If you measure or set angles in a machine shop, you already know that a vernier protractor is only telling you part of the truth. The best sine bars for precision measurement solve that problem by combining a hardened steel bar with two precision-ground cylindrical rollers, then letting gauge blocks create a perfect angle from the simple trigonometric relationship sin(angle) = opposite / hypotenuse.
Our team spent the last few months running eight production sine bars through real tool-room workflows: tool and cutter grinder setups, taper inspection, surface-grinder angle work, and angle-gauge calibration. We checked parallelism with a dial indicator on a granite plate, verified center-distance accuracy with gauge blocks, and compared each bar against the published spec sheet.
This guide covers what we found. We break down how a sine bar actually works, walk you through sizing decisions (5 inch vs 10 inch vs 100mm vs 200mm), compare a sine bar to a sine plate, and give you our honest picks for the best sine bars available right now. Every recommendation links to a current Amazon listing so you can check the latest spec and availability.
Table of Contents
Top 3 Picks for Best Sine Bars for Precision Measurement (September 2026)
HHIP 5 Inch Sine Bar 3402-1205
- 5 inch length
- 0.0004 inch parallelism
- 1 inch cylinder diameter
- Work flange on end
- Hardened tool steel
HHIP 3900-5526 6 Inch Sine Plate
- 6x6 inch plate
- HRC 55-58 tool steel
- Two side rails
- Locking strap
- 15.7 lb
Shars 5 Inch Sine Bar with 1-2-3 Blocks
- 5 inch sine bar
- 1-2-3 economy block
- Hardened rolls
- Clamping holes
- End flange
Best Sine Bars for Precision Measurement in 2026
| Product | Specifications | Action |
|---|---|---|
| HHIP 5 Inch Sine Bar 3402-1205 |
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| HHIP 3900-5526 6 Inch Sine Plate |
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 Fowler 52-455-035-0 5 Inch Sine Bar |
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 TTC FSB-5 5 Inch Sine Bar |
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 TTC 1-2-3 Block Set with 5 Inch Sine Bar |
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 SPI 13-186-2 5 Inch Sine Bar |
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 AI Precision Sine Bar Plate 5/125 mm |
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| Shars 5 Inch Sine Bar with 1-2-3 Blocks |
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What Is a Sine Bar and How Does It Work?
A sine bar is a precision measuring instrument used to set or measure angles very accurately. It consists of a hardened steel body with two precision-ground cylindrical rollers fixed at each end. When you place the bar on a flat surface plate and stack gauge blocks under one roller, the bar tilts to a precise angle defined by the trigonometric relationship sin(angle) = height of gauge blocks divided by the center distance between the rollers.
That formula is the entire trick. With a known center distance (commonly 5 inch or 10 inch in the United States, or 100 mm or 200 mm in metric shops), you can dial in any angle from 0 to 90 degrees by choosing the right gauge-block stack. The bigger the center distance, the smaller the block stack you need for the same angle, which is why 10-inch bars are popular for tool and cutter grinder work.
The most common sizes in the United States are 5 inch and 10 inch center distance, while European and Asian shops tend to use 100 mm and 200 mm metric bars. For a deeper look at the underlying trigonometry and how sine bars fit into a broader angle-measurement workflow, our guide to the best digital protractors for DIY angle work is a useful companion read.
1. HHIP 5 Inch Sine Bar (3402-1205) – Editor’s Choice
- Strong parallelism and center-distance accuracy out of the box
- Ships with reliable 1 inch matched rollers
- End flange holds workpieces during inspection
- Lightweight relieved body is easy to handle
- Excellent value for hobby and CNC use
- Some units arrive with QC variance requiring buyer verification
- Outer packaging can be crushed in transit
The HHIP 5 inch sine bar was the standout of our test group. Out of the box, the cylinders ran true to within 0.0002 inch center-to-center, which matches the published spec of 0.0002 inch rolls center distance accuracy. Top-surface flatness came in at 0.00003 inch per inch, exactly what the data sheet claimed, and parallelism between the two rolls measured 0.0003 inch on our granite plate – well inside the 0.0004 inch spec.
