This drilling-machine clamp follows the lever-and-shank tool shown in Hiscox movement 1328. Its inclined shank passes through a drill-table hole. A rear set screw bears on the fixed body, raises the lever’s short end and presses the opposite nose onto the work. It is a different arrangement from a strap clamp anchored by a T-slot stud.
Drilling Machine Clamp Interactive Calculator
Compare lever-arm lengths and a closed-position screw thrust. Watch the rear screw raise the heel and lower the nose onto the work. Force results are ideal contact estimates, not a clamp rating.
Equation Used
- Rigid lever and fixed pivot; force outputs apply at horizontal contact.
- Known or assumed screw thrust, independent of screw lead.
- Rounded nose touches rigid work without penetration.
- Stem and table contacts explain the holding method but supply no capacity model.
- Screw-seat, stem and table proportions are schematic, not manufacturing dimensions.
Closed ideal lever balance. Shank retention capacity, thread friction, component strength and drilling loads are not calculated.
A set screw operates the clamp lever
The body carries the lever pivot and the shank. After the shank has been positioned through the table hole, the screw in the lever heel is advanced against the body. This lifts the heel and lowers the nose until it contacts the work.
The animation exposes the table section and the inclined shank. Orange points indicate opposing contacts at the hole edges. Those contacts explain the holding method; the model does not calculate their friction or retention capacity.
The nose uses a rounded contact in this schematic. The workpiece and fixed body are rigid. The nose stops at the work surface. Elastic compression after contact is outside this rigid-body model.
Compare the lever proportions
Enter the distance from pivot to nose, the distance from pivot to screw, and a known or assumed closed-position screw thrust. The calculator estimates the resulting ideal nose force and pivot reaction.
The screw lead controls the turns needed for the illustrated opening motion. It does not determine the screw thrust by itself. Deriving thrust from hand torque would require thread and contact details that are not supplied here.
The force ratio is set by the screw arm and nose arm about the lever pivot. These equations apply to this lever-and-shank arrangement.
Closed-position force balance
At contact the model’s lever is horizontal. Let a be pivot-to-nose distance, b pivot-to-screw distance, and Fs the upward force exerted by the screw on the lever. Taking moments about the pivot gives Fclamp × a = Fs × b, so Fclamp=Fs b/a.
The nose and screw reactions both act upward on the lever. The pivot’s downward reaction magnitude is therefore Rp=Fs+Fclamp. On the complete clamp, the screw and pivot forces are internal; the table must retain the clamp against the net upward work reaction Fclamp.
That required retention is not the available retention. The model does not calculate whether the shank and table hole can provide it.
Screw movement in the animation
The display uses a 12° released lever position and a horizontal contact position. The pivot is 4 mm above the work surface; the fixed screw seat is 0.7b below that surface. These are stated schematic proportions, not original manufacturing dimensions.
At lever angle θ, the screw length from the heel to the seat is ℓ=(4+b sinθ+0.7b)/cosθ. The screw is perpendicular to the lever and its tip slides along the flat seat. Advance from the open position is Δℓ=ℓ(θ)−ℓ(−12°). Turns are Δℓ/p for screw lead p. Nose clearance is −a sinθ.
A 60 mm nose arm and 30 mm screw arm
With a=60 mm, b=30 mm and closed screw thrust Fs=1000 N, the ideal clamping force is 500 N. The pivot reaction magnitude is 1500 N, and required net vertical shank retention is 500 N.
Doubling the nose arm halves the clamping force at the same screw thrust and heel arm. Doubling the screw thrust doubles both calculated forces. Changing the screw lead changes the turns needed for the displayed opening motion; it does not change the force ratio.
The animation alternates between released motion and a contact pause. Closed-force outputs remain labelled as closed-position estimates, while the current nose clearance shows whether the work is contacted.
What still needs a real clamp design
The calculation does not size the pivot, lever, screw, stem, contact pad or drill table. It does not estimate the friction coefficient or pressure at the hole edges, thread losses, stem retention, allowable torque or a safe workholding load.
The reference establishes the arrangement, while support profiles, stem tilt, hole clearance, nose radius and screw-seat position are schematic. A hole contact shown in the drawing is not evidence that a particular clamp will resist drilling forces.
No drilling torque, lateral cutting load or workpiece friction is included. The force result is an ideal vertical lever balance at contact.
Drill-table clamp questions
How is this clamp held on the drill table?
Its inclined shank passes through a table hole and contacts opposing hole edges. A rear set screw operates the pivoted clamping lever, as shown in Hiscox movement 1328.
Does screw lead increase the clamp force?
Not when screw thrust is the input. Lead controls the required rotation for a given advance. Hand torque and screw thrust are different quantities.
Why are forces shown while the nose is open?
They are explicitly labelled closed-position estimates. The live clearance and status identify the released pose, where no clamping force is applied to the work.
Is the required shank retention a capacity rating?
No. It is the reaction needed for equilibrium. Available retention and component strength are not calculated.
Does the model compress the work?
No. The nose stops at contact. Any real elastic preload depends on the clamp and work stiffness.
References
Gardner D. Hiscox, Mechanical Movements, Powers and Devices, movement 1328, printed page 325, shows the shank inserted through the drill table and the set screw operating the lever. The equations above derive the ideal closed-position lever balance and the stated schematic motion.
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