Re-alignment after dis-assembly - getting all parts into position at the new location

[kanankeban]

Hi,
I almost done with the table fabrication, in my case my second step will be to fabricate the rails. My table is not welded, is 100% bolted, although after assamble it presents just .1 degree error in flatness and 1/32 in squarness I have a issue that differs in a bolted table and a welded one. Each time you dissassble and assamble the squarness between table (rails) and board might be different...solution: instead of plain circle holes on the rails, Im wondering if using oblongs in the rails on size larger than the bolts might give me a margin to align rails with the board each time I assamble the table??? :confused:

[Gerald D]

I'm wondering if using oblongs in the rails on size larger than the bolts might give me a margin to align rails with the board each time I assamble the table??? :confused:

Oblong holes are difficult to make. It is far easier to make a bigger round hole with a drill. For our MechMate construction, it is absolutely no problem to drill the holes 1 to 3mm oversize.

With that freedom of movement, everything can be aligned quite easily, and then bolted up tight.

Before you dis-assemble a joint, drill a another small hole alongside the bolt. A 4mm hole is a good size. Drill right through:

3404

When you re-assemble the joint, put a "roll-pin" through the small hole:

3405

A nominal 4mm roll pin fits correctly in a drilled 4mm hole. (That pin will be about 5mm before hammering it in)

[sailfl]

This is a great idea.

[kanankeban]

Oblong holes are difficult to make. It is far easier to make a bigger round hole with a drill. For our MechMate construction, it is absolutely no problem to drill the holes 1 to 3mm oversize.

With that freedom of movement, everything can be aligned quite easily, and then bolted up tight.

Before you dis-assemble a joint, drill a another small hole alongside the bolt. A 4mm hole is a good size. Drill right through:

3404

When you re-assemble the joint, put a "roll-pin" through the small hole:

3405

A nominal 4mm roll pin fits correctly in a drilled 4mm hole. (That pin will be about 5mm before hammering it in)

After I posted...It came to my mind same thoughts :o...just a oversize hole will solve the problem of the necesarry play needed for alingment. The pin idea sound great...I was also thinking of welding some stops in specific locations to force a squarnes when assembling ;)

[Doug_Ford]

Gerald,

You are truly a genius. I know this isn't an original idea but you keep coming up with all of these solutions. Only a genius could do that.

[Leko]

Wouldn't two small holes with pins work better? I don't see how 1 pin and 1 bolt in an over sized hole will realign things back to where they were. Won't the members revolve around the pin to the extent allowed by the bolt in the big hole thereby letting the whole frame rack out of square?3421

[Gerald D]

The frame has diagonal braces which hold it square. You could never rely on a single bolt to hold squareness.

Or, put another way, outside of the view that we show above, there is some other part that holds it square.

Doug, the pin idea is not my original.

[Leko]

Well of course there are other pieces, cross members, braces, and a big spoil board to hold things square. But, I thought the intention here was to take apart a machine that has been assembled and squared and ease reassembly after moving it. My intention was not that the drive pins would keep things square while cutting. My understanding was that they are to realign all the pieces (frame, cross members & braces) during reassembly. All of the holes in these various pieces have some adjustability but the addition of the small drive pins allow the pieces to register back to their previous locations so that you can tighten up all of those other pieces. My point was that with the addition of 1 pin as you suggested could remove maybe 85% of the required realignment, whereas the addition of a second pin at each location would remove almost all of the realignment. I also thought that one would put these alignment pins in all of the cross members, frames, and braces.

[Gerald D]

Here is the bigger picture. In both of these examples, the key is that there is some bracing to prevent bolted joints from rotating/twisting. If that is taken care of, single pins per bolt are enough. If there is no bracing to prevent rotating forces at single bolts, the basic design is faulty - spend energy on fixing the design instead of doubling up on pins.

3423

3424

[kanankeban]

Gerald,
I went to my thoughts again and I really thing that no more squerness mechanisms backups are needed if the table is fully bolted, of course with the rails having a way of adjusting as mentioned earlier, is matter of tunning the table each time is assemled, do you thing so?...it will be just a couple of minutes worth of work.

[Gerald D]

The major alignment work is to get the rails straight when they are screwed to the main beams. That is when we will use loose shims. When the table is moved, we will leave the rails fixed to the main beams and we will not adjust those shims again. Therefore, the problem after a move is to get the two main beams exactly as they were before. That type of tuning is quite quick, especially if the roll pins are used.

[hennie]

My five cents.