Frustrated cutting consistently sized pieces.

[Anthony Scott]

I spent the weekend trying to build what I thought would be a fairly simple storage project. It is essentially a rectangular case 30" x 12.5" deep and 15"wide with a couple of dividers. The joinery is either rabbet or dado, all made of 3/4" MDF. Something like this, but this isn't the exact plan:
http://www.woodstore.net/alsancab.html

I rough cut the pieces with my track saw and cut them to final length and width at the table saw.
When I went to dry fit the pieces, some of the dividers were a little to long and protrude from the front by as much as a 1/4"... on ONE side. Argh.... Also, the top and bottoms are not flush (the same width) as the sides.... Argh again....
I checked my table saw to make sure the blade is parallel to the fence, etc. All looks fine there.
I feel like I am missing something with the process of cutting the pieces. There must be a "strategy" with cutting the pieces so they wind up consistent....
What am I missing?
Thanks

[Bob Riefer]

So, to clarify, if you set your fence and make the same cut twice in a row, you'll get two different sized pieces?

[Victor Robinson]

Were you setting and resetting your fence frequently? I've set the wrong measurement many times before - it's easy to be off by a 1/4", especially if you are working quickly.

The key in terms of strategy is to minimize how many times you move the fence. So rip all the identical pieces to width at the same fence setting at once, then crosscut all at once to length using a stop block, and so on. Following that approach you should end up with pieces that are identical.

[glenn bradley]

A little more info will help get better answers. The fact that the dividers protrude "as much as a 1/4"... on ONE side" says you have non-parallel and/or non-perpendicular sides and/or the carcass is grossly out of square. If I had a board 8 feet long that I had ripped to 12-1/2" wide AND it was really 12-1/2" wide along it's entire length, I would:

1- cross cut it (jigsaw, circ-saw, mitersaw) into a few boards of rough length; closer to my end measurement.
2- use my tablesaw and sled to square one end of each board.
3- set a stop bock and using the sled, cut each board to final length.

That being said I have a variety of sleds and can directly crosscut boards approaching 8' directly. The size of board that is reliably workable in your shop will vary with how you are set up. In general, you should not be trying to cut a piece of material to final size if the blank is not comfortably manageable. If you are having to muscle things around, precision suffers. Use stops, sleds and roller stands to make things easy to handle. Use an unchanging setup (fence, stops, whatever) anytime you are doing repeat sizes. HTH.

[Anthony Scott]

I found a pic of the exact project I am trying to build.
I probably did move the fence unnecessarily. That is what I meant when I said I must be missing a strategy. So to summarize... in the plans the sides are both the same length of course, the top and bottom are the same length, and the two dividers are the same (just slightly different depth than the top and bottom to allow for the back).
However, both sides and the top and bottom are all the same depth.
So in order to cut this properly... I would:
1. cut the two sides to length,
2. cut the top, bottom and dividers to length
3. cut the sides, top and bottom to width
4. cut the dividers to width

Thanks

[Andrew Pitonyak]

One of my miter gauges was about 1/4 degree out of square with the table saw blade. I took my piece of wood, and trimmed one end. From here, a couple of things went wrong.



When I placed the "trimmed" end against the saw fence, I was not consistent with respect to which side of the board was against my miter gauge. I should have kept the same edge against the miter gauge for the first cut as the second in case the two edges are not parallel.
When I placed the "trimmed" end against the saw fence, that "trimmed" edge was not square, and the cut was also not square.
Uneven pressure while holding an edge against a fence or stop block.
Piece shifts after pressing against a small stop block while clamping piece in place. I found this to be more problematic with a small stop block (such as a small round piece of metal, such as that found on my Incra cross-cut table. Note that this also is more difficult to get a consistent hold when the end is not square, or if it is small.

[Anthony Scott]

One of my miter gauges was about 1/4 degree out of square with the table saw blade. I took my piece of wood, and trimmed one end. From here, a couple of things went wrong.



When I placed the "trimmed" end against the saw fence, I was not consistent with respect to which side of the board was against my miter gauge. I should have kept the same edge against the miter gauge for the first cut as the second in case the two edges are not parallel.
When I placed the "trimmed" end against the saw fence, that "trimmed" edge was not square, and the cut was also not square.
Uneven pressure while holding an edge against a fence or stop block.
Piece shifts after pressing against a small stop block while clamping piece in place. I found this to be more problematic with a small stop block (such as a small round piece of metal, such as that found on my Incra cross-cut table. Note that this also is more difficult to get a consistent hold when the end is not square, or if it is small.


I could see my issue being related to point number 2. Basically what I did is break down the sheet of MDF to rough size with my Dewalt TrackSaw. I used the table saw to cut them to finished size. For the sides I just used the fence as the guide since they where long. For the rest of the pieces I used my crosscut sled.
So I should ensure one edge is square before going to the table saw?

[Don Jarvie]

My process, which I have been working on, is to cut to width then length. I also group the pieces together so I rip (width) the 2 sides together, then the shelves, etc. Then I crosscut (length) the same groups again.

