Today, we are going to discuss the "Regarding the shaft clamp force (holding force) of a shaft holderA note on "The
I sometimes perform assembly work on simple units.The other day, I learned something from assembling part of a unit I designed myself.
That is.The shaft clamping force of a shaft holder, which I hadn't particularly paid attention to before.While assembling itI noticed that the shaft clamp force of the shaft holder is weak.
That shaft holder is the slit type that you all use frequently. Technically, it's a lateral slit type.
Also, I used it with another unit. This one has a slit-type shaft holder.
This shaft holder,I tightened it to the specified torque, but just to be sure, I lightly tapped it axially with a plastic hammer.It moved in the axial direction.
*Ugh...*Since I noticed the situation early, I tightened it strongly and the rebuild is complete.
This isn't a part where an accident would occur, butI thought it would be a disaster if an accident happened. So,On this occasionDoes the shaft holder have guaranteed clamping force, and if not, how should it be understood and selected?I decided to look into it.
Today, I'll jot down that information. If you're a design beginner, please use it as a reference.
Shaft holder
Let's start by taking notes on the clamping force of the shaft holder.
Shaft holder shaft clamp (holding) force
There are several types of shaft holders. First, I will note down the shapes and characteristics from general knowledge. Here, I will note down Misumi's reference models (φ10 fixed) that I often use and their (current) prices, so I would appreciate it if you could look at the prices as well.
A standard type that directly presses and fixes the shaft with a set screw.
The shaft's holding power is weak, and the shaft can only be inserted from the side.
*Reference Model: SHTBM1020 (MISUMI)990円
Slit type with vertical or horizontal notch
The shaft's holding power is relatively strong, but the shaft can only be inserted from the side.
*Reference Model: SHAM10 (MISUMI)970円
・Separate type that can be detached
Since the shaft is bolted from both sides, it has strong holding power and is easy to assemble the shaft.
*Reference model: SHTDM1020 (MISUMI)1,560円
Hinge type
Stronger clamping force than the slit type, easier to assemble shafts, but requires space around the hinge due to its movability.
※Reference model: SHHTM10-20 (MISUMI)2,650円
Considering the price and featuresThe slit type has a good cost performance as a shaft holder.you can understand, and in terms of holding power this time, Misumiwith your information,The slit type is said to have "strong holding power for the shaft, providing reliability."（https://jp.misumi-ec.com/tech-info/categories/machine_design/md01/c1223.html）
However,Its reliability is not something that is particularly quantified.
The reason there's no guaranteed value is likely due to the wide variation in the relationship between the shaft diameter (tolerance) and the hole tolerance on the holder side. Also, the material is a factor. The holder side comes in materials such as S45C, SUS, and aluminum.
Selection method prioritizing shaft holder retention force
Well, thatWhen prioritizing holding power, what kind of selection would be made?
Come to think of it, it's simple, but in order of holding power:
It turns out like this.Since there is no guaranteed holding force, the separate type should be able to provide (easier to provide) a certain level of guarantee at the design stage.This is because the axial force of the two tightening screws can be directly converted into clamping force. In a hinge, one part is a rotating part (which is fixed and has only one screw), making the holding force weaker than a separate type.
The slit has one basic screw, but the holding power is lower than that of a hinge because it receives the repulsion from the material coming from the opposite side. Since the material was S45C this time, the repulsion might have been even stronger. For example, if it were an aluminum material, the repulsive force would be less, and I think the clamping force would have been higher.
Finally.
I had a really good experience this time. It's embarrassing, butI have reflected on how we have prioritized price and shape in our designs up to now.Now I can select and use it with a reason.
That's it.
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