Saturday, October 18, 2014

Square Bores, Hollow Shafts, and a Sausage Stuffer!

We want to first start out by thanking and crediting Walter W., who was the very first user to submit a coupling question on our Have A Coupling Question? Fire Away! form.

Walter's specific application and coupling requirements: Walter was looking "to motorize a sausage stuffer with a VFD controlled 3-phase AC motor" and need "a coupling to connect a gearbox with 7/8" hollow / 3/16" key to a (approx., can provide exact) 11/16" square shaft.  1/3 HP motor is driving the gearbox." "The 11/16" square is where the hand-crank handle connects.  Max 825 in-lbs. torque at 25 rpm.  Service factor of 1.  It will probably see less than 2000 revolutions in a given session, only a couple of times a year."

On Square Bores & Hollow Shafts: Before getting to our formal response to Walter, we wanted to specifically call out square bores and hollow shafts. Square bores (while a bit unusual) are certainly not a problem for us and generally do not change the torque rating of a coupling. On hollow shafts, as long as the shaft is robust enough to take the load (not deform, deflect, or introduce vibrations), the coupling is not really going to care all that much.

Our Response to Walter: Given a 1/3 HP motor (VFD), gearbox with 7/8" hollow / 3/16" Keyway, 11/16" square shaft, and max 825 in-lbs. torque at 25 rpm...  the L150 Jaw coupling will be able to accommodate both the 7/8” shaft and a 11/16” Square shaft, while providing a torque rating of 1,240 in-lbs. with a standard rubber insert. 

However, if Walter is anything more than a hobbyist making sausage for himself, he will want to ensure his system is FDA compliant... which sintered iron and rubber generally are not. The L-Line coupling is available in a dimensionally interchangeable stainless steel  (a material much preferred by the FDA), and the coupling spiders are also available in Urethane (another material more preferred by the FDA). Urethane spiders have a higher torque carrying capability relative to SOX (NBR) Rubber (at the expense of dampening capacity), so the same size coupling hubs (SS150) could still be used.

Note: Even using stainless steel & urethane, couplings are generally reserved for use beneath the food preparatory table, so Walter will need to thoroughly review his application against all relevant local, state, and federal food safety guidelines. (A list of solutions targeted at the food and beverage industry can be found here.)

In addition to material selection, we requested that Walter let us know if he preferred a setscrew to attach the 11/16” square bore to the square shaft, and forwarded him the performance data and dimensional information regarding our jaw couplings so he could double check everything we were telling him.  

Lastly, we offered to help point Walter towards a knowledgeable distributor of our couplings, where he could obtain pricing and availability for this specific product.

Now It's Your Turn to Do a Good Deed...and Ask A Question! If you have a coupling question (be it a basic question or highly focused), please do not hesitate to share it with us. If the question is in your head, other folks will likely soon be looking for the same type of information. After you ask it, we will review it and do our best to incorporate the answer into an upcoming post... making the world just ever so slightly a better more collaborative place to live!


  1. Hi,

    Can you please let me know if the L150 coupling that you recommend actually has a square bore? Or does it just have a round bore that is capable of accepting a square shaft?

    I currently have a L95 lovejoy flexible coupling that I use to connect a gear motor to a 1" stainless steel shaft that I use for a pig spit. I'm interested in switching to a square stainless steel shaft in order to more easily insure that the pig doesn't spin around on the shaft. With this in mind, are there any couplings that you recommend that could adapt a 1" round shaft to a 1" square shaft? Thanks.


    1. Hey Ryan,

      Yes, Lovejoy can and does manufacturer coupling hubs with actual square bores. Given there is not a huge demand for them, they are generally not stocked by your local distributors... but your local distributor can ordered such a coupling from the factory in Downers Grove, IL.

      If the parts aren't already in stock, they will make them on premise and ship within a few days. (Note: If you are looking for a more sanitary/wash down solution for a bit more money, be sure to request stainless steel hubs and use a urethane elastomeric spider.)

      To talk with a Lovejoy application engineer to size and select the hubs and spider you will need... and get the correct part numbers... you can reach them at 630-852-0500 between 7:00 am - 5:00 pm CST.

      Once you've got the part numbers you need, call over to your preferred local Lovejoy distributor ( and get the parts on order!


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