I have heard that HSS tools make a better finish with light cuts on a mini-lathe than carbide tools. I have been using indexable carbide tools on my Central Machinery 7 x 10 Mini-Lathe, but not pleased with the results. I'm considering trying some pre-ground HSS tools, since I mainly turn aluminum or mild steel. Opinions or recommendations?
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HSS or Carbide Tools for Mini-Lathe
- Thread starter HarryJ
- Start date
This may be of interest to you. Helped me a bunch. Probably more inexpensive to grind your own.
https://www.hobby-machinist.com/threads/models-for-grinding-hss-lathe-tools.62111/
https://www.hobby-machinist.com/threads/models-for-grinding-hss-lathe-tools.62111/
- Joined
- Jul 31, 2020
- Messages
- 765
To cut to the chase, Carbide inserts are geared towards higher speeds and feeds (and cut depths) than some many mini-lathes can dish out. They often have less ideal edge geometry and require higher pressure against the metal to get a bite. I am saying this from the perspective of having a mini-lathe that is 0.67 Horsepower.
Do I use carbide inserts? Yes, some of the time, but I consider all of the above factors. I often use carbide which has a generous nose radius to gain a better finish. My best finishes with carbide inserts are via Round inserts which are about a half inch across. Most mini-lathe users are a bit timid at cranking up the speeds and feeds it takes to make carbide inserts happy.
I also have an 0XA post which accepts 1/2 inch (12mm) tools. That extra rigidity is important for a decent finish. If you talk to some of the Sherline users around here, they will tell you that tool geometry is king. They get a lot done with less rigidity and less horsepower.
Do I use carbide inserts? Yes, some of the time, but I consider all of the above factors. I often use carbide which has a generous nose radius to gain a better finish. My best finishes with carbide inserts are via Round inserts which are about a half inch across. Most mini-lathe users are a bit timid at cranking up the speeds and feeds it takes to make carbide inserts happy.
I also have an 0XA post which accepts 1/2 inch (12mm) tools. That extra rigidity is important for a decent finish. If you talk to some of the Sherline users around here, they will tell you that tool geometry is king. They get a lot done with less rigidity and less horsepower.
- Joined
- Apr 30, 2015
- Messages
- 11,349
Couldn't have said it better than above
-M
-M
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- Mar 22, 2020
- Messages
- 175
HSS and it’s not even close.
A belt sander is ideal for grinding bits. But more expensive. Equipment and consumables.
Sent from my iPhone using Tapatalk
A belt sander is ideal for grinding bits. But more expensive. Equipment and consumables.
Sent from my iPhone using Tapatalk
- Joined
- May 4, 2019
- Messages
- 792
For best finish with HSS make a vertical shear tool. It will only take off a few thou but the finish is beautiful.
- Joined
- Jul 28, 2017
- Messages
- 2,390
I came across a type of vertical shear bit that is a lot simpler to make, with just one ground facet. Here's a photo of the one I made:
The facet was ground parallel to the sharpie mark. Since it was a prototype, I didn't continue the grinding all the way to the bottom of the tool-- the cutter is quite forgiving w/regard to tool height, as long as its cutting edge is the part that encounters the work (this is handy because you can just change the height a bit to get a fresh cutting edge).
FYI, It took awhile to remove that much material, and this WAS a prototype. So that's why I didn't continue the grind all the way to the bottom of the tool
. IIRC, the facet was ground at about a 40 degree angle. To use it, the cutter is installed in the tool holder in the same orientation as shown in the photo. The cutting edge is on the same side as the sharpie mark, and was on top when I ground it on my grinding wheel. The grinder support was at about a 10 degree angle, the same angle I use when I grind my conventional HSS cutters (it's a compromise for all the various relief angles needed for them).
To get the necessary relief, the cutter is presented to the work at a shallow angle:
The top view should clarify how the cutter works. I used it to improve the finish on the mounting post for my home-made QCTP.
It probably would be better to use a belt sander to grind the facet because the curve created by a grinding wheel makes it difficult (impossible?) to hone the edge.
Since I made the tool, I built myself a diamond lapping wheel that I can use to flatten and hone the facet of my VSB. At some point I will see if that's something to recommend.
The VSB isn't meant for bulk removal, so you still will want to have an assortment of the usual suspects, whether they be carbide or HSS.
The facet was ground parallel to the sharpie mark. Since it was a prototype, I didn't continue the grinding all the way to the bottom of the tool-- the cutter is quite forgiving w/regard to tool height, as long as its cutting edge is the part that encounters the work (this is handy because you can just change the height a bit to get a fresh cutting edge).
