Grinding chip breakers on HSS toolbits

This is where bits of wisdom will be stored, a frequently asked question section with answers.

Moderators: Harold_V, WJH

Harold_V
Posts: 16370
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Grinding chip breakers on HSS toolbits

Postby Harold_V » Wed Jul 14, 2010 1:01 am

Yep---a wheel that floats side to side is trouble. Fact is, when I was grinding the chip breaker on that RH tool, I slipped, partially destroying the cutting edge. Takes a steady hand, but most importantly, a wheel that runs dead true, on the periphery and the side.

As far as the slip goes, a sure sign I'm getting old. I used to handle chip breakers in stride. Not so easy anymore, it appears! :-)

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

Haderimouve
Posts: 1
Joined: Mon Oct 21, 2013 11:51 am

Re: Grinding chip breakers on HSS toolbits

Postby Haderimouve » Tue Oct 22, 2013 12:34 am

Hi, everybody ! I'm new here since yesterday. I'm french but living in Spain. Completely professional in the violin construction for more than 30 years but newbie in the metal machining !
I started using a Schaublin 102 lathe one year ago and used to pick up technical informations on the Internet ... I've no teacher here in Madrid that can help me do use the lathe correctly and give me the essential tips to start machining in good conditions !
Especially the borings I tried to achieve were catastrophic ... Using exclusively HSS tools, I wanted then to try carbid inserts ! Till yesterday ... that I got a try with grinding a chip breaker following Harold_V rules : Whaouuuuuuuuuuuuuuuuuuuu it works VERY WELL !!!! :lol: :lol: :lol: I spent all my afternoon in front of my grinder to experiment new profiles. Used to grind carbon steel tools for my instruments, I don't have not any tech problems to use the grinder : I put off all my grinder's guides off and started to work "in the air". After two or three minutes, I started to be well in this way of grinding ... I shaped some tool bits and after trying them on the lathe, I discovered that I would get high quality finish and very efficient cuts : Thank you very much Harold_V. because yesterday started for me a new life in machining !!!
:lol: :P :lol:
One question ... What will I do with these insert carbide boring bars I recently ordered and that arrived yesterday evening to my workshop ? :?: :?: ?

Haderimouve

Harold_V
Posts: 16370
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Grinding chip breakers on HSS toolbits

Postby Harold_V » Tue Oct 22, 2013 3:45 am

Haderimouve wrote:One question ... What will I do with these insert carbide boring bars I recently ordered and that arrived yesterday evening to my workshop ? :?: :?: ?

Haderimouve

One never knows what tomorrow may bring. Insert tooling definitely has its place, and could prove to be quite useful to you for some projects. Key, here, is understanding when carbide would serve better than HSS. If they're positive rake, you may even benefit by using them on wood, but they can really shine if you must machine some hardened materials, or certainly for abrasive materials. If you have the required rigidity and speed that carbide demands, I'm sure you'll put them to good use in due time.

The most important thing I'm taking away from your comments is that you have not chosen to use insert tooling to avoid learning to grind proper HSS cutting tools. My hat is off to you.

I'm quite pleased to read your comment about free hand grinding. It was one of the most difficult things for me to assimilate, but once I did, I realized it was the way to go. Amazing what things we learn from our peers! And to think that I was critical of their setup! :oops:

Welcome to the board.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

User avatar
steamin10
Posts: 6495
Joined: Sun Jun 08, 2003 11:52 pm
Location: NW Indiana. Close to Lake Michigan S. tip

Re: Grinding chip breakers on HSS toolbits

Postby steamin10 » Tue Oct 22, 2013 8:53 pm

:twisted: At my last job they had a SB heavy 10, and nobody could grind a tool bit. I took the rest off, and was immediately jumped on by the 2nd foreman/safty man. He chewed me up like I was the dumbest, and would hear no argument.

It is a shame to work for Psychotic managers, that do not truly understand the processes they control. Being an old hand, I found workarounds for many thngs broken or out of service, and he didn't like my solutions, wanting to appove every step in micromanagement. (phooey! How hard is it to fix a garage door cable? His pet garage door guy charged 4 hours for each cable!) In another plant we went old school and hung counter weights on the doors to stop spring failures, that were killing us. Afterword, we changed only 2 bad cables, in five years, that were non stainless, and rusted near the floor. It was awesome!

I learned to grind tools, like large drill bits, and lathe tools, by eye. When you can, it amazes skeptics that you can outpace them in the work, and some will try to demean your knowledge, or block you. Leave em behind.

Congrats on an easy skill to master. You can grind and regrind whenever it pleases you, adding to your skill set.

By the way - welcome to the board! if you are new here, I encourage you to pick a subject, and peruse the old threads. Get aquanted with the subjects by reading the sticky headers that contain much safty and don't do's.

Be safe and well. Dave
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

Hellchild
Posts: 2
Joined: Tue Nov 18, 2014 1:27 am
Location: Honolulu

Re: Grinding chip breakers on HSS toolbits

Postby Hellchild » Tue Nov 18, 2014 9:43 am

I have always wondered this but have never seen it addressed. If you are grinding a HSS tool and you overheat it so that it changes color, how far do you need to grind it to get to good metal again? Is it just the skin that is affected or does it go deeper down than that?

