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dian
12-14-2013, 01:55 PM
so you have a peice of something and want to know if the saw will cut it.

by bouncing bearing balls on the surface (perhaps in a tube), can you determine by comparison, how hard the stuff is?

Jaakko Fagerlund
12-14-2013, 02:07 PM
Chuck it in the saw and try cutting? Otherwise the only option is indeed hardness measurement, but it doesn't tell you how miserable the material might be to cut.

Toolguy
12-14-2013, 02:16 PM
Try a hacksaw first. Those blades are cheap and easy to replace if needed.

Bob Fisher
12-14-2013, 02:40 PM
Spark it, you can determine carbon content, low carbon at least not hard, may still be miserable to cut tho. Otherwise, I'm in the hacksaw camp, maybe a file to check for hardness. Bob.

Arthur.Marks
12-14-2013, 03:00 PM
I read dian's question less as a practical inquiry and more as a technical curiosity. Does hardness affect the height of rebound from a dropped ball bearing? I don't really know the engineering explanation for that, but I will take a guess and say, "yes." My understanding is that is how these simple, portable hardness testers work: Rebound THT-6 (http://www.travers.com/107728-57-020-886?Category=measuring%20%26%20inspection:298868|| hardness%20testers:298885||rebound). Correct?

PStechPaul
12-14-2013, 06:26 PM
That looks somewhat like the glaucoma test tool that is used for eye exams, although I think now they use compressed air.
http://en.wikipedia.org/wiki/Ocular_tonometry
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3641509/

The rebound hardness test is discussed here:
http://en.wikipedia.org/wiki/Leeb_rebound_hardness_test

Has anyone tried one of these?
http://www.ebay.com/itm/251328119508 (http://www.ebay.com/itm/251328119508?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)

McMaster has various hardness tester tools, but are typically $100-$1000 or more.
http://www.mcmaster.com/#hardness-testers/=pt5oqj

Perhaps it would be possible to get some samples of metal tested at various degrees of hardness and use them to try to scratch the part to be tested. But that might be considered destructive if it is a critical surface.

DATo
12-14-2013, 07:18 PM
Seems to me the easiest way is still to simply try to file it - at least that's what I was taught. If a file cuts the material so will a HSS cutter.

loose nut
12-14-2013, 07:20 PM
Angle grinder with a ZIP wheel, doesn't matter how hard it is.

firbikrhd1
12-14-2013, 09:29 PM
How about Hardenss Testing Files?
http://www.hardnesstesters.com/Products/Accessories/Hardness-Files.aspx

boslab
12-15-2013, 01:32 AM
The bouncy ball test is the scloroscope, thinking shore, a scratch test with a piece if hss like a scriber will be enough to tell you if its sawable, or the old file test, i havent yet found any difficulty with that! I dont think the carbon content will make any difference, it depends on the heat treatment, if it is high carbon steel then anneal it, it would be unusual to be making something out of hardened steel.
There are cast irons that defy sawing as they are chill crystal encased, hard to get through pure Fe3C, cementite, that is as hard as a ferrous metal gets short of nitrided steel, even diamond files have a finite life against that stuff, it kills them by attrition, literally
Mark

Jaakko Fagerlund
12-15-2013, 03:46 AM
Just a note, but OP asked for non destructive testing, so filing, sawing and sparking is out. Basically leaving hardness testing and chemical sniffer analysis as the only options.

vpt
12-15-2013, 08:48 AM
Seems to me the easiest way is still to simply try to file it - at least that's what I was taught. If a file cuts the material so will a HSS cutter.

x2

I file test everything I question on hardness. If the file digs in any bit the saw will cut it.

vpt
12-15-2013, 08:50 AM
Just a note, but OP asked for non destructive testing, so filing, sawing and sparking is out. Basically leaving hardness testing and chemical sniffer analysis as the only options.



I don't find filing "destructive". There is always some spot on a part that can take one swipe with a file and not harm anything.

Mike Nash
12-15-2013, 10:02 AM
I have got to ask (because it has been bugging me every time I see mention of it) if the material is harder than the file, does the file suffer any damage?

Good files seem to be increasingly hard to find and I don't want to damage the few half decent ones I own. The crappy files won't cut much of anything, so they are useless for testing hardness in my eyes.

So, are the files damaged or not?

Lew Hartswick
12-15-2013, 10:10 AM
I have got to ask (because it has been bugging me every time I see mention of it) if the material is harder than the file, does the file suffer any damage?

Good files seem to be increasingly hard to find and I don't want to damage the few half decent ones I own. The crappy files won't cut much of anything, so they are useless for testing hardness in my eyes.

So, are the files damaged or not?
If the material is harder than the file, I don't see any way it could NOT be harmed. At lest the file teeth
that came in contact wiht the material.
...lew...

J Tiers
12-15-2013, 10:54 AM
The bounce test should work. The difference is the depth of hardness.... case or nitriding type hardening with soft material underneath will probably give a wrong reading with nearly any bounce testing. Think of sheet metal over mud, using a baseball.

The real Shore tester can have a pretty light "bouncer", but I understand even it can be fooled.

