Thread: Counterboring options

Am wanting to counterbore M12 capscrews in 4140, a dozen holes. An M12 counterbore from Sutton is well over $200 so that's not an going to happen.
What options do people use?
Would a 20mm 2 flute HSS slot mill be suitable.
I have a Bridgeport style mill with ER32 collets and a drill press.
Although only they only go up to M10, does anyone have any experience with the durability of the H&F counterbore set.

Tony

How urgent is this job?? Asking, as I've a set that will do the job to borrow, PM sent.

A 2-flute slot drill/endmill should do just fine

Endmills will do it just fine, have done it myself a heap of times.

I do have a couple of ebay counterbores though, and im yet to be disappointed. Honestly, Im flat out finding anything on ebay thats worse than the stuff you get from H+F (in terms of cutting tools at least).

If you have an 18.5 drill you could drill down to a suitable depth and then flatten the drill to create the seat for the head, then just resharpen the drill.

Originally Posted by scottyd

Endmills will do it just fine, have done it myself a heap of times.

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Naturally you need to drill the bolt hole first but I prefer to use 4 flute end mills for counter boring also, I seem to get a better finish

Originally Posted by pipeclay

If you have an 18.5 drill you could drill down to a suitable depth and then flatten the drill to create the seat for the head, then just resharpen the drill.

mate gave me a heap of flat bottom drills...took me ages to work out why a tool maker would have broken drills....but I did figure it out.

I now sacrifice a drill when neccessary so that I will build up a collection

I just posted in the "what did you learn today" thread about these people https://shop.gbrengineering.com/inde...unction=SEARCH. They have well priced tooling and I bought counterbores from them a year or so ago, mine are plain shanked and now all I see from them are screwed Shank (Clarkson) versions, but you could get M4, M5, M6, M8, M10 and M12 for less than Au$90, with perhaps postage on top, but sometimes postage is free. The M12 counterbore alone is under $20, and the brand is Europa Tool. I have been happy with mine. As I mentioned in my other posting, they operate in eBay under the name cnc-poorboy, but if you deal directly with them it will cost you less. It is worth checking all their tooling out, prices are excellent, and I have found the quality excellent, as was the service.
Rob.

Will go the end mill route and see how I get on.
Thanks for the offer Kryn but I can see myself wanting to counterbore for cap screws from time to time so will buy instead.
Thanks for the replies.

Tony

Hi Guys,

I bought a set of counterbores from Banggood last year. They work very well ! One thing that I didn’t expect was the guide pin is sized for the thread clearance size. So when using them, they cut the pilot hole slightly oversize. Which is no bad thing. They also put a slight chamfer on the pilot bore as well, so the cap head sits flat without resting on the sharp edge of the hole.