Models for grinding HSS Lathe Tools

mikey said:
No, you're dead on. This is a severe amount of back rake and your hand is close to the belt so be sure to use a push block and concentrate. I do the rake grind in two stages - rough to get close and a bit slower to make sure I stop just as the grind reaches the tip.

You got this, T. You will really like this aluminum cutter.
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Lots of rake indeed. Interesting. I might have to give thought to making the table go around the belt a little more for added control. I usually use another blank as a push stick, perhaps not the best choice. A 36 grit belt at 500+ SFPM is not something I want my fingers getting into. That thing removes HSS fast, I don't want to know how fast it removes fingers. :)
 
ttabbal said:
Lots of rake indeed. Interesting. I might have to give thought to making the table go around the belt a little more for added control. I usually use another blank as a push stick, perhaps not the best choice. A 36 grit belt at 500+ SFPM is not something I want my fingers getting into. That thing removes HSS fast, I don't want to know how fast it removes fingers. :)
Click to expand...
Its just a tickle
 
ttabbal said:
Lots of rake indeed. Interesting. I might have to give thought to making the table go around the belt a little more for added control. I usually use another blank as a push stick, perhaps not the best choice. A 36 grit belt at 500+ SFPM is not something I want my fingers getting into. That thing removes HSS fast, I don't want to know how fast it removes fingers. :)
Click to expand...

I use an auxiliary table that sits on top of my steel table for grinding rake angles. It has a really good support ear on the right side of the belt and that makes all the difference. I highly recommend you use wood for a push block, T; much safer for you.

Trust me; a belt will go down to the bone in a fraction of a second so do not slip and do not lose your focus.
 
Some issue that I have observed from Utube.

All tool holders are not created equal!!!!!!!!

I still use a lamp tool post with a rocker and shims and also some old fashion Atlas/Williams tool holders........ have not invested yet in a small OXA quick change tool post.

It seems that your tools have to be ground to match the tool post you intend to use.

The modern quick change tool post hold the tool/cutter parallel to the bed and Mikey's basic model of 15 degrees all around the 3 sides would work best .

But if I use the basic model in my old fashion Atlas tool holder it is already angled about 16.5 degrees therefore my back rake is now 31 degrees +-
which means I could leave the top flat or just touch it up for sharpeness.

Now if I use the lamp post with a rocker, using a 3/8 cutter, I can leave it flat on the rocker and grind a back rake as a typical Mikey tool for the proper angle......... or curve the rocker and with shims get back to 15 degrees rake with an almost fat top.

Did some grinding today on 5/16 HSS with 80 grit.....worked very well doing the RH side cutter as the belt goes right to the edge of the steel plate backing and I do have over an inch of over hang past the belt to work from...... doing the back rake at 15 degree was fine.......HOWEVER.... when I reverse the process to do a LH cutter my belt will not go close enough to the edge of the backing plate to do a rake grind on the top..... at least not unless I tilt the big D plate and totally re adjust the work table. I do have a pyroglass plate that is exactly 2 inches wide....once installed my problem be solved.

Worked with safety glasses today ( and gloves) and now appreciate the importance of good lighting to see what you are doing....so a goose neck light is a necessity...... usually cheap at flea markets.

With the 80 grit zirconium on HSS the heat is very controllable...... first the work table serves as a good heat sink....and when necessary a quick dip in a plastic butter dish filled with snow works wonders.

Belt speed is at its lowest....direct ratio with the 3450 motor with 4 inch drive pulley..... I don't see the need to go any faster.

Sheepishly I have not yet tried my new cutters on the lathe yet!!!!!!

Bob C
 
Bob, you're right; when using a lantern tool post the back rake angles are built in to many of the holders so you need to modify your tool grind accordingly. You might consider going to a QCTP - way more solid and versatile for altering your lead angles.

Let us know how your tools work out!
 
Try the cutters. I'm really digging mine. There's room for improvement, but I think it's mostly me learning how to use them well and practicing my grinding technique.

I made the aluminum tool. I think @mikey is my patron saint of aluminum cutting now. Grinding it was a little tricky, but I got a decent grind. Using finer belts polishes them up fast. I didn't need to hone as much. I went to 400 this time.

