Thread: Double ended boring bars with HSS

I own one of those double ended boring bars which use HSS. Not really sure how they are suppose to be used. But guessing

• The 90-degree end is for threading Operations
• The 45-degree end is for turning operations
• Most HSS bits are ground for standard threading operations.
• Big advantage over inserts is reduced chatter. Inserts bear forces at the furthest point on the tool.

Is my understanding correct?

Thanks in advance, Tom

Both ends are for boring Tom. The 90 degree end is for through boring and the 45 degree end for boring blind holes (i.e. to a shoulder). You can also use the 90 degree end for cutting internal threads.

You can also use the 45 degree end for screw cutting, you just have to grind the tool differently.

I have a few of them boring bars at different sizes, I like HSS over inserts if it's not needed for hard materials.
HSS is cheap for a home shop and gives a geat finish, even on gummy material if it's ground right.
The little 1/8 HSS on small holes doesn't get much sharpening life though.
As said about you can use then either way depending on how you ground your HSS to suit threading or blind boring etc.

If you have the grind right you can even use the 'other side' of the 45 degree end to chamfer the inside of a bored hole (if it is long enough)

Michael

Originally Posted by Michael G

If you have the grind right you can even use the 'other side' of the 45 degree end to chamfer the inside of a bored hole (if it is long enough)

Michael

Never used it that way, I take it the lathe runs in reverse, or you grind the tool to be used upside down?

No - lathe runs in the 'normal' direction. The tool is ground with a flat end, inserted so it angles back and then wound back to put a chamfer on the inside corner. Bit late for a photo tonight but if there is still confusion I'll set it up tomorrow to demonstrate.

Michael

Originally Posted by Michael G

No - lathe runs in the 'normal' direction. The tool is ground with a flat end, inserted so it angles back and then wound back to put a chamfer on the inside corner. Bit late for a photo tonight but if there is still confusion I'll set it up tomorrow to demonstrate.

Michael

I would like to see a picture.

I

A picture I can do
back chamfer.jpg
Think of this as a section view from the top of the lathe.

Michael

I see wah you mean now, reverse chamfer

Hi Guys,

I had one given to me many years ago, its only quite recently that I have used it. Until you do you don't realise how versatile it is.

Would someone be so kind and post an example of an HSS grind for this type of internal boring or provide the geometry of the HSS bit?

These are screenshots of an old South Bend document on tool grinding. The doc is too big to post here unfortunately. One screenshot refers to the other.

Interesting find http://www.cutterod.com/cutter_zone/...athe_Tools.pdf

Yep, that's the same document.