true flat bottom end mills

[Olaf KundrusParticipant @olafkundrus84366]

[Olaf KundrusParticipant @olafkundrus84366]

Hi, where can I buy a true flat bottom end mill in 13.5mm or 17/32"?

Thanks Olaf

[John HaineParticipant @johnhaine32865]

Er, why do you need one?

[JasonBModerator @jasonb]

By the size I suspect you want it to counterbore for the head of a 5/16" cap screw as that is the correct size then forget about an end mill and buy a proper cap screw counterbore They will give a flat bearing surface and also have a pilot.

In the UK J&L/MSC do several.

J

[Joseph RamonParticipant @josephramon28170]

If you want to counterbore holes, make d-bit. or a 4-tooth cutter from silver steel. It will take about 15 minutes and last for years.

Joey

[blowlampParticipant @blowlamp]

The second set down in this link look quite useful and are resonably priced, I think.

Martin.

[JasonBModerator @jasonb]

The metric sets have the wrong size pilot and the counterbore is generally larger on metric cap screws than imperial. Though the second set are imperial sizes stated in metric

This is one for a 5/16" screw of better quality, really depends on how much you have to do.

J

 

Edited By JasonB on 13/09/2012 09:40:05

[David LittlewoodParticipant @davidlittlewood51847]

Jason,

I would add that in all the ones I have (not the ones in Martin's link, but from top-class named makers) the counterbore hole is also too big; there is a gap large enough for swarf. I suspect the sizes were standardised at a time when a lot of things were made to blacksmith standards on a pillar drill; with a mill used as a precision hole-maker (or a CNC mill of course) you can do much better fits and be sure the holes will match up. I generally find it more satisfactory to use drills and a slot drill to get a snug fit. You can get good location with a couple of dowel pins, but that swarf trap is too much.

Olaf,

I wouldn't worry too much about the true flat-bottomed bit (unless there is some special reason); for normal fixing use a standard slot drill will be fine.

David

Edited By David Littlewood on 13/09/2012 10:40:22

[JasonBModerator @jasonb]

Yes those are the standard American sizes that can be found on any chart. While avoiding a "swarf trap" may be fine if the item being made is a bit of tooling that is also likely to be kept lightly oiled. If the head is too close a fit in conditions where corrosion is likely then it may be difficult to remove the screw at a later date.

J

[pcb1962Participant @pcb1962]

Posted by blowlamp on 13/09/2012 09:29:51:

The second set down in this link look quite useful and are resonably priced, I think.

I have that set. They have a tendency to explode, I've lost 2 so far.

Harry never replied to my email asking if I could buy replacements.

[Olaf KundrusParticipant @olafkundrus84366]

No,no,no I need this for some thing total different. Please take a look on my pictures on the reel album. It is a little bit difficult to explain. The slot is not simple strait trough it follows the curvature. Because of this the bottom of the end mill is not entirely in contact with the alu when milling. The conventional end mill is not completely flat on the bottom because of this I end up that the middle is higher than the sides as you can see on the photo. This is why I need a true flat bottom end mill in 13.5mm or 17/32". There must be a tool like this. And I don't want to grind one my self.

Thanks Olaf

[JasonBModerator @jasonb]

As the item is round can it not be turned on the lathe to cut the 17/32 recess.

If you can't turn it what about several passes with a smaller milling cutter rather than just one pass.

Third option is rather than rotate the work under the 13/32" cutter index it round in small increments and pass the tool right over the work

 

J

PS sorry for side tracking the thread.

Edited By JasonB on 13/09/2012 12:58:16

[MadMikeParticipant @madmike]

It must be me….but as the reel appears to be relatively small in diameter, why not simply put it in a lathe and turn it?

[Olaf KundrusParticipant @olafkundrus84366]

turning can't be done, because the other 3 bridge are in the way.

smaller milling cutter would be a option. But I have to do lot of this so one pass would be preferred.

Third option is what I tried and did not work.

Come on there must be a true flat bottom end mill!

[blowlampParticipant @blowlamp]

Mount the rotary table with its axis parallel to the spindle and use the periphery of a tee-slot style of cutter to make the channel, stepping down and in, until it's the right width and depth.

You might also find that offsetting the cutter from the centre will allow a large(ish) diameter (centre cutting) tool to cut a smoother surface

Martin.

Edited By blowlamp on 13/09/2012 13:55:00

Edited By blowlamp on 13/09/2012 13:58:09

[David Clark 13Participant @davidclark13]

Hi There

Put the cutter into a holder and bring it down onto the top of an oilstone while running in reverse.

That should flat bottom it.

Back it off with a diamond lap if necessary.

regards David

[Ramon WilsonParticipant @ramonwilson3]

Olaf,

I experienced this very situation recently making some bearings for a stationary engine using an FC3 cutter which for all intents and purposes is reasonably flat – but not completely. I understand what you are saying and can appreciate you would prefer to do it in one pass however the only way I could think to get over the problem was to take a series of (flat) cuts around the radius rotating the part for each cut then finishing the segmented radius with a fine file. That method worked extremely well.

Given you would prefer a one pass shot this may not be what you are looking for but after many years milling I have never come across a true flat bottomed end mill though of course that does not mean there is no such thing.

However you solve your problem – good luck with it.

regards – Ramon

[Joseph RamonParticipant @josephramon28170]

My suggestion of a straight ended d-bit will do such a 1-off job perfectly.

Joey

[JasonBModerator @jasonb]

Would a ground off endmill work as the metal is actually being fed up into the end of teh cutter as the work rotates on teh Rotary table so you would need cutting edges on teh end not just a backked off cutter.

Can't see why the incremental rotation method did not work for you, it does need fery small steps though.

Martins method was another I thought of after posting and could be done in 2 or 3 passes so quite quick.

J

[Michael GilliganParticipant @michaelgilligan61133]

Olaf,

Forgive me if I have missed something important, but:

… it looks like you could make a [very] small flycutter to do this job.

… 10mm diameter body, with a 2mm diameter cutter set at 45°

???

MichaelG.

[JasonBModerator @jasonb]

Flycutter would be worse as its like having the endmill ground back at 45deg towards the middle.

J

[Michael GilliganParticipant @michaelgilligan61133]

Sorry Jason … yes, I did miss something.

What I had in mind was to run the flycutter in the vertical milling spindle, and rotate the job on a horizontal spindle directly below it … but I think you would also need to traverse the table [repeatedly] back and forth by at least the full cutting-radius.

Might be possible, but it's starting to sound a bit tricky and, of course, Olaf could do that with his existing cutter.

[think I'll keep my head down for a while]

MichaelG.

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

You can compensate for the hollow grinding of a cutter by presenting the cutter to the work desaxe . By varying the offset you can obtain a convex , concave or flat generatrix .

[Olaf KundrusParticipant @olafkundrus84366]

A lot of ideas here! The idea from Martin with the tee-slot style of cutter is to consider. But I like the simple idea with the d-bit from Joseph. This maybe would work. I searched goggle and it looks like they have to be made self and are not commercial available! Easy to do, but I don't have a grinder to do HSS so I would need to buy extra material for this that can be milled and hardened. I'm not so much in tool making.

Olaf

[Russell EberhardtParticipant @russelleberhardt48058]

As Michael suggested just moving an ordinary hollow ground endmill slightly off axis will acheive the desired result. A bit tricky to calculate the required offset but you can make the cut on axis as you have done then move the cutter back a little at a time until you get a flat section.

Russell.

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