Block and Pin Uni Joints compared to Twin Spring Coupling

Friction bearing U-joints replacement

Block and Pin Universal joints verses Twin Spring Couplings – no maintenance power transmission couplings.

In the world of universal joints there are only two versions, the old block and pin and the newer needle bearing u joints.

Block and Pin universal joints are over 100 years old

Block and Pin u-joints was originally patented in 1904 making it over a century old, and the technology inside it hasnt changed, the introduction of needle bearings gave the manufacturer of uni joints a new option for customers who wanted a uni joint that could run faster and at improved angles of misalignment.

Friction bearings u-joints are cheap, made from steel and used in lots of industries but are slow and need maintaining constantly.

Sadly the design of a universal joint means that both uni joint types require maintenance both greasing to ensure they last longer and in the case of the needle bearing uni joint, new bearings.

Simple design but a lot of maintenance to keep them running

So how does block and pin U-joints work, it is exactly as it sounds a rounded metal cube (block) with 4 pins attaching it to the input and output hubs of the uni joint. Simple design but it has its uses but also its drawbacks.

Slow speed otherwise it overheats and wear causes vibration

The U-joint requires a pivot point to work, whether it be block and pin or needle bearing, the pins in the block allow that pivot to happen, all the way up to 25° but only at 1750 RPM, this means that it is unusable for anything at a higher speed, why?

There are two reasons, 1. Vibration and 2. Created heat

  1. Vibration – The more two shafts become out of alignment means they become more out of “phase”, the being out of phase means the coupling, accelerates and decelerates which means the pulsing creates vibration, the higher the angle of misalignment the higher the vibration.
  2. Created heat – The misalignment and speed means the pins inside the block heat up as the friction from their use increases, and the force (torque) applied increases as well. The only way to avoid this is through a constant application of grease to reduce the friction and absorb the heat rather than the heat being transferred into the block and making the holes the pins are inserted into shrink due to the expansion of the block.

Lots of torque but not very flexible

The friction bearing U-joints are able to transfer lots of torque and work at a typical angle of 8° or less, which is great for most applications but the constant greasing to keep the coupling functioning detracts from its use.

Constant greasing

Machinery has to stopped, protection/grease boots removed and more grease applied, reassembly and the machinery can get back to work.

If this is a bi monthly task it certainly bites into the amount of working time that the machinery can be used per month.

Block and Pin U-joints vs Twin Spring Coupling- How are they different

Twin Spring offers something different in a number of ways

We combine the high torque of a u joint and more flexibility than either  block and pin u-joints and needle bearing u-joints

Add to that high speed, so where you couldn’t use block and pin u joints you now can with Twin Spring Couplings.

No bearings no block or pin, no maintenance or replacement parts

No block and no needle bearings, no we don’t use either, the twin spring design means our coupling pivots on a central ball bearing which only needs to be greased semi annually or annually.

Our coupling is a one piece design so no need for replacement parts bearings, blocks and no broken input or output yokes.

Shear pins make it safer than a universal joint

Installed shear pins mean the Twin Spring Coupling can shear the installed safety pins rather than damaging equipment, new shear pins can be pressed into the hubs and back to business.

As for construction, the Twin Spring Coupling are made of a steel alloy, making them longer lasting compared to block and pin u joints plain steel construction.

Its time for something new, a longer lasting less maintenance high speed power transmission friction bearing u joints replacement

For more information on our range go to for more information on our range of flexible no maintenance coupling


Ruland – UJ-HD1250, UJ-HS1125, UJ-HD1000-1125, UJ-HS875, UJ- HD875, UJ-HS 750, USC32-16-16-F, USKC32-16-16-F,

Lovejoy – D-5B, D-6B, D-7B, D-8B, NB-8B, NB-10B, DD-7B, LOJ-10B,

Belden –UJ-HD2000, UJ-HD2500, UJ-HS1750, UJ-HS2000, UJ-NB2000x1000, SS-UJ-NB2000x1000, UJ-HD1500, UJ-HS1500, UJ-HD1750, UJ-NB1500x750, SS-UJ-NB1500x750, – UJ-HD1250, UJ- HS1000, UJ-HS1250, UJ-NB1000x500

Curtis – CJ648B, CJ646B, CJ647B, CJ644, CJ645.

SKF – FRC70 – FRC110, SKF Flex 70 -100, UJMA40, UJMB32, UJMA32, UJMA25, UJ338, UJ861, N1000, L600, UJ811, UJ812, UJ880, UJ340, UJ514G, UJ1501, UJ840, UJ838, UJ995, UJ507, UJ880, 1200, 1800, UJ341AG, UJ813, UJ964, UJ934, 2200, UJ344AG, UJ814, UJ815, PHE L100, PHE L110, PHE L150, PHE L190, PHE L225, PHE1020TGH, PHE1030TGH, PHE1040TGH.

Boston Gear – FC30 XFCBB Bronze, FC38 XFCA Poly, FC45 Rubber XFCR, XFCA Poly, UJ-J175B, JS250B, JS300B, UJAS 16-16, UJNL 20-20, J200B, UJNL 24-24, FC25 XFCBB, FC30 XFCA Poly, FC38 Rubber XFCR, J150B, JS175B, JS200B, UJAS 12-12, UJNL 16-16.

Spicer – 5-264X, 5-443X, 5-3214X, 5-110X, 5-3215X, 5-3235X, 5-103X, 5-3233X, 5-554X, 5-110X, 5-3232X, 5-129X, 1240, 5-170X, 5-736X, 5-101X, 5-554X, 5-105X, 5-248X, 5-92X, 5-242X, 24-92X.

Neapco – 1-0170, 1-0675, 1200, 1-1875, 1-1475, 1-1275, 1-2075, N1000, 1800, 2200, L600, 1-0221, 1-0005, 1-0616, 1-1001, 2-2421, 1-0475, 1-0443, 1-0121, 2-0456, 1-0300, 2000, 1-0105, 1-0171.

Moog –     338, 838, 237, 344, 340, 240, 880, 341, 437, 882, 437G, 814, 1300, 514G, 436, 466, 995.

Rockwell – CP101X, 1FR, CP456X, L14N, L12N, CP248X

Weasler – 200-0600, 200-0100, 200-8261, 200-8474, 200-1000, 200-8370, 200-1400, 14 series, L6W, 200-1200, 14R, 200-7155, 12RW, 200-1875, 200-6154, 6 Series, 1000 Series, 7 Series, 200-7155, 12 series, 200-7676, 507-9518, 15160616, 3200-8204, 200-6580, 3010-6606-00, 3009-7606-00, 3009-6406-00, AW21 series, AB4 Series, 107-20872, AW19 series, 3009-7106-00, AW10 Series, 212-26155, 15161016, 107-20561, 107-20872, 3200-8202, 3010-7606-00, 3009-206-00, 3002-7306-00, AW20 series, AB2 Series, AW11 Series, AB3 Series, 222-26141, 15161216




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