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Denny Graham

5160 Steel.....For a Real Leaf Spring????

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I suppose this is kind of ars backwards since most of the time Bladesmith's are looking to turn

5160 leaf springs into blades.......but I'm looking to turn 3/16" x 1 1/2" 5160 bar into a leaf spring.

Let me explain a little. Thanks to you guys who are forging blades, these blade forums are the only

place on the net that I've been able to find any real information about heat treating 5160. 

So I'm building these Cyclekarts and the front springs are made from the previously mentioned 

alloy and end up typically around 24" long. So far, all of the guys are using pre-made Amish buggy

seat springs or snowmobile springs for the front of the karts. Well.......being a bull headed old

Irish man, I wanted to make/forge my own springs. 

I built a triple burner propane forge, 10" x 10" x 36", and made a 20 gallon quench tank stocked with

soybean oil, and bought a 100 lb. propane tank and high pressure gauge......then chickened out when it came

time to fire it up. 

I put a lot of time (months) into the the project, that is, building the forge & quench to heat treat the springs.

And a lot of time into forging the eyes and arches on 6 springs (3 sets) and finally decided, rather than experiment

with and screw up all this work, that it would be a lot safer to have my local heat treater finish them off.

I can always experiment with making a blade later.

The was no question at Metals Technology about the oil hardening portion of the job.....but....the final tempering

came into question. I was told that the engineer normally specifies the finished hardness. Well....I taint no engineer,

just an old retired welder/machinist/jack of many trades. I took a guess and based on what I'd seen on a number of

blade forums, settled on 36 to 44 HRC. 

So......the question for ya'll is......do ya think this will work for my application or do you think they may 

either break or flatten out with the first bump I hit wit the car??????

If ya offer an opinion......Thanks in advance.

Denny Graham

Sandwich, IL 

 

Propane Forge-Oven 02.JPG

Quench Tank Finished 01.JPG

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I don't know what kind of road/track/trail you'll be running the cart on, and it has been years since I did any spring application design work, so it is difficult for me to say what they should be.  What I can tell you is that 36-44 is a large window, and your heat treat shop should be able to hit a number plus or minus 2 HRC.  Also, I think you will be hard pressed to break a 5160 leaf spring at 44 HRC.  Whether that is too stiff (or not stiff enough) for the application I couldn't say.  My fencing long-sword is 5160 and is quite stiff (to the extent I try to pull all my thrusts, because if you hurt your sparring partners they can't spar with you any more).  They list their blade hardness at 50 HRC.  

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You might have to reverse-engineer the desired hardness by getting a reading on an existing spring that performs the way you want.  If the HT shop has a tester, just take a spring in and tell them "I want this result."  If your existing spring is too stiff, ask for a few points softer, and vice versa.  

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When I was at the railroad we would temper springs (5160 or 1095) to 42 - 44 HRC plus or minus a bit. 36 would be IMHO too soft.

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Thanks guys. Guess I'll have to wait till next week to see what I end up with. They've got three sets.

They are single leaf that carry around 100 lb. each up front, (200-250 lb. total) Jerrod. And.....used on

closed street racing, dirt ovals and also off road hill climbs, sort of an all round car/kart.

Tks Alan. These are prototypes and it would be kind of hard for me to compare these to others  because

I'm sort of a lone wolf so to speak. I don't run with the pack, in fact, most all of the pack is out on the

west coast and desert south west. There is very little Cyclekart happening around the Midwest at this time.

About the only springs I could compare them to would be those on my 50's Chevy trucks or those at the local

farm store. So...I can't get those on the trucks up on the bench at the heat treater but I suppose I could pickup

a trailer spring for a twenty at Farm & Fleet.

I was originally thinking about timing the tempering in the wife's oven right after they came out of the

quench. Of course I'd have to wait till my "big old wife" was out of town for that. However, the guy I spoke

with at the heat treater said they would probably draw them back around 900°F. That sounded pretty high

from what I'd been seeing here on the forum, had I tried this batch in my shop I'd either had to live with

a pulsating 400-500°F in the kitchen oven or try to hold a temperature in the propane forge. All of that is

pretty iffy when I've got as much time in forming the springs.  

