How To Grind A Hss Turning Tool

[wawoodman]

Great post, thanks.

What grit belt did you use for the roughing? (If I missed it, I apologize!) Do you use any lube on the belt?

 

[sanddan]

I recently bought a large lot of tooling and got a box of HHS cutting bits with most of them pre-ground into many different shapes. They really point out the advantages to grinding your own bits. Thanks for your write up, it went along way to explaining the process.

 

[mikey]

Thank you Mikey you made grinding a tool look easy.

It is easy, Tom; give it a go and see. What is not so easy is to understand what each of those angles do and what happens when you change them - therein lies the magic! There is enough material in the references I listed to get you well on your way - good luck, and show us your results.

 

[mikey]

Thanks for sharing! I thought this was too complicated for me to master in a reasonable length of time so I bought hss inserts. I think I could have mastered your process. Too impatient to wait I guess but I just want to make parts not stuff to make parts. Now if I could just figure out how to get a better finish


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Jim, I think you'll find that grinding is simple once you know what to do and how to do it, and now you do. I also own AR Warner HSS tools and like them but do yourself a favor. Grind the tool I showed above and come to your own conclusions.

 

[mikey]

Thanks for your great post. This is a great set of instructions. Breaking it out to simple steps makes it manageable to learn.

I just started grinding lathe tools about 5 days ago. I watched some videos, http://tomstechniques.com/ and some others. I went at it making a couple of turning tools and a facing tool. They didn't come out beautiful but they worked quite well.

I followed Tom and others advice about skipping the back rake angle so the bit can be indefinitely resharpened.

Brian, thanks for your kind words.

I'm happy to see that you've at least started to grind your own tools. I remember that with only 5 days of effort, I turned a 2-1/2" long tool bit into a burnt 1-1/2" long bit with so many facets on it that it was hard to tell which one was the cutting edge so good for you!

I know that eliminating back rake is a favored thing to do by some well-known guys, and even some guys here on the HM forum. Invariably, they say this makes re-sharpening easier because it does. However, I highly recommend that you grind a tool with back rake to compare performance before you blindly follow their advice. Without getting too technical, back rake reduces shear plane length and this has a significant impact on reducing cutting forces. It also focuses those forces at the tip of the tool and this enhances finishes significantly.

I have some tools in need of re-sharpening. They are all at or beyond a decade of regular use and all have back rake ground into them. They have, and continue to perform as well as they did on the day they were ground because I hone them regularly. For me, honing for a few seconds works better than re-grinding a tool to re-establish a cutting edge. Plus, I have the performance advantages that back rake provides.

Again, sort it out for yourself. Grind a tool with and without back rake and see. I'm guessing that you'll cut deeper without chattering and you'll finish finer.

 

[mikey]

Great post, thanks.

What grit belt did you use for the roughing? (If I missed it, I apologize!) Do you use any lube on the belt?

Thank you!

I use a 24 grit AO belt to shape and an 80 grit AO belt to remove coarse grind marks. I use DoAll wax stick lubricant before grinding each face - just a little dab will do ya! The wax really cuts down on grinding temps and the belt lasts much longer.

 

[BriancCc]

Again, sort it out for yourself. Grind a tool with and without back rake and see. I'm guessing that you'll cut deeper without chattering and you'll finish finer.

I was mostly happy that I succeeded in making tools that worked. Going from zero to steel flying off the tool felt like a solid success. Thanks for the advice to try a back rake, I will give it a go.

 

[ddickey]

I'm ready to give this a go. Now all I need is a grinder. Lol
So not really ready just looking forward to it.

 

[Christian Poulsen]

I drafted the above sometime in September of last year but due to chronic laziness and honest busyness, I only just now put the final touches on it. There have been numerous discussions about tool grinding, carbide vs HSS and so on recently and that got me off my butt. It is my sincere hope that this helps someone get over the hump and learn to grind tools. Most of us don't own big, rigid, fast or powerful lathes. We own hobby lathes, typically in the 10-11" class with max speeds of 2500 rpm or so. For those lathes and smaller, HSS is usually the best tooling option and we can further modify those tools to enhance the performance of your lathes even more.

I hope this gives you a start.

Mikey

Great posts and step by step Mikey....Except dissing on carbide again for home lathes (except for big, rigid, powerful lathes)...which is BS
Smiley Face here!
....Without going back and copying and pasting all the carbide info. and grades I've posted...straight up: The "good" carbide is stronger, harder, tougher and stays sharper many times over HSS
But granted, a common belt sander won't work on carbide....

 

[mikey]

I was mostly happy that I succeeded in making tools that worked. Going from zero to steel flying off the tool felt like a solid success. Thanks for the advice to try a back rake, I will give it a go.

Yup, nothing succeeds like success. I wish you all the best, Brian, and do post pics of your tools if you can.