Plier material

[guimba]

Hello, I am looking to design some pliers with custom jaws and wondered what alloy is commonly used to make your garden-variety slip-joint pliers, and would it be easily machinable, and what kind of plating would I want to apply. Thanks for the help!

 

[israelkk]

Why not buy some pliers and do a metallurgical analysis in a metallurgy lab?

 

[guimba]

Thanks IsraelKK but I don't need the exact alloy composition and would rather not spend the money if someone already knows that the material is. Cheers.

 

[israelkk]

First of all a good quality plier will be probably not be manufactured just by machining, it is probably forged. A metallugraphic analysis will show not kust the chemical analysis and hardness but it will reveal how it was manufactured, the direction of the grains, surface treatments such as nitriding, carburizing, etc.

 

[redpicker]

The cheap pliers are generally made from a low-carbon plain-carbon steel such as AISI 1018, perhaps up to 1030. Something that can be forged easily, perhaps even stamped cold.

Higher quality ones are made from a low-alloy steel with a higher carbon content, so the jaws can be hardened through heat treatment.

As for plating, some are un-plated, others are chrome plated, some have an oxide coating or some other surface conversion coating (phosphate coating?). The coating is mostly for corrosion resistance and aesthetics.

Just using an low-alloy steel won't make a quality tool. Some very high-quality tools are made from stamped plain-carbon steel. The difference is in the design and quality control. The cost of the material is usually only important on large production runs.

rp

 

[guimba]

Thanks redpicker, I only have about two dozen of these to make and each has a different jaw configuration so forging is out of the question. Ideally, the material would be machinable and then heat-treatable to obtain some strength. A zinc or cad plate on the outside I think would be suitable, no need for nice chrome.

 

[redpicker]

You will have to decide what strength level you will need. Does the yield strength need to be 30,000 PSI or will it need to be 100,000 PSI? Or, maybe even greater? Will the jaws need to be hardened? Do they need to be adjustable?

Maybe you can find existing pliers that meet your needs and just modify them by machining new jaws or perhaps welding extensions to the existing jaws. For a small number, this might be easier. You might have to anneal the jaws for machining (then re-harden) or use a very controlled welding process (to prevent cracking), but these problems can be fixed rather easily. This way, you can use someone else's engineering for the basic design (you know it works) and have fewer decisions to make.

rp

 

[CoryPad]

There are different ways to produce these parts. Here are two.

Utica brand pliers
1020 steel, hot forged (with decarburization), through hardened and tempered to 39 HRC (surface) then chromium electroplated.

Craftsman brand pliers
custom alloy steel (Cr-V), through hardened and tempered to 44 HRC (surface), no surface treatment.

Many small hand tools have been made/are made with 6150 Cr-V steel, which is widely available, so you don't have to buy 20-ton lots like Sears does.

 

[guimba]

Thanks for the help, all. Looks like I have a few choices and decisions to make!

 

[MSUKeith]

Cory-
Won't 1020 have a 'hard' time getting to 39 C even at the surface without some sort carburization?

guimba-
Watch out for soft coatings on your jaws, they will wear quick and may cause gripping issues.

 

[TVP]

MSUKeith,

I'm sure Cory will respond too, but the answer to your question is yes, 1020 has difficulty achieving any type of reasonable hardness (> 35 HRC) unless it is water quenched in thin sections (only several mm thick). For pliers, the surface transforms quickly, but the center, even if it is only 2 or 3 mm below the surface, will be 50% martensite or less, meaning lots of ferrite, pearlite, maybe some bainite.

 

[CoryPad]

MSUKeith,

My data was based on actual reverse engineering I did with my tools today. TVP provided the correct answer regarding hardenability problems.

 

[KENAT]

Not sure about where you in the world you are but back in the UK Cadmium plating was getting frowned on and we used it less & less. You may want to bear this in mind.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[unclesyd]

Just got report on some slip-joint pliers subject to PMI analysis.

The first two are pre 1990. The table lot is unknown.

High dollar pliers 8620 46 Rc Cr plated

Mid range 4150 43 Rc Nickel plated

Table Lot Could be 3140 or 4130 Rc 37 Zinc plated

They are going to recheck the high dollar pliers.