Thanks,

Kevin

Harold_V
Posts: 16370
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Grinding chip breakers on HSS toolbits

Postby Harold_V » Tue Nov 18, 2014 5:02 pm

Hellchild wrote:I have always wondered this but have never seen it addressed. If you are grinding a HSS tool and you overheat it so that it changes color, how far do you need to grind it to get to good metal again? Is it just the skin that is affected or does it go deeper down than that?

Thanks,

Kevin

So long as you don't quench the tool, which offers the risk of creating micro-fractures, drastically shorting the tool's edge life, there is no harm done by discoloration. HSS does not readily anneal, and that's the reason one would be concerned. That's a hold-over from the years of use of carbon steel, which would be annealed by over heating.

I strive to grind without discoloring my HSS tools. In my opinion, it shows a lack of ability, although that may not be a widely held view. Some folks will continue to grind until the tool can't be held comfortably because of heat. If a tool is held in a device, it can be ground to completion with no concern for the ending temperature, as it requires furnace cooling to anneal HSS---with a temperature drop of fewer than 50°/hour to accomplish the task.

To help you better understand HSS's ability to be heated, it is common practice for a worker to silver solder a HSS tool bit to a steel shank. So long as the assembly is allowed to air cool, there will be no noticeable difference in the performance of the HSS as compared to one not subjected to the same temperature.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

User avatar
SteveM
Posts: 6201
Joined: Mon Jun 27, 2005 6:18 pm
Location: Connecticut

Re: Grinding chip breakers on HSS toolbits

Postby SteveM » Wed Nov 19, 2014 11:13 am

Harold_V wrote:Some folks will continue to grind until the tool can't be held comfortably because of heat. If a tool is held in a device, it can be ground to completion with no concern for the ending temperature, as it requires furnace cooling to anneal HSS---with a temperature drop of fewer than 50°/hour to accomplish the task.


Harold - is it OK to quench the tool often so that it never really gets to a heat where it might fracture (e.g. before it gets to the point where you hear the hiss of boiling water)?

Do you have a special holder for holding them for the full grind? If so, can you post a picture?

Grinding while it is in the AXA toolholder can get difficult, as the toolholder will get in the way.

Steve

Harold_V
Posts: 16370
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Grinding chip breakers on HSS toolbits

Postby Harold_V » Wed Nov 19, 2014 4:46 pm

SteveM wrote: is it OK to quench the tool often so that it never really gets to a heat where it might fracture (e.g. before it gets to the point where you hear the hiss of boiling water)?

That has always been my practice. If, by chance, the tool is exceedingly hot, I won't water quench immediately. Instead, I place the tool on a heat sink to allow the temperature to drop somewhat slower. I then water quench, using ice water, cooling the entire length of the tool. That allows for greater grind time before a quench is required. I avoid the hissing of water boiling at the tool.

Do you have a special holder for holding them for the full grind? If so, can you post a picture?

Yes, I use a special holder. It's called my hands. No need to post a picture---they're much like all others, only starting to look quite old.

Grinding while it is in the AXA toolholder can get difficult, as the toolholder will get in the way.

That's not the only problem. It also makes it more difficult for the tool to contact the wheel intimately. I rely a great deal on feel when I grind tool bits. I have to know when the tool is in (proper) contact with the wheel, so adding weight complicates the task. Do remember, I do all of my grinding without the use of a tool rest. The wheel, for all practical purposes, becomes the rest, so "feel" is important.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

curtis cutter
Posts: 229
Joined: Fri May 18, 2012 11:46 pm
Location: Curtis, WA

Re: Grinding chip breakers on HSS toolbits

Postby curtis cutter » Mon Sep 04, 2017 10:21 pm

I enjoy reading all of these posts.

My grinder used to be across the shop from the lathe. Some time ago I moved it to about six feet away. It seems I spend more time grinding tools wrong and getting magnifying glasses out to see what the failure was and then back to the grinder. I then repeat the process for the duration of the evening... :)

I too have some of the carbide inserts but honestly, HSS seems to give me better results as long as I pay attention to tool design. Diamond stones help finish the grind.

I am not really worth a hoot at doing machining, it was not my career and I have a hundred other irons in the fire but I do so enjoy going out to the shop and making chips. I am looking forward to the rain returning and the outside chores winding down.

Gregg

User avatar
SteveM
Posts: 6201
Joined: Mon Jun 27, 2005 6:18 pm
Location: Connecticut

Re: Grinding chip breakers on HSS toolbits

Postby SteveM » Tue Sep 05, 2017 8:30 am

curtis cutter wrote:Diamond stones help finish the grind.


Harold can give better specifics, but I believe that you should not use a diamond wheel on HSS - I think it's something about the diamond being absorbed into the steel when it gets hot.

You can use a diamond sharpener to hone the tool, as that is done by hand and won't generate any meaningful heat.

Steve

curtis cutter
Posts: 229
Joined: Fri May 18, 2012 11:46 pm
Location: Curtis, WA

Re: Grinding chip breakers on HSS toolbits

Postby curtis cutter » Tue Sep 05, 2017 10:11 am

I should have been more clear. It is a hand diamond stone.

User avatar
SteveM
Posts: 6201
Joined: Mon Jun 27, 2005 6:18 pm
Location: Connecticut

Re: Grinding chip breakers on HSS toolbits

Postby SteveM » Tue Sep 05, 2017 11:15 am

curtis cutter wrote:I should have been more clear. It is a hand diamond stone.


Perfect.

Steve


Return to “The Resource Library”

Who is online

Users browsing this forum: No registered users and 1 guest