[RobinDobbie]

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?

 

[ryan50hrl]

Keep in mind..... .0015 can make a difference in metal working.......working in woodworking to 1/650 the of an inch is pretty unrealistic. I'd not worry about that. I'm usually pretty happy if things are within 1/64th. Wood expands and shrinks....whats perfect today won't be tomorrow.

 

[RobinDobbie]

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.

 

[RobinDobbie]

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.

 

[toolguy1000]

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. that way, you can start out as snug as possible and gradually tighten the miter slider bars with their adjustable feature until they slide uniformly within the slot. i had a similar issue. i didn't bother sanding anything. i got a second miter slider and, with two of them steadying the sled, there was no slop whatsoever when i employed this technique to construct the sled.:

https://www.ridgidforum.com/forum/t13945/

absolutely 90° to the blade:

 

[ryan50hrl]

The problem I see is how are you going to ensure perfectly straight slots? 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.

 

[RobinDobbie]

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

 

[GeorgeC]

Keep in mind..... .0015 can make a difference in metal working.......working in woodworking to 1/650 the of an inch is pretty unrealistic. I'd not worry about that. I'm usually pretty happy if things are within 1/64th. Wood expands and shrinks....whats perfect today won't be tomorrow.

Read this and memorize it. Woodworking CANNOT make use of those kind of tolerances!!! If you think it can you are only fooling yourself.

I do not even try for 1/64 inch. I am perfectly happy with 1/32" for the vast majority of projects.

George

 

[ryan50hrl]

Have you watched this video? http://youtu.be/UbG-n--LFgQ?t=21m

I have.....and if you can find anyone else on this site that works to within 1/640th ill walk away...

But your imperfect incra bars are yet another example of woodworking being a different standard than metalworking.

It's just not realistic. .....I enjoy perfection as well.....but I think your chasing a pipe dream.

 

[RobinDobbie]

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.

 

[ryan50hrl]

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.

I'm not trying to be negative....I'm trying to keep you from making it worse. If you really want them to be perfect, take the top off, take it to a machine shop with a mill and have them repair it. There's no way (worked in a machine shop for a few years) that I'm aware of to make something accurate in cast iron to the tolerances your looking for BY HAND!!!!

 

[woodnthings]

let's just "assume" you can get the play out ....

... the sliders fit a snug as possible and you can still move the sled easily with no play side to side..... I have done this, so I know it's possible. No, I don't know the tolerance in decimals, just seat of the pants feel and highly trained eyeballs. :laughing:

The next issue will be setting the fence 90 degrees to the blade. This is where real accuracy is required, I did use a digital readout angle gauge, and when you make your test cuts and flip them over you get 90 degree cuts. That gauge will be your best investment.

As to negativity in a post...you post your topic and you get what you get, like it or not. Some responses will be constructive in nature others may poo poo your ideas. You must have a tough skin to post on an open forum like this, I know this for a fact after repeated cynical or sarcastic replys. Ignore those responses you don't like/agree with and you'll be much happier ... just move along.
I gave you a link to E Bay to which you responded in a negative way on another thread and I let it go. There was a solution in the link at $19.00 to which you responded "no way in hell" ...etc.
A simple "thanks, I appreciate your effort in trying" to help would have been more appropriate. :yes:

 

[BWSmith]

No negativity here.....but you might not like what I'm gonna say?

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.

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

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.

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

 

[toolguy1000]

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.



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.



Have you watched this video? http://youtu.be/UbG-n--LFgQ?t=21m

yes, i've watched that video about the 5 cut method and decided niki's method was easier and less pretentious. you should know that the incra miter sliders do come out of my miter slots easily ANYWHERE along the miter slots they ride in. your comment about not using them because the bottoms of the sliders are wider than the top of the sliders thus preventing easy removal from the slots does not bear out in my application. like you, the miter slots in my CC dedicated TS vary slightly in width along their length. that's why i think niki used two runners. any variation in slot width is compensated for by the two runners and how they are applied to the sled.

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.

 

[ryan50hrl]

No negativity here.....but you might not like what I'm gonna say?

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.

.0015 is one third the thickness of a piece of paper....or roughly the thickness of an average human hair...

I don't know of any machines that have adjustments that fine. Certainly none that I've ever used in woodworking. The large wide belt sander I take my stuff to has a readout of .005 or a factor of 3 times smaller than we are talking about.


All I'm trying to say....is that chasing perfection in accuracy is futile as wood expands and contracts rapidly with climate changes. And .0015 seems excessive.....

Just my humble opinion that using a handheld piece of sandpaper will do more harm than good in trying to remedy the situation. And once the material is gone you can't add it back.

 

[RobinDobbie]

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.

 

[ryan50hrl]

Fair enough....it's your saw, and your projects. Good luck.

 

[RobinDobbie]

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.

 

[woodnthings]

interesting discussion here

I have found that not all miter slots are .75" or 3/4". Some of my miter gauge bars are just a bit tighter, others loose. I have several miter gauges, older and newer Craftsman, Grizzly, Osborne, Incras .... others.

I have taken a mill file to the miter slots of my Craftsman table saw because the miter bar would hang at one point or another. A few strokes, then test, and a few more then test again and was "cured"
I suppose one could get a 3/4" steel bar and some lapping compound and work the miter slots to a fine fit. I personally would use steel for the sled bars or as I did on my sled, hardwood runners. I kept ripping strips until a got the precise fit I wanted, gave them a light sanding then attached them to the sled bottom.
There is no discernable play that I can tell.

Here's the real issue.
The miter slots and bars can be made to fit perfectly, but they are joined together by a rather large piece of plywood or MFD or other material which is subject to expansion or contraction. What may have fit and worked perfectly one month may not work as well the next month.
Another issue is the blade must be in perfect alignment to the miter slots or otherwise there will be a "heel" to the cut. It will be parallel kerf, just not a perfect kerf width.
Just sayin' :smile:

 

[RobinDobbie]

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.