This ensures the pieces will be the same width since I adjust the fence at the beginning. I use the 1st crosscut piece to measure each subsequent piece. Sometimes the crosscut pieces need to trimmed but only slightly.

By cutting things in groups and marking everything well I have been a bit more efficient and have cut down my mistakes.

Don

[Anthony Scott]

My process, which I have been working on, is to cut to width then length. I also group the pieces together so I rip (width) the 2 sides together, then the shelves, etc. Then I crosscut (length) the same groups again.

This ensures the pieces will be the same width since I adjust the fence at the beginning. I use the 1st crosscut piece to measure each subsequent piece. Sometimes the crosscut pieces need to trimmed but only slightly.

By cutting things in groups and marking everything well I have been a bit more efficient and have cut down my mistakes.

Don


Makes sense. Thanks

[John Coloccia]

I usually cut everything to a rough dimension first. Not only do I get easier to handle pieces, you potentially get a much more accurate cut especially with solid wood (which can warp slightly as you cut it). The added advantage is that I'm not constantly switching up my setup, i.e. cut a piece to size, setup to get a manageable piece out of what's left, then cut that to size, etc. With pieces that are almost the right dimension, I can usually set the fence once and cut EVERYTHING that needs to be exactly the same dimension. For cross cut pieces that have to match a ripped piece, I setup the ripped piece between the fence and the blade, and then slip a subfence between them. Lock the fence, move the subfence back to act as my stop (so you don't cross cut against the fence), and all of those will be spot on too.

So basically, once I cut one piece to a dimension, I constantly use that as a sort of story stick to cut everything else that dimension. It's much easier making everything the same dimension than it is to make everything a specific dimension. That's just how I do it.

[Myk Rian]

I find I get better accuracy using my DeWalt RAS, than I do with the TS.

[Bruce Wrenn]

Any two parts that use the same dimension, I cut before moving the rip fence. I find it almost impossible to return EXACTLY to previous setting.

[Tom Willoughby]

I find that using a feather board to hold the wood against the fence will help keep everything consistent as well.

[glenn bradley]

Lots of good info here. One tip on construction of this type . . For dados in side panels I will use a piece of material that is a bit more than twice as wide as one side is deep. I cut all the dados on this panel and then rip it to final size. This assures that the dados line up perfectly top to bottom. Here's an ugly example of parts bin storage made out of some old siding and other scrap. I cut the dados in 30" wide material and then ripped the 14" deep sides out of it and cut to length.

[Gary Pennington]

As has been said several times, cutting all parts before you move your rip fence is the best method. However. Sooner or later you're going to be well into your project and find you have to replace one part. In my limited experience, a properly set up Incra fence is totally repeatable and a lifesaver to duplicate cut sizes.

Gary

[Kent A Bathurst]

2 things:
1] search for "5-cut method". Likely here, but definitely on The Googles. This is the best way to get the miter gauge/sleds/etc. aligned accurately. That certainly sounds like the most likely culprit in this case.

2] I will usually setup and run all the same dimension cuts at once, but simply for efficiency's sake. If I have to come back to that dimension again, it bothers me not in the least. Biesemeyer on Uni. I'm pretty confident that I can get within 1/128" [probably less]every time - it's just lining up the cursor on the lense with the rule on the rail. Fence needs to be properly adjusted, of course.

[Jerome Hanby]

Building my daughter's doll house was my first major project. I was so paranoid about getting all the parts matched that I spent way more time building templates than building bed parts. The whole structure is made from MDF. It may not have turned out exactly to the dimensions the plans called for, but every piece that was supposed to be identical was identical. Except for the rear panel and the right angle formed by the back and bottoms of the sides, I don't think any edge was cut with a saw, I routed everything.

Since the router works so well on MDF (especially if you like yellow flour) that's the approach I'd use. Of course, after making all that yellow flour, MDF wouldn't be my first choice for any project these days...

[Jerome Hanby]

Unless you are just that good or have an exact way to repeat your settings (like an Incra fence system), never change a setting if you can possibly help it until everything that needs that size cut is finished. If you have to change and go back, I'd use a previously cut piece to set the fence. It'll probably still come off a bit proud, but you can give the fence a little bump and run it through again...


I found a pic of the exact project I am trying to build.
I probably did move the fence unnecessarily. That is what I meant when I said I must be missing a strategy. So to summarize... in the plans the sides are both the same length of course, the top and bottom are the same length, and the two dividers are the same (just slightly different depth than the top and bottom to allow for the back).
However, both sides and the top and bottom are all the same depth.
So in order to cut this properly... I would:
1. cut the two sides to length,
2. cut the top, bottom and dividers to length
3. cut the sides, top and bottom to width
4. cut the dividers to width

Thanks

[Andrew Pitonyak]

So I should ensure one edge is square before going to the table saw?
If you run one edge along the fence and that edge is not square, that can be a problem. I wanted to cut a straight line on wood with an edge that was not straight, so, I attached a piece of wood to the top that was straight and ran that along the fence.