HSS Lathe Tools chipping, what might cause this?

erikmannie said:
Is there a slight radius at the cutting edge? I don’t imagine that you tried to make it as sharp as possible.
Click to expand...
I think this really is my issue. The tool bit must be rocking a tiny bit as I'm pressing it in. Kind of need a press down action and push action at the same time while keeping your hands away from the belt. The aluminum surface I have on the grinder tool rest isn't helping me.

I marked the face and then partially honed it with a coarse grit. The black parts are near the edges.IMG_20200908_100732.jpg
 
ttabbal said:
Switching belts didn't work as well for me. I ended up creating facets most of the time.
Click to expand...
It's extremely difficult to not create facets without a fixture. That's what's happening! 36 grit makes for some monumental grooves. But facets are even worse.
 
Just take your time, don't get in a rush. Practice. It will come.

Most edge rounding happens on a push stroke.
 
Gee, take your time! It's been a day and 1/2... Getting impatient! I barely have the big long faces done. All I have to get are the very tips. I find when I pull the tool back on the stone too far, I lift. That messes up the edges. Back to hogging off the face to get back to an edge. What a strange cycle. I feel like Sisyphus. Too far of a pull is anything greater than about 1.5 inches.

Confession time. I think the diamonds are prematurely coming off the stones I have. This may be due to excess pressure on my part, although I didn't think I was pressing down that hard. But, a lot of dark grit came off, and some of my stones don't cut very well any more. And yes, there are some bare spots (after cleaning) on the hones. My apologies for tool abuse. Still learning, I guess.

How did I come to this conclusion? I found this 20 year old cheap diamond stone with 1mm perforations in it. Apparently came from Gander Mountain, a now defunct outdoors supplier. Thought to myself, what the heck, why don't I try it? Hey, this seems to cut pretty well - I can tell it is removing material. Is the removal fast? No, but stuff is coming off, as I can see the different scratch pattern. The holes seem to reduce the loading of the stone. Is it really flat? Not really, it's mounted to a little 1/4" thick block of wood. But it's cutting at speeds far exceeding what I had before! And rounding edges and tips at breakneck speed.

At least I've identified some of what's messing up. Take my time, yes, I'll try.
 
I really don't mean to ruffle feathers, but I need to point out that the grinding wheel leaves a flat, mirror-like surface, whereas the belt grinder flaps and jumps around a lot, leaving a heavily ribboned surface that is clearly making more work at the hone. I do my grinding with stones, so from the wheel to the hone there is very little sweat work. I gotta say, as cool as belt grinders are for knifemaking, they are not a good tool for lathe bits. A simple Delta carbide grinder would run circles around a belt grinder on lathe tools. A fixtured grinder, like the Deckel, will outperform the carbide grinder, stretching the gap between the belt grinder and tool grinders even further. Like I said, not out to cause any anger, but one tool in this lot has limited performance when it comes to grinding flats.
 
Not ruffling my feathers. The honing is proving to be more work than ever anticipated. That's because the finish from a belt grinder is not only rough, but perhaps rounded. The slight rounding might just be due to my technique. However, the rounding causes a lot more material to have to be removed (to get back to flat). If I could fix this, perhaps the honing won't be so tedious.

The Delta carbide grinder looks well made with the nice cast iron table. Wish I could find a relatively intact one. The Deckel grinder is in a totally different league, the eBay prices prove it. The Deckel is not in the cards, unless some kind soul donates it to me. I'd love to learn to use all its capabilities.

Somehow, I'll muddle through this. Probably have to modify stuff that I have to work better, rather than buy my way to nirvana. That's how it is in my current circumstances.
 
Do you have a miter slot in the rest on your belt grinder? I'm assuming you are using some type of guide, since your angles look consistent. Can you feed the bit left-right or right-left across the belt with a guide? Your included angles might be harder to achieve, but for your outside angles feeding across the belt may help get a flatter result.
images


The Delta carbide grinders are ideal for lathe bits. I'd still like to get one someday. I use a Deckel clone with lathe bit attachment, and my lathe tools come out like knives.
 
pontiac428 said:
Do you have a miter slot in the rest on your belt grinder? I'm assuming you are using some type of guide, since your angles look consistent. Can you feed the bit left-right or right-left across the belt with a guide? Your included angles might be harder to achieve, but for your outside angles feeding across the belt may help get a flatter result.
images


The Delta carbide grinders are ideal for lathe bits. I'd still like to get one someday. I use a Deckel clone with lathe bit attachment, and my lathe tools come out like knives.
Click to expand...
Gee, I wish. Nope, they are done by hand, almost free hand. I did scribe some lines in the table, so I line up the tool to the line or parallel to the line. I have lines at 10 and 15 degrees, and at 100 and 105 degrees. I try to line up the pusher to the perpendicular line.

This picture gives me an idea. Maybe I can make something like it. It won't be ground, but it could be machined. Probably could find some sort of miter gauge to buy. It would be a lot better than effectively freehand.
 
Yeah, trying to perfect total freehand grinding while learning how to make good lathe bits at the same time is really tough! I'm a fan of fixtures.

There are a few schemes for fixture blocks for lathe bits. If you make a tool holder that is 4-sided and can accept a bit in each side, then set up the groves so they hold different side rake angles, you can use a miter guide to guide your block while making a compound facet... clear as mud.

Here's one:
ltsj-24.jpeg
 
@pontiac428 That's pretty cool. Just a dumb question, whats the advantage of this vs just setting the miter to the correct angle? The fact that the block is bigger and easier to control?
 
You must log in or register to reply here.
Back
Top