Cuts Aren’t Accurate Even With a Circular Saw + Guide
“My circular saw, with a guide rail, still isn’t cutting where I expect.”
I had this problem for a while.
The blade would cut a bit off from my marked line.
My circular-saw guide was shop-built, so I assumed the issue was on the guide side.
It turned out the actual culprit was the saw itself.
This article explains what was wrong and how I fixed it.
(Spoiler: the fix was to buy a better saw…)
The Real Cause
The saw I’d been using was the one I bought when I was still figuring out DIY:
BOSCH (Bosch) DIY-grade PKS 18 LI
Cutting along a guide rail, my cuts kept missing the marked line.
Since the guide was shop-built, I vaguely assumed it was the guide’s fault.
Then one day I noticed: when I changed the blade extension, the actual cut position shifted:
Wait — could the saw itself be out of true? I took a closer look:
I held a steel rule along the blade, like this:
And found that the saw’s baseplate edge wasn’t parallel to the blade!
Worse: when I changed the blade extension and measured the distance from baseplate edge to blade, the distance was different at different extensions.
So of course the cut shifts depending on blade extension — even with a guide rail.
This model has no parallelism adjustment mechanism. (Apparently that adjustment only exists on higher-end saws.)
That settled it — I bought a new circular saw.
Upgraded to the HiKOKI C6MEY (Higher-End Model)
I ended up with the HiKOKI C6MEY (corded). Here’s what’s good about it and how I tuned it.
Cordless or corded?
The first decision when picking a new circular saw:
“Cordless or corded?“
Cordless obviously doesn’t need an outlet — easier to use anywhere, and great for working in a yard with no power.
I’d been on cordless up to this point, but corded does have its advantages.
Corded advantage: cheaper than cordless
For corded, you can get into the top-tier model under 30,000 yen (~$200).
Since the trigger for replacing my saw was accuracy (not portability), I picked a top-tier corded model after some deliberation.
(For deciding which saw to buy, I leaned on the YouTube channel “Kamiya-sensei’s DIY Channel”. Kamiya-sensei’s take: if you can get the best one for around 25,000 yen, just buy it.)
End result: extremely happy with this saw.
<Update>
As of writing this article (July 2023), the C6MEY’s successor “C6MEY2” is now available.
Looks like a minor update, but the price ticked up over 30,000 yen.
For reference, here’s my article about installing power outlets in my yard (Japanese version available; English forthcoming) — having outlets out there made the corded option easier to commit to.
Aluminum baseplate
My old saw had a steel baseplate. The new one has an aluminum baseplate.
Aluminum is reportedly stiffer and less prone to warping than steel.
Handling it confirms that — the saw feels noticeably more solid.
Adjustment mechanisms
The new saw has dedicated adjustment mechanisms for blade squareness and parallelism.
The HiKOKI top-tier saw has good factory accuracy out of the box, but you can fine-tune from there.
Squaring the blade
Let’s adjust blade squareness.
Holding calipers up to the blade and baseplate, I can see the blade isn’t quite 90° to the base:
To fix this, use ① the bevel knob and ② the angle-stop screw shown below.
※ The ② angle-stop screw is missing on most cheaper DIY-grade saws.
First, loosen ① the bevel knob (front/back). Now the blade tilts freely:
To get to exactly 90°, the blade rests against ② the angle-stop screw — the screw determines the 90° stop position.
Adjust how far that screw protrudes (with an Allen key) to dial in true 90°.
(My older saw had no ② adjustment.)
Squared up.
After squaring, retighten ① the bevel knob to lock it in.
■ Verify with an actual cut
Cut a piece of wood to verify. Holding calipers to the cut piece — clean 90°.
Blade parallel to the baseplate
Distance from baseplate edge to blade was the same at front and back — no parallelism issue.
If parallelism does drift over time, this saw also has a dedicated parallelism adjuster.
(The factory parallelism was already correct, so I left the adjuster alone.)
Cut quality comparison
Along with the new saw, I also picked up a “Kuroshachi (Black Plus)” 165 mm blade.
…This is also based on Kamiya-sensei’s recommendation. Thank you, Kamiya-sensei!
The cut quality blew me away.
Maybe my old setup was just particularly bad.
Comparing cut faces:
1. Old setup — Bosch PKS 18 LI (DIY-grade) cut face
With the stock blade.
Cut face is rough and gritty, with burrs along the edge.
2. New setup — HiKOKI C6MEY + Kuroshachi blade
And here’s the cut face from the HiKOKI C6MEY with the Kuroshachi blade.
Smooth cut face, smooth to the touch, very few burrs.
Wrap-up
Bottom line: it really is worth splashing out on a good circular saw.
On corded vs. cordless, I went corded for the price advantage. If your budget allows, cordless is the more convenient choice.
The HiKOKI C6MEY I bought:
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