some bt3 mobile base considerations...

[drumpriest]

I think that I've decided that I need to construct a mobile base for my 3100 with 1/2 rail extension, and build a router table into the extension area. I need the space and my seperate router table isn't all that great anyway.

For the router, I'm thinking a bosch 2.25 hp kit in a jess-em fx lift. No worries there, here are some questions/considerations....

1. What material would you all suggest using? mdf? or ply? if it's MDF, do I just use butt joints and nail away?? Should I bother with dados?

2. The base, torsion frame seems to be the general consensus, I've made an assembly table, and was wondering if it needs to be heavier duty than that? Or is 1/2" MDF for that frame sufficient?

thanks for all who respond, this'll be a big project.

[gmack5]

Were it me, I would use 3/4" Plywood, probably Baltic Birch (If I could get it at a good price). It comes in a strange size (5' X 5'), which may provide you with a small challange.

You might want to look in the "Articles" section as there are several different Mobile BT3X00 configurations shown there. Not that you have to follow any one of them, but they should give you a few ideas.

[RayintheUK]

When I was thinking about making my mobile base, I realized that there would be "raw" edges, whatever I used. I decided to cover them with solid wood. That decision made, I chose MDF because - unlike plywood - there are no splinters!

I used dados for two reasons - easier assembly and less chance of racking during assembly.

The choice of thickness of materials to some degree depends upon the amount of weight the structure will have to carry. I intended mine to include loads of storage, so I went with 3/4" throughout. Turned out fine and although heavy, it's virtually bomb-proof. Details here if you're interested. HTH

Ray.

[TomBar]

I agree with Ray. I used 3/4 MDF with dados and rabbets for most of it. I used 1/2 MDF for the drawers and grid work inside the torsion box. Have fun and don't forget to take pictures for us.

[ssmith1627]

Ray, I've been eyeing your page on the mobile base you built for the past few days. Very impressive.

I picked up a 2nd set of rails from a bt3central member (thank you !) and received them just a week ago. My first thought was just to build a melamine table between the two extended rails and fashioning some leg supports for the end. But I'm leaning more and more toward the mobile base idea now. My shop space is limited and I don't want the saw to be stuck in one place -- you never know what kind of rip or crosscut you might be trying to do and it's hard to find the perfect place to leave it to fit both needs.

Now that I know what a ...torsion box.....IS.....(cough).....I can at least ask some more quesitons. Is it built to give you the strength for the base ? Is it necessary / recommended for a BT3K mobile base ?

I had seen this post the other day in the classified section so I'm just comparing what you bulit and what this other member had done:

http://www.bt3central.com/showthread.php?t=19493

Thanks for any feedback you can offer !

Steve

[lkazista]

When I was thinking about making my mobile base, I realized that there would be "raw" edges, whatever I used. I decided to cover them with solid wood. That decision made, I chose MDF because - unlike plywood - there are no splinters!

I used dados for two reasons - easier assembly and less chance of racking during assembly.

The choice of thickness of materials to some degree depends upon the amount of weight the structure will have to carry. I intended mine to include loads of storage, so I went with 3/4" throughout. Turned out fine and although heavy, it's virtually bomb-proof. Details here if you're interested. HTH

Ray.

Ray, did you build this base at a factory where they manufacture clamps?!

[drumpriest]

Yeah Ray, that's one of the largest collections of bessey clamps that I've seen. More than they have in stock at rockler.

Steve, a torsion box is pretty darned strong construction. I have one as an assembly table. It makes for a nice flat, stable, strong surface. Ray, I do like that 1/8" or so dado joints. you are right that they allow for easier assembly, and that's probably about the perfect dado depth for this applcation, thanks for that idea.

So ply or mdf, either would be fine? MDF is likely to be flatter, but the ply will be stronger. hmmm.....

[cobob]

I've been getting around to this for some time & have been pondering same for longer. I think, as a torsion box is so strong & MDF is so flat, that making it out of 1/2" MDF should be sufficient...IMH(but ignorant)O

[drumpriest]

Here's another question. Even though I have a DC hooked to the shark and the back of the shroud, I get dust directly under the saw, how do you guys who have them on cabinets collect that dust???

[RayintheUK]

Now that I know what a ...torsion box.....IS.....(cough).....I can at least ask some more quesitons. Is it built to give you the strength for the base ? Is it necessary / recommended for a BT3K mobile base ?

Steve, the reason torsion boxes are used is to ensure a perfectly flat and level platform for the saw. As I'm sure you can imagine, if the saw could flex or twist, then the cumulative effect on the rails would be horrendous.
Some members have had issues with getting their stands level, but once acheived the saw performance is as it should be. Therefore, particularly where the saw is to be moved, starting with a base that will NOT flex or twist is key.

