Woodworking Talk banner
1 - 18 of 18 Posts

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #1 · (Edited)
I finally settled on materials and got everything together to make my perfect crosscut sleds. First order of business was an outfeed table. I almost finished my Bob. D. style outfeed table . All that's left is to route the miter slots in the table and make a cut out for the blade guard. I figured I'd use my 24" Incra Miter Sliders to draw the line where the slots are going to go. I'd have them sticking half way off the table saw, and adjusted perfectly, so my lines for the outfeed miter slots would be very accurate. The outfeed slots are, of course, going to be larger than the miter bar, so absolute accuracy wasn't really necessary, I just wanted to do that. Well, I hadn't played with these bars in the table yet, at least not tightened up. I was sadly disappointed when I had a bit of slop in the middle of the table when the adjustment screws were set to barely fit the first 7 inches and the last half inch of the slots. I was only able to get a .0015 feeler gauge in the slot, but the slop is visible to my eye and I can really hear the bar slapping against the slots when I wiggle it back and forth.

Here's a short clip showing the slop:
http://youtu.be/irs8xa30vTw

I really do want perfect cuts and the ability to square boards with crazy precision down to a 1000th of an inch over 4 20+ sides like William Ng got in his 5-cut method video.

Should I fix the slots somehow, or look at a professional grade saw?

EDIT: And, the miter sliders will need work done on them. When adjusted, they can't just drop into the miter slots at just any point. They have to enter from an end. WTF? Why can't stuff just work?
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #3 · (Edited)
But if I double 1/640th 4 times(squaring a board) I'm now off by a 1/40th.

I've been reading, and apparently this isn't entirely uncommon. Saw mention of the Great and Holy Powermatic 66 having a similar issue. A commonly suggested fix is to wrap a long piece of hardwood in 200 - 400 grit and go to town. I want to make sure I do it right so my slots aren't curved, curved against each other, or away from each other when I'm done.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #4 ·
Here's the plan, tell me what you think.

1. Take my miter bar from my Craftsman miter gauge(that's too small for the Ridgid) and build up layers of masking tape until the bar is just perfectly running through the middle of the miter slot with 400 grit on both sides of the bar.

2. Keep adding layers of tape to all but two inches of the bar, until the bar runs perfectly through the middle of the miter slot, with just tape.

3. Orient the side of the bar with the fewest layers of tape toward the front of the table.

4. Put sand paper on both sides of the 2" area with less tape and attempt to widen the tight areas at the front of the table.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #7 ·
if sanding th eslots is what you want to do, i'd employ that technique using the incra miter slider bars as the sandpaper carrier.
I just don't see a way around removing material, since I can't add material to the middle of the slots! With either 1 or 2 runners, if either slot is too tight to travel in once place but not another, and they're adjusted to be able to travel the entire distance in the slots without binding, some slop is inevitable. If I understand it correctly, Niki's sled idea was basically to have the runners hugging the sides of the miter slots closest to the blade. If we knew that the biding was being caused by excess material on the sides of the slots furthest from the blade, Niki's solution might work. The fact is I don't know where the excess material is, I just know that there's some there, on both slots, and in roughly the same places. I will probably have to use the Incra sliders because the Craftsman bar behaved slightly bent and twisted when I laid it on the table surface.

At first, I didn't want to use the Incras because I didn't want to get them dirty(4 bars were $100, I wanted to keep 'em spiffy). Now, I don't want to use the Incaras because they aren't the same width on the bottom as they are on the top. They're 19.08mm wide on the tops, 19.11 - 19.15 on the bottoms. Doesn't sound like much, but it's enough to keep the sliders from coming out of the table saw at any point other than the front or end of the saw when adjusted for perfect fit. I certainly don't want to reinforce that into the actual table surface. I'm leaning toward just returning all of them since that's not a problem I anticipated when I bought them. Looks like Kreg bars might be the way to go.

