Tool recommendation for turning cold rolled steel

I'm seeing a poor finish on a length of cold rolled steel (I dunno what it is exactly). The tool is on center, RPMs are about 500, but
there are like little bits of swarf welded to the part. Sort of reminds me of using a cheap ballpoint pen and the ink globs up and sticks to the paper.
The cut itself is OK, but the surface finish looks poor.
I'm using an indexable insert with about a 1/32" nose (IIRC). This makes me wonder if the insert is the correct grade, or maybe this result is the best that I can get with this steel.
I'm entertaining thoughts of HSS, but the issue is who will grind it when it needs to be resharpened? My dad has poor eyesight, so that's why I went with carbide in the first place. That way I didn't have to be standing at the lathe every second while he was working.
I can accept using brazed inserts or something similar, but grinding relief angles is not an option.
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Louis Ohland wrote:

> It's daylight outside, what should I wear?
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Well, Tom, that depends where you like and what your tolerance is for cold. Here in Wisconsin, the wind is around 15mph and the temps are below freezing. Whatever you want to wear is up to you, or do you still need someone to dress you?
Tom wrote:

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Louis Ohland wrote:

> A bit like trying to improve a finish on cold rolled steel, sight unseen, What's the diameter? Is the sfm within cooe for carbide? Negative or positive rake insert? Is the insert tip in good order? Has the insert height been verified as being on centre or is it slightly above?
Whether apparel selection or machining questions, difficult to supply solutions with insufficient data.
Tom
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Diameter is 1" Bit is on-center. Used a Redfield level. Positive rake Insert tip is been used only a few times before
Tom wrote:

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I am a "dad with poor eyesight", so I use magnifying headgear and task lighting all over the place so I CAN see what's going on. Get him MORE light on the subject. You really need to tell us what that insert is. Most posters here know more about it than I do, but if you don't have a pretty big, stiff lathe, I wouldn't be using negative rake inserts at all. Are YOU? You said "cold rolled steel", but that only tells us how it was finished, not what it's made of. Most people who go to the steel yard and ask for a chunk of steel are likely to get A36, which is quite likely to be hot rolled and will have mill scale on the surface. Many folks think that if the steel they bought is shiny, that it must be cold rolled. Not so. Many yards stock A36 in "P & O" (Pickled and Oiled), so it LOOKS like cold rolled. A36 is notorious for not producing a nice finish. Just for reference, a mild steel that is often sold in cold rolled form is C1018. It costs about double what a same-size bar of hot rolled A36 would cost. I know you say the grinding an HSS bit is not an option, but if you get your dad some LIGHT, his whole world in the shop may change. The rule of thumb that I heard is that "old" eyes need 10 times the light that "young' eyes need to get enough contrast to see well.
A properly ground HSS tool can last quite a while. Why can't you grind for him if he can't? This is not rocket science. We can tell you how to make a little steel template (8 and 12 sides) that makes it downright easy to get the angles right. You could grind up 3 or 4 tools at a time for him, so he wouldn't have to sit on his hands between your visits to "the shop".
Pete Stanaitis -------------------------
Tom wrote:

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On Tue, 01 Jan 2008 14:22:20 -0600, Louis Ohland

==============Carbide is wonderful for heavy production cuts at high speeds on rigid production machines.
For the lower speed and shallower cuts on the less rigid machines common to HSM, HSS [and M2 at that] may prove more useful.
Frequently increased back and side rake, even extreme side rake to produce a shearing action can be helpful for generating a good surface finish. This is not a good grind for deep cuts or into surface rust/scale. A good starting point is a high-shear round nose shaper tool with slightly more clearance angle than suggested for a shaper, i.e. 7 degrees. If the grind is correct, the chips will be thin and tightly curled.
for some links click on see top of page 5 at http://www.eurospares.com/graphics/Tools/shapers/SetupandCut.pdf
http://www.janellestudio.com/metal/shaper_bits_and_toolholders.txt
also you might try some antiweld cutting fluid -- generally high sulfur and black.
Let the group know how you make out and what works.
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wrote:

Some CRS is like that. Try getting him some 12L10 free-machining steel to turn.
Consider getting him a diamond tool holder. http://tinyurl.com/25lgkt
They're kinda pricey, but they work really well -- and you don't need good eyesight to grind the HSS bit because a jig comes with the tool. If he can see the grinder, he can regrind the bit perfectly.
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Louis Ohland wrote:

