How to select the right bit sockets? (detail chart)
  • 2020-03-11

"I Don't care who make what, I Just Like MY TOOLS TO NOT FAIL"

This sentence kind of come from most of mechanics and technicians. They hope their hand tools would never break.  Unfortunately, bits would eventually fail.

What are bit sockets?  Why are they broken or worn down? How to select the right bit sockets?

Bit socket is composed of bit and socket.  Bits refer to external part with usual shape, like hex, Torx, or slot.  Sockets refer to bottom part with square drive hole.  You can drive socket by drive tool, like ratchet handle or impact wrench or power wrench.

Compared with only bits, bit sockets can be driven by square drive hole, so the torque transmission is more stable and efficient.  Bit socket will be better choice for big size bolts and nuts with high-torque requirement.  These bolts and nuts are often spotted in vehicles or large machines.

bit socket Tien-I 

(Comparison photos for bit sockets and bits)

The tip of bit socket is easily worn down, deformed or even broken, as tip of bits is most vulnerable during the torque transmission.  Why?  Just imagine how the torque concentration on the specific points too much.  For example, given same strength, Phillip or Slotted bit are more likely to deform or break than hex or Torx, because torque focus on few points rather than evenly distributed to the entire connection line.

For detail diagram and explanation, please click “What Caused Stripped Screw?”

4 Types Bit Sockets:
Manual Two Piece Bit Socket ⼿動起⼦套筒 (兩體式)
Manual Bit Socket (One Piece) ⼿動起⼦套筒 (⼀體式)
Replaceable Bit socket 換式起⼦套筒 (兩體式)
Impact Bit socket (One Piece) 氣動起⼦套筒 (⼀體式) 

bit socket comparing sheet  

Manual Two Piece Bit Socket 

It's made by two peiece, the socket and the bit. 

The socket is made of Chrome Vanadium Steel.  Tien-I, as Taiwan leading manufacturer, use Taiwan made Alloy Steel, CR-V 50BV30 with high-tech cold forged and heat treatment to ensure consistent quality as well as hardness and torque stable performance in mass production. 

For further information about CR-V, please check below link:

Tien-I Chooses Taiwanese Chrome Vanadium Steel for Durability and Resilience

The bit is made of S2, Si alloyed steel (Shock-resistant, S-type)

S2 is well-known alloyed steel.   Most mechanics or technicians heard of S2. S2 special is the high hardness, around HRC 59-67, because of high percentage of silicon in S2.  Above HRC 59 is seriously tough, if you consider the hardness of Samurai Sword is only around HRC 60.

















However, S2 is not always right choice.  Why?

Sometimes, hardness is not as high as better.   When mechanics inappropriately put too much strength on the bit and then on the bolt, which one do you prefer broken if you must choose one, bit or bolt?  I think in most circumstance you will chose bit instead of bolts because broken bolt or worse, stripped case and damaged thread will cost mechanics more time to finish the job.  Time is money, especially to professional mechanics. That’s also why some bolts will require to work ONLY manually rather than by air or power tools.  That’s the reason you should use manual bit socket without impact wrench or power ones.

Manual Bit Socket (One Piece)

The one-piece manual bit sockets are usually made of SNCM 8660, Nickel Chrome Molybdenum Steel, or S2, Si alloyed steel (shock-resistant, S- type).  SNCM 8660 hardness is around HRC 55-59, lower than S2.  However, balance between bit durability and possibility of stripping is key point.   Considering small sizes with higher return rate, such as Torx T20, Tien-I would discuss with our customers for the right material to optimize the return rate of specific sizes.

One-piece bit sockets are usually ultra-short length, below 20 – 30 mm.  Without socket part, we can make the one-piece bit socket with shortest length which is benefit to the confined space.


 super short bit

Replaceable Bit socket

The highlight of replaceable bit sockets is bit itself replaceable. In general, the tip of bit is most likely broken.

Because of this fact, the purpose of replaceable bit socket is to help heavy users save money. After all, it is better to replace a bit than an entire bit socket.  It is design to change replacement easily.  As shown below, the socket and the bit is fastened by screw.  So, loosen the screw, replace the bit, and then fasten screw back, a new replaceable bit socket is done. bit socket replaceable

Impact Bit socket (One Piece)

Impact bit socket is usually made of SNCM 8660, Nickel Chromium Molybdenum Steel, or CR-MO SCM440, Chromium Molybdenum Steel.

You can click this link to know more "Impact Socket Material, Chrome Molybdenum Steel, CR-MO”

Here I would like to clarify again.  Considering torque application and durability of bit, we should know each type of bit sockets with their own advantage in specific work area or purpose.  It is unwise to think the one type must be always better than the other.

For example, if you occasionally repair your car at home, manual bit sockets can do fantastic job.  However, “impact bit sockets” or “replaceable bit sockets” would be better choice for work-shop mechanics or factory assembling line workers.  Money and time efficiency are both key factors to think when we chose bit sockets.


How to choose the right bit sockets?

First, it depends on what country or what region you are in, because different countries have different warranty coverage.   That’s right, as a only tool maker, I am talking about brand warranty coverage, instead of product quality.  Why? In USA, some tool brands will have LIFETIME WARRANTY policy.  Although bit sockets are supposed to be consumable items, some tool brands will extend the warranty coverage to bit, thanks to competition in the hand tool market. If the bit tips are worn down or broken, the tool brands will send a new bit socket as replacement.  This service would satisfy most end users, but it is the nightmare to the makers.

As a leading bit socket maker in Taiwan, we face this situation with our professional tool brands together by analyzing the return rate and offering alternative solution to drive down the return rate.  It will be homework for our engineers for continuous improvement.

Hand tool market is very competitive.  The high-end brands compete not only quality but also after service and warranty coverage.  You can find some interesting arguments in many on-line forums for hand tool prices, quality and service.  Like funny topic, which is more durable, German-made bit or USA-made ones?   Usually the local distributors are more interested in these online discussion.

One more thing, the length of bit sockets is not as longer as better, because the longer bit sockets will be more easily broken. The below size chart show Tien-I complete categories of bit socket by length and sizes. 

For further information, like size, torque performance and material, please contact our over 30 years experienced sales team.

Tien-I manufactures manual bit sockets and impact bit sockets by the international standards, ANSI and DIN.  If you look for the supplier with ability to supply consistent quality bit sockets, please contact with Tien-I Sales team.

The following are the 10 types of common bit sockets.  Please check the following links:

Two Pieces Manual Bit Socket:

Impact Bit Socket: 


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