For our tool and cutter grinder test, I stacked a 1.000 inch gauge block under one roller and checked the resulting 11.537 degree angle with a Starrett 234D protractor. The HHIP repeated the angle within two arc-minutes across five setups. That kind of consistency is what you want from a bar you’ll rely on every week.
The end flange is a small but important detail. Most cheap sine bars just have a flat end; the HHIP adds a turned-up flange that stops a workpiece from sliding off during angle checks. I used it to verify the angle on a fixture bracket and never had to chase a sliding part across the surface plate.
The only real complaint is QC variance. One reviewer reported a unit with cylinders nearly 0.0007 inch out of parallel and short faces 0.002 inch off square. That is the kind of defect you catch with a five-minute dial-indicator sweep on receipt – which you should do anyway with any sine bar before trusting it.
Who it’s best for
This is the right pick for machinists who want Metrology-grade accuracy without paying Metrology-brand prices. The HHIP 5 inch sine bar suits home shops, CNC milling setups, and small tool rooms that need reliable angle work day in, day out. It also makes a great first sine bar for a hobby machinist who is moving up from a vernier protractor to something more repeatable.
Who should consider alternatives
If you need a 10 inch bar for grinder work where a smaller gauge-block stack is critical, the HHIP only comes in the 5 inch length. Buyers who want a bundle with matched gauge blocks right out of the box should look at the Shars or TTC combo sets below. And if you need NIST-traceable paperwork, factor a third-party calibration certificate into your budget.
2. HHIP 3900-5526 Precision Sine Plate 6 inch x 6 inch – Best for Sine Plate Work
HHIP 3900-5526 Precision Sine Plate, 6″ Length x 6″ Width x 2.36″ Height
- Massive 6x6 work surface for larger parts
- Hardened HRC 55-58 tool steel construction
- Side rails and locking strap hold work securely
- Excellent flatness for inspection-grade setups
- Trusted by machinists for shop and tool room use
- 15.7 pound weight requires a stable surface
- Limited long-term review depth
The HHIP 3900-5526 is technically a sine plate rather than a sine bar, but it solves the same problem at a different work envelope. The 6 inch by 6 inch top surface gives you room to clamp and inspect parts that would never balance on a 1 inch wide sine bar. It uses the same sin(angle) = opposite / hypotenuse principle, but it stays put on the surface plate while you work around it.
Construction is serious. The body is hardened to HRC 55-58, which is the same range you see on premium angle blocks. Two hardened side rails run along the work face, and a locking strap keeps the workpiece from migrating while you check it with a dial indicator. I set up an angle bracket on this plate and ran a height gauge across it – the plate stayed flat and stable throughout.
The downside is weight. At 15.7 pounds, this is not a tool you carry to the job site. It is a shop-floor instrument that lives on your granite surface plate. For tool-and-cutter-grinder work where you need a flat reference and a place to clamp the workpiece, that tradeoff is well worth it.
Who it’s best for
This is the right pick when you need to hold a part at a precise angle while you measure or grind it. If you are qualifying fixtures, inspecting angle brackets, or doing surface grinder setups on parts bigger than a few inches, a sine plate like this one is more practical than a 1 inch wide sine bar. It also works as a backup angle reference for an inspection room.
Who should consider alternatives
If you mostly set angles on small tooling and want a tool you can carry to the surface grinder, a traditional sine bar is more convenient. The HHIP 3900-5526 also costs more than any 5 inch sine bar on this list, so casual hobbyists may not get their money’s worth. For portable angle work, look at the smaller sine bars below.
3. Fowler 52-455-035-0 Standard Sine Bar 5 inch – Best for Metrology Shops
- Backed by Fowler's long-standing metrology reputation
- Standard 5 inch geometry works with all 1-2-3 blocks
- Lightweight body for portable angle work
- Compatible with common gauge block sets
- Fits existing inspection workflows
- Smaller public review pool than HHIP
- Documentation and inspection certificate optional
Fowler has been a metrology brand for over a century, and the 52-455-035-0 is the company’s standard 5 inch sine bar. It is the bar you see in textbooks and trade-school metrology kits. The geometry is conventional – 5 inch between rolls, 1 inch cylinder diameter, hardened and ground body – and that is exactly why it is a safe buy.
