Grinding M42 tool blanks for use on shaper or lathe

Do the "unbelievable shapes" appear to be form tools? If so, they're commonly EDMed, often with wirecut. The finest EDM finish looks like a soft polish.

-- Ed Huntress

Ed, maybe....don't know, I was just so impressed by the smooth finish and the sharp edges that I just wondered what tool was used or could be used. Just wondering if one of those Cincinnati #2 grinders or some other machine can do this. The shapes are not so intricate as they are precise..sharp, smooth, etc...

There is etched writing on them describing the tool shape, what angle, radius, relief, etc...

Interesting. Another tool that can do that is a profile grinder. Without seeing the tools, though, we couldn't tell for sure what did it.

In general, HSS form tools are made with a profiled wheel on a surface grinder; a profile grinder (manual or CNC); or wire EDM. One of the common applications for wire has been dovetail form tools, which are not the same thing you're talking about, but which do have complex shapes.

Grinding can produce a very fine finish, if it's called for, but it will show some linear texture in the direction the wheel moved. An EDMed finish usually is completely directionless. Does that help?

-- Ed Huntress

Oh, I didn't answer your question about the cutter grinder (Cincinnati #2, etc.). Yes, it could be done on a cutter grinder, as well. I'm not following what the shapes are on your tools, so it's hard to be specific. I also don't remember the way the #2 works; some cutter grinders will grind some shapes, but simple ones only index, for such jobs as sharpening the flute-ends on a milling cutter.

-- Ed Huntress

On this topic, but diverging slightly....

Lets say I wanted to be able to grind profiles for making gears on a shaper or by using a single point cutter setup on my Bridgeport. What piece of machinery would be best suited fro creating the required profiles in M42. Would I be looking to add a surface grinder of a Cincinnati #2 cutter grinder, or perhaps, some other type of equipment. Something like the Baldor #500 6 1/2 Hp 1 Phase Carbide Grinder or the Tormek Supergrind 2006. Problem with those is that they would be slow...but, that said, I am not a production shop.

Thanks again all

=================== First thing I suggest is getting the book "Gears and Gear Cutting" by Ivan Law ISBN 0-85242-911-8 [#17 in the Workshop Practice Series] Normally you can get this from powells.com or amazon.com, but in checking they appear to be out of stock. Blue Ridge Machine also stocks these. goto

Law has a very good section on approximating the involute gear form by using a radius. see pages 112-123. Strictly speaking this is not correct, but the difference between the correctly chosen radius and the theoretical involute curve is less that than the error produced when using an involute cutter for their range of gear teeth. Law shows how to calculate for any desired pressure angle for custom gears.

You can cut down considerably on the time/cost to grind these tools if you will rough out on a belt sander to approximently an Acme thread form.

FWIW a CAD program is a big help. If it would be helpful I have excel spreadsheets that will calculate the required radii and other dimensions using Laws approximations with either DP or module input for 14-1/2, 20 and 30 degree PAs. If you want a copy drop me an email.

Your problem then reduces to how to generate a precise radius on a grinding wheel. You will need an external radius or bulge to produce an internal radius on the tool. for examples goto

?ProductID=800-5210Most likely you should be able to jury-rig a radius dresser using a spindex fixture. Most likely you will also want to make a grinding fixture to hold the tool bit at the correct angle for the front and side relief.

FWIW -- you don't want to use a boring bar as a tool holder in the mill because boring bars mount the tool above center causing negative rake. You can make it work after a fashion by grinding in enough hook, but it is a pain to maintain the form and so much must be ground away it weakens the tool and it is hard to sharpen. If you grind the tool with radial relief as Law shows and mount on center, the tool is easy to sharpen by simply grinding down the top. Most likely you will have to make your own tool holder. Lots of fly-cutters, but gear cutters [horizontal fly cutters] don't seem to be made anymore.

Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.

John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).

I have two friends. One bought a German lathe without change gears; the other is a really good home machinist. They are both exceptionally smart guys. They got together. They wrote a Python script to generate a bunch of points which, when plotted, generated a gear tooth form 20X it's size. They plotted this out on a piece of transparency paper and clipped it to the screen of a 20X optical comparator (shop-built, very cool). Then they took a piece of HSS, think it was just 1/4" square, and roughed it out on a belt sander. Then they took a piece of copper round bar (or similar) and rolled it in abrasive (think it was diamond paste) to make it into a lapping tool, then they spun the lapping tool in the spindle of a milling machine and they'd lap a little bit and then compare the cutter to the image using the optical comparator, iterating until they had a nice fit. Then they had their single point cutter.

They turned gear blanks on a lathe and (I believe) cut the gear teeth using a 7" Atlas shaper, but it might have been in the mill.

I had halfway expected one of those guys to post here but apparently they don't follow this NG that closely anymore.

They got very usable change gears, and the German lathe (Swiss?) is in service today.

I have a version of the Python script. I hacked it to make it be 10X back before I sold my 10X optical comparator, but I failed to make the line plot using the tools I had available on a Windows platform, and never pursued it. But if you want to follow their steps exactly, let me know and I'll dig out the script for you. Python is an easy scripting language if you're into programming at all.

GWE

================= If you have access to autocad or one of the clones such as intellicad that will run LISP see

?qid=157290&page=4 a whole bunch more Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.

John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).