[ryan50hrl]

I felt like the force required to move the caliper open and closed was enough to deflect the blade a tiny bit. If the lug-back indicators are typically smoother, I'll buy one immediately.

Yes they are

 

[woodnthings]

just thinkin' outside the "box"

Most rotating devices or assemblies are dynamically "balanced".. crankshafts etc., We use 10" blades that rotate at high RPMs and they may have some runout static or dynamic. I can measure runout with a dial indicator on my lathe at low RPMs, why not on the table saw? Then take the average between the extremes rather than one tooth which may or may not rotate "in plane".... There are some sanding plates that are advertised as table saw set up devices:

No teeth present to measure from, just a "flat plate". A dial indicator can now ride the extremity of the plate and give the "combined" run out of the plate and arbor. We are really splitting hairs here but for those who feel it necessary it should work fine.

I do use one to set my RAS blade square to the fence. :yes:

 

[RobinDobbie]

I've been thinking about getting one of those discs and a second, cheap table saw to use as a dedicated sander. The only reason I haven't is that I'm very limited on space. But you know, I was cutting some plywood today and the cut quality was extremely nice on both sides, no noticeable blade pattern. I may hold off on getting the blade any better than it is because it's obviously pretty good right now. My main concern is keeping sleds going 100% straight as they travel across.

 

[ryan50hrl]

The sanding discs don't work very well as tablesaws spin to fast for sanding. You'll burn/gum up the discs really fast.

 

[RobinDobbie]

Well yeah I'd have to play with pulley ratios, but that might be more trouble that it's worth.

 

[BWSmith]

Just for the record....I think you're wasting time trying for any kind of *real accuracy on a table saw,as there's too much stacked tolerances.And this is to include Martin's,Altendorf's etc.....*real accuracy:even getting into the .001's

But TS's in general seem to be the "darling" pce of equipment of the woodworker crowd....so any advice or direction that dosen't place them at the head of the pecking order,usually goes unheeded.Just sayin TS's within the industry are most often held for accuracy jobs pretty far down the list of importance.

Next is the chicken and the egg....horse and cart.If you don't have anyway of measuring,how and why would you be on a journey chasing .oooo's?You want a square pce of panel...lets say 2'x2'.My point is,how are you going to measure the 2'(24")?You gonna use a tape measure?


Dig around in below link.They're used by a lot of folks in the accuracy biz.May answer some instrument questions.

http://www.longislandindicator.com/p4.html

 

[RobinDobbie]

If not a table saw, what would be your choice for accuracy? Again, I'm all ears. Out of all the consumer grade equipment used to make cabinets, it was apparent to me that a table saw with various jigs and sleds was the most universal tool. Tracksaws coming in a close second. Again, my accuracy goals at the moment are more about consistent cut quality and 90 degree squaring. I'm not going to be making cabinets and saying to myself, "Yeah, I think this drawer front should be 14.0015 wide." I would be chasing the pipe dream everyone thinks I'm chasing.

The way I measure large panel 90 degree accuracy is with cumulative error over a 4 sided board. Cut a board, rotate 90 degrees and cut. Do that 4 times. The 4th cut(technically the 5th) can be as narrow as a half inch, but the difference in width at one end of the board and the other(which is the result of cumulative error over all 4 sides) can be easily measured with 6" calipers. The results can be used to calculate exactly which feeler gauge should be used to space the sled fence forwards or backwards. Freakin genius.

 

[BWSmith]

First off,drops ain't called "drops" for nuthin,lame attempt at humor.But seriously,don't think I've ever(40+ years)measured a drop to see what effect it had on the part?


I figured you were pulling a diagonal on largish panels.Or making spot measures to see if both ends were the same.....I now see thats not what you're intending,apologies.

 

[woodnthings]

is your square "square"?

There are several means to make a square line or measure a square cut. Use a framing square. Use a T square either drafting or drywall. I use a digital protractor if it has to be exact.

Measure or register off one edge. Scribe your mark using the framing square. flip it over make a mark "parallel" to the first one. Is it parallel? Out at the end it will show the greatest deviation. Once you have square, it then it becomes the "master for checking 90 degrees. There is a way to peen the corner of a square to get it right on. http://zo-d.com/stuff/how-do-i/how-to-check-and-adjust-a-framing-square.html

I wouldn't bother chasing a piece of panel around the miter gauge or sled 4 times. It's either square or not. What if it's not square, now what? How much error so you adjust for ... ? Were all the pieces registered exactly the same...:blink:

You can measure the diagonals, but the result will only be as good as your registration, your measuring tool and as good as your eyeballs can read it.... usually good enough for woodworking. You got to get a collection of measuring and checking tools you trust, then move on to the making part of the project. If you are always questioning your measuring process, you will not only NOT enjoy it, you won't get anything finished.

