Boring bar

I have read through the very informative threads and associated links, dated 16/4/204, 13/2/2012 and 13/9/2010 on the subject of suitable cutting tools (for us learners) for use on my Proxxon PD400 lathe that takes 10mm square tools.

Although I do not have much confidence in my ability to sharpen bits of metal I accepted the considered opinion that HSS is the best way to go for starters. Even so, it did not prevent me from snapping a parting off tool because I did not realize that the newly supplied tool had to be sharpened first.

I now need a boring bar to open out some very thick washers from around 13mm. I looked at a boring bar that is one piece and I understand that there is another type with the cutting part clamped into the end. Can someone please advice which way to go.

Thanks.

Hi,

This type of boring bar is available which takes HSS inserts at the end. One end has a square hole which is perpendicular to the axis and another hole at the other end at 45 degrees. The HSS cutter is held in place by a grub screw in the end of the holder. They are available in different sizes to accept 1/8", 3/16" 1/4" and 5/16" square HSS cutters. Just bought one for 3/16" cutters for $25. The cutter tip is easy to sharpen and a little practice will get it right.

Paul.

The bars that take hss inserts are very good, and great for bigger jobs

Making the insert itself is a fiddly annoyance but once you have one made it does loads of work and lasts for ages, they can actually be "self sharpening" because of the angles involved in boring a workpiece

I cut a little piece of hss off with one of those dremel cutting discs in my headstock, and the toolbit to be cut secured in the lathe toolholder.

Doing it by hand usually broke the disc for me, they are very brittle

three simple ways to get a tool to bore hole in a thick washer,get a square toolbit and grind it so that you have a boring tool at the end, this will bore your washer to a depth of twice the bit size ie 20mm,advantage --the tool is very stiff and will not deflect, a purchased hss boring tool forged to boring bar shape works ok but I have that they will chatter when pushed to the limit,whereas a bit ground ffrom a hss toolbit does not chatter so readily.yet another way is to have a commercial boring bar like in the Adys post, I always make mine from a length of round silver steel,grinding small hss toolbits for these bars is fiddly for the beginner,so get a long round toolbit grind the end to the cutting shape you require then cut then tool to length. The old method was to grind a nick in the tool bit on the edge of the grinding wheel to about half depth,put it in the vice,place bit of rag over it and clout it with a hammer to break it where it is nicked, modern way is to use a 1 mm thick cutting disk in an angle grinder. The 1mm discs can also be used when shaping up large hss bits,then finish off on the grindstone.lot quicker.

No need to spend real money. Find an old, manky or broken drill around 3mm and cut off a bit 11mm-ish long from the back end. This is suitable to make a boring bar similar to the second post but more convenient since th ehole is round. Use a bit of ordinary mild steel 10mm ir 3/8 square, hold it in the toolpost and drill it sideways 3mm or whatever with the new drill you got to replace the broken one above. Drill and tap the end for a grub screw.

This will do you for the moment and beyond while you save up for a fancy tipped tool.

Save all broken taps, end mills, and center drills, these are hardened full length, the shank end of drills are soft. The hard HSS makes good tools, and round material makes fitting in home made boring bars easy, saves the time needed to put a square hole through a bar. My smallest bar is ground up from a bit of 1/4" HSS, and will bore a little under 3/16" / 5 mm to adepth of about 1 1/4". The biggest I have is 1 1/2" dia bar for between centres, used to bore a 2" bore cylinder for an open crank IC engine(that doesn't work[yet]).

Ian S C