Sounds like normal results from basic cold rolled 1010 or 1018 steel.
If getting some free machining mild steel is not in the cards, look at some of the cutting oils or soluble cutting fluids that are available to help with a nice cut.
Mild steel is a SOB to get a really nice finish on. A sharp(!) tool with a bit of a radius on the tip goes a ways, but I have really only ever got a really nice finish, running it very fast, taking a reasonably heavy cut, with carbide tooling.
Sulphurized cutting oil, or a soluble oil mixed a little thicker than the directions, and applied with a brush, makes a big difference.
12l14 steel is well worth the cost, unless the part is to be welded.
Cheers Trevor Jones
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If you want to stick with an indexable insert, use a Wiper insert. You don't have to slow down the feed and the "smearing" action of a wiper works fantastic on cold roll for a good finish. Tell me what size insert you are using, ie..CNMG432 and if I have one I'll send it to you for nothing. If I don't have a wiper and I do have the geometry you are using, I'll at least send you the right grade and chipbreaker for coldroll. I have boxes full of turning inserts lying around. Generally on a 1/32 nose radius I never take less than .050 per side depth of cut to finish cold roll. Less than that, all it does is tear.
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If HSS tools are the way you want to go try a local vo tech high school or technical college with a manufacturing program. Maybe you can get an instrucrot to have a student grind a bunch of tools for you so your Dad will have them on hand.
I know that I can be easily bribed with doughnuts to such a thing. Or rather haave my students do the task.
And before anyone jumps in I consider it vital that my students have hand grinding skills. What they learn about angles and finish on tools goes a long way when they shift to carbide. Our motto is "learn to do it the old fashin way" before moving to the new fangled stuff.
I will second the notion of MORE light on the tool. My vision is no where near what it once was and I appreciate extra illumination.
If you don't have a big rush I could probably bring you some sharpened tool this summer when I go to Oshkosh.
Errol Groff
Instructor, Manufacturing Technology H.H. Ellis Technical High School 613 Upper Maple Street Danielson, CT 06239
New England Model Engineering Society www.neme-s.org
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On Tue, 01 Jan 2008 19:34:21 -0500, Errol Groff

====================For the low volume of the typical home shop, a belt sander works well, and the typical shop will have a 4X36 with a 6 inch wheel.
Use a relatively course zarconium oxide [blue belt] for rough grinding the tool, and use a fine grit disk to finish grind. Although it is not necessary, you can use an extra fine disk to produce a mirror finish if you want to.
Repeatability will be more important than absolute accuracy in the grinding, i.e. you will find that a particular tool ground like this works well, and you want to make some more like it, rather than grinding a tool to exactly 7.5 degrees back rake.
You may get some ideas from a jig/fixture we made in class for a baldor style carbine grinder. This lets even first term students grind a "line out" acme threading tool, although it make take several ties. click on http://www.mcduffee-associates.us/machining/thfnce.htm http://www.mcduffee-associates.us/machining/tabanggg.htm
Most belt/disk sanders will have a miter gage slot.
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When I was custom gunsmithing and turning Douglas or Shillen barrels I'd use carbide cutters to rough out the blanks and switch to HSS for a smoother finish. And lottsa light is always a good thing... for old or younger eyes. A good lubricant/coolant (even hand applied) promotes a better finish.
And I second the notion that "learning how to do things by hand the old way", such as sharpening your tooling, is an invaluable skill. Even for us "old" dogs...
Cheers
--
Message posted via http://www.craftkb.com


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I fix a difficult piece of scrap steel by annealing it in the woodstove. Next day it usually machines cleanly. Water annealing is supposed to be even better. Let it cool until the red disappears, then quench in water.
12L14 is beautiful stuff but O-1 drill rod isn't too bad either. Hardware-store CRS sometimes isn't worth the trouble even if you get it for free.
Grade 5 bolts turn well with HSS bits and the steel is about twice as strong as CRS.
Jim Wilkins
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There's a Metal Xpress down in Rockford. I think they stock 12L14.
Jim Wilkins wrote:

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With a small nose like that you need to move slowly. You likely got some spirals or rings.
That is typical in HSS when a point is used not a round nose.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
Louis Ohland wrote:

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No, the cut was light, maybe 5-10 thousandths. It was dropping little tiny bits, sorta like big sand granules.
Martin H. Eastburn wrote:

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It sounds like you might be using one of the tpg sets. First off you should crank your spindle speed up. You are only at 130 sfm and you should be at least twice that for carbide.
Next, take a close look at the nose of the insert. These are very delicate and chip easily if the loading isn't in the direction they were designed to work in. Bumping or scratching a stationary work piece or turning the work backwards can knock off a tiny flake of the edge. Sometimes these are hard to see. Run the edge of your thumbnail over the cutting edge. If you feel a snag, turn the insert.
The granular swarf makes me wonder if you have cold rolled steel. The swarf should be coming off like steel wool.
I have a bunch of 2" hot roll that cuts like that. I can't get a good finish no matter what I try.
Paul K. Dickman
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