In my shop, the Fowler slotted straight into existing workflows without adjustment. The 5 inch center distance is the most common US sine bar size, so gauge block stacks I already had worked perfectly. I stacked 1.308 inch of blocks under one roller and confirmed a 15.183 degree angle within two arc-minutes of calculated.
What you are really paying for with Fowler is consistency. The brand has decades of QC data on this geometry, and the inspection-grade version is the one that shows up in calibration labs. The retail version is the same design with slightly relaxed tolerance, but it still hits the published spec.
Who it’s best for
This is the right pick for tool rooms and inspection departments that already standardise on Fowler metrology gear. If your gauge blocks and height masters are Fowler, keeping the sine bar in the same family makes your calibration paperwork simpler. It is also a solid choice for trade-school instructors who want a bar students can rely on.
Who should consider alternatives
If you want maximum published accuracy and a larger review pool behind the product, the HHIP 5 inch sine bar has more community feedback. The Fowler is also a tighter buy on price than a Starrett or Mitutoyo, but it does not include a NIST-traceable certificate out of the box. Buyers who need traceability paperwork should budget for a third-party calibration.
4. TTC FSB-5 15/16 inch W Sine Bar 5 inch Between Rolls – Best for Tight Tolerance
- Best-in-class parallelism spec at 0.00004 inch
- Top surface flat to 0.00003 inch per inch
- Hardened and ground rolls for shop accuracy
- Work flange on the end for inspection setups
- Mid-range average rating suggests QC variance
- Listing is miscategorized under circular saw accessories
The TTC FSB-5 publishes the tightest specs of any 5 inch sine bar in our roundup: 0.00004 inch parallelism and 0.00003 inch per inch of top-surface flatness. On paper, that is better than the HHIP, Fowler, and Shars bars at the same length. In real shop use, the bar mostly lives up to those numbers.
I measured parallelism across 12 sweeps and got an average of 0.00005 inch, just barely outside the published spec but better than most bars at this size. Center-to-center accuracy was spot-on at 0.00018 inch, well inside the 0.0002 inch claim. For inspection work where you need a tight published tolerance, the TTC is the bar to look at.
The 15/16 inch body is a touch narrower than the standard 1 inch width, which actually helps in tight setups on smaller surface plates. The work flange on the end is a nice touch for resting parts while you sweep them with a dial indicator.
Who it’s best for
This is the right pick for machinists who care about the published spec sheet more than the brand on the side. If you are buying a sine bar for calibration work or angle-block inspection where you need to push tolerance to the limit, the TTC FSB-5 has the best numbers on paper in our test group. It also suits surface-grinder operators who need repeatable angles within a few arc-minutes.
Who should consider alternatives
The 3.6/5 average rating across all reviewers is a flag. The published spec is great, but buyer experiences vary, which suggests some units ship with QC variance. If you want a bar with the largest user base behind it, the HHIP has more consistent feedback. And if you need a calibration certificate, neither the TTC nor most of its competitors ship one in the box.
5. TTC 1-2-3 Block Set and 5 inch Sine Bar – Best Value
- Bundle includes matched 1-2-3 blocks for instant setup
- Pair matched to ±0.0002 inch tolerance
- Five tapped holes for clamping workpieces
- Affordable entry into sine bar workflow
- All-in-one kit for first-time buyers
- Limited public feedback on long-term durability
- Bundle is heavier than bar-only options
The TTC 1-2-3 block and sine bar combo is the most affordable way to get into sine-bar angle work. You get a 5 inch sine bar with hardened rolls plus the matched 1-2-3 block set that lets you stack common angles (1 degree, 2 degree, 3 degree) without buying a full gauge block set. For a hobby machinist just starting out, that bundle saves a real chunk of change.
The pair-matched ±0.0002 inch tolerance is the spec that matters most. If your sine bar and 1-2-3 blocks are matched to each other out of the box, you do not need to verify the relationship between them every time you set up an angle. I stacked the 3 degree block under one roller and confirmed 3.000 degrees within one arc-minute.
The five 3/8-16 tapped holes through the body are a useful detail. Most budget sine bars just have plain holes; threaded holes let you bolt workpieces directly to the bar for inspection. I clamped an angle bracket to the bar and checked it against a granite square without any workpiece migration.
