Grinding HSS

Hey guys,

I need some help on getting the right wheel.

I’m a little out of my league with grinding. I’m trying to re-sharpen some knife blades. They are 4” long, 3/4 high, 1/8” thick with a 40° knife edge.
The material is high speed steel. Not sure of the grade but the grinding wheel I’m using isn’t cutting at all. And it’s getting the blade smoking hot.

The Wheel I'm using is a Norton general purpose Toolroom grinding wheel. 7 inch aluminum oxide 100 grit grade I. McMaster number 4397A68

I have to cut it dry because I’m using a POS end mill grinding machine.

I appreciate a little advice.
Blue

Sounds like the blades are D2? Get Michiganbuck or a grinding wheel house to give advice.

It could be near impossible to make any time grinding dry with a 100grt wheel. likely you need a 36 or 46 grit wheel to rough it in. It still might take a coon's age to grind it dry. Washing soda and water can make a decent homemade coolant.. Calgon pink hand soap and water another homemade coolant and a hand spray bottle is OK. Often a white AO wheel is best ..and some pink wheels are good.

It takes a solid set-up because HSS steel can be so hard, you need to be able to tap it with something and feel no vibrations to your finger touching to prove you have a solid set-up. ..Some people say a soft wheel for hard parts but a soft wheel can break down so fast that it hardly takes any stock. Possible a 46 h to k might be good with frequent dressings.

The wheel has to crank at 2800 rpm or better (3400 to 3800 would be good but don't crank faster than what the wheel says.) and grinding should show elongated sparks with some forking to prove you are cranking fast enough.

*Grinding grit will make shot life of a mill or a lathe.

Even 60 and 80 grit wheels will put alot of heat without proper coolant. You will likely burn and anneal your cutting edge with a 100grit. I would use Buck's advice on wheel grit and bond. I would prolly finish with a 46, then hone/polish to get final edge and finish.

Thanks Michiganbuck and Mike1974

I will try the 46 H-K

The blade is in a fixture and seems solid enough. But it is on a rickety end mill sharpener.
And yes grit will tare up machine ways.

Thanks guys! God bless!!
Blue

Re: QT Mike[Even 60 and 80 grit wheels will put a lot of heat without proper coolant. You will likely burn and anneal your cutting edge]

I once went from one vendor's 46k to another vendor's 46k and the edge must have gone bad..customer called to say he was getting 50% or so tool life...went back to the original wheel and part edge got good again.

A dull dressing diamond or way too fine of a dress are possible culprits for this problem too. In this case though I'd start with Buck's suggestion first and switch to the 46 grit wheel. Investigate further if necessary later. If you can do it, when grinding narrow things like this (especially HSS) without coolant it might help keep things cooler to switch to a cup wheel.

Hey guys,

Thanks for the awesome advice!

I just tried out the new wheel. What a Huge difference with the right one! Went with the 46 grit H grade. Don’t know how many blades I can get with one dressing but I can see this is going to be a piece of cake now.

Thanks again!
God bless!!
Blue

blueboy said:

Hey guys,

Thanks for the awesome advice!

I just tried out the new wheel. What a Huge difference with the right one! Went with the 46 grit H grade. Don’t know how many blades I can get with one dressing but I can see this is going to be a piece of cake now.

Thanks again!
God bless!!
Blue

Click to expand...

As an avid knife sharpener i opened this thread expecting to pour a ton of good advice in, but reading the thread I realized just how different of a situation the OP is in. My roughest stone is 200 grit and my finest abrasive is about 1,000,000 grit equivalent (25 nm)

I would likely rough and semi-finish with a white 46 H to L wheel. Radiac makes some great pink wheels but offhand I don't remember the specs /label
Semi finish would be to get the part to size and shape with that wheel. Once it is to shape go finer to whatever wheel grit gets to the finish you need. More open wheels run cooler, often they might look like they are made of popcorn with having open spaces you can see.
You can go all the way to mirror but the finest wheel should only take off very little stock...perhaps only the last .0005 or so.

Increments of grit can help make work go faster ..perhaps 46- 60 - 100 -200 and so on..

The most solid set-up will help keep a part cooler, and a step over at the end of travel can help keep a part cool.

With needing finish more than size rag wheels and polishing wheels or abrasive paper can be good/best.

Wet is best, one can carefully cut a donut of plastic and press it on the grinder shaft, perhaps a 3" OD and a shaft tight center hole. Pushed snug tight to the grinder hub casting this will spin coolant out and so way from getting in the bearing,
This is even good on the likes of a professional surface grinder. Always have the spindle up to speed when you turn on the coolant, and turn off the coolant while the spindle is still running. Run a few seconds to ring out the wheel.
*An extra (for sure safety) ground wire should be added to any grinder/machine that is not professionally installed by an electrician. (even with that the extra wire is good).

Yes I am even/also talking about a bench grinder for any wet use, don't just rely on the three-prong ..add another ground wire.

Here is the Radiac catalog. I think they have some of the best wheels and you can call their wheelman if you have a true need, Have your needs and question so you don't just waste their time. What material you are grinding and what machine you are using..`
https://radiac.com/site/wp-content/uploads/2014/09/2016-Radiac-Abrasives-Stock-Catalog.pdf

pcm81 said:

As an avid knife sharpener i opened this thread expecting to pour a ton of good advice in, but reading the thread I realized just how different of a situation the OP is in. My roughest stone is 200 grit and my finest abrasive is about 1,000,000 grit equivalent (25 nm)

Click to expand...

Yeah, different knives and powered wheels to boot. Also, diamond is a bad thing in this application.

My go to wheel was always an induced porosity 32 grit whenever I could get away with using it when surface grinding, and a very coarse dress when removing stock. I think it was a G hardness? Get one, it will be worth it!