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View dbhost's profile

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

by dbhost
posted 08-23-2012 03:28 PM


22 replies so far

View Bill White's profile

Bill White

3500 posts in 2651 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.
Bill

-- bill@magraphics.us

View jmos's profile

jmos

681 posts in 1060 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

dbhost

5386 posts in 1922 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 http://daves-workshop.blogspot.com

View teejk's profile

teejk

1215 posts in 1375 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

OggieOglethorpe

904 posts in 800 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

lumberjoe

2842 posts in 938 days


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

Indexed drill bits.

-- www.etsy.com/shop/KandJWoodCrafts

View Tennessee's profile

Tennessee

1471 posts in 1205 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, http://www.tsunamiguitars.com

View dbhost's profile

dbhost

5386 posts in 1922 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 http://daves-workshop.blogspot.com

View lumberjoe's profile

lumberjoe

2842 posts in 938 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.

-- www.etsy.com/shop/KandJWoodCrafts

View dbhost's profile

dbhost

5386 posts in 1922 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 http://daves-workshop.blogspot.com

View Rex B's profile

Rex B

314 posts in 941 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

dbhost

5386 posts in 1922 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 http://daves-workshop.blogspot.com

View David Kirtley's profile

David Kirtley

1281 posts in 1688 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: http://lowbudgetwoodworker.blogspot.com/

View lumberjoe's profile

lumberjoe

2842 posts in 938 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.

-- www.etsy.com/shop/KandJWoodCrafts

View gfadvm's profile (online now)

gfadvm

11242 posts in 1380 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

View NiteWalker's profile

NiteWalker

2710 posts in 1267 days


#16 posted 08-24-2012 04:04 AM

I use actual workpieces as height gauges, along with a 6” steel rule with end markings.

-- He who dies with the most tools... dies with the emptiest wallet.

View Jim Bertelson's profile

Jim Bertelson

3675 posts in 1855 days


#17 posted 08-24-2012 03:10 PM

Being really OCD, I have a number of measuring devices that are very accurate, and use whichever one is the easiest. But the best one, is a piece of scrap wood cut up to make sure that my setting is accurate. I also make MDF setup blocks for odd measurements to use for the rest of the project.

I use digital calipers, digital height guage, digital angle and incline guages, digital table saw readout, and keep a bunch of extra batteries around…..(-:

Also, Incra rules, setup blocks, etc. The Incr rules, the ones with the holes for the pencil, are the most used item in the shop. But right behind it is the Wixey digital calipers. As a result, most of my little projects are fairly solid just with the dry fit.

I’ll be honest…...I really like making precise cuts and measurements. It is part of the fun for me. Not always practical, but fun….....(-:

-- Jim, Anchorage Alaska

View Tenfingers58's profile

Tenfingers58

79 posts in 1368 days


#18 posted 08-24-2012 04:04 PM

Jim,

That’s the fun that I’m in the shop for.
The feeling of a cut well made, and a project well put together.
The project will last as long as it took the tree that was made from to grow.

View lumberjoe's profile

lumberjoe

2842 posts in 938 days


#19 posted 08-24-2012 04:14 PM

Jim, I’ve been secretly longing for one of the Incra/woodpeckers rules with the pencil holes for a while. Is it really worth it?

-- www.etsy.com/shop/KandJWoodCrafts

View CharlieM1958's profile

CharlieM1958

15706 posts in 2908 days


#20 posted 08-24-2012 04:56 PM

I use one similar to this. It covers the the most common heights I want to use.

-- Charlie M. "Woodworking - patience = firewood"

View jmartel's profile

jmartel

2325 posts in 840 days


#21 posted 08-24-2012 05:49 PM

If you take a straight and flat stick/ruler and divide it into equal lengths, you can reliabily get an accurate fraction of the thickness of your stock.

Say you want a dado that is 1/2 the depth of your workpiece. You take something flat, divide it into 2 equal sections (with a line at the halfway point). One end goes on your workpiece edge, one end is touching the table. Raise the saw blade/router bit until it just touches the line on the bottom of the piece.

If you want it at 1/3 deep, divide it into 3 sections, and use the line closest to the table rather than the one closest to your stock.

-- End grain is like a belly button. Yes, I know you have one. No, I don't want to see it.

View Jim Bertelson's profile

Jim Bertelson

3675 posts in 1855 days


#22 posted 08-25-2012 04:36 PM

Joe
Yes, the incra rules are worth it, as far as I am concerned. It gives you a perfectly accurate ruler to both ends and easy ways to mark things. I have the 18” varieties.

Tenfingers
Right now, I am just itching to get back in the shop. Way too much work, and working at home. But that is about to end.

-- Jim, Anchorage Alaska

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