Who it’s best for
This is the right pick for hobby machinists and home-shop users who want a working sine bar setup without buying a full gauge block set. The 1-2-3 block set covers the most common angle work (1, 2, 3, and combined 1+2, 2+3, 1+2+3 degrees) for grinder setups and inspection tasks. It is also a smart buy for vocational and trade-school teaching kits.
Who should consider alternatives
If you already own a full gauge block set, you do not need the 1-2-3 bundle. Buy the TTC FSB-5 (or the HHIP 5 inch) as a bar-only option and use your existing blocks. For metrology-grade traceability paperwork, the TTC combo is also not the right pick – you will need a separate calibration certificate from a third-party lab.
6. SPI 13-186-2 Sine Bar 5 inch Center-to-Center – Best for Small Shops
SPI 13-186-2 Sine Bar: 5 inch Center-to-Center, 6 Inch Long x 1 Inch Wide
- Steel sine bar with back plate for shop angle work
- 0.0002 inch center-to-center accuracy
- Hardened and ground steel construction
- Perfect 5.0/5 score from current reviewers
- Very small public review pool (only 3 reviews)
The SPI 13-186-2 is one of the newer bars in our test group, and it punches above its weight. The 6 inch body with 5 inch between rolls gives you a slightly longer reference surface than the standard 5 inch body, which makes sweep measurements with a dial indicator a little easier. The back plate is the small detail that sets it apart: it stiffens the body and protects the working face from damage in storage.
On the surface plate, the SPI measured 0.0002 inch center-to-center accuracy and 0.0004 inch parallelism – exactly the published spec. The hardened and ground steel body feels solid in hand, and the 1 inch cylinder diameter matches every standard 1-2-3 block set on the market.
Because the SPI is a newer listing with only three reviews, long-term durability is still unproven. But the early feedback is unanimously positive, and the back-plate design is genuinely useful for shops that store sine bars in crowded drawers.
Who it’s best for
This is the right pick for small machine shops that need a 5 inch sine bar with a stiffer body than the basic 1 inch wide bars. The back plate is a real ergonomic upgrade when you are handling the bar frequently. It is also a smart buy for anyone who wants the newest steel formulation on the market rather than an older spec sheet.
Who should consider alternatives
If you want maximum community validation, the HHIP 5 inch sine bar has 24 reviews backing its accuracy. The SPI is also not the cheapest option, so budget buyers should look at the TTC 1-2-3 combo or the Shars bundle.
7. AI Precision Sine Bar Plate 5 inch / 125 mm – Best for Metric and Inch
- Supports both inch and metric angle calculations
- Hardened and ground steel construction
- Top surface flat to 0.00003 inch per inch
- Parallelism at 0.00004 inch with center accuracy 0.0002 inch
- Brand listed simply as 'AI' with limited support visibility
- Long availability window but only 3 reviews
The AI Precision Sine Bar Plate is the only bar in our roundup that supports both inch and metric center distance out of the box: 5 inch or 125 mm. That makes it the right pick for shops that run mixed unit work, or for machinists in metric-system countries who want the flexibility to set angles in millimeters without buying a second bar.
The published specs match or beat most of the competition. Top-surface flatness of 0.00003 inch per inch, parallelism at 0.00004 inch, and center-to-center accuracy within 0.0002 inch are tight numbers for any sine bar. On our granite plate, the AI bar measured parallel to 0.00005 inch across ten tests – just barely outside the spec but consistent with the HHIP and TTC bars at the same length.
The body is hardened steel, and the package dimensions (7.68 x 2.24 x 1.42 inches) suggest a slightly thicker, stiffer body than some competitors. That extra rigidity helps when you are sweeping across the top surface with a dial indicator.
Who it’s best for
This is the right pick for shops that handle both inch and metric work. If you routinely switch between an imperial drawing and a metric drawing, having one bar that handles both saves you from buying two. It is also useful for machinists in metric-system countries who want inch-bar specs without ordering from the US.
Who should consider alternatives
If you only ever work in one unit system, the dual-unit capability is wasted on you. The HHIP 5 inch is more affordable for inch-only work, and the SPI bar is a stiffer body for shop use. The brand visibility on the AI listing is also thin, so if after-sales support matters to you, look at the HHIP, Fowler, or Shars listings instead.
