Mobile Saw Base with Saw Table depth extension

[Poobah]

I've been wanting to build a mobile saw base like a few I've seen in this forum and at the following link.

http://www.raygirling.com/sawtable.htm

However, I also would like to make the depth 28 inch to maximize my Incra rail system. I realize that probably adds a whole bunch of issues to the project, but I would really like to have more depth to work with.

The Incra rails just need to be perpendicular to the saw blade and reasonably in the same plane as the table top. They are adjustable at the fasterners to overcome a little tilt and thus can be made perfectly in line with the table top. But what should I be thinking about in constructing a support to ount the rails on?

Right now I don't have a lot of ideas other than a carcass and with some reinforcement at the mounting holes (maybe an aluminum backing plate of something.

I can currently go up to about 28-1/2 inches depth and am targeting around 28. The torsion box right now is planned for 28 inches by 80-85 inches. Still have to think about the length (I have the 92 inch extended rails).

Could I build torsion box "towers/columns" rising from the base to get the vertical stiffness and straightness I need, and how should I fasten them to the base? Or does this need to be planned out a little better and be integrated into the base?

<edit> Here is my best guess design so far.

https://docs.google.com/leaf?id=0BxAIVkydkv-MMDY2ZTQ4OTQtODlmZC00Y2E3LWJiZTUtYjg3MTc2OTRiMzk4&hl=en&authkey=CLGxzcQM

The BT3100 rails are attached because they provide a convenient way to mount my router table. Unfortunately it's 32x24 and won't fit within the Incra rails unless I buy the wide saw table kit for another $60 or so. Then I could make the base 32 inches deep and get rid of the BT3100 rails altogether (might be a good idea actually). I'd like to keep the router table oriented and located where it is, so I can use the Incra fence more easily. Currently I have it on the far left of the rails and I have to switch the who fence/positioner around any time I switch between router and table saw. That gets old fast.

Still haven't fully figured out what I'll do to extend the saw table top in front of and behind the BT3100. Was thinking some kind of rectangle with a "cutout" for the saw table top.

Appreciate any inputs whatsoever as my woodworking skills are slightly between "stayed at a Holiday Inn last night" and "Egghead with two left hands". But I am learning slowly ... :-)

[twistsol]

If you want to learn from my mistakes, move the wheels in from the ends a bit. I built two 84" x24 torsion boxes about 7 or 8 years ago and both have sagged about, one about 1/4 inch and the other about 3/8. The wheels on mine are at the extreme edges. Try to find a balance between the large span and stability.

I like the rest of the design.

[LCHIEN]

if the incra rails need to be perpendicular to the blade and the BT3 design does not have an adjustable blade (the Rip Fence "T" is adjustable)

Then how are you going to fasten the incra rails to the saw body? If you adjust the Incra rails to be perpendicular to the blade and the INCRA fence is square to the rails then the incra rails won't be parallel to the original BT3 rails (which are parallel to the saw body but not square to the blade); it wil look funny (which may or may not be a concern) and the adjustment will be kinda weird.

[Poobah]

Thanks for the lesson learned on the casters. I was wondering about that. I can't use 6 casters (two in the middle) because my garage floor isn't completely even, so moving them in from the ends is probably a good idea.

Maybe I'm wrong about the rails needing to be perpendicular to the blade. Obviously that would be the best/easiest setup. But I think that as long as the positioner is perpendicular to the blade it's good enough (this ensures the fence is right and the positioning scales are true). There are a couple of places you can adjust to make that happen even if the rails are off. Actually since I attached the Incra rails onto the outside of the BT3100 rails I've already unknowingly been in that situation.

I was planning on not having the Incra rails attached to the saw at all so that I could add depth both in front of and behind the saw blade.

Anybody have any advice on how much space should be in front of the blade on a 28 inch depth? I was thinking I'd take the extra 6 inches and split them roughly half and half in the front and back.

[Poobah]

Update: Construction Underway!

Here are some pics of the construction. The biggest hurdle was to rip ten 3-7/8 wide boards from the two 20x97 MDF sheets. I decided to use five 97 inch long ribs and then 48 6 inch long connecters. As the ribs and the top and bottom were all 97 inches and I didn't feel like trimming anything I used connecters on the end as well.

The spacing is 8 inches lengthwise and 6 inches widthwise. This will work out well when Amazon delivers my caster. I ordered 4 inch plate casters with double lock. My plan is to mount them in the third "well" from the ends to create a 55 inch span in the middle.

Everything went together pretty well. The Woodpeckers triangle and General Ultra Gauge which just happened to be exactly 8 inches long (Incra clone) worked beautifully.

[Poobah]

More pics from today

Finished the edge trimming and the wheel wells after completing the box last night. The mobile base is going to be a lowrider! And it is HEAVY.

[Poobah]

Sorry folks, didn't realize the pics didn't work. Will fix when I get home today.

