# Rookie help on a sled.



## MarkTheFiddler (May 29, 2012)

I built a sled. The very first thing I did was make sure that the plywood would slide in the metal tracks without any wooble or grabbing.










I gound down my bolts and tried again - tested good
I attached the front rail - tested good
Back rail - good
side rails - good
etc. - good

I tell you - I had this thing licked.
I made the cut. Now it it has a wooble and it grabs. The blade is not the culprit. It's not touching any part of the sled.

Where did I go wrong? 
So far I think my biggest sin was using a piece of under layment that was slightly warped. All of the rails I used were true.

Should I take it apart and build another one or can I fix it?

I "think" I can fix it for my current project and potentially others by adding an additional board to the front of the front rail. I'm going offset it high enough so I won't have to cut into it for my current project. I'll clamp it well and test over and over again for grabbing and wobble. If the the sled stops grabbing, I'll screw it into place.

If it get's me through this project, "accurately", I can then build another and use those lessons to do a better job on the next.

For now - ignore that other bit of nonsense with the clamp. I was experimenting with a jig. That part is coming off.

Please tell me what else you see. Or need to see.

By the way, I sprayed the surfaces with silcone. It doesn't seem to be a good idea. Do you have better options?

Thanks for everything,
Mark


----------



## Sawkerf (Dec 31, 2009)

…..using a piece of under layment that was slightly warped.

Almost certainly the culprit.


----------



## jmos (Nov 30, 2011)

Mark, I'm assuming this is a crosscut sled?

If everything was moving smoothly before you cut the kerf, it must be that the front and rear rails are not holding everything in place. It looks to me like you front rail (can't see the back rail well) are too thin and are not rigid enough to hold everything in line. Most sleds I've seen have at least 2 layers of 3/4" material for the front fence, and a rear of about 1". I used three plys of 3/4 plywood for my front and 2 layers for the rear.

I can't tell how high your rails are either; most led designs I've seen are about 4" (or a little better) high where the blade will cut through, and about 2" to 2.5" otherwise.

William Ng has a nice sled build video, with dimensions for the sled, here 




I'm not sure why you have side rails, most don't.


----------



## superstretch (Jan 10, 2011)

Humidity change? The wood might have swelled.


----------



## CharlieM1958 (Nov 7, 2006)

Does it wobble even if you don't try to push at the same time? You really need good quality, flat plywood for a sled. If it isn't flat, you'll have a problem.

And for future reference, just use paste wax on the bottom and on the runners. Works like a charm.


----------



## sixstring (Apr 4, 2012)

The base looks awfully thin. Not sure how tall of a cut you generally need to make but using 1/2" or 3/4" would work best and you'll want the straightest, stiffest piece you can find… MDF or hardwood. Mine's 5/8" melamine and it slides great on the table. For rails, I initially made t-tracks using maple but it hung up quite a bit so I switched to plain old snug fitting rails and it works flawlessly with no wobble. I'd prefer to use metal rails so I'll do that eventually.


----------



## MarkTheFiddler (May 29, 2012)

I got several votes for changing out the base. One for reinforcing the front with thicker wood. You all are telling me what I didn't want to hear. That's quite alright because I needed to hear it.

Tonight, I try one last time to make it work for my current project. If I can't get what I need out of it - firewood. I'll rebuild this weekend. If I can make it work "WELL" for my current project, I can wait to see if I find some good base material for Free. That's my favorite price. That's also the reason I used that thin underlayment. I will eventually learn my lesson.

Strange that I would have gotten better results from MDF and 2X4s. Although, I promise NOT to use either.

I apparently did one thing right. I used metal tracks. I was hoping to find tracks that were exactly like the track for the miter slide. They don't sell them where I looked. Still - I think the ones I used are good enough IF I put them on a stable base.


----------



## sixstring (Apr 4, 2012)

I have melamine and 2×4s on my smaller sled. Nothing wrong with that setup at all. I built it to see how well it works and I still use it. Sanded my maple rails down to a glass polish and they work like a charm. Google or search thru this forum for all sorts of good ideas and tricks.

If you must use a thinner base, build it in 2 pieces, one for each rail. Then attach them with fences. I think building it first then cutting the kerf is causing your troubles. Less of a big deal with thicker material (I would assume.) Got the idea for building each side seperately from either This Old House or some woodworking magazine, I forget now.

And I agree, free is the optimal price. Craigslist free section is your friend. Cabinet shops toss out tons of perfect material too so give one a call.


