Choosing between two Mitutoyo instruments in dimensional metrology machine inspection comes down to a practical question: do you need a complete measuring tool or a machine-specific replacement part? The Mitutoyo Surftest SJ-210 Portable Surface Roughness Tester is a self-contained finish gauge. The Mitutoyo 908926 SRD Head 10/10 For Mitutoyo BHN506 Coordinate Measuring CNC is a reading head for a specific coordinate measuring machine. The price gap between them is significant, and the right pick depends on what your shop needs to measure and fix.
Quick verdict: Choose the Surftest SJ-210 if you need a surface roughness gauge you can move around the shop and can handle sourcing its missing power supply. Choose the 908926 SRD Head if you need the reading head for a Mitutoyo BHN506 CMM. Both are used Mitutoyo units from Japan, so the real decision comes down to job function, not brand.
| Product | Listed Price | Price Indicator | Condition | What It Is | Best For |
|---|---|---|---|---|---|
| Mitutoyo Surftest SJ-210 Portable Surface Roughness Tester | USD 1,500.00 | Used | Portable surface roughness measuring instrument | Finish checks on parts you can bring to the gauge | |
| Mitutoyo 908926 SRD Head 10/10 For Mitutoyo BHN506 Coordinate Measuring CNC | USD 399.00 | Used | Sensor reading head for BHN506 CMM | Replacing or servicing the reading head on a CMM |
Where each product wins
Mitutoyo Surftest SJ-210: wins on completeness as a measuring instrument. The Surftest is a full surface roughness tester built for finish measurement on workpieces. Its main barrier is the missing power supply: the unit was not tested before being offered, and it was barely used before that power supply was lost. If you can replace it and verify operation, you have a ready finish gauge for dimensional metrology work.
Mitutoyo 908926 SRD Head: wins on price and machine-specific purpose. At USD 399.00, it is the lower-priced item by USD 1,101.00. It exists to solve one specific problem: providing the reading head for a Mitutoyo BHN506 CMM. If you need that part, it is the right buy. If you do not have that machine, it has no role as a stand-alone measuring tool.
Mitutoyo Surftest SJ-210 Portable Surface Roughness Tester
If your priority is a complete instrument you can carry to a workpiece, this is the standout candidate. It is designed for surface finish measurement, so it fits a dimensional metrology machine inspection workflow when you need a direct read on how smooth a surface is. The practical limitation is the missing power supply. The unit was not tested before being offered, and it was barely used prior to losing that power supply. You will need to source the correct power supply and check the tester before relying on it. If you are comfortable with that setup work, the Surftest gives you a finish gauge from Mitutoyo's SJ-210 line that had seen little use before the power supply was lost.
Mitutoyo 908926 SRD Head 10/10 For Mitutoyo BHN506 Coordinate Measuring CNC
This part is the clear pick when you own or maintain a Mitutoyo BHN506 coordinate measuring machine. The 908926 SRD head reads linear scale graduations and translates axis movement into electronic signals for the CMM controller. It carries the model reference 908926 SRD Head and is intended for the BHN506. That makes it a replacement component rather than a bench instrument, which is the main limitation to keep in mind. It will not perform a measurement on its own; its value depends on being installed in the machine it was made for. For a shop that already runs the BHN506, this Mitutoyo part is a targeted way to keep the CMM's position feedback chain complete.
Final choice by use case
- Choose the Mitutoyo Surftest SJ-210 if you measure surface finish on parts and want a gauge you can move around. Be ready to handle the missing power supply before use.
- Choose the Mitutoyo 908926 SRD Head if you maintain or repair a Mitutoyo BHN506 Coordinate Measuring CNC and need the reading head that keeps axis feedback accurate.
- If you are shopping for dimensional metrology machine inspection and do not have a BHN506, the lower-priced SRD head is not a substitute for a surface roughness tester.