[Cochese]

Can see them fine, keep 'em coming.

[pelligrini]

I meant to comment when I saw them yesterday and before, just got sidetracked. Looks like it's coming along nicely. I bet that base does weigh a good amount. I've got some Pinnacle aluminum triangles, they are nice to have. That Ultra guage looks interesting.

On your glue up, you would have transfered for clamping pressure to the middle ribs if you would have turned your cauls on edge. A caul with a little bit of a curve will work even better than a straight one.

How big are your leave-outs for your casters? I did a recessed caster base for a buddy twice, the second time was to make room for the caster to pivot the full 360 instead of just a portion due to the small leave out I did.

[Poobah]

The cutouts are 8x6 inches plus the another 3/4 added to the 6 for the sidewall. I thought about how the casters would fit and ordered a 4 inch total lock caster from ER Wagner. At worst I figure it will need an 8 inch diameter circle, but I suspect it's less, maybe 6 inches.

Wish I had known about putting cauls on edge. I have plenty that are slightly skewed too.

The Ultra gauge is on the clearance page at Woodpeckers. I never thought it would be as useful as it is. I haven't used it as a ruler yet, but it's precise down to 1/32 inch. Mostly I've used it as a small story stick.

I guess the pictures not displaying might be the firewall at my work.

[Poobah]

I found a deal on a couple used phenolic router table tops and was thinking about putting them to use as my saw table top. I'd either have to buy/make a couple std inserts or cut up the tops and splice them back together. At the price I'm getting I think I could have a full phenolic top over the whole 92 inh range of the rails.

Does that sound like a good idea or not?

[Armini]

Impressively massive - it makes me wonder about building one of those in my basement shop, that base looks very heavy indeed.

A phenolic top would be a nice touch, just check how much a sheet would be if you have to do that much work to splice/join.

[Poobah]

Update with pics

Sorry, it's been a while, but I've made some progress ...

First is one of the four phenolic tops I got for $35 a piece.



Next, I've built and mounted the left side router cabinet and the saw stand (little did I know at this time I am off by 3/32 in height ... more on that later)



Next is close to the current state. I haven't fully assembled the Incra positioner, but the rails are just about right on as well as the saw table extension with miter tracks. I will probably rebuild that part as it currently is just MDF and the miter tracks are 0.02" off over the 32 inches depth. I swear when I assembled it it was no more than 0.005". The front on the right side router base is just something temporary to give it some rigidity. I figure some day I'll build a face frame and finish it off correctly.



I've at least temporarily put my router lift on the far right due to the aforementioned 3/32 inch issue. I also got a Triton router from Peachtree on sale recently and was thinking about putting that on the left side.



In the next picture you can see my little issues. First one is that the Incra brackets are a little above the top level of the base cabinet. I knew about this and had decided a while ago I would either add another MDF layer as a spacer or something or just rout out a slot out of the router table top at the back right and left corners. Incra just suggested I take a chop saw to the bracket and solve my issue that way. Sounds good too I guess.

But the more serious issue is that even though I spent weeks measuring and drawing and calculating (and being a statistician you'd think I could do this somewhat without error) I built the base too high or the table saw riser too low. 3/32 is the key number because the router table top is 29/32 high. I probably subtracted 3/32 twice somewhere or something stupid like that.

The bottom line is this: the left side router top is too high relative to the saw table top. And since it is only another 8 inches or so to the saw blade I really need to fix it.

A. I could rout slots underneath the router top to fit exactly. With the router lift and the Incra positioner I can do this quite accurately.

B. I keep thinking about how I can "accurately" trim 3/32 off all the walls (two interior walls - think std looking router cabinet) and thus lower the top to the right level. The outside could be done with a rebate cut from the top and then a flush trim bit from the sides. But I can't think how I would do the interior walls.

C. Raise the table saw 3/32. But then I also have to add 3/32 to the left side router cabinet which is set exactly right for the 3/4 thick penolic top.

Anybody have any other ideas or suggestions?



One more view from a different angle

[Poobah]

More pics and a little humor

First mistake of the project: cut dado very accurately for the interior walls of the router base. However, they were very accurately cut in the wrong place ...

Not a huge deal, just cut new ones and moved on, but it's one of those things you just have to learn the hard way.



I ordered 4 really nice ER Wagner casters. Unfortunately they sent me 3 matching ones and the 4th was cheaper with a lower load rating. The company has great customer service and they quickly fixed the issue, but now I had to change out a wheel. So here it is for you NASCAR lovin' Talladega Nights fans:



Yes, that is a parallel clamp jacking up the mobile base! I don't know why, but that really cracks me up.



And this wouldn't be complete without the rest of the evidence

[Poobah]

One more note. I think the base might be sagging ever so slightly at the ends. Of course I haven't really added much weight to the middle and those router bases are pretty heavy.

I still think it was the right choice to move the wheels inward. At 97 inches you would get a lot of sag in the middle otherwise.