Hss blanks

One thing to consider is that old time lathe tools were ground for use with lantern style tool holders. The tool holders generally had a built-in rake angle so the top surface could be used as-is. Modern QCTP and 4-way tool holders present the tool to the work horizontally so the back rake must be ground into the tool. Also affected is the end relief. Tools used in the lantern style holder needed more relief ground into the tool because of the lantern style holder.

When grinding tools, it is important to look at how the tool is presented to the work. The rotating work sees the tool in a plane containing the axis of rotation and the cutting edge of the tool. Normally, that plane is horizontal (parallel to the cross feed ways as this ensures that the cutting edge will pass through the center of the work and that movement of the cross feed is exactly 1/2 the reduction in diameter. However, changing the cutter height slightly can have benefits. Raising cutter height above the centerline has the effect of increasing back rake and decreasing the end relief.

Each lathe has its own characteristics. The available power, and rigidity of the lathe play an important part in lathe tool design. Large lathes usually have power to burn and are massive. What works for them will not necessarily work for a small bench top lathe. This should be taken into consideration when grinding your tools. It would be very frustrating to grind a tool exactly like one known to work well for another lathe and find that it gives totally unsatisfactory results on your lathe. Use some of the principles as a starting point and do some experimenting for your particular best geometry.
 
RJSakowski said:
One thing to consider is that old time lathe tools were ground for use with lantern style tool holders. The tool holders generally had a built-in rake angle so the top surface could be used as-is. Modern QCTP and 4-way tool holders present the tool to the work horizontally so the back rake must be ground into the tool. Also affected is the end relief. Tools used in the lantern style holder needed more relief ground into the tool because of the lantern style holder.

When grinding tools, it is important to look at how the tool is presented to the work. The rotating work sees the tool in a plane containing the axis of rotation and the cutting edge of the tool. Normally, that plane is horizontal (parallel to the cross feed ways as this ensures that the cutting edge will pass through the center of the work and that movement of the cross feed is exactly 1/2 the reduction in diameter. However, changing the cutter height slightly can have benefits. Raising cutter height above the centerline has the effect of increasing back rake and decreasing the end relief.

Each lathe has its own characteristics. The available power, and rigidity of the lathe play an important part in lathe tool design. Large lathes usually have power to burn and are massive. What works for them will not necessarily work for a small bench top lathe. This should be taken into consideration when grinding your tools. It would be very frustrating to grind a tool exactly like one known to work well for another lathe and find that it gives totally unsatisfactory results on your lathe. Use some of the principles as a starting point and do some experimenting for your particular best geometry.
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Great post, RJ!
 
I have very limited experience. Recently, I was given a wooden box of old school carbide tipped tools with a shaper I bought. Most or all had chipped or missing carbide. I wondered their value until I tried one on the grinder -very hard stuff and difficult to even grind. I looked through box and found one had back end ground into a shaper bit. I'm not sure if its tool steel or HSS but does a real nice job in my 1920s? Ohio shaper. I'm not saying anyone should hunt for broken carbide tipped tools, but I wouldn't necessarily scrap them either.

It's my understanding, HSS wasn't widely used until the 1930s, so tool steel isn't necessarily a bad choice for home shop use. I assume it has less heat and wear tolerance.
 
Actually, the first tool that was truly classified as HSS was T-1, formulated by Crucible in 1910. The M-class of HSS came out in the 1930's.

I would guess that the tool shank on your carbide tools is some kind of low to medium carbon steel, not tool steel. I may be wrong but I would think that using tool steel for a tool shank would be economically prohibitive. Some medium carbon steels will work harden with the heat of grinding and that might allow it to be used as a cutting tool, albeit with limited edge life.
 
Bob, John York and RJ are mentors worth listening to.
This forum has some very smart and experienced consultants IMHO
And, they are willing to share their skills willingly.
God bless us all.
Sorry, I got carried away.
 
mikey said:
Actually, the first tool that was truly classified as HSS was T-1, formulated by Crucible in 1910. The M-class of HSS came out in the 1930's.

I would guess that the tool shank on your carbide tools is some kind of low to medium carbon steel, not tool steel. I may be wrong but I would think that using tool steel for a tool shank would be economically prohibitive. Some medium carbon steels will work harden with the heat of grinding and that might allow it to be used as a cutting tool, albeit with limited edge life.
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Brazed on tool shanks are something like 1040 or 1045 carbon steel, they are hardenable to a fair degree.
 
benmychree said:
Sometimes, HSS tool bits have a gash ground on one end; grind your tool on the other end, not the gashed end, it marks the gate end that the bits were cast from, where there might be defects lurking. Bob's suggestion about grinding tools on both ends, brought this to mind. The gash thing is likely to be seen in old stock tool bits, less likely on new bits.
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Do you mean the vertical gash on some bits?
 
I have seen bits that had a single gash, and some with a cross cut into the end, like with a cut off wheel or some such thing. Vertical: define vertical on a square tool bit --- If the bit were cut on an angle on the ends, as they frequently were, if the bit was viewed with the angle sloping down , the gash would be vertical.
 
Most likely someone ground a chip breaker into it . Cutting plastic at high speed with that grooved nose will land your chips directly into a trash can at 5 ft away !
 
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