Thread: Drill and tap an endmill

I have a need for a special counterbore. It will be a 13mm four flute end mill (which I have now) drilled and tapped to 4mm in the cutting end so a 4mm SHCS can be fitted to act as a pilot. Head of SCHS needs to be 6mm so have turned one down to suit. It's a tool to counterbore the rear of some gate hinges so the counterbore fits over the top of nutserts to be fitted to the fence and gate posts. Original screws were installed too tightly and simply pulled out of the posts which are very thin walled. The endmill is threaded on the shank end so I can make up a T handle, as this will be done by hand. Only need about 1.2mm depth of counterbore. What I need to know is how hard will the end mill be. It's HSS. Can I drill and tap this?

One of these might save you a bit of drama Nev https://www.ebay.com.au/itm/13mm-HSS...oAAOSw~gRV1~58

It just so happens that the inner part of the end mill cutting edges just allow enough clearance for the 6mm pilot section, so just a matter of drilling and tapping for the SHCS. Just not sure if I will need a carbide drill. Easier to make a handle as well because the other end has a M12 x 1.25 thread.

IMO drilling and tapping a HSS endmill isn’t practical.
Even if you got the hole drilled you would need a tap that is harder than HSS.
Grab a piece of 6 or 8mm flat steel. Drill a 10mm hole in it and place where you want to have the counterbore and clamp it there.
If you want it perfectly aligned with the hole then make up a stepped pin 10mm down to 6mm to line up the guide bar and the hole while you clamp it.
Stick your endmill in the guide bar and counterbore away

If you were doing more than a couple of holes the mill flutes might start to eat the guide and it would be better to make it out of something that could be hardened. Doesn’t sound like it will be an issue for you.

Another solution would be a thin spacer plate with holes to clear the nutserts. That’s what I would use if doing it myself.

Steve

I’d get the die grinder (or Dremel if the air hose wouldn’t reach) and just go to town on the areas that needed a touch up. There are some jobs that need three decimals of precision, to me this is not one of them. You’re making recesses to clear heads of rivnuts, that won’t be seen. I’d say at this point I’ve probably proven you have a higher desire for accuracy than I do .

To answer your original question.. it will be nigh on impossible to drill and tap a HSS end mill.

I lie..

I wouldn’t even bother with the die grinder unless my other half wanted me to do something. If I was really keen I’d bolt it up and put a bead of silicon on it to fill the gap on the top edge to stop the water getting in...

Nothing to do with being seen or not.The reason I need a counterbore is because the hinges are corner fitting. Unless they are flush with both faces of the post the holes will no longer align. Counterbore back of hinges and they will fit flush against posts and over nutsert flange.

These are the hinges -

https://media.bunnings.com.au/Produc...42b2382d76.jpg

Originally Posted by SurfinNev

It just so happens that the inner part of the end mill cutting edges just allow enough clearance for the 6mm pilot section, so just a matter of drilling and tapping for the SHCS. Just not sure if I will need a carbide drill. Easier to make a handle as well because the other end has a M12 x 1.25 thread.

Nev the cutter that I posted the link to above is 13mm dia and has a 6.25 mm pilot hole, isn't that pretty much what you wanted?
If you or anyone else can drill and tap a 4mm thread in an endmill then i sure would be keen to know how to do it, a spark eroder could do the hole, but the thread.......

Says they’re made from engineered polymer and stainless, which I’d assume means they’re from plastic with a stainless pin, in which case a piloted router bit might be an option.

Originally Posted by OxxAndBert

Grab a piece of 6 or 8mm flat steel. Drill a 10mm hole in it and place where you want to have the counterbore and clamp it there.
If you want it perfectly aligned with the hole then make up a stepped pin 10mm down to 6mm to line up the guide bar and the hole while you clamp it.
Stick your endmill in the guide bar and counterbore away

If you were doing more than a couple of holes the mill flutes might start to eat the guide and it would be better to make it out of something that could be hardened. Doesn’t sound like it will be an issue for you.
Steve

Eight per hinge equals 32 nutserts screws and counterbores. A guide of some sort may work but a lot more work to align each hole. I would need 13mm hole not 10mm. I have a 6mm counterbore but the pilot is 6.4mm and the counterbore is 11mm. Not close enough.

This fence and gates was only installed about two months ago and are falling apart. Typical contractor working for a government department. The guy who did most of the work on it was a truck driver who had lost his licence for DD and had been doing fences for about two weeks.

Originally Posted by shedhappens

Nev the cutter that I posted the link to above is 13mm dia and has a 6.25 mm pilot hole, isn't that pretty much what you wanted?

Pretty close, although the pilot hole is 6.35mm. I need 6mm. I could just epoxy in a piece of 1/4" bar and turn down to 6mm I suppose. May have to abandon my plan and do that if I can't fix a pilot to the end mill. Believe it or not I have 12,14 and a variety of other sizes in these cutter here, but not a 13mm.

Originally Posted by SurfinNev

Pretty close, although the pilot hole is 6.35mm. I need 6mm. I could just epoxy in a piece of 1/4" bar and turn down to 6mm I suppose. May have to abandon my plan and do that if I can't fix a pilot to the end mill. Believe it or not I have 12,14 and a variety of other sizes in these cutter here, but not a 13mm.

Hi Nev,

As far as I'm aware 13 mm isn't a standard end mill size.

What is wrong with turning a piece of 01 drill rod to size and milling flats on it, then hardening. Basically what Steve said !

These nutserts with the big flange work well but also make flush fitting impossible without some sort of modification to the piece being fitted. Maybe not as strong but certainly a better option for a flush fit are these http://www.avdel-global.com/fileadmi...rt_9658_mm.pdf

I give the hole receiving the nutsert a small chamfer and when the nutsert is set the surface is level.

Grind the pilot into a 13mm drill and touch the cutting edge up to cut flat. You can then put a stop on the drill and do the cutting under power with a drill

Originally Posted by BaronJ

Hi Nev,

As far as I'm aware 13 mm isn't a standard end mill size.

https://www.ausee.com.au/shop/item.aspx?itemid=232