The problem I see is how are you going to ensure perfectly straight slots?
I was hoping that the length of whatever bar I use that's sliding in the "good" areas of the slot would lend straightness to the material removal process in the bad areas. Kinda like a jointer, a long enough bar in the back would ensure a straight slot up front.

If you double 1/640th your at 1/320 th. again, I don't know a whole lot of guys working in wood to those tolerances.
Have you watched this video? http://youtu.be/UbG-n--LFgQ?t=21m
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #10 ·
I wish I knew how to better put into words how frustrating it is to expect help and get negativity. I appreciate your desire to tell me that your personal goals for accuracy are lower than mine. I'll will even admit that you two are probably(definitely) better craftsmen than I currently am. However, if you or anyone else would do me the courtesy of refraining from commenting on this thread unless you have some suggestion that you think may improve my miter slots, I would greatly appreciate it.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #16 · (Edited)
No negativity here.....but you might not like what I'm gonna say?
The thing I don't like is this: asking for help with a specific problem, but getting told that I'm striving for unneeded accuracy after reading and watching well known woodworkers like William Ng, Marc Spagnuolo, or pretty much anyone who's had a cross-cut sled tutorial on the internet, in a magazine, or video on youtube, say it's possible and CRUCIAL to not have any slop when making and using sled runners. I spent hours and hours on the internet(including this forum) researching what table saw features I need to replace my benchtop Skilsaw(which I spent 20-30 hours with trying(and failing) to get a good, slop free sled). I spent:
$200 on a TS3650,
$100 on Incra Miter Sliders,
$100+ on additional materials for new crosscut sleds.
$75 on materials to make an outfeed table for the TS3650,

All of that was after I spent a couple of weekends trying(and failing) to get good cuts with a circular saw and brand new aluminum guide, then a brand new $120 circular saw, then going back to get a DIABLO blade for the brand new circular saw. Then trying(and failing) with a router and the guide to get good, repeated cuts. I probably could have used the router, but it's so time consuming to set up for each cut and I somehow was off 1/8th of an inch sometimes. BS! I want quick, accurate cuts. I want to be confident that when something's off, it's because I made a mistake(which happens enough).

We ROUTINELY work wood to .0015....and infact a lot of shops do.Heck,take a look at any decent shaper or moulding machine,widebelt sander,etc.etc.

But the discussion here is about TS sleds.....correct me if that's wrong.It seems you've taken an idea or design from your readings and research and you're "running" with it......correct me if thats wrong.
What I'm running with is the idea that sled runners should have no slop, if that's what you mean.

Where you got derailed,so to speak,was in your assumption on "that" process or "best practice".
Literally derailed by uneven miter slots.

Even in a machine shop,"cutting" only gets you so far(metrology).....at some point in the quest for high accuracy work you'll be utilizing other processes.It's not a dang bit different in high accuracy wood machining.

So,not disparaging your need/want for accuracy.....but can present a rather compelling arguement why/how a "sled",irrespective of its build quality......can only,go so far.You need to understand,there are other processes that are infanately faster/cheaper/better if you're chasing .oooo's.
My goal is 1/1000th. I'm all ears as far as cheaper and easier, but I think I'm on the right track.

If you insist on using sleds....read,and understand how "backlash" effects/affects the process.And interetingly,is the "flip-side" arguement to machine vs hand work in the quest for accuracy.

Best of luck,BW
Sleds have been presented to me as being one of the safest, quickest, easiest, and best looking cuts one can get with large or small panels of wood.

I Google'd "backlash" and didn't see a direct definition of the term. I suspect it has something to do with the blade's position changing when either the motor is running or the height is changed? I don't think this will bother me, since I don't plan on changing blade height while in operation or stopping the motor while in a cut.

When I have the miter sliders adjusted so that there's only .0015 slop in the middle of the sled, it takes 6lbs of pressure for one slider to be pushed through the front of the saw. Imagine I have 2 runners now, so that's 12lbs of pressure to push the runners through. By the way, the rough areas are the same on both slots, imagine when I have a delicate cut and I need clean edges. Is that going to be possible when those 12lbs of resistance instantly let up? I think not. And I think that any of you would do what you could to rectify the situation.

