Advice and experience building your own alignment table

[Weldingfellow]

Hello everyone,
May I first introduce myself, my name is Chris Sherwood, I'm a journeyman welder and metal fabricator.I'm the owner/operator of a small metal fabrication business, Sherwood Metalcraft.
I've built the occasional frameset over the last 27 years, and have found myself about to take the next step over the threshold if you will...
Also, may i please, profusely apologise for being a lurker. and more importantly, thank you all for such excellent sharing!!!!

My question:

Given what i'm about to describe for materials, could you offer any advice and experience you may have had in building your own alignment table?

I've chosen these options as there is only so much space in the shop, and it's what is on hand..


Bringheli style table.

I'm considering using a piece of 12" wide x 50" long x 1/2" thick steel channel i have lying around, which i would have ground flat, drill some holes and mount to a frame. of course there are other parts and components to make.

the other option is,

using a 24" wide x 48" long 1/2" plate. which again would be mounted to a table and ground flat. holes and other parts to be made/machined as well...


thoughts and comments?

thanks again
Chris

[Andrew R Stewart]

Chris- I think you'll want to have some ability to adjust the plate on the table's framework so it actually ends up fairly flat. I can't say how much overhang or distance between support points is needed to avoid gravity induced droop but know it is an issue. I also would suggest a surface dimension which allows a full frame to be played with without re mounting the frame on your bb post (assuming you use a whipping post). Each time you loosen, shift and re secure a frame on a post you get slightly different measurements, this induces error potential. A 2'x3' surface isn't quite large enough to do this (although a common flat surface size). Think how you attach, support, hold down your surface to the bench structure. When bending frames there's a lot of force being applied and a 3' wide table of significant mass (greater then your 1/2" thick one) will rock up/off the support at times. When it comes time to make a whipping post consider your measuring tools' heights and the width of a frame's rear end during it's aligning spring back. Andy

[Weldingfellow]

Thanks Andrew, great advice.
the frame to be made, will be significant...i'd thought about these options for attaching the flat surface:
making "feet" and using large bolts to secure. there's a variety of ways for this route...
welding the channel or plate onto the frame. then getting top machined/ground flat.
What have others done?

Chris Sherwood

[Nate Zukas]

My table is 2' X3' and is perfect. I use a BB tower mounted in the corner using a cone on the bottom with a I.D. fitting puck on top. Consistent every time especially when readjusting to measure different points of the frame. Many will advise that holding the HT is better but due to my tables size the BB works best. The only "tweaking" I do is light leverage on the chainstays after heating, no more than .10" to .25" max. Main triangle is adjusted after tacking with slight heat from additional tacks if necessary on the table while determining a brazing or welding sequence. Tight, accurate miters(copes) will produce a near straight main triangle that won't require leverage that lifts your table off of its mount. If you feel that its necessary to do some heavy cold setting I would flip the frame over so its pushing down onto the table, but for me if it needs that kind of re working I would start over. I do like the idea of welding the plate onto the frame then machining the surface, but I may be wrong and that the machined surface needs to float on its stand? You must have some nice large machines at your disposal!

[Andrew R Stewart]

A follow up to clarify. My bending so strongly that a surface plate might lift is not done to frames I build (any longer, I got past that a long time ago). But I do play with old stuff and explore what are the limits of frame aligning sometimes. What I do for my knowledge is different that what I will do for others. Just like I have taken cars beyond their limits (on parking lots, think of them like an auto flat surface) but I understand the reasons to not drive like that on the streets with others around.

As to whether a floating surface or a fixed one is the best path to take I would find inspiration in production made surface plates. Steel plates are cast with a webbing understructure that provides a stable/still unit. This is then ground/scraped flat to a spec and has three feet to sit on.

But frames don't need the kind of precision that machinist flat surfaces are held to. IMO what is needed is a repeatable and consistent set up. Hence my suggestion for a large enough plate to allow the entire frame to be worked on with no repositioning. I'll add that being able to explore the HT mounted method of frame alignment checking is worth the exercise, even if you don't use it.

My 2'x3' cast steel plate was chosen due to weight/size and moving it reasons. If I were to do it again and had the ability I'd have a 3'x4' one. (But at a bit more then twice the weight my basement stairs might not hold up and what is a four person moving job becomes a fork lift one). Andy.

[cicli polito]

Hi Chris - some good points all around here. As Andy mentioned, go with a 3x4 if at all possible. One of the other big benefits of that size, in addition to most frames being accesible in all directions during one set-up, is that you can set up a dedicated fork alignment system on the same plate. It's handy not having to take fixtures off just to check a fork.

Also remember that once you get that table, you are "a person with a table." Like being the "person with a pick-up." So while your frames may not require much tweaking, there's a good chance that you'll be offered some outside work now and again.

Regarding the plate itself, if you're going with 1/2" I would recommend buying it already blanchard ground. The grinder will have used stress-relieved steel and it will be f-l-a-t to a known tolerance. There are a few different grinders here in my city who won't accept 1/2" or less with a plate they can't verify, as it can "bowl" really easily and will not meet their spec. A 5/8" plate in 2x3 is only 30 pounds heavier than a 1/2, and $70-$100 more. Worth the extra effort.

My opinion on attachment is to not attach at all. Leveling feet or screws (whether 3 airy points like true surface plates or 4 on the corners) are the way to go. The other way would be leveling feet/shims/screws on the base itself, but I find that much more of a hassle to level for some reason. I used red-heads to lag my base to the floor and leveled the table. Don't weld the working surface to the frame.

Have fun!

[Weldingfellow]

Thanks Guys.
to be clear, no...i don't have the heavy machinery but i'm friendly with the large mining/engineering firm that is close by. we do smallish aerospace type work here.

You've all raised some excellent points, exactly the advice i was after.

I think what i'll do is re-examine the plan. I was feeling that using materials i had here taking up space..was going to be a compromise, minor, but still...if i'm putting in the effort, might as well do it how i see right to begin with.

I'll find some substantial 3ft x 4ft plate, build a frame and bolt it all together, drilling and tapping the underside of the plate, that way i can level or adjust if ever need to..
i won't get involved in airy points..i think has more to do with using granite anyway...but yes i'll support it all around.

i used a alignment table many many years ago,(when i was a framebuilder..) that if i recall was an enormous piece of cast iron mounted on a steel frame, i remember it being way to low to ground and having constant back pain when using it...lol

anyway, as i progress i'll post the results.

thanks again!!!!

Chris Sherwood