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Crosscut sled binding trouble

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Forum topic by JakeK posted 05-01-2017 03:58 PM 1830 views 0 times favorited 27 replies Add to Favorites Watch
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JakeK

42 posts in 516 days


05-01-2017 03:58 PM

Topic tags/keywords: crosscut sled kreg incra sawstop microjig binding bind runners miter slots

Hey Guys, first off, this is kind of a long read (sorry for that) but i wanted to put in all of the detail to avoid suggestions of things i have already tried. I have a new sawstop PCS 3HP 52” table saw which is replacing my Bosch jobsite saw. Big upgrade for me. I was pretty excited. I have since started rebuilding some of the sleds i used to have and I wanted to take advantage of the larger table top. The crosscut sled I am working on is 40” wide by 28” deep which after attaching a 1.5” front and back fence will allow me to crosscut a 25” wide panel. It is made of 3/4” baltic birch. MY ISSUE IS THE RUNNERS BINDING. I tried several different products thinking i’d return what i didn’t use in the end. Here is what I have tried so far:

1) 2 x Kreg 30” aluminum miter bars. I followed the instructions and set them to the width of the slots after elevating them to the level they would be when they are attached to the sled (with spacers). They rode fine in the slots individually. I then used CA glue and laid the plywood on top and let it dry. Flipped it over and ran the supplied wood screws in through the runners and into the plywood. I tried it on the sawstop and it binds. If i remove the front (farthest away from the sled operator) 2 screws on both runners, it doesnt bind as bad but still not as good as i would expect it to run. I thought that maybe the tapered head screws were slightly moving the runners as i attached them (even though i pre-drilled with a vix bit) so i went onto step 2 to see if it would help.

2) Incra Steel Miter Slider SE 25.5”
https://www.amazon.com/INCRA-IMS2SE-Slider-25-5-Inch-Special/dp/B002GU68DA
These things are stupid expensive but the reason i decided to try them was because my incra miter gauge uses a shorter version of this and it works well on this saw. Also I thought I’d be able to avoid the possible “taper screw issue” from the kreg runners by attaching these from the top using a slightly oversized hole in the sled and a flat bottomed machine screw. This test didnt even get off the ground. I was unable to get the runners to even slide in the slots by themselves. These runners have 3 points of contact with the miter slots. I’d get 2 of them in and moving nicely but as soon as the 3rd one would begin to enter the miter slot, the black (fixed) nylon disc would immediately bind. I was unable to get even the runner by itself to run nicely. On to my 3rd try.

3) Microjig Zeroplay runners. 4 total since they are not very long.
http://www.microjig.com/products/zeroplay/
I figured that this product would be good because you can get them all in the slots and then run in the machine screws from the top and since they are supported in the slots, you shouldnt have any trouble when them moving as you attach them. I’ve used these in the past (different saw) and they worked well for me. Here again, i followed the instructions getting them setup in the slot. I even tested each one individually on a scrap piece of wood. They were kind of finicky. When you attach them to a sled, they expand very slightly (.002 or so according to the instructions) so there was some trial and error getting them set properly to where they would run individually on this test piece of plywood – so they would run smoothly but without any play. I put them in the slots and attached them to my larger piece of plywood (what would be the sled) through counterbored and oversized holes. I did not overtighten them. The sled ran like crap. It would bind up on me. Not to the point where it couldnt be moved but way too tight for a crosscut sled.

I have done everything I can think of to test my miter slots which includes checking the width with calipers (they seem pretty consistent down the length), feeling for burrs, cleaning out any visible debris. To check if the slots are parallel i used my incra miter gauge and adjusted the fence so that it was lined up with the right slot (with the runner in the left slot) and just ran it down the depth of the table looking for it to move closer or farther away from the slot. It seems like they are parallel but i did not test with a dial indicator or anything. I kind of figured that there were some thick spots in the miter slots that i’d have to sand down but i cant detect them with my calipers.

I have avoided using hardwood runners just because I dont want to deal with humidity issues. I am hoping for a 1 and done solution. I would’ve thought at least one of these products would’ve worked for me but i’m beginning to think the issue isnt with the runners but the saw. Problem is, with the tests i’ve done i cant figure out what that problem might be.

