Jump to content
I Forge Iron

Difficulty forging 5160 leaf spring


Recommended Posts

Hi everyone.

This is an amazing forum and source of information you have here, I've been reading with interest for the last 8 months or so but I have encountered a problem which doesn't seem to have been discussed...

I am a new knife maker based in the Cape Town area of South Africa. Recently I was given some 5160 leaf springs which I intend to use to make some fairly simple camp knives for my friends and family as practice. The only problem is that the darn things hardly move under the hammer...

From what I've read 5160 is supposed to be soft and easy to forge, hence why I'm using it as a practice material. I know that using scrap steel is less than ideal, but due to my location it's going to be another month or two before I can get some nice 'known' steel to play with.

I read somewhere that it might be because the steel is unannealed, and that annealing it should solve the problem. I would really appreciate it if someone with more knowledge on the matter could give me their opinion on whether or not this would help.


Link to comment
Share on other sites

5160 doesn't move like mild steel.  Generally, the harder to forge the better the steel for knifemaking.  From my experiance 5160 doesn't want to forge down thinner than 1/4" then it really gets hard to move.  It is however more forgiving than 1095.  Keep it hot, there's no point to hammering when the steel starts turning red.  A good anvil and hammer can make all the difference also.

I really don't understand the forging in an anealled state.  When the steel is heated past the austinitic state it becomes moot.

Keep practicing, try different hammer configuations.  Remember, if forging was easy everybody would do it.

Link to comment
Share on other sites

Soft is a relative term. This steel at forging heat is harder to forge than mild steel at forging heat. All knife steels are. You did not tell us a lot about what you use for heat and about your hammer and anvils. Or about how you use them. Steel at forging heat after first being annealed will be just as hard to move as this steel at forging heat that has not been annealed.

If yoiu are using a hammer with a failry flat face and trying to do this over a flat faced solid anvil it will be harder to do than if yoi use a rounded or pein faced hammer over a bottom fuller like the horn of a solid anvil. We covered just this in our wednesday evening knife chats..Every wed at ten pm EST..and for those far from our time zones they are posted in the knife forums...click this link if you wish..



Link to comment
Share on other sites

Thanks very much for the reply.

Aha, so red isn't hot enough... I think the problem is that I've been trying to work it too cold because I'm terrified of letting the grain grow. I'll definitely try heating it more and hopefully I'll have something to post about in the near future!

Edit: Rich's reply snuck in while I was typing... Oh the joys of cellphones haha..

Thanks Rich, I read all of those knife making posts as soon as I can. I have a gas forge which I've built myself out of a small propane tank. It gets plenty hot enough if I let it.

I use a big piece of scrap steel for an anvil, and based on the advice from those classes I've radiused one of the edges to act as an approximation of a bottom fuller. Unfortunately there aren't many blacksmiths in my area so anvils are hard to come by, and shipping a block of steel across the country is a bit beyond my budget haha.

I've also rounded the faces of all of my hammers which range from 2-3.5 lbs. Unfortunately I don't have a nice engineer's hammer yet - that's next on my list - so I don't have a nice stright peen to work with.

I guess I just underestimated how different mild and knife steels are to work. I'll try working it hotter and see if I can find some way to make my 'fuller' more effective.

Thanks for all the info

Link to comment
Share on other sites

This is from Wikipedia. Physics of hammering Hammer as a force amplifier

A hammer is basically a force amplifier that works by converting mechanical work into kinetic energy and back.

In the swing that precedes each blow, a certain amount of kinetic energy gets stored in the hammer's head, equal to the length D of the swing times the force f produced by the muscles of the arm and by gravity. When the hammer strikes, the head gets stopped by an opposite force coming from the target; which is equal and opposite to the force applied by the head to the target. If the target is a hard and heavy object, or if it is resting on some sort of anvil, the head can travel only a very short distance d before stopping. Since the stopping force F times that distance must be equal to the head's kinetic energy, it follows that F will be much greater than the original driving force f — roughly, by a factor D/d. In this way, great strength is not needed to produce a force strong enough to bend steel, or crack the hardest stone.

Effect of the head's mass

The amount of energy delivered to the target by the hammer-blow is equivalent to one half the mass of the head times the square of the head's speed at the time of impact (8ac4afe868ab54cec61fddfa35a87bdb.png). While the energy delivered to the target increases linearly with mass, it increases geometrically with the speed (see the effect of the handle, below). High tech titanium heads are lighter and allow for longer handles, thus increasing velocity and delivering more energy with less arm fatigue than that of a steel head hammer of the same weight. As hammers must be used in many circumstances, where the position of the person using them cannot be taken for granted, trade-offs are made for the sake of practicality. In areas where one has plenty of room, a long handle with a heavy head (like a sledge hammer) can deliver the maximum amount of energy to the target. It is not practical to use such a large hammer for all tasks, however, and thus the overall design has been modified repeatedly to achieve the optimum utility in a wide variety of situations.

