8" 3600rpm Grinder Ok For Hss Bits?

[Cavediver]

Is an 8" 3600rpm grinder OK for HSS lathe bits, or will it generate too much heat and ruin the tool?

I think the answer is yes, but thinking gets me in trouble sometimes...

I have a 6" grinder, but it is set up with wheels for sharpening wood tools and I don't want to change it if the 8" will work.

 

[RJSakowski]

Is an 8" 3600rpm grinder OK for HSS lathe bits, or will it generate too much heat and ruin the tool?

I think the answer is yes, but thinking gets me in trouble sometimes...

I have a 6" grinder, but it is set up with wheels for sharpening wood tools and I don't want to change it if the 8" will work.

HSS tools will not lose their temper below a red heat. You should be good using the 3600 rpm grinder. Use periodic quenching in water to control the temperature. It is a different matter for carbon steels such as O1 or W1 or 1095. They will soften easily, particularly at sharp edges.

 

[Cavediver]

Good deal.

It's an inexpensive Ryobi with stock wheels. I will try to true them up this weekend, though I am not going to hold my breath on that part. I will likely start looking for replacement sometime next week if I can't get them to run a little smoother.

 

[Terrywerm]

I have an 8" grinder that runs at 3600 and it works just great for HSS lathe tools, drill bits, etc. Like RJ pointed out, you will need to keep some water nearby so that you can keep the tool cool enough to hold on to, much less worry about getting it too hot and ruining the steel. One thing that I really like about the 8" grinder running at that speed is that the fast surface speed really helps to speed up the job at hand, but only requires light pressure on the tool.

 

[RJSakowski]

When grinding lathe tools, I mount the tool bit in a QCTP holder. It's easier on the hands and easier to get angles right. Extend the tool far enough to give you clearance for grinds you have to make.

 

[f350ca]

I have an 8 inch for rough work in the welding area. Thats the first place I go to get a tool bit to the rough shape I want. Toss the STONES that came with it and get a couple of quality grinding wheels. The 8 inch had what was supposed to be a 46 grit wheel on it, I used it for a couple of years, it sort of melted the metal away. Replaced it with a 46 grit I forgot I had. It was absolute night and day difference. It now removes metal rather than just heating it.

Greg

 

[Cavediver]

So... Do you guys use the stock (typically plastic?) bushings that come with the grinding wheels, or is it better to replace them with machined metal spacers?

I had a terrible time setting up my 6" grinder until I bought the Oneway balancing system. Now that cheap grinder with mid-grade wheels runs beautifully with minimal vibration. I love it, at least as much as one can love a cheap grinder. I am already wondering if this is the direction I will have to go. I guess the only thing to do is to mess with the setup first and see how it goes.



Final two questions:
If I choose to replace the wheels, would I be better served by the Norton 3x wheels, the Norton white wheels, or maybe something else altogether?
Finally, what grit(s) should I choose for sharpening metal lathe tools? This will (likely) be used for both metal lathe bits and my HSS wood turning tools. Will a really low grit (46?) be fine enough to put a decent edge on the metal tools, or will I need to 2-step it with a pair of wheels?

Thanks all, this forum has been a great deal of help for me as I get started in metal land. I try to do my research and answer these questions on my own, but sometimes I get overloaded with research and then can't make up my mind.

 

[f350ca]

The plastic bushings should be fine, they only rough centre it, the side washers hold it. When you dress the wheel it should run true.
The white aluminum oxide wheels cut cooler, and are great if your grinding carbon steel tools, if its HSS your grinding they're a waste, the heat from a regular wheel won't hurt HSS.
I like 46 grit for roughing but you'll need finer to get an edge that can be hand stoned.

Greg

 

[royesses]

I made my own adapter and integrated flange for my porter cable china 8" grinder. This really makes a world of difference in vibration and runout both radial and axial. They still need to be trued up at first use. It took a while to whittle down all that aluminum on my little mini lathe, but it was worth it. I made the longer adapter half to go towards the grinder motor and shorter half goes on the outside because the china grinders have a shaft that is too short. This way the outer washer is long enough to be centered by the shaft. See the attached poor sketch of the adapter. I use a 8" x 1" x 1.25 Camel CGW Blue wheel on one side for HSS tools and a Camel CGW green silicon carbide on the other side for roughing carbide. For final sharpening I use a carbide grinder with CBN wheel on one side for HSS and diamond on the other side for carbide. It's an Enco china grinder that I have done many modifications to. It's exactly the same as the HF carbide grinder (in fact the instruction manual that came with it says to call HF for any questions, I guess they forgot to remove that part)and Grizzly. Grizzly sells the parts for it.