Oh well........... it's an experiment, worst case is if they come back at 36 and as ;you suggest, that's to soft,

I'll end up flattening them out. At least from what Jim posted, if they're at 44, well......I might be in for a rough

ride.

You know......as I said before......you guys are the only ones I've found on the net that are willing to discuss

working with heat treating of spring steels. 

Thanks for taking an interest in a not so sharp object which is a bit off topic for a blade forum.

Denny Graham

Sandwich, IL

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You could probably have them shoot for the higher end of the range and try the springs out.  Then have the heat treater temper them again a little higher if the ride is too rough.

You'll have to share pics of the cyclekart with us when it's done Denny.  With the quality of work you put into your quench tank just to make the springs, I bet the kart is going to be great :)

 

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Thanks Brian, thought about having them shoot for the high side and possibly

drawing them back later if they were to stiff. But....I think the train's already left

the station. I'd also read where you want to temper soon after the quench. Maybe

those discussions were about tempering soon after the heat to prevent cracking

while in the hardened condition?

Besides....the springs are in their hands now and I should be getting a call first of

the week. It's an experiment, a learning process so if this batch doesn't pan out

I'll be better informed the next time around.

I'm pretty bad when posting to forums by veering off topic, just as this thread has been,

since this has not been about blades on a blade forum.

Soooooo.....I don't think the moderators and some of the members would be very pleased

by my posting to much more about my projects. I was posting to the Cyclekartclub.com

forum for a couple of years, but got so badly beat up there for posting my opinions and

more than one liners and that I just decided to keep it to myself. I can be sort of windy

at times. 

But briefly, the car is a 3/4 scale of a 1928 Riley Monoposto Brooklands. An all metal

chassis and aluminum body work ( finishing up the chassis, body yet to be done).

I'm using a Predator 212cc engine at present with plans for 420cc in the future. Speeds

are typically 40-60 mph depending on the gearing. I've gathered up enough parts

and material to build 2 more, a GN and a Bugatti, that's why I bent three sets of these

springs this time round.

Thanks for putting up with me guys. I've been following this forum with interest for several

years with special interest in the heat treating. I spent most of the day yesterday

(Saturday) watching Youtube videos about  traditional Japanese  Sword makers and the

Katana's  history. Also been studying Jim Hrisoulas's "The Complete Bladesmith" to 

learn more about heat treat.

Enough babel.......time to head for the barn with my fresh cup of coffee and get some

heat goin'.

G'day.

Denny Graham

Sandwich, IL  

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The way I see it, the more we learn about heat treating 5160 (for any application) and the more we hear about dealing with outside HT places, the better off we all are.  Please do keep us informed on how it all plays out (service from the heat treater, final hardnesses, how stiff the springs were, EVERYTHING!).  Springs are very important to smiths.  Check out the DIY power hammer posts on the forum some time.  

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Okey dokey, since you axed. Picked up the springs Monday morning. They came out at 

41.8 to 42 HRC. Had a little warpage but I can readjust them in my hydraulic press.

I haven't had a chance to test the spring rate but that's something I well be doing in the 

near future, just to much going on right now.

Thanks again guys,

Denny Graham

Sandwich, IL

Front Springs w-hardware 05.JPG

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Posted (edited)

Now, if ya'll will bare with me for a few more questions, not related to weaponry. 

"Spring Rate" is the pressure  it takes to deflect a leaf spring 1". I'm not an engineer

so I'm not familiar with all the technical terms like Modulus of elasticity, Bulk Modulus,

Shear modulus, Poissons ratio, etc.  From what I've been able to gather, the Spring Rate

is determined by the alloy, length, width & thickness. That comes out to just a little over 

60 lbs. from all the charts and calculators that I've run the numbers thru. They all agree

within a couple of lbs from each other. And that is where I expected to be for this

application.

To test these springs, 5160 alloy, 24"long x 1.500" wide x .1875" thick were supported at each end

on a beam, on a single scale and in my hydralic press, compressing them down 1", they all come out

at around 130 to 150 lbs.

