Another carbide shank boring bar

[old mart]

I have a home made 12mm carbide shank boring bar with DCMT 07 tips and fancied another with CCMT 060204, which I prefer for steel.
The donor bar end was made as short as possible (1/2") by holding the cut end in a custom made collet ring in one of the lathes collets to face off the joint.
The bar end was about 11.5mm diameter, so I bored a short tube 11.5mm/ 12mm to hold the parts while silver soldering.
Some flux and pieces of silver solder were put in the assembly, held vertically in a vise and heated with a MAPP torch. When it had cooled, I turned the tube down to the carbide diameter and cleaned up the tool.
Then I had a bit of luck.
I dropped it. It bounced off my foot and the tip fell off. Only flux was holding it together, the silver solder pieces were just on the point of melting onto the steel part. The remaining bit of tube peeled off the tip and I made another stepped tube and started afresh.
This time, I pressed the tip down with a thin rod and applied more heat. I felt the joint close up as the solder melted, everything is ok now.

[Ed ke6bnl]

sounds like a good plan, nice to see some pictures.

[MattiJ]

In my plans also but I'm still waiting for cheap carbide bar stock to show up..

[old mart]

I have bought 7mm, two lots of 12mm and 1/2". I had to go for 12mm as the 1/2" was out of stock for the pair. The carbide I bought is manufactured in the UK, so should be quality kit. The ends were ground square and I used a DMT diamond lap to improve the surface for better silver solder adhesion. The 12mm bars are both 109mm long, so about 121mm including the end.
I have made a toolpost for the Smart & Brown dedicated to 12mm boring bars and 26mm cutoff blades. It holds exactly at 90 degrees to the compound and I have blades with 1.6mm, 2mm and 3mm Kennametal A2 tips. The boring bars fit in a 12mm reamed hole in the toolpost and are gripped by four grubscrews with their ends faced smooth. The boring bars don't have flats, so I have a height gauge to set the tip height.

[DR]

At one time I had a few steel heads with insert pockets ready for brazing to carbide shanks. The head's braze area was drilled in with a 90 degree point drill to match the 90 degree point ground on the carbide shank. That gave a lot of contact area for the braze material. The problem was to do it correctly you had to grind the point on the carbide shank which is no fun to do.

[Danl]

In my plans also but I'm still waiting for cheap carbide bar stock to show up..

I agree, Matt, on the waiting. And waiting. And waiting.

I've got the insert end of a solid carbide shank bar that my brother gave me, 0.750" Φ, and have been looking for a couple of years for a replacement shank. He tells me that I should really use a special type of silver solder to join them together when I finally do find one.

Dan L