mine bought a Deckel OS cutter grinder, but I think it's more suited for D bit grinding and end work, and we still haven't worked out how to grind an end mill on the OD on it, just doesn't seem to have anything that will guide the cutter as the stone is worked on the right hand side and the cutter edges are pointing upwards on their left side, no place to put the guide finger, unless the guide finger hangs down from the top somehow, also the cutter head swings in an arc as opposed to a sliding traversing mode.

Unless there's a sliding thingy that goes in place of the work head with provision for a guide finger, I dunno' how it works, probably not intended to really grind the OD of end mills etc, as it's described as a D bit grinder, and that's all end work, plus a bit of side work but not with a helix.

Anyone who can throw light on that subject will get a Knighthood with oak leaves and diamonds and a mention in dispatches etc, LOL.
Ian.

[handlewanker]

Carefull Tolegrinder, you could be accused of spamming....nice range of grinders on that link you posted.

BTW, you CAN grind an ordinary endmill and slot drill on the end faces by hand, (not the side helix ) by using a common Vee block to hold the tool steady and at the right angle....it's not quite as good as a regular cutter grinder, but it does a pretty good job if'n you have a good eye and steady hand.

At the same time, I had to grind the end of a 19mm (3/4") diam ball nose slot drill and I used the Vee block method.....you only have to grind the teensie weensiest amount off to get it to cut again....and you don't have to worry about a helix on an end face.

I used the diamond type lap (CBN) which we used for grinding carbide, 'cos it had the small table that you can incline very accurately to get the back clearance angle on the cutter.

Again, it works for general work, but if'n you were in an industrial environment and had to contend with CNC requirements, this method would not work.
Ian.