So I'm wondering if the temper has any bearing on this? It just seems to me that

the harder the spring is the more pressure it would take to compress it. At 42 HRC

it would seem that these should be fairly close to the charts and calculators.

Am I missing something here?????

tks

Denny Graham

Sandwich, IL

 

Edited by Denny Graham

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By my understanding, I think you are spot on in your thinking.  If you soften it up a little bit the will flex a little more easily.  I would highly recommend trying them as is before tempering them again, though.  At that hardness you are going to be very hard pressed to damage them with a bit of service (road/track time).  I trust they would be relatively easy to take back off and re-temper, yes?  

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Were the charts you used calculating the deflection of just one end by chance?  If I understand your test setup, you are deflecting both ends, and would end up with about twice the load than if one end was held stationary.

 

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On 9/25/2018 at 1:33 PM, Jerrod Miller said:

I don't know what kind of road/track/trail you'll be running the cart on, and it has been years since I did any spring application design work, so it is difficult for me to say what they should be.  What I can tell you is that 36-44 is a large window, and your heat treat shop should be able to hit a number plus or minus 2 HRC.  Also, I think you will be hard pressed to break a 5160 leaf spring at 44 HRC.  Whether that is too stiff (or not stiff enough) for the application I couldn't say.  My fencing long-sword is 5160 and is quite stiff (to the extent I try to pull all my thrusts, because if you hurt your sparring partners they can't spar with you any more).  They list their blade hardness at 50 HRC.  

I think stiffness is more a factor of cross-sectional thickness rather than actual hardness. A very thin cavalry sword in my collection rockwells out about Rc55 and yet flexes quite easilly. A much softer short sword with a thickness of nearly1/4" throughout, more or less, is much more difficult to flex.

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It is definitely related to both, with geometry being a very strong factor, but hardness will play into it as well (as that effects the modulus of elasticity).  You'll often see that modulus of elasticity is a material constant, but 5160 tempered to 50 HRC is effectively a different material than 5160 tempered to 40 HRC or 60 HRC.  In the case of my federschwert versus the newer models the same maker offers, I think it is purely a change in thickness.  I will try to measure my buddy's newer model sword soon and see how it compares to my sword's thickness (and width).  

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1 hour ago, Al Massey said:

I think stiffness is more a factor of cross-sectional thickness rather than actual hardness. A very thin cavalry sword in my collection rockwells out about Rc55 and yet flexes quite easilly. A much softer short sword with a thickness of nearly1/4" throughout, more or less, is much more difficult to flex.

That is my understanding as well. I always thought that hardness just determined how easily it would break or take a set.

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Yes Jerrod, thru bolt and shackle.

Nope Brian, using standard three point compression test used by all the testers for spring rate.

They were right at the high side Al, (42 HRC) which I discussed with the metallurgist when I dropped

them off. 38 to 42 was the window we settled on. Metals Technology Corp. has been in business

since 1963 and we always used them back when we were in business, (machine shop/welding shop),

so I trust their advice and work.  I didn't bring it up  but I assumed that they left them on the high side

in case we needed to draw them back more.

I don't have any way to check the hardness on conventional leaf springs, so I'm really in the dark as

to what the industry standard is. But it seems a little hard to believe that a few points difference could 

mean that the spring rate could double. 

Denny G

  

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From my understanding once the fabrication of sword blades became a higher tech industry with more controlled heat treating, military swords tended to run from the low 40's to the low 50's depending on manufacturer.

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Posted (edited)

Sorry Al, that link run me around like a puppy on a leash. Apparently I can't see the article

without joining something and I've joined so many I can't keep  track of them anymore.

No where near fully understanding heat treat, but 50+ HRC is just shy of 5160's high limit of 60.

I'm afraid that would make for a super rough ride.....that is until I hit a rut and the spring snapped.

Does anyone have an inexpensive, sort of layman's way of testing the hardness after heat treat????

That said......I did see a 1" id tube about 6" long with a window slot milled in the side and the guy

would drop a 1" steel ball bearing thru it and observe how high it bounce. I suppose you could eventually

mark calibration lines on it if you had enough samples of known hardness. Doesn't seem like that would

give you much more than a rough idea of hardness, certainly not an accurate determination. And again.....

applying a little logic, seems like dropping the ball from a higher point would tend to raise the resolution.  

