Our first carbide chamber reamers - the results

[borbal]

One thing I have been pleased about with our reamers is the good finish they are leaving inside the chamber and the stability of the reamers (don’t chatter and leave nice round holes). Up to now we have been concentrating on steel reamers, but getting carbide reamers to work well in these matters can be tricky. Achieving a fine edge with carbide can be difficult unless a really fine grain carbide is used, and carbide reamers have a reputation for being rather “aggressive” and uncontrollable if they are too sharp.

However, as part of our onward march to becoming the world’s premier chamber reamer maker, (why not?), we made our first carbide chamber reamers the other day. We had to change over to diamond wheels, instead of the CBN (Cubic Boron Nitride) wheels we use for our steel reamers, and the reamer has to be carved out of the solid rather than roughed out first on our CNC lathe and CNC milling machine as are our steel reamers.

We made a rougher and a finisher for 6.5 Creedmoor, which a customer had ordered, but we thought we should try them out first to ensure they would perform as expected. I was delighted with the results, which exceeded my expectations. Indeed, in thirty years of cutting chambers in barrels, I have to say I cannot remember seeing a nicer chamber!

I took it easy with the rougher, which is very sharp and could easily ‘take a bite’ and destroy itself if I pushed it too hard, especially before a margin has worn on the leading edge. I have always used a neat chlorinated “extreme pressure” cutting oil as the coolant when chambering and took it slow and easy at 90 rpm.

 

What follows is a series of photos I took through our Hawkeye borescope. The barrel was a 6.5 calibre barrel made by Border Barrels. This series of photos starts at the lead at the front of the chamber and moves back to the body of the chamber.

 

In this first image, you can see the original land of the barrel to the left and you can see where the tapered lead (to the right) finished in the middle of the photo.

Here, you can see the end of the throat to the right, and the start of the lead.

The neck of the chamber is to the left, with the chamfered step down to the start of the throat in the middle of the photo. The throat is to the right.

The body of the chamber is to the left, and the shoulder to the right, with the junction visible in the middle of the photo. It is difficult to get rid of the fluff from the cleaning patch!

And this final photo is in the main body of the chamber. The magnification here must about 50x and the finish is similar to what a fine ground finish would look like at this magnification.

I made a short video of the inside of the chamber, with some commentary on what I was looking at. You can see the video at www.bbt.scot/video.htm

[bradders]

Good work Geoff

I cut a 6.5x55 chamber on Friday with the new reamer you did for me and have to say it's about the best finished chamber I think I've seen :-)

[Wapinschaw]

Good work Geoff

I cut a 6.5x55 chamber on Friday with the new reamer you did for me and have to say it's about the best finished chamber I think I've seen :-)

 

I cut a 6.5x55 chamber on Friday ........ about the best finished chamber I think I've seen