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Boring News

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vtsteam:
Today I welded up a base for a clamping fixture for the new lathe out of some rusty steel cutoffs that happened to be lying near the bandsaw in the far shed.

It will bolt down to the carriage boring table and is sized to accommodate the cylinders and pistons I've been casting. Looks like it will actually handle round stock up to 5" dia. I have yet to make the top clamping bar(s) which will bolt into the threaded holes.

I think it will be useful around the drill press and mill, as well.

vtsteam:
Next thing I need is s sturdy boring bar. I found a piece of hot rolled 1-1/4" rod and cut off a 13" length. This boring bar  will be run between centers and needs a cutter right in the middle. Often shop made bars feature a round tool slot, so it can be simply drilled. But this limits the tool to only round cutters -- often drill rod hardened and ground.

Instead I'm going to use a 1/4" lathe tool -- that way I can use either HSS, brazed carbide or even a 1/4" insert holder. But this requires a square hole. I don't have broaches, so I have to square the hole by hand.

I did consider slotting the bar with a 1/4" end mill, then brazing a piece back in to form a square slot. But it is just too cold today to go out to the shop and work with the mill. We've had about a foot of new snow, and after plowing today, I just wanted to sit indoors and do this via hand work.

I drilled a 1/4" hole in the bar, 1/8" off-center by first filing a narrow flat, setting the bar in the vice, and using just a steel rule scratching a mark 3/4" in from one of the vise jaws. The hole is off center so that the lathe tool will have its cutting face on center. Since this bar has the tool in the middle and since the lathe tool can be inserted in the bar from either direction, this boring bar is not "handed". That makes it simpler to lay out.

vtsteam:
Then it was just a matter of slowly hand working the round hole into a square. I usually try to get the corners going first with a triangular file:

vtsteam:
Gettin' there..... I use an HSS lathe tool as a gauge.

vtsteam:
Lookin pretty square. At this point I gently tap the lathe tool into the unfinished hole. The sharp factory edges of the tool raise a burr in the hole, which helps mark where material needs to be removed. At this stage I also usually switch to a very small chisel. I do some cleanup with the file. too. It's mostly just a lot of try-and-fit.

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