FYI, It took awhile to remove that much material, and this WAS a prototype. So that's why I didn't continue the grind all the way to the bottom of the tool
. IIRC, the facet was ground at about a 40 degree angle. To use it, the cutter is installed in the tool holder in the same orientation as shown in the photo. The cutting edge is on the same side as the sharpie mark, and was on top when I ground it on my grinding wheel. The grinder support was at about a 10 degree angle, the same angle I use when I grind my conventional HSS cutters (it's a compromise for all the various relief angles needed for them).To get the necessary relief, the cutter is presented to the work at a shallow angle:
The top view should clarify how the cutter works. I used it to improve the finish on the mounting post for my home-made QCTP.
It probably would be better to use a belt sander to grind the facet because the curve created by a grinding wheel makes it difficult (impossible?) to hone the edge.
Since I made the tool, I built myself a diamond lapping wheel that I can use to flatten and hone the facet of my VSB. At some point I will see if that's something to recommend.
The VSB isn't meant for bulk removal, so you still will want to have an assortment of the usual suspects, whether they be carbide or HSS.
- Joined
- Aug 22, 2012
- Messages
- 4,124
I like a razor sharp rounded nose braised carbide tool on aluminium. I hone the edge with a small hand held diamond hone.
But to be honest you cant beat razor sharp hss, again I use the diamond hone to ensure its really sharp.
On my 9x20 I dislike carbide inserts.
The vertical shear bit is awesome for finishing on those horrible bits of steel that somehow do not like giving you a
But to be honest you cant beat razor sharp hss, again I use the diamond hone to ensure its really sharp.
On my 9x20 I dislike carbide inserts.
The vertical shear bit is awesome for finishing on those horrible bits of steel that somehow do not like giving you a
- Joined
- Oct 18, 2016
- Messages
- 2,872
If you aren't familiar with them, a good source of tools and supplies for mini lathes is Little Machine Shop.
My first lathe was a 6" Atlas and since I was just
getting started I wanted some off the shelf tools that would work for me without having to learn how to grind
tools. LMS sells kits from A R Warner which have both HSS and carbide inserts. I got started with the
HSS inserts and had good results with them. They have their limitations, but I've made a lot of parts
with them, they're dead simple to sharpen (I hone them on a flat stone) and though folks complain about
the cost of inserts, the kits come with spares and I've never had to replace one.
littlemachineshop.com
Here's another option: The Diamond Tool Holder
This product is made in Australia but available in the US through Village Press:
This is an example of a Tangential tool, which is an old concept and not invented by Diamond.
The tool holds a standard piece of HSS steel (cheap and available) in an almost vertical orientation
which, when ground at an angle produces a diamond shaped surface: the point of contact with
the work is one corner of the tool. It is sharpened in a jig supplied with the tool on a bench grinder
or belt sander, and is very quick and easy to accomplish. Mine has become my go-to general purpose
turning and facing tool (it does both without changing your setup) and I use it all the time.
Lots of YouTube vids available for this tool. They come in different sizes, so it's necessary to choose
the correct size for your machine. Diamond's website explains this.
Having said all this, it's still a good idea to learn to grind your own tools.
My first lathe was a 6" Atlas and since I was just
getting started I wanted some off the shelf tools that would work for me without having to learn how to grind
tools. LMS sells kits from A R Warner which have both HSS and carbide inserts. I got started with the
HSS inserts and had good results with them. They have their limitations, but I've made a lot of parts
with them, they're dead simple to sharpen (I hone them on a flat stone) and though folks complain about
the cost of inserts, the kits come with spares and I've never had to replace one.
Tooling, parts, and accessories for bench top machinists
The premier source of tooling, parts, and accessories for bench top machinists.
Here's another option: The Diamond Tool Holder
This product is made in Australia but available in the US through Village Press:
This is an example of a Tangential tool, which is an old concept and not invented by Diamond.
The tool holds a standard piece of HSS steel (cheap and available) in an almost vertical orientation
which, when ground at an angle produces a diamond shaped surface: the point of contact with
the work is one corner of the tool. It is sharpened in a jig supplied with the tool on a bench grinder
or belt sander, and is very quick and easy to accomplish. Mine has become my go-to general purpose
turning and facing tool (it does both without changing your setup) and I use it all the time.
Lots of YouTube vids available for this tool. They come in different sizes, so it's necessary to choose
the correct size for your machine. Diamond's website explains this.
Having said all this, it's still a good idea to learn to grind your own tools.