Miter bar set screws

[Robin Dobbie]

I've had good luck with my Kreg 30" miter bars. I set them up and they seem to stay adjusted fairly well. I can go out to the shop when it's 40ish and get some work done, or wait until it's 100. In either case, the sleds aren't impossible to use in one extreme or the other.

I wanted to make a new crosscut sled that has 36" of cut capacity, so I tried the Rockler 36-inch miter bars. They're unusable as-is. The set screws are loose, making them pointless, and there aren't even as many on their 36-inch bars as the Kreg put on their 30-inch bars. I noticed the threads are much coarser than the Kreg set screws. I really enjoy the adjustability of the Kreg bars, and I find that even with their very fine TPI set screws(probably 32 TPI), the smallest turn can be the difference between slop and too much resistance. 

I thought I'd look for some set screws like come with the Kreg bars. I found some nylon 6/6 set screws on Amazoozoo for $3. They're white/transparent, the Kreg ones are black. Not sure if that alone is any indication. Looking at the thermal stability of nylon 6/6, it appears that it gains or loses .001" per inch per 10 degrees. I feel like that's kind of a lot. I looked at Kreg's miter bar description, and they say the set screws are nylon, don't specify a type. Maybe I got that thermal expansion wrong, I'm terrible at math. 

Then again, maybe I should try and fix the included set screws and just hope for the best. My first thought for making them tighter was maybe take a cigarette lighter to a paper clip and try to mess up of one of the threads a little bit by melting one of the last threads to engage. My second thought is taking some sticky ant/bug guard and dabbing some on the threads. If that doesn't work, I can at least clean it off. 

I really want a sliding table saw, I tell you hwhat.

[Chuck 80]

I've had good luck with my Kreg 30" miter bars. I set them up and they seem to stay adjusted fairly well. I can go out to the shop when it's 40ish and get some work done, or wait until it's 100. In either case, the sleds aren't impossible to use in one extreme or the other.

I wanted to make a new crosscut sled that has 36" of cut capacity, so I tried the Rockler 36-inch miter bars. They're unusable as-is. The set screws are loose, making them pointless, and there aren't even as many on their 36-inch bars as the Kreg put on their 30-inch bars. I noticed the threads are much coarser than the Kreg set screws. I really enjoy the adjustability of the Kreg bars, and I find that even with their very fine TPI set screws(probably 32 TPI), the smallest turn can be the difference between slop and too much resistance. 

I thought I'd look for some set screws like come with the Kreg bars. I found some nylon 6/6 set screws on Amazoozoo for $3. They're white/transparent, the Kreg ones are black. Not sure if that alone is any indication. Looking at the thermal stability of nylon 6/6, it appears that it gains or loses .001" per inch per 10 degrees. I feel like that's kind of a lot. I looked at Kreg's miter bar description, and they say the set screws are nylon, don't specify a type. Maybe I got that thermal expansion wrong, I'm terrible at math. 

Then again, maybe I should try and fix the included set screws and just hope for the best. My first thought for making them tighter was maybe take a cigarette lighter to a paper clip and try to mess up of one of the threads a little bit by melting one of the last threads to engage. My second thought is taking some sticky ant/bug guard and dabbing some on the threads. If that doesn't work, I can at least clean it off. 

I really want a sliding table saw, I tell you hwhat.

If the Rockler bars are not useable send them back and tell them why. They are good about returns

[Robin Dobbie]

If the Rockler bars are not useable send them back and tell them why. They are good about returns

Any ideas on alternate 36" aluminum miter bars? Or longer? I found some 8-foot aluminum 3/4 x 3/8 bar on Amazoo for $25 and free shipping. I have no idea how. And, who knows how straight that would end up being. 

I wanna try and use these if I can.

[Robin Dobbie]

The melty thing worked, at least on the first one I tried. Now I suppose they're not returnable. But hey if they work now, then that's dandy.

[Cooler]

That cut would be so easy with a track saw. 

Even a well-made circular saw guide and careful attention to technique would be simpler. 

The 36" miter guide sounds a lot like "trying to get a race horse to run on his hind legs".  You can probably make it happen, but it is never going to be efficient or elegant or easy.  And it might end up costing as much as a track saw. (That last point is not likely.)

[bennybmn]

Wrapping the threads with something like teflon tape could work. Or maybe dental floss or something? Just to make the fit more snug. Or find a gap-filling thread locker. Or maybe hit the screw with some hot glue and screw it in while it's still hot? Just spitballing...

You could drill and tap whatever size you want for some extra screws also. Whatever nylon the Kreg ones are made of, I doubt it's much different if any different.

[Robin Dobbie]

I'm still surprised the Kreg ones work in the temperature extremes. I took a nylon bolt and popped it in the freezer for a few minutes then pulled it out and measured it. It was definitely shorter. Measured it again after warming up and it was back to its original length. Put it back in the freezer, then stuck it in the calipers and left it there. I could watch the rate of expansion increase while I was blowing on it to warm it up more quickly. I don't know what the freezer temperature is, and I don't know what the temperature of the bolt was when I tested it, but the rate of expansion scaled down to 3/4" would theoretically be enough to grind the sled to a halt, it just never did.

As far as the size of the sled, it's probably too large. A track saw would be nice. I need to make a new base for my circular saw. It belonged to my gramps and it's seen its share of drops, so there's some warpage. And it's probably not aligned, and there's probably some runout. I went out and bought a new circular saw for like a hundred bucks or something like that, but it wasn't aligned either, nor was there a way to align it. Probably have to spend a bit more money to get one that's fixable.