Stern
12-15-2013, 10:57 AM
Does doing the "ball bounce" test actually give an indication of the materials hardness, or just the surface hardness ? Often wondered if the surface coating played a role in it, so while the material could be softer inside, but still have a hard treated surface. how would this make the ball react in relation to material that was "uniform hardness" throughout ?

Toolguy
12-15-2013, 11:50 AM
The OP was asking if the part was soft enough to be cut by his saw. That is why I said try a hacksaw. You could try a hacksaw on the spot where the saw would cut. I don't know that non destructive testing matters for something you're going to cut up.

dian
12-15-2013, 12:56 PM
so, 10 mm bearing ball dropped fromm 500 mm bounces 180 mm on mild steel. 440 mm on a big parallel, 400 mm on "toolmakers vice", 300 mm on chunk of railroad track and 460 mm on the surface plate (granit). but it bounces 170 m on a smaller peice of ground tool steel (toolox44) not to be heatthreated, even with weights on it to make it stick to surface plate. so i believe mass is as important as hardness as is "workholding". maybe some samples clamped in a big vice would yield other results. interesting, that the commercially available contraption works (does it?).

J Tiers
12-15-2013, 12:58 PM
I would have suggested maybe a 4mm bearing ball.

dian
12-15-2013, 01:11 PM
and further, concerning the blades i have read that hss will cut hss. only how long will it last? i hate buying blades, changing them and tightening them properly.

J.: are you kidding or can you substantiate?

J Tiers
12-15-2013, 01:28 PM
and further, concerning the blades i have read that hss will cut hss. only how long will it last? i hate buying blades, changing them and tightening them properly.

J.: are you kidding or can you substantiate?

Which "J"? Substantiate what?

HSS cut with HSS? Maybe, but why bother when there are abrasives around?

Diamonds are cut with diamonds, but there is really no choice there......


4mm bearing ball? I figure a 4mm diameter ball is less massive than most test pieces, and should give a better reading of smaller items.

The testers have an "anvil" to back up the piece, which needs to rest securely on it, or else be very much more massive than the ball used as a tester.

dian
12-15-2013, 01:51 PM
makes sence, will try a smaller ball tomorrow.

dian
12-16-2013, 10:15 AM
so i played around some more with a smaller ball and samples clamped in the vice. the results are very good. you get 30% rebound from mild steel, 45% from a gear, 50% from from a vice jaw, 55% from toolox44, 90% from a parallel and 95% from hss. a simple and effective method to check hardness, i think.

i can finally make a judgement on the hardness of my chuck jaws: 85%, so around 50 hrc, i figure. now, if i only had a clear plastic tube, around 500mm.

J Tiers
12-16-2013, 08:20 PM
I was looking a few years back for a lower cost hardness tester, and some folks here, I forget who, suggested the idea of ball and tube.

As it happened, my need for a tester was just for one project, and it was over before I got to try the idea. But now that you have reported positively, I think the project is moving up the list, even if only as a matter of interesting investigation.

A "real" Shore Scleroscope is pricey, but some types can test even items like the face of gear teeth. That could get a little difficult with a ball and tube....

PStechPaul
12-16-2013, 09:13 PM
What do you think of this for $37:
http://www.ebay.com/itm/251328119508 (http://www.ebay.com/itm/251328119508?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)

http://i1186.photobucket.com/albums/z378/bobmelinda2008/c.jpg

dian
12-17-2013, 02:26 PM
its for rubber, right?

lakeside53
12-17-2013, 03:10 PM
Na... it's to determine the correct dosage of Viagra ;)


But yes, "Shore A-D Durometer" is mostly used for rubber, plastics etc.

gstprecision
12-18-2013, 04:54 PM
The first thing in Non Destructive testing is normally to determine what you are working with. Then charts should give you some fairly accurate specs, alloy Composition, conductivity, hardness etc.

GST

PStechPaul
12-18-2013, 10:18 PM
I found many others similar to that one, and they are for rubber (tires) and plastics. Here is an interesting old hardness tester:

http://www.ebay.com/itm/SWARD-HARDNESS-TESTER-HENRY-A-GARDNER-LABS-BETHESDA-MARYLAND-/131074140491

http://thumbs4.ebaystatic.com/d/l225/m/m9NkhuDJMoQNYsf4d1W6i7g.jpg

Here is one for sale very close to me in Baltimore. It looks to be in decent shape:

http://www.ebay.com/itm/Rams-Rockford-Vintage-Portable-Rockwell-Hardness-Tester-Model-30-R-/390727468578

http://thumbs3.ebaystatic.com/d/l225/m/mAOAiMa_wWO_FrPWGY7mMxQ.jpg

And this looks pretty nice for $200:

http://www.ebay.com/itm/Portable-Hammer-Hitting-Brinell-Hardness-tester-with-readout-microscope-/200999478185

http://thumbs2.ebaystatic.com/d/l225/m/m6TlSPbGg6-IkxDjdEUewmQ.jpg

I even found some fruit hardness testers!

http://www.testequipmentdepot.com/general/garden/fht801.htm?gdftrk=gdfV26236_a_7c2784_a_7c10459_a_7 cFHT801

http://www.testequipmentdepot.com/general/images/fht_thumb.gif

The more professional new hardness testers for metal are about $500 and way up. There seem to be a lot of different methods. Interesting...