For those who aren’t familiar with the Starrett brand, they are the industry leader for fine precision tools and manufacture every type of measuring instrument under the sun. All of their products are made in America.
Key Takeaways
- Quality seems to vary greatly across the Amazon versions, although the price justifies the risk.
- The $16 Groz and $13 DDWT were accurate to their advertised tolerances.
- The $8 Steelex was not accurate to its tolerance specification.
- It’s undetermined how long these cheap squares will hold their tolerance specs - durability has not yet been tested.
The only downside or negative about Starrett is that, unless you are in the manufacturing industry or can stomach the price, their tools are generally out of the price range of the hobbyist woodworker.
Thus, an option on Amazon for a similar product, that is 1/20th the price of the Starrett, seems like a risk worth taking.
Here are the results, details on the measurement procedures can be found at the bottom of this article.
Data Location | Steelex | Groz | DDWT |
|---|---|---|---|
Top Measurement | 32.67mm | 33.10mm | 29.30mm |
Bottom Measurement | 32.84mm | 33.12mm | 29.28mm |
Variation Total | +0.17mm | +0.02mm | -0.02mm |
Starrett No. 3020, 3” blade vs. Steelex D3383 4” Precision square
Do not buy the Steelex. You’re better off spending another $10 on one of the other squares we cover below.
The Steelex advertises being accurate within +/- 0.0006” (0.01524mm). This is not the case.
When compared back to back to the Starrett on a milled surface, it varied approximately +0.00669” (0.17mm) from top to bottom.
However, the false advertisement isn’t the only issue. For the square we received, the blade was welded on crooked. In the photo below the Starrett is on the left and the Steelex is on the right. The Steelex’s blade leans away from the light and is crooked out of the base.
Starrett No. 3020, 3” blade vs. Groz 01002 4” Precision Square
The Groz was the most accurate of the 3 Amazon squares tested and is accurate to what is advertised. For the hobbyist woodworker, this square will do the job.
The Groz advertises being accurate within +/- 0.00063” (0.016002mm)
When compared back to back with the Starrett on a milled surface, it varied approximately +0.0007” (0.02mm) from top to bottom. This is acceptable as we must consider the variation in the Starrett and surface the squares sat on.
Starrett No. 3020, 3” blade vs. DDWT Precision 2” Machinist Square
The DDWT falls somewhere in the middle between the Steelex and Groz. It had the same variation measurement as the Groz, but because it’s half the size, we were hoping for less variation.
Regardless, for the price ($13 USD), it’s also a suitable option for the hobbyist woodworker.
The DDWT doesn’t advertise a tolerance window, but we found variance to be -0.0007” (0.02mm) from top to bottom. That’s acceptable for a $13 square.
How measurements were taken
All of the Amazon Squares were compared to the Starrett 3” square on a milled surface. The Starrett has a known tolerance of 0.0002” (0.005mm). However, the variance of the surface these squares sat on is unknown.
The squares were placed on top of new Wen jointer, which is milled flat. To get a better sample size, the squares were placed on multiple points on the jointer’s surface.
After the squares were placed side by side to the Starrett, a Mituotyo digital caliper was used to measure the width of both squares at the highest point where they met, and then at the lowest point the caliper could reach on the blades.
The difference between these two measurements is what provided the variance number. The table below summarizes those measurements.
Data Location | Steelex | Groz | DDWT |
|---|---|---|---|
Top Measurement | 32.67mm | 33.10mm | 29.30mm |
Bottom Measurement | 32.84mm | 33.12mm | 29.28mm |
Variation Total | +0.17mm | +0.02mm | -0.02mm |
Furthermore, to capture the images in this article, a light was placed behind the squares as they faced back-to-back. The purpose of this was to better highlight the gap between the squares. Be aware, the light tends to flare out from the gap, making the gap appear slightly larger.
Ending Recommendations
If you’re on a budget, the Amazon squares will do the job. Be careful with them as it’s still unknown how well they will stay square if dropped or bumped.
You get what you pay for when it comes to tools - buy once, cry once.