Effect of the handle

The handle of the hammer helps in several ways. It keeps the user's hands away from the point of impact. It provides a broad area that is better-suited for gripping by the hand. Most importantly, it allows the user to maximize the speed of the head on each blow. The primary constraint on additional handle length is the lack of space in which to swing the hammer. This is why sledge hammers, largely used in open spaces, can have handles that are much longer than a standard carpenter's hammer. The second most important constraint is more subtle. Even without considering the effects of fatigue, the longer the handle, the harder it is to guide the head of the hammer to its target at full speed. Most designs are a compromise between practicality and energy efficiency. Too long a handle: the hammer is inefficient because it delivers force to the wrong place, off-target. Too short a handle: the hammer is inefficient because it doesn't deliver enough force, requiring more blows to complete a given task. Recently, modifications have also been made with respect to the effect of the hammer on the user. A titanium head has about 3% recoil and can result in greater efficiency and less fatigue when compared to a steel head with about 27% recoil. Handles made of shock-absorbing materials or varying angles attempt to make it easier for the user to continue to wield this age-old device, even as nail guns and other powered drivers encroach on its traditional field of use.

Effect of gravity

Gravity will exert a force on the hammer head. If hammering downwards gravity will increase the acceleration during the hammer stroke and increase the energy delivered with each blow. If hammering upwards gravity will reduce the acceleration during the hammer stroke and therefore reduce the energy delivered with each blow. Some hammering methods rely entirely on gravity for acceleration on the down stroke.


we do not advise anyone to use Wikipedia as a primary source for anything. because while a PhD can post so can the 12 yr old arm chair experts.

Link to comment
Share on other sites

 High tech titanium heads are lighter and allow for longer handles, thus increasing velocity and delivering more energy with less arm fatigue than that of a steel head hammer of the same weight


Swede reread that and consider it a bit......the part about them both being the same weight is the key....Theywill both ,at the same speed. impact with the same force. However we know that Ti is a much lighter material than steel. So for the same weight it must be larger,,a lot larger....really big!

Wot thata would mean to me and the way I swing a hammer is that I would smack myself in the hammer side ear both on the upswing adn the downswing...I am too old to take many hits like that.

It will not decrease the arm fatigue,,it is the same weight. And if it is fitted with a longer handle it will in fact increase the arm fatigue,,again as it is the same weight. And depending on the face contours it may have more cdontact area and that translates into more effort needed to do the same amount of work as it is spread over a larger area to move steel.

That said wot you posted is a must read for anyone using hand tools.

Link to comment
Share on other sites

Welcome aboard Daven, glad to have you. If you'll put your general location in your header you may be pleasantly surprised to discover how many folk in SA are hanging out on IFI.


Your question about forging annealed steel leads me to suspect a lot of your info comes from the internet. Be careful  believing what you read on the web, good info can be well hidden by folk with no better training than roll playing games. JMC and Rich are both accomplished and well known bladesmiths and they aren't making it up as they go. Heck, when they do make it up as they go it's based on knowledge and experience so it's a good bet.


As said, forging mild steel is going to be a lot easier (for various values of easy) than higher carbon steels or high alloys. 5160 spring is a good place to start as it's pretty forgiving of heat treat mistakes.


Keeping steel hot longer than necessary will allow grain growth, however the hammer breaks the crystal boundries and refines the grain.


Here's my personal caveat, I hold myself up as an example, I'm not a bladesmith, I've made a few and know how to work tool steel but I'm NOT a blade guy. This means my opinion is just that MY opinion and what it's worth.


Frosty The Lucky.

Link to comment
Share on other sites

While a good blacksmith hammer of modest weight [2 to 4 lbs] will move the metal the way you want for knife making the same weight hammer with a smaller face and a mild radius would be more effecent.  Check out the style of cuttler or knife maker hammers and see the difference.  Even a 2 lb ballpeen with a radius face will move the hot steel better than a square face that is flat.  By a mild radius I mean real mild.  Once the blank is close to finish go to the flat face and finish up.  There are several smiths on this site the make cuttler hammers that you may find by searching.

Good luck and keep it up

Link to comment
Share on other sites

Hey everybody


Thanks so much for all of the input. I rounded my hammer face a bit more and let the steel get hotter - problem solved!


Just finished my first "knife" - a letter opener for my girlfriend for Christmas. Well, I call it a letter opener but it's actually pretty sharp haha.


I'll be sure to post a pic later with her permission.


Thanks again, and happy holidays everyone!


Link to comment
Share on other sites

  • 8 years later...
On 12/22/2012 at 11:35 AM, jmccustomknives said:

5160 doesn't move like mild steel. 

Well I’ll tell you from my experience with 5160 spring steel when I started forging I went out and bought two full leaf spring sets to play with, and I took and cut a 12” piece off and then cut that down the middle lengthwise and started heating and hammering one piece out and man it was hard to move, took 6 hours forging to thin it down and draw it out but I ended up with an 18” x2” billet and made two knives from it, the second piece I annealed overnight in vermiculite and the next day I started drawing that piece put and what took 6 hours before took a hour to draw out o the second piece that I annealed, so I can definitely tell you that annealing 5160 spring steel for me at least made it a lot easier to work and just heating it up doesn’t harden it, you need to quench it to make it harden back up, mine worked so easy I thought I had a different type steel at first, also I always forge my leaf spring steel down to 3/16” to 1/8” and if I draw it out to 3/16” I grind it down to 1/8” for making my blades from it and then thin the steel more on the grinder if I need it thinner then that



Edited by Mod30
Trim excessive quote
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...