 

[RobinDobbie]

I would use a framing square to check the square of a box or drawer when I'm gluing it. To square up multiple identical panels where consistency will make the project fit together more accurately, I would use the sled and stopblocks and treat each panel to the exact same cuts. Again, I doubt my accuracy with the initial measurements would be that great, but consistency of each panel would hopefully be amazing.

I'll be making all sorts of sized panels. Anywhere from 3' x 3' to 2' x 4', compound miters, parallelograms, circles(router territory), to name a few.

One of the projects I started in January:

Terrible accuracy, burn marks bad enough to smell like Chinese barbecue, and it was slow, tedious work.
Sometimes things just didn't quite line up, and sometimes they didn't line up by a long shot. Some of that was poor measuring and marking, some of that was the guide moving after I started cutting, not being absolutely sure where the blade was going to enter the wood, ect..

 

[RobinDobbie]

Kreg bars arrived. One problem that I perceive with them is that the holes for the screws that attach the bars to the sled/jig are countesinked. If your screw hole into the sled or jig is off center just the smallest amount, the screw head will pull the bar whatever direction is necessary to bring the hole and bar into perfect alignment. Not good. I got some forstner bits and some flat bottom screws that I believe are the perfect size. The screw heads are not even 1/8th, so I don't have to go very far down. And, aluminum is very soft. I've cut a bit of it lately on the table saw while making my outfeed table. Keeping in mind I don't have to go very deep, I'm pondering just trying to add some flat area to the existing holes. Is this a terrible idea? Should I start new holes so the center part of the forstner will be able to guide the bit? Should I lubricate the bit? I don't have very deep to go, but I do have a total of 24 holes that need attention, between the two sleds.

 

[woodnthings]

I don't understand a few things...

The screw you show has an oval head and is not meant for a countersunk hole as you show in the bar. :blink:
Why not use the bar and the holes there in as the drill jig when locating the pilot holes going into the sled?

I would not alter the bar in any way, just use the proper flat head screws to attach the bar to the sled. :no:

Unless I am completely missing your issue... :boat:

 

[ryan50hrl]

The screw you show has an oval head and is not meant for a countersunk hole as you show in the bar. :blink:
Why not use the bar and the holes there in as the drill jig when locating the pilot holes going into the sled?

I would not alter the bar in any way, just use the proper flat head screws to attach the bar to the sled. :no:

Unless I am completely missing your issue... :boat:

I agree, but I think he's saying he can't drill them precise enough?

 

[RobinDobbie]

Yeah, I don't think I can expect to get 24 holes so precisely drilled in the center of the pre-drilled holes in the jig bar that the position of the miter bar isn't going to shift when the screw head is pulled into the wedge-shaped hole. IF The countersink in the jig bar and hole in the sled base were drilled at the same time by the same bit, it wouldn't be a problem. But getting them to line up after the fact seems impossible. A flat area and a flat bottomed screw is the only way I can see to keep the screw action limited to just bringing the two pieces together and not shifting them.

 

[toolguy1000]

Yeah, I don't think I can expect to get 24 holes so precisely drilled in the center of the pre-drilled holes in the jig bar that the position of the miter bar isn't going to shift when the screw head is pulled into the wedge-shaped hole. IF The countersink in the jig bar and hole in the sled base were drilled at the same time by the same bit, it wouldn't be a problem. But getting them to line up after the fact seems impossible.

what about getting a brad point drill bit that's the same size as the through hole in the kreg fixture bar and use it to mark the pilot hole for the sled attachment screws?

A flat area and a flat bottomed screw is the only way I can see to keep the screw action limited to just bringing the two pieces together and not shifting them.

in principle, you're right. what you're describing is how the incra bars work.

or how about using a machine screw with a tapered head that matches the countersink of the miter bars? drill a flat recessed hole to receive the nut in the bed of the sled, with a slightly oversized through hole for the machine screw? that way, there's no need to drill the miter bar, and the oversized hole will allow for some wiggle room to facilitate any alignment issues. this could work pretty easily in 3/4" material since most nuts that small are less than 3/8" thick.