Ray, did you build this base at a factory where they manufacture clamps?!

lkazista I wish I had - never have enough clamps! I've got another six really long ones since that project, plus four (2 x 18" and 2 x 24") of their new DuoKlamps - also brilliant!

I get dust directly under the saw, how do you guys who have them on cabinets collect that dust???

drumpriest My saw is on a flip-up hinged base for maintenance, but I have to admit I've never needed to use the feature since I incorporated it. I simply whizz off the left-hand side for an annual "deep clean" or stick the shop vac nozzle through the exhaust eyebrow cut-out for day-to-day sprucing-up.

BTW, I doubt whether strength will be an issue, unless you intend to drive a truck up on it. Whilst MDF may seem weaker than ply, with a rabbeted or dadoed glue-up, the crushing strength will be sufficient to withstand anything workshop use could throw at it. HTH

Ray.

[JimD]

I used 3/4 "Sandeply" plywood from Home Depot for most of my base. The Article is in the Articles section (Spruce and Sandeply). I do not like working with MDF. It does not take fasteners very well, the dust is pretty nasty, it soaks up glue and finish something fierce, etc.. It is nice and flat, however, and relatively cheap. Around here you can get 3/4 Chinese birch plywood for $30/sheet which is not the nicest but better than MDF to me. I also used shallow dados for ease of assembly. My base is a torsion box but a bit different in that I used a clear 2x4 for the outer frame. This let me incorporate a HF mobile base that I don't think they sell anymore - but others have an equivalent base.

Since I took the pictures for the Article I have put doors or drawers on all the openings and also added additional suction beneith the BT3100. My drawer for extra blades is directly below the BT3100 and I reduced it's depth so I could get another suction port into the area beneith the saw. It helps although I still tilt the saw up once per year to clean it and the dust that still is under there.

My auxiliary table is melamine particle board with plywood edges and support underneith. When waxed, the melamine is a very slick surface that is more wear resistant than MDF or plywood with poly on it. To get the height of the extension table right, I made the plywood upright pieces for the extension table which, in my design, clamp to the rails. I put them between the saw table and extension table and marked a line on them at the height of these surfaces. Next I ripped them to this width and then glued and pneumatically nailed the MDF flush with the top of the plywood. The pictures in the Article should help. My extension table also has router table capability.

I downloaded the articles on Rod's and Sam's and a couple other mobile bases when planning mine. I did not use all their ideas but I still found the information very helpful. I would suggest that anybody contemplating this project do the same.

Jim

[ssmith1627]

And the above......is why I continue to read this board on a daily basis. It's woodworking college for the beginner.....haha.

In making the torsion box pieces, I'm assuming those slots are made with dado blades on the saw ? Can't see a router being quite up to making those so may have to invest in a dado set.

Thanks for the conversation on the topic. Great stuff.

Steve

[JimD]

I used dado blades and clamped all the inner torsion box members together and cut them with the SMT so they would be identical. The cuts took nearly no time, changing to the dado blade and getting it cutting the right thickness and height too awhile.

Jim

[Tom Miller]

If you're thinking of using mdf, it sure looks like you can't beat Ray's edge-joining technique. That not only looks good and bomb-proof, but not that difficult to do.

Another point: If your base is made such that it doesn't rack, you may very well have only 3 of the four casters on the floor at any one time. For that reason, I added two leveler feet on the front of my mobile BT. The added advantage is that when in place it's rock solid. It also means locking casters are of no use. Take that FWIW.

Regards,
Tom

[vaking]

My mobile base is not yet complete but below is a picture as it is today.
The design is mostly stolen from a book by Danny Proulx. The design is different from most designs here at the site. There is no torsion box at all. Most bases here have 2 main cabinets sitting on one platform. Torsion box is needed to make that platform steady. Here there is only one cabinet going full length of a base. The whole cabinet is made of 3/4" MDF including the back wall. The entire cabinet is working as a torsion box as a result. The bottom of the base is made of 2 sheets of MDF. My casters are of the threaded stem type - so wheels are bolted through the bottom sheet and then the bottom sheet is screwed to the main cabinet. The second sheed has nuts recessed inside. On top of the cabinet there is a sheet of 3/4" birch plywood. The saw body as well as rails, router table - everything is mounted on that sheet. There is an opening under the saw for dust collection - I need to make a drawer for this as well for other things. The sheet of plywood is hinged on the back - I can flip the saw with all the rails attached at once. Of course I would take routers off to make it lighter.