Models for grinding HSS Lathe Tools

Alcap said:
Lots of great info here on HSS , is there a thread like this for carbide tool bit sharpening ? I have plenty the came with my lathe and some in a tool box I bought , most with chipped tips , .
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No, there is no equivalent thread like this for brazed carbide tooling on HM. Used to be a guy named Chris Poulsen (sp?) who could have done it but he left the site. If you have a green Silicone wheel and a diamond wheel then you can recondition and reshape brazed carbide tools. One of the Baldor-type tool grinding machines with cup wheels would do it easily. I have not worked much with brazed carbide tool grinding but I would imagine that the tool geometry would be similar.
 
I received the set of sample tools last weekend and I sat down and measured them and compared my numbers with the documented as a first step.

My question is not related to this, tho. I there any hack for judging the size of the radius on a tool, some common item that is typically 1/64 or 1/32? I don't have the urge to spend for a set of gauges when there is probably something lying on the workbench that will work. Eye of newt? Ball in a Bic pen?
 
fcs said:
My question is not related to this, tho. I there any hack for judging the size of the radius on a tool, some common item that is typically 1/64 or 1/32? I don't have the urge to spend for a set of gauges when there is probably something lying on the workbench that will work. Eye of newt? Ball in a Bic pen?
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If you're just looking for a quick and available reference, how about the end of a drill bit shank?
Hold them side by side with good light and magnification if required.
-brino
 
There are a number of ways to do the nose radius - radius gauges, using drills or pins as examples, etc. I just grind a flat with my diamond stones about 1/64" across (I do this by eye; I don't use a ruler) and get that flat even from the top to the bottom of the tool. Then I just round and blend the edges of that flat into the side and end faces and call it good.

It is not necessary to have the nose radius be an exact size but it is important for it not to be too big, at least in my opinion.
 
I talked to a retired machinist, mentioning how I was thinking of building a 2x72" belt sander for dressing HSS. He's used a belt sander himself for tool grinding, and somewhat surprised me by instead strongly recommended a used Baldor tool grinder. Just another data point on what people who know use.
 
A Baldor tool grinder is a nice tool to have. Slower than a belt sander with ceramic belts for shaping HSS but you can grind carbide on them, something that you cannot do on a belt sander. I don't think it matters a whole lot what you use to grind your tools; that is up to the user. However, I think it does matter that you understand WHAT you're grinding and WHY you're grinding it that way.
 
Mikey,
I was working thru your first PDF and grinding the knife tool today, and in your writeup where you say " The end cutting edge angle is 65-70 degrees. " I think you mean (using the standard picture as reference) the angle is 30-35 degrees. I should have looked at the grinding pictures more closely. 65 really does make a KNIFE tool. I may be the first person dense enough to make that mistake; glad it was in keystock.
IMG_0241.JPG
 
Yeah, you need to grind it like the model. Sorry for the confusion.
 
First cut on aluminum with the tool I ground a couple months ago.
and I am pleased with the results

Use the same tool to finish the chuck key for the bison I bought a while back as well.

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finsruskw said:
First cut on aluminum with the tool I ground a couple months ago.
and I am pleased with the results

Use the same tool to finish the chuck key for the bison I bought a while back as well.
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I meant to get back and respond to this post but life is truly hectic of late. My apologies.

For those of you who have not seen a tool like this before, it is called a Round Nose tool. It is characterized by the round nose radius, essentially identical side cutting edge profile on either side and typically has zero top rake. It is able to cut in either direction, which is helpful if you have to cut a section between two shoulders or collars. Due to the relatively large nose radius, a Round Nose tool tends to finish okay but it cannot take huge cuts without chattering. This is because the nose radius generates a lot of radial cutting forces. When compared to a general purpose turning tool, it is not capable of deeper cuts because of this.

In order for this tool to finish well you must do one of two things: slow the feed considerably or it will inscribe fine lines OR you can create a much smaller nose radius and alter your lead angle and use the edges just back/adjacent to the nose radius. This latter method will finish much, much better for you. Typically, I use a parting tool to make two adjacent cuts to create the shoulders on each side of the section being turned, then angle the tool so I am cutting with an edge instead of the nose. The finish is usually much better and because the edge cuts more accurately, it is easier to come in on size with this method.

For those of you who have not tried this tool in brass, you are in for a treat. This tool will put a mirror finish on brass with almost no effort. Due to its versatility, this is a tool that is worth grinding. I suggest 15 degree side relief angles. Keep the nose radius small, about 1/32" will do. If you plan to use this tool strictly on brass, try grinding about 5-7 degrees of back rake on top; you will be very pleased at how well this tool cuts when modified this way. For use in other materials, use zero rake on top.
 
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