And just to clarify, I'm not designing projects with wood measurements that are say 29.0015 inches. I do plan on having boards that are square to 90 degrees to within a 200th of an inch. If my sled is accurate to 1/1000th, I believe that will be possible. And, I do want boards that didn't move more than 1/1000th of an inch while the blade was in motion. I want clean cuts, and I want crazy accurate 90 degree square-ups.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #18 ·
i would humbly suggest rethinking the kreg miter bars. they adjust only at specific points along their length with set screws that are side mounted. this can, according to wood magazine when they last tested miter bars, make their adjustment for a snug fit tedious. incra miter sliders exert pressure from "within" the miter bar along a portion of the length of the slider. i found them easy to install and adjust, especially with their top mounted adjustability.
There are several reasons why Incra Miter Sliders are inferior to the Kreg or Rockler solid aluminum miter bars. I will list my reasons for not being a fan:

1. They appear rectangular, but the actual shape of the Incra bars is trapezoidal. On table saws with t-slot miter slots, the bars have to enter and exit from the front or rear of a saw, when adjusted. Even when there was that slop visible in the video, the miter bars wouldn't come back up through the table at any given point. The bars don't simply not come up, they get wedged in and stuck.

2. When adjusting the exceedingly tiny-headed allen screw to remove slop, the adjustment mechanism "jumps" from one level of tightness to quite another, often too far. This means as you're tightening it up, the actual movement of the expanders is not gradual. It will jump and get too tight, then you have to back it off. Then the contraction isn't gradual either. I found that to get it just right, I had to thump the bar to get it to pop when I thought I needed it to.

3. The actual contact area with the slot is quite small, in a horizontal line. I don't believe the contact surface area is anywhere close to what a Kreg or Rockler bar, with 1/4 -20 nylon set screws.

In this picture, you can see a 1/4-20 threaded rod for reference next to the friction area on the incra slider.


4. On a 24" bar, there are only 3 contact areas the length of the bar. On the Kreg you have 5 on a 30 inch bar(which are the ones I ordered).

5. Unless you have a hole pre-cut on your sled, you can not adjust the bar after it's attached to the sled.

Obviously, there's is a large quantity of people that have no problems with these shortcomings. However, had I known about them before I bought them, I wouldn't have bought them.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #20 ·
Hmm, I would've happily gotten steel miter bars. Ah well.

I chose melamine as my sled base, so hopefully it won't change as much as other wood products.

I got my blade to within .003. I know, very sloppy. Nowhere near my lofty .001 goal. I think part of the difficulty getting it any better is the caliper I used. Maybe someone who's worked with lug-back dial indicators can tell me if they're much better than calipers. 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.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #23 ·
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.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #27 ·
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.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #30 · (Edited)
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..
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #31 ·
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.

 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #34 ·
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.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #37 ·
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.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #38 ·
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.
 

· Dumbest Smart Person
Joined
·
434 Posts
Discussion Starter · #44 ·
It's not that we have an aversion to modifying metal things that need modifying....it's that we tend to use things in the way they were intended to be used. There are thousands of guys that have bought these bars and use them with the tapered holes....and they work great. I think most of us are just against extra work for the sake of extra work.
I hear ya. But I checked out the reviews on amazon for these miter bars and the first review was expressing my same concern for the coutersink holes. The one comment in response was to the effect that the double stick tape would keep the bars from moving, and ten out of ten people found that comment useful. I must be the only one who's dealt with adhesive in the heat. It likes to get gooey and slide around. I don't have an air conditioned shop. If the doors are closed and the fan's off, I have no idea how freakin hot it must get in there. I just know as much as I've gone through, I'm not going to rely on tape.

And, my miter slots in the table saw certainly weren't intended to be tight in the front and back. Modification was the only remedy, there, if I wanted to take full advantage of adjustable miter bars.

In no way did I mean to imply anyone here wasn't competent with metal. I was sure you were, which is why I asked about it. Does that make sense?
 
1 - 18 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top