Models for grinding HSS Lathe Tools

[Iron-Iceberg]

 

[mikey]

Wow, you did great! Not sure I could have done better myself, and I really mean that. Geometry looks good and those tools should work well for you. I really like your knife tool and the LH square tool - very nicely done, Sir! And yeah, I'm a ceramic fan, too.

I noticed a bit of light reflection at the tips of the turning tools - maybe hone them a bit more? Also, I cannot see a flat on the threading tool but that might just be the pic; if it is there then you should be good to go.

Have you tried cutting with them?

 

[Iron-Iceberg]

Thanks mikey, they're really sharp. Got a few slices on my fingers to prove it. Haha. One problem I’m having with the grinding wheel is that they are glued on and I cant change grits with out trashing the disk. So I picked a pretty aggressive disk for most work. This means that it takes a lot of work with the diamond cards to get the grinding marks out and get a good finish. One day I’ll get a belt grinder so that I can swap grits easier.
The threading tool had a small flat on the end but I haven’t tried it out yet. I’ve mainly been using the LH square tool. That why it’s a little smaller as I’ve needed to regrind it a few times from dumb mistakes.
I’ve saved a bunch of pages from this thread and need to go back and reread some of them on how to use the tools. I’m new to this so I’m not sure what is going wrong when I’m not getting a good finish. Yesterday I was getting a really bad finish before I realized that the tool was floating back and forth. It turned out the Gibbs where loose on the compound and I needed to tighten them up. I had cleaned the compound when I got the lathe and adjusted them but they must have worked loose in use.
I also had been practicing on some cheep hot rolled steel bar I had, just to get used to the machine and I don’t think it machines very good in the first place.
I’m sure I’ll have more questions so thanks for the all help you have given here.

 

[mcdanlj]

@Iron-Iceberg those are nice clear pictures that show the shapes nicely!

 

[mikey]

Thanks mikey, they're really sharp. Got a few slices on my fingers to prove it. Haha. One problem I’m having with the grinding wheel is that they are glued on and I cant change grits with out trashing the disk. So I picked a pretty aggressive disk for most work. This means that it takes a lot of work with the diamond cards to get the grinding marks out and get a good finish. One day I’ll get a belt grinder so that I can swap grits easier.

This is what I'm talking about. The circled areas reflect light and that tells you the intersection between the planes of the tool are not quite sharp. When they are, there is no light reflection at all:



I would hone them until that reflection is gone. Not only will the tool cut better but it will hold the edge longer. And yeah, I always get cut when honing my tools, too.

I do agree with getting a belt sander someday. They are so much faster and easier to use, especially with ceramic belts.

The threading tool had a small flat on the end but I haven’t tried it out yet. I’ve mainly been using the LH square tool. That why it’s a little smaller as I’ve needed to regrind it a few times from dumb mistakes.

That tool on the right end is your RH square tool and its my most used tool, too. I'm way past needing to grind another one; I've honed off my back rake!

The flat on the tip of the threading tool is really important and not just from a thread form standpoint. That flat will keep the tip of the tool from cracking off; trust me. You kept it small enough so we can't see it in the pic; that should do fine.

I’ve saved a bunch of pages from this thread and need to go back and reread some of them on how to use the tools. I’m new to this so I’m not sure what is going wrong when I’m not getting a good finish. Yesterday I was getting a really bad finish before I realized that the tool was floating back and forth. It turned out the Gibbs where loose on the compound and I needed to tighten them up. I had cleaned the compound when I got the lathe and adjusted them but they must have worked loose in use.
I also had been practicing on some cheep hot rolled steel bar I had, just to get used to the machine and I don’t think it machines very good in the first place.
I’m sure I’ll have more questions so thanks for the all help you have given here.

If you're using steel from the hardware store then its probably 1018, which does not finish well with most tools. A Shear tool is supposed to do well with it but I have to make one and confirm it.

Check to be sure the tool is on center height. This is more important than you might think. I don't mean eyeballing it using a center in the tailstock. I mean measure the center height of your lathe and make a height gauge that puts the tip of your tool dead on center. Some guys think this is not important but on a small lathe, it is. PM me if you're stuck for ideas on how to make a height gauge.

@Aukai asked a similar question about tool position and I've been waiting for Dave to respond. If he doesn't within a few days I'll have a go at it again. What it boils down to is understanding how the tool cuts and then playing with tool position until it does what you want it to. I've been doing it for so long that I don't even think about it or notice what my tool angle is anymore. Hang on, though. We WILL make it clear very soon.

 

[tmenyc]

Well, I finally got the knife tool done close to correctly, in HSS! I watched Adam's (Machine Tech Video) videos last week, 2-3 times, and it finally clicked into place. And it cuts well! Not perfect, and the radius needs a bit of work, but i got over the hump. It was so much easier working with HSS than keystock, for me at any rate.
Pictures below: HSS on left, keystock model right.

Now I want to cut the others , which I had no issues with, in HSS.
Thanks so very much for the help and patience.

Tim

 

[mikey]

Looks good, Tim. Let us know how your tools work for you.

 

[Z2V]

It was so much easier working with HSS than keystock, for me at any rate.
Pictures below: HSS on left, keystock model right.
View attachment 289514View attachment 289515View attachment 289516View attachment 289517
Now I want to cut the others , which I had no issues with, in HSS.
Thanks so very much for the help and patience.

Tim

Tim
Looks good. Glad to hear that it’s clicking for you. I have to agree with you on working the HSS compared to key stock. The key stock is so soft it’s easy to go too far when grinding, but it keeps you paying attention to what you are doing and it’s inexpensive. If you mess up, cut the end off and start over.

 

[tmenyc]

I'm finally getting a bit of time to grind the rest of my first set of HSS tool bits. Other than the fact that it takes longer and is more work cutting 3/8 than 1/4 (and I've now done both, and enjoy the process of grinding the 3/8 more, actually), what is the functional reason to choose one over the other? My tool holders are AXA, so can handle either. Seems to me that the actual cutting area is not that much larger on the 3/8, but there is more chip relief. Is it width/height of the cut? Is cutting speed affected? Once I really get the hang of turning soft steel, most of my work will be in acrylics, delrin, and ebonite with some smaller work in brass and bronze, although I will be having fun with steel and aluminum. I haven't been able to find the reasons one chooses one or the other anywhere. Guidance please?

Many thanks,
Tim

 

[ttabbal]

It's mostly rigidity. The thicker tool will deflect less. It won't matter on really light cuts, but it can be an issue. It's the same reason that you want to limit how much the tool or the work sticks out from the holder. I also have some 1/2" blanks for my AXA. They are about as thick as I can go and still center the tool.

The smaller bits are nice to keep around as they are faster to make, cost less, and fit in tight spaces. I mostly use 3/8.