Tools - Mill Table Stops
Mill Table Stops for the Model 3900 HiTorque Mini Mill
Mill table stops make it possible to pre-set limits of travel, or stops, for the x-axis motion of the table. This is useful when making multiple copies of a part, as the required limits of travel can be set so that repetitive cuts can be made without constant measuring. The Model 3900 mill has a t-slot machined into the front of the table, as well as pre-drilled mounting holes in the base, so construction of table stops is relatively easy.
The picture to the left shows the completed fixed stop, and one of the two moveable stops (to the right of the fixed stop). There is one moveable stop on either side of the fixed stop; these can be locked down with a hex wrench to any desired position.
Measured Drawings
Measured drawing are available for the work shown here, at the links below. While these measurements are specific for the Model 3900 HiTorque Mini Mill, they may prove useful as a starting point for other machines.
- Drawing in PDF format: https://drive.google.com/file/d/0Bykt5WZ092aWWXB0SFZzVGdiNkE/edit?usp=sharing
- Drawing in LibreOffice Draw format: https://drive.google.com/file/d/0Bykt5WZ092aWd1ZJUFZ4eEVBN3M/edit?usp=sharing
The Completed Project
The photo to the left shows the completed project. On the far left is one of the moveable work stops. At the top are some spare t-nuts. At the right is a moveable work stop, partially dis-assembled. At the bottom center is the fixed work stop.
Making the T-nuts
The photo to the left of the right front of the mill table shows the T-slot and access hole on the front of the table. This t-slot is significantly smaller than the t-slots on the top of the table, so the t-nuts must be sized accordingly.
Making the t-nuts is a simple milling operation. I made a single t-nut to start, to verify that the measurements were appropriate. After that, it made more sense to do a "production run" as shown below.
First, a long workpiece was milled to the required t-slot dimensions.
Next, the workpiece was mounted vertically in the vise, using an angle plate to ensure that the piece was vertical.
A slitting saw was then used to slice off appropriate lengths. This operation was repeated until the workpiece was "used up."
The individual pieces were set up, one by one, in a vise using a vise stop, and drilled and tapped as required. This made it possible to drill and tap every t-nut without repeating any measurements after set up of the first piece.
Here we see a completed t-nut. I only needed two for this project, but I made a few spares for possible future projects.
Making the Fixed Stop
As shown in the pictures below, the mill table has a ruler strip, with a center line indicator below it. This indicator is removed to make room for the fixed stop. The indicator is simply a small aluminum plate "riveted" in place with two aluminum rivets; it is a simple matter to pry out the rivets using the sharp edge of a wood chisel, and remove the plate. Below the plate are two pre-drilled holes (M4-0.7) which will be used for mounting the fixed stop.
The center line indicator, shown in place below.
The indicator removed.
As shown in the pictures below, the fixed stop is milled from cold rolled steel; a 0.75" cutter is used to mill the rounded cut. Note that the mounting holes were drilled and counter-bored before milling. These are clearance holes for M4-0.7; I do not have metric counter-bores, but I found that a #8 counter-bore worked just fine. You may also note that the counter-bores overlap the edge of the piece by a small amount (because I was using 1.25" width material I had available); a larger width material would have avoided this issue, but the piece works fine in any case.
Milling one side of the stop.
Milling the other side of the stop.
The final step in completing the fixed stop was to mount it in the vise at a 45° angle in order to mill a small chamfer.
Making the Moveable Stops
The moveable stops were milled in a manner similar to the t-nuts, according to the dimensions given in the measured drawing. This is a straightforward bit of milling which really does not need to be illustrated.
The moveable stop fits into the top of the slot and straddles the t-nut. Tightening the #10-32x5/8" socket cap screw which holds both pieces together clamps the stop against the t-slot and holds it in place. In practice, the table is moved to the desired stop position, the moveable stop is then slid into place next to the fixed stop and locked in place.