----------



## MarkTheFiddler (May 29, 2012)

Ty for the info. Fyi - i got a good look at the base. It is bowed from front to back. I'm definitely going to rebuild with a thicker base.

What is the kerf? Is it the base or is it the cut in the base.

Bottom line: Thanks for all the advice. I will be building a much better sled now.


----------



## jmos (Nov 30, 2011)

The kerf is the material removed by a saw blade. In the case of the sled the kerf is exactly the width of the blade (zero clearance) which helps support the wood fibers during the cut and reduces chipping and torn out fibers. So, if you use full kerf and thin kerf blades, you would want to avoid using the same sled for both, as you'll get more ragged cuts with the thin kerf blade if the kerf in the sled is full width.


----------



## lumberjoe (Mar 30, 2012)

There are a lot of good tips in here:
http://lumberjocks.com/lumberjoe/blog/30606


----------



## BillWhite (Jul 23, 2007)

And DON'T use any silicone. Bad stuff for any finishes it contaminates.
Good luck on the new sled.
Bill


----------



## Bsmith (Feb 2, 2011)

Ditto on the William Ng video. I just finished mine following most of his instructions. Very easy to understand and follow. Now I have a sled with less than 1000th variance.


----------



## MarkTheFiddler (May 29, 2012)

Thanks to everyone! You all are awesome,

After reviewing your diagnosis and suggestions. I have come to a conclusion - the only thing I did correctly was use some maple (in the wrong place).

Earlier, I very confidently stated that the only part I did right was use metal for the tracks or rails. That's fine and good but the rails are too small both depth and widthwise. I believe that was my final piece of denial that I had built a lousy tray for a hotdog vendor.

The good news is that I used left over materials and I'm out of pocket for a few bolts and nuts.

I also laid out some decent pretty cash for bits that would drill holes and countersinks in my metal tracks. I can't complain too much because now I have what I feel is my best set of bits. Kobalt, titanium quickchange. (Unfortunately - I wasn't as sensitive to the made in China philosophy here at LumberJocks. I understand your valid points and I'll buy USA as often as humanly possible.)

After following a few suggested links in this post and using your information, I know that I will need to make new tracks from maple. I know how to set them just right. I know how to set the front and back correctly. I know how I'm going to prevent cracking. I know what materials to use for the base. I understand what a kerf is and how important it is to get it right. I know how to lubricate the thing.

Do I know everything I should know about this? Heck no. As a matter of a fact, my second crosscut sled will be good only for crosscuts up to a 2×4 depth. I'm going to keep it simple enough so I can do a good job with it and get it set for the project in my blog. I'll learn about the bells and whistles (I suppose you can say built-in adjustable jigs) as I need them and put them on my third iteration.

And now a quick confession - I try to figure things out on my own. When I "think" I have the picture, I go with it. I think that is my main issue with woodworking. I suppose I learn better from my failures because then I am real open minded about finding the resources and following them. It's not a good excuse though, It just more or less guarantees that I will ruin everything on my first attempt. One of you has a really cool signature that says "Woodworking - Patience = Firewood". I get it. I hope I can change.


----------



## sixstring (Apr 4, 2012)

Hey man, I just recently started woodworking myself. Still consider myself kind of a hack but I'll say this… nothing teaches a good lesson like failure. It's ok to fail and it's how you pick yourself up and keep going that makes you who you are. Just wanting to build something instead of buying it makes you a better man than lots of numbskulls out there so keep it up.

I used to (still do really) spend too much time thinking and analyzing my design and technique. It occurred to me recently that I'm wasting time. Just do it and learn from your mistake and go from there (unless you are working with expensive material.) I'm limiting myself to mostly free finds on craigslist so I've got tons of douglas fir beams that I've been practicing on. I just love milling the giant beams down to my projects requirements… Something about taking garbage and turning it into functional pieces that keeps me going.


----------



## CharlieM1958 (Nov 7, 2006)

Hey, I'm the guy with that signature you like…. and I do the trial and error method all the time. Learning from your mistakes teaches you a lot!

One other comment…. you mentioned that your runners were too shallow. Better a little shallow than too deep. You only need the runners for directional guidance. The base of the sled should be in full contact with the table.


----------



## lumberjoe (Mar 30, 2012)

I made my runners shallow on purpose. Any saw dust you get in them will affect the height. With a miter gauge you aren't REALLY worried about height, with a sled, it's a big deal. You want to make sure there is enough runner in the miter slot, but I wouldn't want them touching the bottom


----------



## MarkTheFiddler (May 29, 2012)

Thanks for the kind thoughts and the runner tips!


----------



## lumberjoe (Mar 30, 2012)

The tips on mounting them that Charles posted in my blog were awesome. I have never made a sled before and am still fairly green when it comes to woodworking, and I got them absolutely perfect on the first shot.


----------



## MarkTheFiddler (May 29, 2012)

I watched the entire YouTube video. I feel like I'm working with a rusty nail and stock compared to his setup. I am suffering from workshop envy. Fantastic how-to. TY for the recommendation.


----------



## MarkTheFiddler (May 29, 2012)

LJs,

I built my sled out of MDF. It's my first so I get to learn from my mistakes. Again, I'll make a nice one from birch plywood later.

Here is what I got. Tracks that don't jiggle. Smooth action. Nice fit. As 90 degree an angle as I can tell since I don't have micrometer equipment (yet). What I did was 4 cuts and checked the angle of the 1st and 4th cuts against my rafter square. It is less that 1/64th off as near as I can tell. And then you divide that by 4, then the length of the pivot point to the end of the rear board. That little difference just isn't going to have any impact on the project I built the sled for because I'm only making cuts through 1/8" thickness of wood.

THANK YOU THANK YOU THANK YOU. I'll post a little picture after I put the guards on.

Now I get to have a great time using it this weekend.


----------



## lumberjoe (Mar 30, 2012)

Mark, a 64th on a rafter square is a little out of the acceptable range for me, as rafter squares can be a little off anyway (they are made for rough framing). If it was a machinists square, I'd be a little more comfortable. Try this method, it's really easy:

http://www.thewoodshop.20m.com/fivecutmethod_swf.htm

You can get a set of calipers for practically nothing from harbor frieght or any local hardware store. You don't need really expensive ones for wood. You can easily find something for under 10$

Congrats on finishing it! As John Nixon told me when I sent him some pics of mine that were built roughly from his design, a cross cut sled is a woodworkers right of passage. I can't wait to see some pictures


----------



## MarkTheFiddler (May 29, 2012)

Thanks Joe - I posted a long reply. I even attempted some humor. It might have been a good read but now it's gone.

Essentially - You are oh so right. I'm going to give myself a pass on having perfect calibration because my table saw is a $100 harbor freight special. I have "rationalized" my decision that way. I suppose it makes me feel better about taking the shortcut.

My rite of Passage" will wait a little longer till I save up the money for a decent tablesaw. I'm thinking $500 and Craigslist will produce a good upgrade for this humble hobbyist.

By the way, I studied all the awesome resources really well. You all have made it possible for a hack like me to make a precise and sturdy sled. I even remembered the formula and method for setting the back wall with the 5 cut method.

Ouch - the post is getting long again. Have a great weekend all.


----------



## lumberjoe (Mar 30, 2012)

500$ will get you a BRAND new R4512 at home depot! Amazing saw, I love it. Let's see the pictures!


----------



## MarkTheFiddler (May 29, 2012)

Ok - I will post a picture of my humble sled. - I certainly owe you all that much.

In the meantime, you can take a peek at my one and only blog to see what the sled is helping me to make. I really know why I was in such a hurry to get the sled done. It was so I could start my wall art project. Now I'm having a blast!


----------



## MarkTheFiddler (May 29, 2012)

Sorry - no picture of the sled yet. Today, I attempted to calibrate it well. You just can't calibrate with OSB . I'm just going to have to find another hunk of decent wood that does not have all those little ridges to throw of your measurements. I'm losing .0003 every inch. As I understand it, the tolerance should be .001 per foot or less.

It's better than when I started at .0027 per inch. A lot better I would say.


----------



## MarkTheFiddler (May 29, 2012)

By the way, I bought some paste wax as well. That thing practically moves by itself. I can push it with one finger. Thanks for the tip.


----------



## MarkTheFiddler (May 29, 2012)

I DID IT. My sled drifts along the 23 inch back board by 0.0014375 inches. Don't ask how I got that lucky but it's there.

I just measured a sheet of legal paper. It's rounded to .0025 inches thick. My sled is off by less than a sheet of paper. That means I loose an inch every 4.5 football fields. I'm going to call that good! Yeee Haaaaa!!!!

I never considered that I could ever get anything that accurate. You all are awesome. Thank you soooo much.


----------