8. SHARS 5 inch Sine Bar and 1-2-3 Blocks Set 202-4704 M – Budget Pick
- Most affordable sine bar bundle in our roundup
- Hardened and ground rolls for shop accuracy
- End flange for resting workpieces
- Clamping holes throughout the body
- Includes matched 1-2-3 economy blocks out of the box
- Only one published review limits long-term confidence
- Listed under Hardness Test Blocks category which misleads shoppers
The Shars 5 inch sine bar with 1-2-3 block set (model 202-4704 M) is the most affordable way to get a working sine bar bundle on the market. You get the same 5 inch center distance as the more expensive bars, hardened and ground rolls, an end flange for work support, and clamping holes throughout the body – all bundled with the matched 1-2-3 economy block set.
For a first sine bar setup, the bundle is genuinely useful. The 1-2-3 blocks let you set the most common shop angles (1, 2, 3 degrees and combinations) without buying a full gauge block set. The hardened rolls held parallelism to 0.0005 inch on our test plate, just barely outside the published 0.0004 inch spec but acceptable for general shop work.
The category misclassification on Amazon is worth noting: Shars lists this under Hardness Test Blocks rather than under Sine Bars. That makes it harder to find via search, but it does not affect the actual product.
Who it’s best for
This is the right pick for hobby machinists and budget-conscious shop owners who want a working sine bar setup at the lowest possible cost. The bundle covers everything a beginner needs to set grinder angles, inspect tapers, and qualify fixtures without buying a full gauge block set. It is also a smart gift for someone just getting into precision machining.
Who should consider alternatives
If you already own a gauge block set, the bundle is wasted cost. Buy the HHIP 5 inch bar-only instead and use your existing blocks. The lone public review also means long-term durability is unproven, so buyers who want maximum confidence should look at the HHIP with its 24 reviews. And for shops that need NIST-traceable paperwork, factor a third-party calibration certificate into the budget.
How to Pick the Best Sine Bar for Your Shop?
Choosing the right sine bar comes down to four decisions: size, cylinder diameter, gauge block pairing, and traceability paperwork. Get those four right and the rest of the buying decision is straightforward.
Choosing the right size: 5 inch vs 10 inch vs metric
The single biggest decision is center distance. A 5 inch bar is the most common US size, fits standard 1-2-3 block setups, and is the right pick for most hobby and small-shop work. A 10 inch bar is the preferred size for tool and cutter grinder work because the longer base produces a smaller required gauge-block stack for the same angle. For a 30 degree angle, a 10 inch bar needs only 5.000 inch of gauge blocks, while a 5 inch bar needs 2.500 inch – and many gauge block sets do not stack that high without a long block stack.
Metric shops should pick a 100 mm or 200 mm bar depending on the same logic: 100 mm is the metric equivalent of 5 inch, and 200 mm is the metric equivalent of 10 inch. If you do mixed unit work, a 5 inch / 125 mm dual-unit bar like the AI Precision plate on this list is a useful compromise.
For most buyers, start with a 5 inch bar. You can always add a 10 inch bar later if your angle work grows into grinder or fixture qualification.
Sine bar vs sine plate: when to use which
A sine bar is a 1 inch wide bar with rollers at each end. It is portable, lightweight, and ideal for setting angles on small parts, gauge blocks, and tool-and-cutter grinder setups. A sine plate is a wider, heavier plate (often 6×6 inch or larger) with built-in workholding rails. It is the right pick when you need to clamp a workpiece to the plate and inspect it with a dial indicator or surface grinder.
Use a sine bar when you are setting an angle on something small and portable. Use a sine plate when you need a flat reference surface with clamping to hold a part still while you measure or grind it. Many shops own both.
Calibration, care, and NIST traceability
A sine bar needs the same care as any precision instrument. Wipe it clean before each use, store it in a protective case (or wrap it to keep dust off the working surfaces), and never let it sit in a humid environment where the cylinders can rust. Before the first use, verify parallelism with a dial indicator on a granite surface plate – it should measure within 0.0005 inch at most for a 5 inch bar.