Looks like it's a homemade version of a Flexbar drop tester or a Shore Scleroscope? 

Denny Graham

Sandwich, IL

Edited by Denny Graham

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Thing is, you want the same thing from both swords and leaf springs, that being a flexible stiffness that will not break.  5160 is a lot tougher than the old Solingen alloys, and as such can take being a little harder.  Of course, an unbreakable sword is great, while a leaf spring that rattles you off the track is not.

I think you're probably good where you are, hardness-wise.  

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Thanks Alan. The question was asked, "what a standard leaf spring is hardened" to and 

that's my quest now. After doing some reading this morning, I just ordered a 6 foot length of 

1 inch id. acrylic tubing and a couple of 440C hardened SS balls. 

I can do a drop test with several spring samples that I've got around the ship and compare

the results to the springs I got back last week. 

At the very least, it will tell me if I'm anyway near close.

I want to thank the guy here for letting me pose this question even though it's not Blade

related. It's helped me get a better understanding of the factors involved with this project.

Denny Graham

Sandwich, IL 

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Hey, it's applicable!  And we like all things metal here.  Several of us use jewelry techniques on our blades, it's all good.

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Speaking of ball drop hardness testers.....does anyone have or have access to one of those

"Quick-Check Hardness Tester" ball drop portable testers that J&L (now bought by MSC) used to sell??

MSC doesn't sell them any more. The unit came with a plastic sheet/chart that had the instructions and

Rockwell C scale on it. I'll post a picture that I have of it, but it's so blurry I can't make out most of it.

And......I can't don't have any idea what size the sheet is so I could scale it myself and reproduce it. 

I'd sure like to get a clear picture of one of those charts with a ruler along side of it.

I did make a tube up from some 1 1/2" conduit 24" long with a 1/2" window milled in it's side

and I used an 1.25" steel ball bearing and it indeed does work to compare a soft sample from a hard one.

Also leaves a dent in the sample.  But......that's about all it does. I think the tube is to long

and the ball to big.    

Denny Graham

Sandwich, IL

 

Quick-Check Hardness Tester conversion chart.jpg

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The rebound test generally used in industry is the Leeb Rebound Hardness Test.  We have one at work. 

To sum it up: A spring loaded shuttle is shot at the surface to be tested.  The speed just before impact and the speed of the rebound just after impact are compared (1000*vr/vi = Leeb Hardness).  That can then be converted to  HRC. 

Given the light weight of the shuttle at just a few grams (the whole unit is the size of a slightly bulky pen), it is interesting to note that the sample to be tested must be at least 11 pounds.  

For what it is worth, I don't trust these things at all and wish nobody would every call out a specification with them.  Traditional Rockwell or Brinell are both MUCH more reliable.  I would even take a file comparison test over rebound tests.  The place a rebound test really makes sense is when you are interested in the rebound properties of the part (as opposed to hardness).  Obviously, the first thing that comes to mind here is the ball bearing rebound on an anvil.  In material science, hardness is defined as "resistance to plastic deformation".  Note the distinct lack of the word "rebound".  

Sorry, but much like "temper colors indicating temperature", this is one of my buttons, apparently.  

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Well I certainly wouldn't argue the accuracy of this type of testing Jarrod, but...for the guy

that has nothing in a small home shop they seem better than nothing. I just found a Quick-Check

on ebay for fifty bucks and that's much cheaper than any set of hardness files from any of the 

vendors. As is reading the color for heat treat to the average guy in is home shop, a plain old

bastard of a file tells me only that it's either hard or soft, not much more feed back than that

to the inexperienced eye.

And that was the reason I balked at treating my springs this time around, just to iffy so I chose

to let a legitimate shop to do them. 

The experiment that I did with my quickly thrown together bounce tester, although it lacked any

real information does seem to show the difference between soft - hard and in between.

From what I've read, you need at least 1/4" of material for a valid reading. That puts almost all

blades outside of it's usefulness unless you're checking a battle ax.

Denny Graham

Sandwich, IL   

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