Parker Collars like their jaws have to be custom fit. Parker did not make their parts simple. The jaws were all hand fit and stamped with ID numbers to keep them with the right vise where the Collars were just bolted on to rough casting in many of their models. This gives a un even wear or rub of the Spindle when opening the vise. Not really a big deal unless you like little backlash. I am sure you have seen some with a stack of shims to eliminate some of the backlash. Here is how I fit the Collars I make and sell on my website HERE.
To find which collar to purchase first you need to take a few measurements. I ask that you measure the large diameter of your vise casting since this is a good start and weeds out many sizes.
On each Collar listing I add a machinist drawing and on the listing description I list this dimension as the width. On the drawing I list the width of the top part of the Collar where it bolts up to the vise.
The next dimension that is important is from the shoulder to the center of the mounting threads. This dimension is listed in the description as center of hole to shoulder and the dimension I list is the maximum your vise can be. This means if your vise measures less then no problem if it measures more then I need to alter the collar for you. To find this dimension first I measure the thread hole diameter.
I divide this number by two and add it to this measurementThis example says the shoulder to the hole center is .210.
Next the collar needs to be fit in the depth area. The collar has two radial bosses that form the major diameter of the collar and rest and wrap around the Spindle lip. There is three surfaces that need to all touch evenly for a proper fit. I have machines that cut the two steps evenly but if you do not have access to a milling machine then it has to be done with angle grinders and files. Look at this picture of a 954 Parker collar area that is raw casting on both levels. Also show a broken screw but hat was fairly easy to pull out.
Here is how I cut my two levels on the Parker Dynamic Jaw Support.
I then cut the next level so I can match the collar level;s
Again this will have to be done with a file to do it the right way. I did the math with this collar steps and it should fit like this.
If you want to eliminate backlash then you will either shorten the two ears and adjust the casting for a close gap between the collar and spindle lip or add Stainless Steel shims or a rather thick one like this one below.
I wish there was a easier way to fit these collars. i am showing the best way but these Parker collars will work just bolting them on since most were never fit properly.