looking for ideas/help on mobile base

[Jim O'Dell]

I've pretty much got the basic structure decided on for my mobile base. I'm going to use 6 of these: moble base feet.gif from McMaster-Carr rated at 500 lbs each. (Yes, overkill) 1/2" threaded, 13 tpi. Base is slightly over 2 3/4" diameter. I'm afraid the regular T-nuts won't hold up to the weight. I'll have almost three 4X4X8 Douglas Fir lumber, four of the Grizzly G8172 casters G8172.jpg, about 22 lbs, two 30" sections of black pipe, some end caps and washers, plus I'd like to build some storage under the right extension. This will not be base to extension table high as I'll have the DC ducting running there also. OH! and a little over 600 lbs of saw and torsion box extension table. So I'm guessing I'll be between 800 and 950 lbs by the time I'm finished.
Anyway, I was looking for something like the black pipe floor flanges to use for mounts, but the threads per inch on the pipe is not 13 tpi. The OD of the 1/4" pipe looks about right. So, any ideas on something that is heavier duty than the T-nuts? I did see some cast alloy ones at McMaster-Carr that have 3 mounting holes on the flange, but I'm afraid those won't be heavy duty enough either. There are no load ratings on them or the T-nuts.
As always, any help or ideas would be greatly appreciated! Jim.

[Mike Heidrick]

Jim, I recently was given (traded wood working for it) a pallet jack. I keep my shaper on the platform it was delivered on as it NICELY raises its table up above my table saw so I can easily shap long stock. The Ras has just been given its own custom all wood platform that is SUPER heavy duty and will serve as teh base for my side tables - cost was $12 in 2x wood from the borg. Bother platforms are designed to be moved with the same pallet jack. Even if you buy one new, they are only $200 for a pallet jack that will move 4400lbs. Just an idea.

[Chip Lindley]

Jim, as you found out, 1/4" Pipe threads are tapered, and join only other 1/4" pipe fittings. A 1/2" thread will support a lot of weight. If you can find 1/2" threaded T-nuts, I have no doubt they will work for your base. Remember that the total weight of your saw (800 lbs?) will be divided by every point of contact on the floor. Four casters = 200 lbs. each. The torsion-box extension table is not nearly as heavy as the saw per se'. 1/2" T-nuts should be just fine.

[Jim O'Dell]

And a really good idea Mike. But unfortunately I don't have a place to store a pallet jack. So it would end up being in the way. But I like how you're thinking!

I did find some T-nuts of sorts on McMaster-Carr that have the same size base as the T-nuts with the prongs, but it has 3 small holes instead. They are called weld nuts. weld nuts.gif These might work. Cheap enough too. I might try them if I, or someone else, can't find something better. These have a 1 1/4" round base with the integrated barrel nut for the 1/2" threads. I'd rather have a larger base to mount them with but this may be the best there is without custom making something.
Thanks for the note! Jim.

Thanks Chip! That makes me feel better about it.

[Steve Leverich]

Jim, I'm not sure what you consider "custom making something", but maybe try using those weld nuts with an improvement - get some 1/4" thick flat bar steel, maybe 3" wide - cut it into square pads 3" long, drill a clearance hole in the center that the weld nut threaded part will slip into, then 3 small holes to mount the weld nut to the square plate, and finally 4 holes at the corners of the square plate and mount it like a caster.

You'd need to drill a relief hole in your wood frame to accept the 1/2" stem of the leveler, but this mounting plate would spread out the stress on your wood... Steve

[Jim O'Dell]

Yes Steve. That may just be the ticket. I had thought about welding it to another piece of steel, but hadn't thought about using the holes to screw it into the steel. I like it! Now to find the steel! Jim.

[Jim O'Dell]

Well, now to find the steel is right! Looking on McMaster-Carr, and a 3" X 12" piece of 4140 alloy steel is 14.83. Not too bad. A 3" X 18 " piece of the same stuff jumps to 36.96!! WOW I looked at the plate aluminum, and it's higher. Might have to take another day off from work and go hit the scrap steel yards!! I'd probably spend twice as much in gas just finding the places. Guess I'll get the 12" one, and make them roughly 3 X 3. That should work fine. Just looked, the 4" width of the same material in 12" length is 98.00!!! This makes no sense. 3 X 3 squares are looking better and better! Jim.

[Jerry Bruette]

Jim you could skip the t-nuts altogether and there's no need to go with 4140 steel. Just order some regular hot or cold rolled steel and some extra heavy 1/2-13 nuts and have the nuts welded to the steel.

Trust me on this, part of my job is to make or modify machine mounting frames. 4140 steel is an alloy that's used to make stuff like rifle barrels and vehicle axles, way over kill. I'd use the extra heavy nuts, they'll be 7/8 instead of 3/4 inch hex, so you don't warp them when you weld them onto the hot rolled steel.

You should be able to find this material locally and save on shipping costs.

Jerry

[Jim O'Dell]

Thanks for the note Jerry. The 4140 was, within a few dollars, the cheapest they had. The one that was cheaper said it was poor for welding. And since that may end up having to be done, I wanted something that was at least fair in that area. I admit, I don't know the different grades of steel, so was going by the rated categories that McMaster-Carr had on their site.
Oh, and I can't divide today. The pieces will be 2 X 3 not 3 X 3.
On a better note, I have the design and plans finished out. All the sizes marked down, and my build list written. It will take 4 of the 4 X 4 x 8' lumber to build this. I'm thinking I'll have about 150.00 in it when I'm through, and that's not counting what the casters would have cost if I had had to buy them. I hope I can match the Grizzly green and paint it. Will look very Christmasy with the red wheels! Jim.

[Garrett Ellis]

not sure how far west of ft worth you are but i always go to Garland Steel for metal... they usually have a ton of drop that you can buy cheap ($10 minimum purchase, IIRC)

but- may not be worth the drive. i'm sure there are places closer to you anyway...

[Jim O'Dell]

Garrett, I'm still in Tarrant County, but just barely!! I know there are several places off Henderson just north of downtown. But it would require a day off from work to do it (I work 8-6 right now. If I wasn't closing, I could take off early one day to do it). And I'd rather save my vacation days at the moment. But I will keep them in my memory bank for future use. Jim.

[Daryl Henderson]

Jim, Have you looked for a welding or fabrication shop near you? They usually have scrap iron they will sell by the pound and can probably cut it for you for a small fee.

I make ALL my mobil bases out of angle iron and channel iron. I usually use 6" x 4" angle iron for the base, welded on the bottom and outside corners so the inside is still flat.

I add extension wings on each side of the base out of 5" channel iron and bolt the casters to these. The length of the wings are determined by the size of the wheels. You want them to swivel 360 deg. without hitting the base.

I weld the channel iron to the base at a height so that the base just clears the floor with the size wheels I am using. That also is determined by the size of the wheels. This keeps the machine at the height I want. I use 4 locking casters and the machine never moves.

I know that 6" x 4" angle is overkill, but I use the 6" angle for the sides of the base so I can adjust the height of the base from the floor. You could use 4" x 3" or even 2" x 2", but you would be limited on how close your base would be to the floor.

If you don't care if your tool is higher off the floor, you could just bolt the wheels to the base and do away with the wings. However, unless you are tall, this might make the operating height uncomfortable.

I can make one in about an 1 1/2 hours. Get touchup paint from Griz and it will look like factory.