Methods and devices for accurate table saw blade and router bit height measurement.

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Forum topic by dbhost posted 08-23-2012 03:28 PM 4258 views 0 times favorited 22 replies Add to Favorites Watch
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5604 posts in 2694 days

08-23-2012 03:28 PM

Topic tags/keywords: question

After a few too many errors in setting up heights for dado and rabbet joints with both the TS and the router, it is obvious I am not doing this right. I have been able to make adjustments (knocking longish rabbets down with a hand plane) but that effects things down the rest of the project.

So what devices / methods are you using to accurately measure table saw blade and router bit height? If you have come up with, or are using a jig of some sort post up pics or links to the project. I’d like to see it.

-- My workshop blog can be found at

22 replies so far

View Bill White's profile

Bill White

4450 posts in 3422 days

#1 posted 08-23-2012 04:16 PM

I use a simple Starett 6” square. Accurate, inexpensive (bought it used), no stupid battery stuff.


View jmos's profile (online now)


736 posts in 1831 days

#2 posted 08-23-2012 04:39 PM

I have a 6” Starrett steel rule I use a lot, as well as a 4” Starrett double square. Sometimes I’ll use my 1-2-3 MicroGauge I bought it for tool setup, but find it very useful for setting bit/blade heights as well.

I have a digital caliper I use a lot, but I’ve found it difficult to use for setting bits/blades.

-- John

View dbhost's profile


5604 posts in 2694 days

#3 posted 08-23-2012 06:02 PM

I have a Johnson 12” steel combination square. I was hoping for more accurate measurements. Not OCD accuracy, but within hundredths… FWIW, the Johnson combination square rule rusted VERY quickly and is now pretty much mostly brown / orange colored and very hard to read. I need to dunk it in Evaporust to get it back to speed…

-- My workshop blog can be found at

View teejk's profile


1215 posts in 2146 days

#4 posted 08-23-2012 06:12 PM

On the TS I use scraps of plywood…set next to the blade, raise/lower until I’m happy with my thumbnail. I only use a router overhand and that’s just trial and error for me…set high on the initial pass and then dial down. I only use PC routers so it’s pretty easy…the increments are minute.

View OggieOglethorpe's profile


1211 posts in 1572 days

#5 posted 08-23-2012 06:13 PM

Same with Bill….

Set the blade extension to my depth of cut, put the end of the blade against the table or sled floor, and raise the blade or bit until it makes contact. It usually helps to rock the blade or rotate the bit and listen / feel for a scrape.

On another note, I usually don’t see it as all that big of a deal if my 1/2” deep dados are 31/64, 1/2, or 33/64 deep, as I cut them all at once.

For those occasions like lock miter or cope and stick bits, that need a precise setting, once it’s perfect, I’ll normally make a UMHW or MDF setup block for next time.

Yet another thought is to make sure any sleds you use have floors that ride on the surface of the machine, not the bottoms of miter slots. If a sled rides in the slots, varying operator pressure can affect dado depth.

View lumberjoe's profile


2893 posts in 1710 days

#6 posted 08-23-2012 06:18 PM

View Tennessee's profile


2410 posts in 1976 days

#7 posted 08-23-2012 06:31 PM

I use a scrap piece for the initial cut. Usually a piece of scrap oak, so I get a nice cut. Measure, adjust as needed. Just put in a .020” groove in the side of a guitar for binding that way. Just kept making micro adjustments until the binding fit the scrap cut perfectly. Cut the groove in the guitar, mounted the binding. Perfect.
For other more gross measurements, like others, I keep multiple 6” Starrett rulers and squares lying around, bought over the years. Always have more than one, since I lay things down….(old age)

-- Paul, Tennessee,

View dbhost's profile


5604 posts in 2694 days

#8 posted 08-23-2012 07:34 PM

Lumberjoe, you are a freaking GENIUS! How the heck did I never think of that one?!

I love solutions that are forehead slapping simple…

-- My workshop blog can be found at

View lumberjoe's profile


2893 posts in 1710 days

#9 posted 08-23-2012 07:44 PM

I figured that out making the picnic table I HATED making. The top boards had to be spaced 3/8 a part. I was looking around the shop and thought “there has to be something in there that’s 3/8”. Then it dawned on me do grab a drill bit. After that I had the same forehead slapping session remembering all the time I wasted trying to set bit/blade heights when I had a box of “precise set up blocks” in virtually any size I ever needed.


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5604 posts in 2694 days

#10 posted 08-23-2012 08:50 PM

Funny thing is, 3/8” is the most common setup height for non through cuts for me as I like to cut my dadoes halfway through 3/4” stock… And I have plenty of extra 3/8” bits (I kept losing them, buying replacements, lather rinse repeat until they all sort of showed back up one day!)

-- My workshop blog can be found at

View Rex B's profile

Rex B

320 posts in 1712 days

#11 posted 08-23-2012 09:40 PM

Be careful, a machinist once taught me that drill bit shanks are not reliably sized, just the cutting flutes (which make a reliably sized hole). So you might double check with a set of calipers before you use a drill bit shank to set your blade/bit height. Then again, I don’t think it would be off more than a couple thousandths, so shouldn’t really matter.

-- Rex

View dbhost's profile


5604 posts in 2694 days

#12 posted 08-23-2012 11:43 PM

Us the high points of the outer edge of the flutes I assume…

-- My workshop blog can be found at

View David Kirtley's profile

David Kirtley

1286 posts in 2460 days

#13 posted 08-24-2012 12:12 AM

Setup blocks.

Put together a set to add up to the size you want.

These are from Woodcraft:

-- Woodworking shouldn't cost a fortune:

View lumberjoe's profile


2893 posts in 1710 days

#14 posted 08-24-2012 01:09 AM

Us the high points of the outer edge of the flutes I assume

That’s what I do. I bought a large cheap index set on Amazon after my revelation. I never drill with them, just set up tools. I measured them with dial calipers before using them and they were extremely close (within a thousandth). That doesn’t solve the problem that just because I think half of 3/4” is 3/8” that it actually is. I still always do test cuts unless I am 100% sure I want the depth chosen, then I just go for it. I’ve used these enough to trust them.


View gfadvm's profile


14940 posts in 2152 days

#15 posted 08-24-2012 02:14 AM

I made a set of set up blocks from Jatoba drum sanded to exact thickness. Finding TDC on the tablesaw is critical so I usually lay a straight edge across my set up block and raise the blade while turning it until it just kisses the straight edge. Then I ALWAYS cut a piece of scrap to confirm the setting. I have used drill bit/router shanks for spacers when setting up my box joint jig but have learned that all 1/4” shanks are not the same.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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