I Broke My

D

ddickey

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Apr 21, 2016
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Favorite Circle Machine carbide boring bar. Started the lathe while looking at something other than the tool. I was threading an internal thread and the half nut was still engaged. Slammed it into the back of the bore. Ah man this was an expensive mistake.
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Ouch!
Was the work also ruined? Then, naturally, one asks if the work was a greater loss than the boring bar and tool?
 
That stinks . Anyway that can be repaired ?
 
@graham-xrf No the work was not. The force did skew the workpiece in the 4J pretty good and raised a giant burr in the back of the bore. Realigned the part and cleaned up the burr.
@Alcap IDK. I was wondering that. The front part that mounts the insert I think they're steel?? They must be silver soldered or brazed onto the carbide.
 
My lathe must have some sort of clutch mechanism that I didn't know it had. The lathe stopped but other than the insert holder on the bar there was no damage.
 
Wonder if it can be brazed. Might consider a high silver brazing material. Should have a lower melt temperature than bronze brazing material. Probably will need to retap the hole post brazing.

Had a lathe mishap yesterday while boring using a 3/8" Circle Machine carbide boring bar. Loud bang. Thought I lost the bar or insert. In my case, a bushing bearing in the gear train seized. Spindle kept going but leadscrew stopped. Workpiece was unharmed. I'm on edge when ever using the carbide bar.
 
ddickey said:
@graham-xrf No the work was not. The force did skew the workpiece in the 4J pretty good and raised a giant burr in the back of the bore. Realigned the part and cleaned up the burr.
@Alcap IDK. I was wondering that. The front part that mounts the insert I think they're steel?? They must be silver soldered or brazed onto the carbide.
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The front that mounts the insert usually are steel. So some sort of silver solder might be a good choice for the crack. You have nothing to lose at the moment. It's broken now. Worst that can happen is it stays broken. Maybe you can fix it. Silver braze is really strong. Find the thinnest wire you can buy, 1/16" is way too thick. The material is sold by weight (troy ounce!) due to the silver. If you can get 0.015" diameter or under it would be best. Safety-Silv by Harris is even food safety certified.

Unfortunately this stuff is expensive. So much so that you could probably buy another used boring bar for less. :( 1/32" Safety-Silv-56 goes for $114 at Airgas. (1 troy oz. or 31 grams). Do you know a jeweler? Maybe you could buy an inch of it? You will need probably a whopping 1/2" to fill the joint based on your picture. You also need a little dab of flux.
 
Don't know if this is legit, but found a place that sells Silver solder by %silver and by the inch! 56% silver solder is $1.47/inch, which is a heck of a lot more palatable than buying an ounce of silver. You want the 56% silver solder. Silver solder by the inch
I don't know the wire diameter, so you will need to contact them. If larger diameter, maybe you can cut off tiny pieces and use them. 56% silver solder flows and wicks very well.
 
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