View Full Version : Urgent - Locating Jigs On the Mill Table

10-22-2003, 07:51 PM
Tell me if I am being sacrilegious, please!

I need to make a jig for some repeatable jobs. My thought was to make a jig to locate the work precisely and clamp.

However, it would be nice to be able to mount the jig to the mill's table quickly and be assured that it is square in relation to the table. I have two ideas that I could do.

1) Mill one of the T slots just enough to yield a smooth set of parallel edges. I would only take off about 0.010 to 0.025", just enough to get a smooth parallel surface at a uniform width to fit a rectangular block on the jig.

2) Drill two precision holes into the table for locating pins in the jig. This has the advantage to always place the jig in the same X as well as Y coordinate on the table. However, the zero point for my DRO is not fixed.

Is there a better way or which way should I proceed? The most important aspect to me is to make sure the jig sits square when removed and replaced.

Thanks in advance,


10-22-2003, 08:11 PM
It is your mill table, do what you want.
If it were me, I would make a sub table, keyed to the T slots that could be removed and replaced when needed. Aluminum is often used for this application.

Forrest Addy
10-22-2003, 08:12 PM
The traditional way to locat jigs on machine tables is by fitted keys in the T slots.

The center T slot of a mill table is specified to e parallel to the table ways in terms of a half thou on the length of the table.

Many people have added location features to their machine tables. Usually only one in the form of a bored hole furnished with a hardened liner bushing. It doesn't matter where you put it so long as the tooling bushing's location is precisely known so that jigs and fixtures can be accurately made to suit it.

10-22-2003, 09:50 PM
I use a large piece of aluminum (18x8x3") that has T slots milled in it. I build my jigs on it. All I do when I want to reuse it is to make sure I'm parallel on the X-axis then clamp it down. Everything else is relative.

10-22-2003, 10:17 PM
I determined that the back of my mill table is parallel to the table travel, then I drilled/tapped a series of 3/8-16 holes along the back. When I want to locate something, I bolt a couple of blocks to the back of the table and use them as a reference.

10-23-2003, 03:07 AM

If accuracy is important you can buy tooling plates to permanently set up on the machine. If you do multiple modular set ups they are worth their substantial investment. The plates are never removed - your milling vise can even be used on the plate and quickly set up too.

http://www.miteebite.com/ has some products that you may find useful or applicable - or just give you some ideas...

[This message has been edited by Thrud (edited 10-23-2003).]

10-23-2003, 03:32 AM
I'm very interesting in this topic because I am just learning about work holding and fixturing. One Idea that I am toying with in my head is to build an alignment tool along the X and Y-axes using inexpensive laser pointers with vertical beam spreaders. This would be mounted on the side and back of the table and be indexable and repositionable. It should be possible quickly mount the work pretty accurately and might be useful in layout too.

10-23-2003, 07:59 AM
Thrud, Thanks for the link. I love ideas! :-)

Thanks to the rest of you guys, too! I have learned a lot about fixturing and jigs. I also now recognize I know far less than I thought I knew!!!