Unusual "tool" Steel Use Question

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PGB1

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Hello All!
I have never been educated on machine tool use, other than reading & experimenting, so please pardon me if this is a really basic question. My experience with the lathe has been using almost exclusively 5/16" carbide tipped throw-away tools. I do have a couple of HSS tool bits for fine & aluminum work. (It's a South Bend 13" 34-BQ from 1922.)

I acquired many of what look like HSS lathe tool bits. They are 1/2" square. Each is ground to particular shape, most of which are normal turning tool angles & profiles. A few are radius tools & 2 look like threading tools.

But, when I tried to turn some scrap 12L14, the edges simply rounded over & no steel was cut. I tried again on mystery steel (a hardware store bolt). I got the same result.

I cleaned some of them up and found tattle-tale words stamped on a few. The words lead me to believe these used to be disposable carbide tipped tools that someone re-ground after the carbide was broken (no carbide is left). Some of the words are " Carbaloy 78-R AR 8", "Super Tool Co D-8 Steel Use", "Wesson BR-8 WM".

Once suspicious, I re-ground some on my bench grinder & noticed that sparks are quite a bit brighter orange than the dull orange I see with known HSS. (Grey wheel). They ground faster, too.

Do these sound to you like they are shanks from former carbide tipped tools?
Can you think of what material the former owner used these on?

If I may sneak in another 2 questions:
When I grind a bit on my 8" bench grinder, the ground surface has the expected concave curve of the wheel. Studying photos on line of ground bits, I never see that curve. Is it OK to have the curve? (I always learned not to use the side of the wheel fearing shattering of the stone.)
And, what stone material do you all prefer for grinding HSS tool bits?

Thanks to All for you advice on these questions. Your help is appreciated.
Enjoy Today!
Paul
 
1 You sure you're running in the right direction ?
2 Cemented carbide bits are usually painted and marked with the carbide grade . ( stamped)
3 HSS bits are usually very shiny .

You may have cemented bits ground below the carbide as you say . Aluminum oxide for HSS , Silicon carbide ( green ) for carbide bits .
 
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The model designations - AR 8, D 8 - suggest that these are indeed shanks for formerly tipped carbide tools. They are useless for cutting and you may as well dump them unless you need some thick spacers for something.

The curve induced by grinding is unavoidable when grinding tools on a bench grinder. This is not only okay, it is preferable for some because a lot less material needs to be honed when final honing or retouching - that is, only the upper and lower edges of the face contact the hone so you get an edge very quickly. Flat ground faces result from flat grinding media - belt sanders, flat-faced wheels, etc. These cut just as well as those done on a bench grinder. An advantage, if there is one, is that there is more material below the cutting edge so there is a marginal improvement in strength. Either way works. The shape of the tool is far more important than what you grind it on.

I use a belt sander now and use a 24 grit AlOx belt for shaping. Back when I used a bench grinder I preferred a 60 grit Norton white wheel. I'm sure others who regularly use bench grinders for tool grinding will have other opinions. If you insist on using a bench grinder you might want to look at the CBN wheels the wood turners are using. These are intended for grinding HSS and supposedly work well. I haven't used them myself but will sometime in the future.

I would suggest that you buy some diamond stones to hone your lathe tools with after shaping. You can also use natural or synthetic stones to hone with but the diamond stones cut faster, stay flat and last longer without requiring attention. I prefer DMT over EZ-Lap but both work well. For lathe tools I like the credit card sized ones and recommend you buy the coarse, fine and extra-fine stones.
 
Thank You Mmcmdl & Mikey for taking the time to reply & sharing your great information.
Your Item #3, Mmcmdl sealed those items' fate. The ones that don't cut are very dull grey in color & the few real tools I have that are marked HSS & /or 5% cobalt are much brighter in color and more silver than grey.

Thanks for the great information about grinding & wheel selection, Mikey. Perhaps this summer will present an opportunity to buy a belt sander at a garage sale. I seem to see them fairly often. Your diamond hone plan sounds very good to me. I saw DMT at a woodworking store & was tempted. Now I have an excuse to buy.

I'll use those non-HSS tool shanks to practice my grinding & honing skills.

Thanks Again Guys & Enjoy This Day!
Paul
 
Paul , what size bits are you looking for ? I've got drawers full that will be going to the dump . I'll send you a selection if you want at no charge . PM me if you want .
 
WOW! That is certainly a very generous offer, Mmcmdl!
I think I sent you a PM. (I'm not great with computers, but I try) The page I used was titled "Start A Conversation". Was that the right place to PM?
Thanks Again!
Paul
 
Got it Paul . Here is a pic of a high speed vs. a cemented carbide bit . Once you see them and use them it's very easy to tell them apart . When you do regrind the carbide bits , knock the bark off the shank with a aluminum oxide wheel ( providing clearance) and then follow everyone's above advise . Remember this to make it simple . AO wheels don't like carbide , SC and diamond wheels don't like soft steel . I'll get into those drawers shortly . IMG_6201.JPG IMG_6202.JPG IMG_6203.JPG
 
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Paul , couple of LH , RH . 45 degree and a square end . The weather has gotten so nice I got to open a drawer . Yippee ! These are 1/2" and will fit your BXA nicely . All different grades . Cut and grind away buddy . Experiment , have fun . Tell me where they're going , I want no $$$ . If you want and can afford to , make a small donation to the site . We all win . Dave

IMG_6204.JPG
 
Thanks Again, Dave! I sent the mailing details on a "PM" (And I learned a new term today-"PM" Gee, there's hope for me yet!)

Thanks for the photos & tips for re-grinding carbides. The ones I have have had the tip mounting places ground off & are ground to look like HSS tooling. But I can see by your photos that the material on my mystery bits looks just like the steel in the tool marked "ACT". I do wonder what the person did with those soft tools? My only guesses are A) Practice grinding (like I'm doing with them now) or B) Maybe plastic or nylon?

I want to send my Sincere Thanks To Everyone who helped me out with this question post. I learned quite a bit and much more than I ever could find out on my own about grinding tools, grinding wheel types & their uses.

I Hope You All Enjoy This Day!
Paul
 
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