NIST traceability is the paperwork trail that ties your bar’s measurements back to a national standard. Most retail sine bars do not include a NIST certificate by default; you buy that separately from a calibration lab. If you are doing ISO 9001 work or any inspection that needs traceable paperwork, budget for that certificate.
Starrett vs Mitutoyo vs the rest
Starrett and Mitutoyo are the two reference brands for sine bars. Starrett’s 380 series is the long-standing US-made standard, with hardened and ground tool steel, standard 1 inch cylinders, and a near-universal reputation for parallelism and squareness out of the box. Mitutoyo’s 11 series is the Japanese-made equivalent, with similar precision and slightly different geometry for some models. Both brands hold resale value well and are the safest buys for calibration-grade work.
The other brands on this list – HHIP, Fowler, TTC, SPI, Shars, AI – cover the rest of the price range. They all meet published specs out of the box most of the time, and they offer the best value for hobby and small-shop work. The trade-off is more QC variance between individual units, which is why verifying parallelism on receipt is the single most important habit with any sine bar you buy.
If you want the same kind of repeatable angle measurement for shop tasks outside of sine-bar work, our guide to the best precision screwdriver sets covers another corner of the precision-toolkit world.
Frequently Asked Questions
What is a sine bar used for in precision measurement?
A sine bar is used to set or measure angles very accurately in a tool room or machine shop. You place it on a flat surface plate, stack gauge blocks under one of the two rollers, and the bar tilts to a precise angle defined by sin(angle) = height of blocks divided by the center distance between the rollers. It is the simplest and most repeatable way to dial in any angle from 0 to 90 degrees when paired with a quality set of gauge blocks.
How accurate is a sine bar?
A good sine bar is accurate to within a few arc-minutes when paired with a calibrated gauge block set and a surface plate. Premium bars like the HHIP 3402-1205 publish parallelism of 0.0004 inch and center-distance accuracy of 0.0002 inch. For most shop angle work that is more than enough; for ISO 9001 inspection you should add a NIST-traceable calibration certificate.
What is the difference between a sine bar and a sine plate?
A sine bar is a narrow (usually 1 inch wide) hardened bar with two cylindrical rollers at each end, designed for portable angle work and gauge-block setups. A sine plate is a wider, heavier plate (typically 6×6 inch or larger) with built-in clamping rails, designed for stationary work where you need to hold a part still during inspection or grinding. Sine bars are portable; sine plates are shop-floor instruments.
What size sine bar do I need: 5 inch, 10 inch, or metric?
Most US buyers start with a 5 inch sine bar because it fits standard 1-2-3 block setups and handles the majority of hobby and small-shop angle work. A 10 inch bar is preferred for tool and cutter grinder work because the longer center distance produces a smaller gauge-block stack for the same angle. Metric shops should choose a 100 mm bar (equivalent to 5 inch) or 200 mm bar (equivalent to 10 inch).
Are cheap sine bars accurate enough for tool room work?
For general tool room and shop use, yes. Most sine bars in the budget and mid-range price bands meet published parallelism and flatness specs out of the box. For ISO 9001 inspection or calibration-grade work, you should verify parallelism on receipt with a dial indicator and budget for a NIST-traceable calibration certificate from a third-party lab.
Final Verdict: Which Sine Bar Should You Buy in 2026?
After eight bars and several months of testing, our Editor’s Choice for the best sine bar for precision measurement is the HHIP 5 Inch Sine Bar (3402-1205). It hits the published parallelism and center-distance specs out of the box, has the largest review base of any 5 inch bar on the market, and offers the best balance of accuracy and price for hobby and small-shop use.
If you want maximum value, the Shars 5 inch sine bar with 1-2-3 blocks is the cheapest working setup we tested, and the matched bundle gets you angle work done from day one. For tool rooms that need a sine plate instead of a sine bar, the HHIP 3900-5526 6 inch sine plate is a serious shop instrument.
Whichever bar you pick, verify parallelism on a granite surface plate with a dial indicator the day it arrives. That five-minute check protects you from the small percentage of units that ship with QC variance and ensures the sine bar you trust is the sine bar you actually have. For more precision-shop tool recommendations, see our guide to the best table saws for precision woodworking.