Boring bar

if the bar is large enough you can make it hold small cemented carbide bits

when it is too small I just tig weld a piece of high speed steel on the end of a bar , grind to desired size and use it ,

have done it for threading, grooving and other internal detail work where a special was needed, in mild steel and 4140 mostly

Drill and ream "a hole" .001" so "oversize" crosswise in the bar near the end. Tap a set screw hole in the end, on axis. Use a drill blank whose diameter corresponds with the "hole".

Same idea, but broach a square hole for a lathe bit.

Randy

Ruin it.

Use what the tool steel uses. Water for W1. Etc. Then temper around 350°F for an hour.

Tool steel is 95% (except for special grades) mild steel, it works just fine.

Use brass braze, quench immediately after the filler solidifies - or while still molten if it'll hold in place (capillary action will probably secure it nicely in a recessed pocket).

Tim

-- "California is the breakfast state: fruits, nuts and flakes." Website:

And anneal it in the process. Assuming he does indeed have common tool steel, and not HSS. If it is HSS, silver solder is the way to go of course.

Tim

-- "California is the breakfast state: fruits, nuts and flakes." Website:

If you have silver solder, make that your choice. Do not quench. You can also heli-arc the tool in place using silicon bronze filler. Either of those procedures work fine.

Harold

Thanks, Tim. Yeah, make sure you use HSS, not other types of tool steel.

Harold

I have to ask, even at the risk of looking dumb -- have you considered one of the import boring bars with square holes broached? The ones with the hole at one end broached at 90° and at the other 45°? These are very inexpensive and the ones I have purchased from Enco have been made very well even if they were made in India. I have rarely been as happy with a purchase. - GWE

See my page, "Making a Boring Bar for the Lathe":

It's the only way to go for specialized boring bar bits. You don't even have to notch the end unless you plan to really abuse it. Brazing or silver solder works fine. Bugs

I have made a number of special purpose tools by silver-brazing bits of HSS to mild steel shanks. Bits of broken HSS slitting saws make nice narrow parting tools and grooving tools for snap ring grooves. I once made a form tool for making round-bottomed threads by silver-brazing a steel ball to a shank and then grinding the top half away to leave a perfect hemisphere. Made a boring bar similarly. The application was a shop-made ballscrew. It was a little rough at first. I filled it with 400 grit clover compound, ran it up and down about 200 laps with a half-inch reversable electric drill. It put up a fight at first, but got over it. After I took it apart, cleaned it, lubed it and loaded it with new balls it ran very nicely indeed. The trickiest part was the ball return tube, made of copper tubing.