Gash and holes - tool needed

[6ply]

I've been regrinding HSS end mills with good success, grinding new primary and secondary cutting edges with the use of a grinding jig on my surface grinder.

I have a mixed source of good, not so good and positively ugly end mills that need attention.

The really ugly ones need the ends grinding down (not a problem) and in some cases a new gash and centre hole cut (see image below if you don't know what I am talking about).

Can someone suggest a suitable cutting disc for cutting the gash (possibly an ultra thin disk in a 4.5" hand held grinder, or maybe something in my pencil air grinder?) For smaller end mills (e.g. 6mm) I would rather use the pencil grinder if possible.

I can probably find the disc without help, but I'm unsure what to use to cut / reform the centre hole. Suggestions, please.

Thanks

 

[gaz1]

you will need a home made grinder or a quorn tool and cutter grinder to get those gashes done

ive referenced the flute guide as it really does help to sharpen the flute of the drill bits

Tool and Cutter Grinder Build

Did anyone on here win that Weldon head of ebay Cheers

www.mig-welding.co.uk

 

[6ply]

@minimutly apparently I need that Quorn back

 

[gaz1]

sharpening the flutes

helix ( helicol ) sharpening its the same thing for both homemade and the quorn tool cutter and grinders

 

[gaz1]

@minimutly apparently I need that Quorn back

you could always build one or build a homemade one instead

 

[JOEPRO]

Thought I was on a different forum for a second there

 

[6ply]

@gaz1 I don't want to sharpen the flutes, well not yet anyway. I'm touching up the ends and sometimes doing a bit more. But returning to my original question?

 

[Chippie]

If you gash the centre of the cutter there’s no need to remake the hole….

 

[Agroshield]

...what to use to cut/reform the centre hole...

In some respects the centre hole itself is unnecessary unless you need to grind the flutes, which you have said you do not. It allows the user to mount the tool between centres and grind the flutes using a follower on an adjacent tooth to achieve the correct helical progression.

Many modern end mills are centre-cutting and thus cannot have a centre hole, as one flute has to reach the centre. Their flutes would be re-ground using a method that does not require mounting between centres.

If you wanted to deepen the end recess, carbide will cut HSS, but finding the correct size might be difficult and lining it all up also time consuming. A carbide centre drill would redrill the centre, but you need the correct equipment (ridgid, high speed and concentric).

I think that in commercial use, once a cutting tool gets to the stage that the centre hole disappears, it has earned its money and would be scrapped.

A thin wheel is used for gashing. See page 17 of Clarkson manual here: https://pdfcoffee.com/clarkson-cutter-grinder-manual-pdf-free.html

The same place has the KO Lee manual (see page 88, salvaging tools) and the Quorn manual.

 

[RichardM]

Easiest way I have found for doing the gashes is using a small cutting disk in a Dremmel.
This sort of thing, but I think I got the last lot from Lidl:

Page Not Found - Aliexpress.com

 

[6ply]

Easiest way I have found for doing the gashes is using a small cutting disk in a Dremmel.
This sort of thing, but I think I got the last lot from Lidl:

Page Not Found - Aliexpress.com

My cheapo pencil type air die grinder is excellent but it came with some terrible accessories. I wonder whether those AliExpress specials would cope with a HSS end mill. I suppose there is only one way to find out.

 

[RichardM]

That style are pretty good and what I prefer to use. The non re-inforced ones tend to destroy themselves easily, wear safety glasses.