BTW, what do the instructions that come with the kreg bars say about the problem you're anticipating?

 

[woodnthings]

Ok I get it

Drill the sled for 3 holes, 1 on each end and 1 in the center. Put the screws to it to hold it in place then drill the rest of the holes. You can use a bit that's the same diameter as the bar hole to center your pilot drill. Just drill in a slight amount to create a center. :yes:

 

[RobinDobbie]

or how about using a machine screw with a tapered head that matches the countersink of the miter bars? drill a flat recessed hole to receive the nut in the bed of the sled, with a slightly oversized through hole for the machine screw? that way, there's no need to drill the miter bar, and the oversized hole will allow for some wiggle room to facilitate any alignment issues. this could work pretty easily in 3/4" material since most nuts that small are less than 3/8" thick.

BTW, what do the instructions that come with the kreg bars say about the problem you're anticipating?

Hmm, I did use 3/4 melamine. I just don't know how I feel about a bunch of giant holes on the top of the sled. There's certainly enough support, it's not like they'd cause a problem as far as that goes. I could even cover them with bondo if I thought they were catching sawdust or whatever.

I'll be honest, I was a tad scared when I saw you mention the instructions. I hadn't read them. Now that I've read them, I know they're as pointless as I had first imagined them being. It's a single page outlining the uses of the jig, which one should already freakin' know by the time they open the package. The mention of screws is limited to listing the type of screws included. Oh wow. Like I really needed to know that.

in principle, you're right. what you're describing is how the incra bars work.

As annoyed as I am with the fact that I'm having to think about my miter bars even more than I already have, these are way better than incras, given all the cons I listed for incra on the precious page.

By the way, remember I mentioned that the kreg bars had 5 set screws the length of the bar? The package said six, but there are actually 8 on each bar, ensuring that there are still at least 2, possibly 3 set screws in the slots, even when the wood in the sled is past the blade. With the incra and it's 3 TOTAL adjustment points, there's only one adjustment point in the slot at the end of a cut. The down side is that the actual set screws aren't 1/4-20, there're a lot smaller. But, given that the bars are 3/8" thick, there'd only be 1/16th of aluminum above or below the set screw, leaving the bar sort of weak.

what about getting a brad point drill bit that's the same size as the through hole in the kreg fixture bar and use it to mark the pilot hole for the sled attachment screws?

Good idea. I just feel I'd like the completely eliminate the possibility of the bar getting pulled to the side due to a mistake in drilling.

 

[RobinDobbie]

Drill the sled for 3 holes, 1 on each and and 1 in the center. Put the screws to it to hold it in place then drill the rest of the holes. You can use a bit that's the same diameter as the bar hole to center your pilot drill. Just drill in a slight amount to create a center. :yes:

I'm not entirely certain I understand your process.

For initial contact, I planned on using poster tape(very thin double-sided sticky tape) to give a quick connection to the bars and the sled.

I'd put the bars in the slots over a 1/8th or less shim laying in the slots.

I'd get the bars perfectly centered, then lay the sled base over them and get it positioned where I wanted it.

I'd slide the ripfence to where it was just touching the edge of the sled base, lock the rip fence, then remove the sled base.

Add poster tape to the bars, then using the rip fence as a guide, lower the sled base onto the bars.

I could then lift the sled up with the bars attached and remaining perfectly aligned so I could flip it over and attach permanent screws/bolts.

 

[toolguy1000]

well, it'll be fun to see how this project turns out.

 

[woodnthings]

exactly

Do this:

I'd put the bars in the slots over a 1/8th or less shim laying in the slots.

I'd get the bars perfectly centered, then lay the sled base over them and get it positioned where I wanted it.

I'd slide the rip fence to where it was just touching the edge of the sled base, lock the rip fence, then remove the sled base.

Add poster tape to the bars, then using the rip fence as a guide, lower the sled base onto the bars.

I could then lift the sled up with the bars attached and remaining perfectly aligned so I could flip it over and attach permanent screws/bolts.

Then this:

Drill the sled for 3 holes, 1 on each end and 1 in the center. Put the screws to it to hold it in place then drill the rest of the holes. You can use a bit that's the same diameter as the bar hole to center your pilot drill. Just drill in a slight amount to create a center. :yes:

This should help avoid any shifting in the bars as you add the remaining screws. :yes: