I’ve just built my first crosscut sled and I’m in the process of aligning the back fence for square 90 degree cuts. I have made many adjustments and I’m about 1/16th of an inch from a true square cut. Should I keep trying for absolute perfection or am I close enough? How square are your cuts on your crosscut sleds?
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Replies
go for absolute perfection, 1/16 off true square is a lot, as errors can easily add up.
-pjw
1/16th of an inch is huge, IMHO. Look at this thread for a test for your cuts (shown on miter saw, works on table saw of course). Pictures 3 and 4.
As mentioned above, it's the cumulative effects of an error that come back to bite you. I just finished two hanging shelf/cupboard units that were about 9" deep. If the 90° cuts on the shelves and door had been 1/16" off, it would have been a nightmare.
Well, I had an interesting experience today. I am building a bathroom cabinet - using 3/4" birch for the sides. I went ahead and made my cuts for the sides, laid one on top of the other and guess what? Not square, nor do they match!!
Boy howdy was I shocked!! I had just tuned up my equipment about 3 months ago and have only made one set of cabinets and pool cue holder - so not much work, or so I thought!
(Hard) Lesson Learned - prior to starting a project check you equipment for alignment. It only takes a few minutes and will save you much heartache, time and money.
dlb
p.s. the saw fense was out of alignment by 1/32".The undisciplined life is not worth examining.
When I make a cross cut sled I screw on the back fence. cut 3/4 of the way through the sled and align the fence with the saw curf using a framing square (check it first!) attach with screws DONT use glue!!! on the front fence as you may need to ajust this at some point! also see http://www.taunton.com/finewoodworking/Workshop/WorkshopPDF.aspx?id=2511
or http://www.taunton.com/finewoodworking/SkillsAndTechniques/SkillsAndTechniquesPDF.aspx?id=27684
Chaim
1/16" off isn't even close!
Take as long as it takes to get it as "dead-on" as possible. Anything less will haunt you for as long as you use that sled.
One method that works for me is to lay out a right triangle using the 3-4-5 method. Draw a line then attach your fence exactly on the line. You should be as close to "dead-on" as is humanly possible.
Final Report:I’ve adjusted and drilled the rear support of my crosscut sled more times than I can count. My final test on a 14 inch wide piece of wood is 1/64th of an inch from being perfectly square. I can’t get it any better than that. Maybe the back support is not perfectly flat. With the variables involved with wood, I have a lot of trouble believing anybody has achieved caliper type perfection on a homemade crosscut sled.
Woodman,
Yup, and you can get that 1/64th with few swipes on a shooting board with a sharp plane. Works for me anyway.
Regards,
Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Edited 7/30/2007 1:35 pm ET by KiddervilleAcres
Woodman, I, too, just built a cross-cut sled and it's definitely not as easy I thought it would be nor as time consuming. Norm "throws" one together in what looks to be no more than 15 minues and it appears as though he's not being precise, yet the outcome is dead-on.
The problem I'm having is that with the stock riding in the miter slot and extending out about 7" past the back of the sled, the sled shifts slightly (left to right) as the front of the sled extends into my outfeed table due to the stock being so thin and narrow. I used hard maple for both the miter slot and the fence but the miter slot stock has some flexibility. I extended it 7" to help give some rididity to the sled as it's pushed through the blade. Is there a way around this? Thanks.
After 3 attempts I gave up on making my own sliders for the miter slots. I did a good job but they never were as perfect as they needed to be, and because they were wood, they would never maintain their shape. I ordered adjustable metal sliders. As for Norm “throwing one together in 15 minutes”, I suspect the final product that comes from his crosscut sled would not measure perfectly on both sides using a caliper. But that gets back to the basic difference between wood and metal. Metal can be machined to fine tolerances and will maintain it’s shape, but wood requires an artist who knows how to make imperfection into perfection. In the end I think all wood projects require some sanding, grinding, or scrapping to make all parts fit properly, but we never see Norm do those kinds of things.
Be careful about "Norm". What you see on TV is mostly the "finished" product. You have no idea how much time was spent "off" camera or how many craftsmen were involved.Ray
Masking tape shim, replace as it wears out.
You're right on with the MASKING TAPE suggestion.
Woodman,There have been many, many discussions of crosscut sled construction here.Try this thread:http://forums.taunton.com/fw-knots/messages?msg=30255.1It will take you a few minutes to read through it. There are several contributors. You'll find my description of a sled that is self-aligning and has zero "slop" between the wood runners and the saw table's miter slots, despite changes in humidity. I also give the reference for the Taunton publication on Table saw jigs from which I based my design.In message 28, I describe an easy, general "machine-shop" technique for aligning the sled (or anything else) square and true to a degree of precision far better than even a precision square can produce. For woodworking purposes, the amount of error it produces is negligible. A 12" cut would not have more than .010" (1/100") start to finish, and .005" is easily possible and repeatable.These methods are not difficult. They only require some patience and reasonable craftsmanship.Good luck,Rich
Dear woodman,I'm not sure what you mean by "caliper" accuracy, but it is possible to quickly build a fence that is accurate to a few thousandths of an inch over the length (depth) of your saw fence and have fun doing so. The requirement of course is that the fence and the blade are aligned, each to the equivalent accuracy. Unlike most of the tutorials, which suggest trial and adjustment by inspection of cut stock, it is useful to first use a dial indicator and fixture aids in measuring and adjusting each of the two items, saw blade and fence. A dial indicator and a fixture that allows the dial to travel in the miter slot and measure the 'run out' or variance from parallel and then adjust the saw blade and fence are essential. I recently installed a Biesemeyer fence on my old table saw. I found a number of problems getting the fence to make parallel and then stay parallel when locking down, but it is doable to better than +/- .002" over the 27" run of the miter slot in my saw. Several of my 10" saw blades are just a little better, several are worse. I made a steel fixture to fit up on the arbor and run the span of the table to measure and adjust the arbor angle. There are similar parts you can buy to tune up the blade. All of my circular saw blades, and I have developed a true lust for the very best saw blades (...in sickness and in health, for richer or for poorer, but not the other stuff...), benefit from high quality supports and zero clearance inserts. One good thing is that when two components are both within the same variance and not suffering from some systematic offset, the variances, being Gaussian, will tend to average. Many such components can stack up and result in an assembly with a smaller distribution from the mean than any one component. One part is thicker, one is thinner, so stuff can get better, tighter, when the variances stack up in assembly! The most important two things for the accurate cross cut sled are the runners in the miter slots and the use of the fence and rear apron edge of the saw table to get the assembly 'dead parallel' over the throw of it's travel and square to the cut line. With all the discussion of moisture effects on wood, I'm surprised to see anyone heroic enough to make these out of wood, quarter swan oak or no and suffer with the result, no doubt some kind of cumulative trauma or another at work here! Not so long ago, as I was making miter sleds, someone on this blog suggested to just buy some high quality aluminum miter slides. He said, come back in five years and they will be as true as you made them to the sled on day one, with a little care. That was right-on. I got many very useful tips. Make them long enough so that the whole of the miter slot is filled with slider over the cut length of the sled. This way the angular guidance will be constant as you cut and will not be degraded by shortening of the length of the guides in the slot during the cut. They are going to 'stick out' but it's a good thing! The advice to make a smaller sled first time is also very good.I've had the best result with a hard coated, exterior, fine grade ~ 1/2" plywood, such as phenolic coated Finnish or Baltic plywood. MDF is a second best, and when sealed and finished with a lubricating finish is a value for the cost. But this two or three square feet of plywood is no place to scrape out a few bucks of cost or force 'scrap' into service. If you want to go big time, use a high grade of solid phenolic sheet material. Or laminate a thin sheet of phenolic to the top and/or bottom of the MDF for toughness, low friction, moisture control, temperature stability and durability.Next make the sled sheet a true "parallelepiped". Many tricks can be used here, check the diagonals, etc. Square is one such good shape. Then make sure the part fits on your saw against the clamped fence and has no detectable variance when fit up to the front edge of the saw table. If it does then check the table, it might not be square to the miter slot, but chances are good that the saw table and the miter slot are square (orthogonal). Really, your table and miter slot right angle is as good a reference as ya'all gonn'a get! You might even say, when you 'go to sled with the saw ya' got!. And even if the plate isn't perfect to the table edge, that doesn't impact the parallel translation on the slides to the saw blade. It does impact the squareness of the rear cleat to the translation which is very important but can be adjusted by clamped fit of the rear sled cleat as suggested in one of the pdfs on miter sleds. My preference today is to make the assembly solid and without adjustment as follows.After you adjust and fit the two slides into the miter slots, apply high strength double sided tape on the top of each. Adjust them in tight, but with usefully low friction. Then set one edge of the sled top against the fence and on the table at the desired distance. Lower the other edge slowly until the sled top is firm onto the sliders and attached by the tape. One trick here is to put a half radius on the top of the sled in contact with the fence, so there is no lateral movement as you lower the high edge down. Another trick is to shim up the sliders, but the tape should have provided the clearance you need to rest on the slides and not on the table. No doubt there will be two schools of thought here, one will be the 'full face sled and table contact school', and one will be the 'fly the sled off the saw table top school'. They both have good and bad aspects, but they don't mix. So you decide and shim accordingly. Either you fly the sled or you fly the slides. Once the sled top is firm against the fence and bonded to the slides, press down and then slide the assembly along the fence. If it slides smoothly and freely, tight along the fence without any play, you will have the most accurate and tightest sled possible given your fence to miter slot accuracy. It is likely that the angular play of the assembly in the two miter slots is less than the play of either slider alone and will represent the averaged or smoothed variance of the blade, fence, etc. The result should be tighter(have less angular variance)than any of the individual parts and require no further adjustment so lubrication is important when tight parts are also intended to move in close contact. Move the fence away and use your hands and a dial indicator to check for any change in play or 'stiction' which is the extra friction upon starting and stopping movement. Also, do take seriously all the very good advice regarding the fasteners for the slides and the fore and aft cleats. The tougher the material and the fasteners, glue and screws, the better. I use the highest strength tape adhesive I can find and leave it in while I drill from the bottom and screw from the top. You can drill the holes from the back, take off the tape and then screw on the slides, but my experience is that process always adds back some variance (slop) and perceptable 'bureau drawer shudder'. I also hang my miter sled up and treat the guides with care in fit up and fit down. Another secret I have is I use wax furniture spray and a clean cloth to clean and polish and lubricate the fence, the sled, the slides and even cut stock at times. I like the lemony smell! You can do it. It'll be fun and good sledding.red
Portola Valley CA
What I mean by “caliper” type perfection is using a measuring device that for the most part is used for metal type perfection. In other words, as a younger man I once worked in a machine shop that machined parts to 1/1000 of an inch. Since wood is susceptible to changing conditions (primarily from moisture), I think such perfection is ridiculous in woodworking. I appreciate your tips.
Woodman,
Going back to your comment #10, that is the little secret bout woodworking. Machines are great but cannot deliver the perfection...at least not at the level we can afford so it really comes down to handtools and a good workbench.
Whenever I get in a conversation with students from NBSS, I find it interesting that they all complain about the same issue: sharpening tools...all kinds of tools on all kinds of surfaces...spend half our time..blah,blah. Hmmm...
I beg to differ about "1/1000 in" being "ridiculous". Being as I spent yrs as a Luthier, lemme tell ya..a steel string that measures .008 in thickness, stretched to pitch ( about 300lbs roughly) is a pretty damm straight line, and thee fingerboard/fret interface with that sting is measured with .001's and even .0005.
When "woodworkers" think being as accurate as possible is not important, just shows where they draw the line. And then one wonders about the other lines they may think is not important.
We had a machine operater that had worked at NASA in Huntsville, Al. ( He grew despondant from making "War Machines" in his mind) and boasted.
"At NASA we worked to a .002 inch tolerance"
I told him, 'we are Luthiers, we get it right on"
Yes wood moves, being able to predict it and compensate for that, is what a decent measuring device allows. I'd not want to build anything of musical ambition with out a reference to the smallest standard of measurement that is reasonable for the smallest ingredient that plays a part in the construct.
I had to look up the definition of "Luthier". I guess that means you're smarter than me - you win!
I just recently needed to build another crosscut sled and this time wanted to make something decent that would be more enjoyable to use than the quickies I've done before. I read up on sleds a bit and thought that Gary Rogowski's method of attaching the back fence made the most sense -- it's bolted on and the bolt holes are a little bit oversize. You back off the bolts a touch and make an easy adjustment. If you used a fairly massive piece of hardwood for the fence, you can really tighten down those bolts. The adjustability is great for when you drop the thing.
Screw a small block of wood to the sled, and your fence, with about an 1/8th inch of shims between the fence and the block, out at the far end away from the kerf.
Take out all the screws securing the fence except the one closest to the kerf.
Adjust the angle by adding or removing shims until you get it dead on. Then put some more screws in to hold the fence in place, and lock it true.
Take off the adjustment block if it will be in your way. If it won't leave it there for future adjustments if needed.
Re. Norm: I wouldn't call him sloppy in the construction of the ones he does on the show, rather relaxed. He has probably done dozens at the minimum, and has developed a methodology that works. Most guys see Norm do one, or read about them in a magazine, and make an attempt at one fairly early in their "career", with disastrous results. My first couple were scary, and I had spent a fair bit of time figuring out how to make a good one. I can now build one in about half an hour that is true and stays that way.
I use uhmw poly for the guides, cut to 5/8 or 11/16 wide by 5/16 high, so it is narrower than the slots. I then attach one runner to a piece of plywood and pulling it away from the blade run it through and trim the edge, this leaves it a little proud. I then do the same for the other side. This gives me two base parts that are both proud.
Then using a framing square, ( the use of stair gauges lets you convert it into a good try square), to get close to ninety degrees to the cut edge, I attach a fence and the adjustment block as described above, to the left base. I then push the sled against the inside of the slot and trim it to zero clearance, and adjust the fence.
Now with the sled still on the saw and slid out just until you can get at the bottom you push the other half up against it and screw that side to the fence. One pass to trim it to zero clearance, add the front cross support and your done. It is probably a good idea to add some kind of receiver to keep the blade shrouded.
The idea is to pinch the insides of the two slots with the guides, to keep things parallel.
Please don’t misunderstand my comments. I’m a Norm fan. I would credit him with getting me started in woodworking. I read an article about Norm in which he admitted he also has his bad days like the rest of us. As I recall he said something about putting a piece together backwards. The point I was trying to make is that his show is edited and the entire process looks very simply as he works. I saw the show in which he built a crosscut sled and I don’t recall him using a caliper to check his results. I suspect he did not use such a measuring device because he realizes with wood (unlike metal) it is somewhat useless to be so perfect because wood is constantly expanding and contracting with moisture.
I don't use calipers either, just flip the wood. See how off it is and adjust.
Wood does move, but if you have decent wood, the movement should be pretty consistent across it's width. If one side is a sixteenth longer than the other, it will always be pretty close to a sixteenth longer. It may cup, or twist, but the one side will pretty much be that same sixteenth longer.
Be sure to contact cement a strip of rough sanding belt material to the fence (To avoid 'creeping"
I don’t want to sound like an idiot but what does “creeping” mean?
Slipping of the stock against the fence during a cut. This is not a problem I've ever encountered. It should be handled, if it happens, with clamps, not a glued on strip of abrasive, as that will adversely affect the accuracy, because it will interfere with seating of the stock in a variable way, each time a cut is made.
Woodman,
I get the stock to stay put I use one o' them QuickClamps to hold it against the fence after setting the length with either a stop block or gage block/fence combination. The clamp is quick (as the name implies).
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
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