pinning an existing fixture plate

[krymis]

I have 2 fixture plates from HTS that are already drilled and tapped with 170 holes on a 1/2 grid pattern.  How would i go about pinning the fixture plate to the mill table properly.  I guess my biggest confusion would be squaring it up first and then drilling where the dowel holes are in the mill table already.  How should you square the fixture?   I could put 2 pins a certain distance apart and then put a peice of steel square stock against them and use a DTI to set the stock square inturn squaring the dowel and table ??just thinking out loud. 

[RICH]

Clamp the fixture to the table and use the holes for aligning it via a straight edge against the locating screws in two of the fixtures holes.
My fixtures have at least have the  sides ground square and perpendicular to the hole pattern though, so i don't need to use aligning screws.
RICH

[BR549]

Normally when you buy a predrilled subplate the holes are parallel with the sides.

Just a thought(;-) TP

[krymis]

how do i go about setting an origin for this plate as opposed to one i cut on my own?  do i just put a bolt with the head cut off in one corner and use that as an origin dowel? 

[BR549]

That is entirely up to you (;-) There is no set standard.

(;-)TP

[krymis]

do you think that would work and what would be some other options. 

[RICH]

You can do anything you want to do as long as the location satisfies  your set up. For example, you could use a shoulder bolt in one of the holes, drill and ream a hole somewhere and put a pin in it, drill and ream a hole for a taper ended locating ball , use scribed lines on the plate. Depends on how accurately you want the reference point or reference lines to be relative to what ever your going to mount on the plate.  

If you made one yourself maybe align the holes with the X & Y axis and machine the sides.
 Whatever works for you on it's intended use.

RICH

[krymis]

thanks guys.