Modular Tombstone Fixtures for Horizontal Machining Centers (HMC)
Modular tombstones (column fixtures) provide 4, 6, or 8 precision ground vertical clamping faces on HMC rotary pallets, enabling high-density multi-part batch production and massive spindle uptime gains.
Engineering Specifications & Parameters
Grid Pattern
50 mm or 40 mm Pitch (M12/M16 Thread + 12F7 Dowel)
Column Geometry
4-Sided Square, 6-Sided Hexagonal, 2-Sided Window
Base Pallet Sizes
400 x 400 mm, 500 x 500 mm, 630 x 630 mm, 800 x 800 mm
Material Construction
Meehanite Cast Iron (FC300) or 7075-T6 Aluminum
Squareness & Parallelism
< 0.010 mm / 300 mm
Horizontal Machining Center (HMC) Architecture
On an HMC with a B-axis rotary pallet, a tombstone fixture mounts vertically. As the B-axis indexes 360 degrees, the horizontal spindle accesses parts on all column faces.
Core Production Benefits
High-Density Part Loading: Load 8 to 32 parts per pallet swap, allowing the CNC to run unattended for hours.
Natural Gravity Chip Evacuation: In horizontal milling, chips fall straight down into the chip conveyor via gravity rather than pooling in deep cavities.
Modular Grid & Zero-Point Interfaces: Precision M12/M16 grid holes and hardened dowel bushings allow rapid repositioning of modular vises.
Cast Iron vs Aluminum Tombstones
Dense Meehanite cast iron (FC300) provides superior vibration dampening and thermal stability for steel cutting; 7075-T6 aluminum reduces pallet weight for fast B-axis acceleration.
Frequently Asked Questions
Why does horizontal milling on tombstones provide better tool life than vertical milling?
Horizontal cutting allows gravity to instantly drop chips away from the cut, eliminating catastrophic chip recutting inside pockets.
How does tombstone batch loading reduce tool change overhead?
The machine loads a tool once and executes that operation across all 16 parts on the tombstone before changing tools, cutting tool-change downtime by 90%.