Rough cuts are amazing with this thing. I stopped at 50 thou but the lathe didn't even seem to notice it was cutting. Finish cuts took a few tries with the nose radius and tool angle, but I got some nice finish passes down to 1 thou. Turning to a shoulder and facing out is easy as well.
 
That aluminum tool cuts great, I agree. I have ground left and right hand for turning and facing. I’m with you also on needing more tool holders. I’ve made tools for stainless, brass, aluminum, and steel, not to mention 60* threading tools. I talked to Matt at PM today but forgot to order more holders.
Good depth of the work table on the grinder wheel or belt definitely makes a difference in hitting the rake angles easily.
The best part for me out of this thread is understanding how to relate the tool angles to the grinder cutting them. A combination of work table angle related to grinding surface and the angle of tool on that table related to the grinding surface.
Mike has done a great job explaining these angles in the grinding process.
It’s a work in progress and a fun time doing it.
 
ttabbal said:
I made the aluminum tool. I think @mikey is my patron saint of aluminum cutting now. Grinding it was a little tricky, but I got a decent grind. Using finer belts polishes them up fast. I didn't need to hone as much. I went to 400 this time.

Rough cuts are amazing with this thing. I stopped at 50 thou but the lathe didn't even seem to notice it was cutting. Finish cuts took a few tries with the nose radius and tool angle, but I got some nice finish passes down to 1 thou. Turning to a shoulder and facing out is easy as well.
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Been called a lot of things but never a saint!

Glad that tool worked out for you guys. When a tool cuts what you dial in, whether its a heavy cut or a tiny one, it is a pleasure to use. This is what I meant about optimizing the geometry to accommodate a material class; the tool just works better than a standard geometry tool. For those of you who haven't tried grinding this aluminum turning tool, you might want to have a go at it. Hobby guys turn a lot of aluminum and this tool makes it easy and it finishes well, too.

The one area where you will really see the value of this tool is when trying to come in on a critical dimension. When using an inserted carbide tool, you cannot take too fine a cut because the insert will deflect or may not cut at all. Not so with a sharp HSS tool like this one. If you can dial in the cut, the tool will usually cut it. For example, say you need to take off 0.0014" off the diameter. With a carbide tool, this is going to be really tough to do but with a sharp HSS tool, you can usually interpolate that 0.0007" and come in on size.

This is why I suggested to HB and Ttalbbal to try taking both heavy and tiny cuts - to see what the tool can do. How deep can the tool rough and at what speed and feed? How far away from your target size do you need to slow down and take sizing cuts to get close enough to dial in that final pass? These are things you must know if you want to do accurate work and the only way to know it is to cut it.

I should tell you that when using inserts, get to know them well, too. You will find that when an insert is broken in and stable, it will cut consistently. If you take a roughing cut twice in a row, the reduction in diameter will be proportionally the same. If you know that the insert finishes well with a certain depth of cut then you can rough until you are at that finishing depth of cut away, then dial it in. Knowing how your tool likes to cut is really important, with carbide or with HSS. It is up to you to figure this out and the only way to do that is to cut with it and learn what it wants from you.
 
To be fair, it's not a very good position. No pay, benefits etc.. You just answer endless questions from goofy noobs like me about aluminum tools. :)

I still have a lot to learn about tool geometry etc, but it makes a lot more sense now. Still working my way to better finishes and tolerances. I expect that's a never ending pursuit. But I have a grinder and a pile of bits to try it out with.

Thinking of new things, I'm going to be working with graphite in the near future. I know it's dusty and messy and will have a shop vac set up with a water trap for most of the dust. And breathing protection, don't want to inhale that crap. And of course through cleaning afterward. But what about tools? I suspect the angles don't need to be very sharp as it's going to mostly turn to dust as I cut it. It will need to be sharp to get a decent finish I would think. Any other considerations I should have when making a tool for something like this?
 
Hmm, interesting question. I have not worked with graphite before so I do not know the properties of it. I do know it is very abrasive so perhaps this is an instance where a carbide tool might be best?

What are you making - a nozzle for one of your rockets?
 
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