I called sawstop thinking they may have tackled an issue like this in the past. The tech more or less told me that the miter slots are rated to run their miter gauge which means that they are good for a miter bar of up to whatever it is – 13” maybe? He recommended that i take my sled to my local sawstop dealer and ask to try it on their demo PCS. I thought about that and I’m sure that the miter slots will vary in width between 2 different saws and I didnt want to be sitting there micro-adjusting individual runners in the middle of the store.

I’m getting seriously frustrated after having spent many hours working on this. I obviously need working miter slots to do anything more than ripping with this saw so i’m hoping for a positive outcome. If anybody has any ideas or suggestions i’d love to hear them. Thank you for reading.


27 replies so far

View papadan's profile

papadan

3584 posts in 3204 days


#1 posted 05-01-2017 04:24 PM

If the first try only binds in the back end of the track, there has to be some problem with the track. Have you checked the straightness of the new rails. You mentioned making wood rails, use some of you Baltic birch ply and don’t worry about moisture changing them.

View JakeK's profile

JakeK

42 posts in 516 days


#2 posted 05-01-2017 04:27 PM

Thanks for replying. I checked them using a veritas straightedge and to my eye they look pretty straight. They did run in the slot fine when not attached to anything.

View diverlloyd's profile

diverlloyd

2331 posts in 1693 days


#3 posted 05-01-2017 04:57 PM

Try wood runners. But it sounds like one runner is off and not running parallel causing the whole thing to bind. The good thing about wood runners is if it binds it leaves a mark on the runner then you can plane it or sand it until it slides good.

View JakeK's profile

JakeK

42 posts in 516 days


#4 posted 05-01-2017 06:55 PM

I might try wood runners as a last resort but doesnt it seem like something else must be up if 3 different products have a similar end result? I cant be the only guy trying to use non-wood runners. The last time i used them they ended up binding with the humidity. I sanded it down and it worked great. later on they were too loose. This is what i’m trying to avoid.

View builtinbkyn's profile

builtinbkyn

1921 posts in 776 days


#5 posted 05-01-2017 07:08 PM

Have you looked at the cheaper Incra Miter Slider bars?

I understand your frustration, but there must be a simple answer to this that you’re overlooking unless the two slots are not parallel. That would obviously cause this to occur. But it’s also very unlikely unless the top was poorly machined.

Try removing one bar and see how it runs. Then do the other. That may reveal something.

-- Bill, Yo!......in Brooklyn & Steel City :)

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JakeK

42 posts in 516 days


#6 posted 05-01-2017 07:13 PM

Yep i looked at them. I’m not sure i can bring myself to purchase a 4th option. There cant be something wrong with all 3 of the items i already have. I wish i knew some woodworkers in the area. It’d be nice to get a 2nd set of eyes on this. I’ve made sleds before. I cant imagine i’m doing something too stupid.

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MrUnix

5990 posts in 2034 days


#7 posted 05-01-2017 07:30 PM

Have you tried applying a little wax to the runners/miter slots?

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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JakeK

42 posts in 516 days


#8 posted 05-01-2017 07:32 PM

No, honestly i havent. This seems like way too much binding to be solved with wax, but then again, i could be wrong. Thanks for the reply.

View builtinbkyn's profile

builtinbkyn

1921 posts in 776 days


#9 posted 05-01-2017 07:55 PM

I know I may be asking an obvious question, but with the Incra slides, did you back the nylon disks off all the way? They have a tapered Allen screw that when tightened expands the nylon washer to the width of the miter slot. Also, what did you use to raise the bars to be slightly elevated above the top? How did you affix them to the bottom of the sled prior to using the bolts? I used some washers to elevate and carpet tape to bond them to the sled to ensure they wouldn’t move when I flipped the assembly over. Also, look at the bars themselves. They should tell you where the binding is occurring. There will be rub marks. Just spitballing ideas. Oh and yes, wax will help, but probably not cure something out of the ordinary.

-- Bill, Yo!......in Brooklyn & Steel City :)

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JakeK

42 posts in 516 days


#10 posted 05-01-2017 08:07 PM

Thanks for replying. Yes, i know they are adjusted with the nylon disks. My process, and i’m not sure it was the right one, was to do one disk at a time. I’d insert the 1st pair from the front of the saw and set them. Push it in a little farther and do the 2nd set. I figured this was necessary because with a deeper sled, there will be times where only 2 disks are engaged and there cant be slop at that point. Anyway, when i got to the 3rd set of disks, it would bind on the black disk (before the 3rd white disk was even introduced).

