This question pops up nearly every time I have a 401 or 500 (Rocketeer) for sale on eBay. Both models are excellent heavy duty household machines and are nearly identical mechanically. But there are some critical differences.
Singer 401 Slant-o-Matic
Slant needle Rotary hook Steel Gears .72 Amp direct drive motor Double-thread capacity tensioner Double capacity needle clamp 25+ stitch patterns built in Special Disc compartment ---- Front-mount, exposed bobbin winder 2 top-mount, fixed-position spindles
Simply stated, the 401 is the better-built machine. The Rocketeer is the begining of the end of all-metal slant-needle machines. It is still metal where it counts, but it suffers from a severe case of 'style-over-substance'-itis. The futuristic "Jetsons" styling is super cool but comes at a price. Enclosing the bobbin winder stream-lined the styling, but the auto-stop kick-out spring is prone to breakage from metal fatigue. The spring-loaded fold-down spool spindles are also prone to breakage. The removable top-mount spindle is easily lost and can be difficult to replace.
On the other hand, the Rocketeer does allow you to leave the top open while sewing so you can easily change stitch-patterns. The 401 spool spindles sit right on top of the pattern chart, which can be awkward. The 401 spindles are also vulnerable to snapping off during shipping or storage, but they are simpler to replace than the 500 spindles.
Bottom line? The 401 is tougher-built, but the Rocketeer is not far behind it. Both models are wonderful vintage Singer machines.
If you can't find a 401 in your price range, the Rocketeer may be the machine for you. A very good condition 500 will typically cost less than an equivalent 401.
Happy sewing! Barbara OldSewinGear...dedicated to helping you get the most out of your old sewing gear.
OldSewinGear is the collaborative effort of retired repairman Gary and daughter Barbara. We love old sewing gear and enjoy sharing what we've learned in our vintage sewing machine adventures. We are located in Roseburg, Oregon.