Festool FSK670 Cross-Cut Rail: Portable Precision for Montana Job Sites

The Festool FSK670 transforms circular saws into portable compound miter saws with -60° to +60° angular range and automatic saw return functionality. This 26-3/8” rail connects to specific Festool saws through a quick-fastener system, creating a single unit that delivers repeatable precision cuts without hauling a full miter saw to remote job sites.

For Montana contractors working hours from their shop, the FSK670’s 3.59-pound weight beats dragging a 50-pound compound miter saw up mountain access roads. The integrated rubber spring returns the saw to start position after each cut — a small detail that adds up across hundreds of cuts on trim jobs.

Angular Range and Precision That Exceeds Standard Miter Saws

The -60° to +60° range outperforms most job site miter saws. Standard 12” compound miter saws typically max out at 45-50° in each direction. The FSK670’s adjustable stop with scale locks in specific angles for repeat cuts — critical when matching existing trim angles in older Montana homes where nothing’s quite square.

The 670mm (26-3/8”) cutting length capacity handles standard 2x12 dimensional lumber and most cabinet components. The quick-action screw clamp (4-11/16” capacity) secures workpieces without additional clamps or jigs.

Specification	FSK670 Value
Angular Range	-60° to +60°
Cutting Length	26-3/8” (670mm)
Weight	3.59 lbs (1.63 kg)
Clamp Capacity	4-11/16”
Material	Aluminum and steel components

The splinter guard delivers clean cuts on both sides of the kerf. Combined with the adhesive cushion strip that protects workpiece surfaces, you get finish-quality cuts without the typical chipout that forces touch-up work. The slide-way lining keeps saw movement smooth even after months of job site dust exposure.

Compatibility: Know Your Saw Before You Buy

The FSK670 only works with specific Festool models. This isn’t universal — check your saw model before ordering.

Compatible saws:

• HK 55
• HKC 55
• HK 85
• TS 60 K
• TSV 60 K

NOT compatible:

• TS 55
• TSC 55
• TS 75
• Any non-Festool circular saws

The incompatibility with TS/TSC plunge saws catches some buyers off guard. The FSK system is specifically engineered for Festool’s HK series carpentry saws and select track saws. The quick-fastener connection won’t mate with standard plunge saw bases.

Real-World Performance vs. Traditional Solutions

Professional forum feedback consistently praises “speed of setup” and “accuracy for repeated cross-cuts.” Users describe it as more portable than a miter saw for on-site work. The 670mm length gets called bulky for small trim pieces but essential for wider panels — typical trade-off thinking from contractors who’ve used it.

Standard Festool FS guide rails excel at long rips but lack the FSK’s dedicated cross-cutting speed and integrated attachments. Aftermarket squares from TSO Products or Woodpeckers offer fixed 90-degree reference but can’t match the FSK’s full angular range.

The automatic return spring sounds gimmicky until you’re making 50 identical cuts on window trim. That spring pulls the saw back to start position while you’re repositioning the workpiece. Small time savings compound across a full day’s work.

Bottom Line for Montana Contractors

Worth it for finish carpenters and cabinet installers who need portable precision. The angular range handles complex trim profiles. The weight makes it practical for remote sites. The integrated quick-fastener system means setup takes seconds, not minutes.

Not worth it for framers or rough carpentry. At 26-3/8” capacity, it won’t handle full sheets. The HK-series saw compatibility limits who can use it. For contractors already invested in Festool’s track saw ecosystem with TS models, this won’t work without buying a compatible saw.

The FSK670 fills a specific niche — high-precision angled cuts away from the shop. For Montana contractors bouncing between job sites from Kalispell to Eureka, that portability matters. The price stings less when you factor in fuel savings from not hauling a full miter saw setup to every trim job.

Frequently Asked Questions

Can I use the FSK670 with my Festool TS 55 track saw?

No. The FSK system only works with HK series saws (HK 55, HKC 55, HK 85) and select track saws (TS 60 K, TSV 60 K). The quick-fastener won’t connect to TS 55, TSC 55, or TS 75 plunge saws.

What’s included with the FSK670?

The kit includes the FSK 670 cross-cutting guide rail, FSZ 120 screw clamp (4-11/16”), and protective end caps. Optional accessories include a transport bag, one-handed clamps, replacement splinter guards, and glide strips.

How does the automatic return spring actually work?

An integrated rubber spring connects between the rail and saw. After completing a cut, the spring tension pulls the saw back to the starting position automatically. The retract function saves time on repetitive cuts by eliminating manual saw repositioning.

Is the FSK670 covered under Festool’s warranty?

Yes, it’s covered by Festool’s All-Inclusive 3-year warranty when registered. This includes wear-and-tear and accidental damage coverage, plus 10-year spare part availability and a 30-day money-back guarantee.

Can I connect multiple FSK rails for longer cuts?

The product documentation doesn’t indicate FSK rails can be connected together like standard FS guide rails. The 670mm model is the longest FSK option available for maximum single-cut capacity.