What i used to elevate the slides varied. For the Kreg i used nickels, for the incras i used dimes (they are thicker than the kreg ones) and for the Microjig i used nickels and dimes stacked.

For attaching them, i tried a few different things. For the Kreg i used CA glue. I tried it on another test piece of plywood with 2 sided tape. For the microjig i used 2 sided tape to line them up on the plywood so i could them drill a through hole in each of the spots where machine screws would eventually attach. I then removed the slides, the 2 sided tape and loosely reattached the runners to the sled. Put the sled into the table saw with the runners in the slots. Then tightened up the machine screws. In my view, the runners being in the slots means they are aligned.

View Rick_M's profile (online now)

Rick_M

10614 posts in 2215 days


#11 posted 05-01-2017 08:39 PM

It almost seems like each set of runners had different problems although 1 & 3 were similar. That suggests a defective product or user problem but slides aren’t rocket science and you are probably doing it right. If they slide but get progressively more difficult until they will not slide (my interpretation of what you mean by binding) then something isn’t parallel to something else and it wouldn’t have to be off very much to cause a problem.

I think your next step should be to double check the miter slots on the saw. You can use a tape measure, if they are off it should be fairly obvious. Next do the same to the runners on your sled. You could also build a mini-sled with 6” runners, just to see if you can make it slide.

-- http://thewoodknack.blogspot.com/

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JakeK

42 posts in 516 days


#12 posted 05-01-2017 08:47 PM

Yeah, that’s pretty much why i’m super confused right now. I thought for sure my slots had high spots or something but i’m not able to see it with calipers.

What i mean by binding is that they slide very hard but i can get it through from front to back. Definitely way too hard to A) be solved by wax and B) make the sled usable as it is.

I cant think of a really accurate way to test the slots being parallel. Like i said, i tried eyeballing by using my miter gauge and it seemed ok. One thing i can say is that when i set my blade to right miter slot alignment with my starrett combination square, i was able to get the same blade tooth to scrape and pass the end of the square. When i did the same test in the left miter slot, it would scrape on the front of the saw (towards the user) and hit-and-stop at the rear of the saw. This made me think that maybe my miter slots arent parallel but then again you’d be trusting your blade to tell you that.

For the 6” test, i have removed both rear (2 of the 4) microjig runners and the sled does run more freely – i’d describe it as borderline. This isnt a solution obviously but I figured it was just due to there being less surface area in the slot.

View JBrow's profile

JBrow

1273 posts in 755 days


#13 posted 05-02-2017 01:21 AM

JakeK,

I simple jig might confirm that the mitre slots are milled equidistant from each other along their length or reveal that there is a problem.

The jig I have in mind is a pair of straight measuring sticks milled ¾” square and with a length that equals about ¾ the distance between the mitre slots. A washer is secured at one end of each measuring stick, positioned so that the washer overhangs the face of the measuring stick. The washer would then fit into the mitre slot without bottoming out in the mitre slot when the measuring stick rests flat on the table saw surface.

The washer of one measuring stick is placed into and butted up against the right mitre slot’s edge. The other measuring stick is similarly placed, but the washer of the second measuring stick is in the left mitre slot. The two measuring sticks are slid together (side by side) while the washer of each measuring stick is held against the edge of the mitre slot. A witness mark can be drawn across both measured sticks. If the mitre slots are parallel, the witness mark should stay aligned as additionally places along the length of the mitre slots are checked.

If a short block is attached to the top of each measuring sticks, a set of calipers could be used in lieu of the witness mark to measure how far out of parallel the mitre slots are.

Since I suspect this description may be confusing, I include a couple of sketches to show that which I attempt to describe.

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Rick_M

10614 posts in 2215 days


#14 posted 05-02-2017 01:48 AM

That’s a really good design jbrow. I feel like the miter slots being out of parallel is a long shot but it’s worth checking.

-- http://thewoodknack.blogspot.com/

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JakeK

42 posts in 516 days


#15 posted 05-02-2017 05:03 AM

Jbrow, thanks for taking the time to come up with that solution and make drawings. It is a very interesting idea. The one possible flaw I see is that if they are not slid forward perfectly in line you will get false readings. I suppose i could pair a combination square along with this to help keep it consistent. I will give it a shot. Thanks again.

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