Repair - Drill Press Vise
[Additional repair work added Jan. 26, 2013 - see below]
[Comment added Feb. 12, 2013]
My Ryobi drill press came with a 2-1/2" vise. I'm generally happy with the drill press itself - it has given good service and seems reasonably well made for the price (although I have never dis-assembled it to really check). However, the vise that came with it (see at left) is another story. Although it worked, the action was always a bit rough.
I decided to take the vise apart to see if I could make improvements.
I never really looked at it to find out why, until recently, when it seemed to get even worse. First, a bit of background: The moveable jaw is clamped with a simple steel plate to the underside of the vise; the plate slides along two "runners" which are part of the base casting. I dis-assembled the vise and found two problems. First, the set screw holding the adjustment screw to the moveable jaw had a broken off dog point. Second, the "runners" were very rough - they had been only lightly ground (or perhaps never ground at all, and what looked like grinding was just wear).
The picture to the left shows the bottom of the vise (with clamping plate removed). It's a little hard to see in the picture, but the "runners" are just barely flat. The clamping plate was sliding on a very rough surface, and not making much contact with surface in any case.
Using a flat piece of steel bar, wrapped with 80 grit sandpaper, I lapped the runners to smooth out the bumps and provide more contact surface (see next picture). I considered lapping with finer grits, but the surface seemed smooth enough for practical purposes.
I also lapped the mating surface of the clamping plate. Notice that the lapping is only around the edges, as the plate has a slight bow in it. The bow may be intentional, in order to give the clamping a bit of "spring." In any case, it is only necessary to lap the part of the surface that contacts the runners.
At left is the re-assembled clamping plate. Notice the very rough edges on the non-mating ("upper" in the picture) surface of the clamping plate; it was simply stamped out, with no further finishing. A light film of lithium grease was placed on the mating surfaces.
Note that you can see part of the movable jaw adjustment screw on the right side of the picture. The screw is detached from the movable jaw in this picture. At the end of the screw you can see a groove; a dog point set screws fits in this groove to lock the screw into the movable jaw while allowing the screw to rotate.
The vise was then fully re-assembled. The original slotted set screw (holding the adjustment screw to the moveable jaw) was damaged - part of the dog point was sheared off, probably due to the previous "stickiness" of the moveable jaw. It was replaced with a hex socket set screw with a lathe turned dog point; lithium grease was again used on the groove (for the dog point) in the adjusting screw (you can see the groove in the photo above left). A bit of Loktite thread locker was used on the set screw to make sure it didn't work loose.
The repaired vise now works much more smoothly. Of course, it will never be a precision vise, but will still be a very useful tool so long as its limitations are kept in mind.
The vise before repair.
The "runners" before repair (looking at vise from the bottom).
"Runners" after lapping with 80 grit paper.
The clamping plate was also lapped.
Re-assembled clamping plate.
Completed and re-assembled vise.
Additional Repair Work
When I made the repairs explained above, I did not have a mill, so there was a practical limit to what I could do. Since then I have acquired a mini-mill, so I was able to perform additional repairs (as well as a small repair I could have done earlier using my lathe). Below is a description of the additional improvements, which have made the vise perform much more smoothly and accurately.
To ensure that the bed on which the moveable jaw moved was smooth and flat, I clamped the vise to my mill table and used a fly cutter with a carbide cutting tool to mill it smooth. I milled just deeply enough to get a flat even surface.
The cast iron milled easily, and the resulting surface had a much improved appearance.
The two photos to the left show the surface before (far left) and after (immediate left) milling.
As can be seen from the photo, the "factory surface" was quite rough; the milling left ridges in the surface which could be both seen and felt.
At this point the moveable jaw was put back into the vise, and the jaws were clamped tight. The moveable jaw was now "low" compared to the fixed jaw due to the milling. There was also another pre-existing problem: The tops of the jaws were not parallel to the base. Both of these issues were corrected by milling the tops of the jaws (while clamped together), again using the carbide tool fly cutter.
In the photo far left you can see the milling in progress. Note that the moveable jaw sits below the fixed jaw. Also, the far left side is partially milled, while the right side is not yet touched (because the jaw surfaces angle down to the right).
The photo on the immediate left shows the tops of the two jaws after milling - smooth, flat, and parallel to the base. Note that the removable jaw faces were left in place for milling.
Another issue with the clamping screw was that the hole drilled for it in the movable jaw had a conical bottom left by the drill used to make the hole.
To correct for this, a small brass piece was turned on the lathe (see photo far left).
You can see the brass piece on the end of the screw in the photo on the immediate left ("stuck" on with a dab of molybdenum grease). The groove for the retaining screw was also widened a bit (in the lathe) to compensate for the increased length of the end.
These improvements changed the screw tightening from rough and "ratchety" to firm and smooth.
The bottom surface of the moveable jaw was also milled flat and smooth, using the same fly cutter a before.
In the photo to the left, the movable jaw can be seen before milling. Not pretty!
Since the top of the jaw was not (at this point) parallel to the base, it was necessary to clamp it upside down on the mill table at a slight angle to compensate, after which the two bearing surfaces were milled flat and smooth.
Here is another problem to be corrected: The face of the screw that contacts the moveable jaw is not flat or square!
This was corrected by clamping the screw in the lathe and facing the end flat.
Next, the two surfaces on the bottom of the vise (for the adjustable jaw clamp), were milled flat, smooth, and parallel. Due to the poor nature of the casting, there was not much surface to work with, so as little milling as possible was done.
The original movable jaw clamp - a rough steel stamping - was replaced with a 1/4" thick piece of brass. On the face of this brass piece which faces the movable jaw, a shallow "trough" was milled to ensure that the brass would contact the milled surfaces (the "bottom" face of the brass piece seen in the photo at left.
In the photo can be seen the new brass clamp, and the old stamped steel clamp next to it.
The repaired and improved vise!
While this will never be a precision vise, it is now a much improved general purpose drill press vise. Where before the tightening of the vise jaw was rough and jerky, it is now smooth, and tightens with a firm feel.
Finally, I can now use a square on the top of the jaws with some confidence that it will align at a right angle to a drill bit.
All in all - well worth the effort for about an hour of work.
Additional comment:
In GrizHFMinimill@yahoogroups.com, Bill Williams suggested:
I have done the same for various cheap vises but I usually started
by placing the stripped vise body upside down on a flat surface (surface
plate) with a pair of parallels under the ways. If it rocked then I had
to set it up on the base shimming it to approximately level and cutting
the ways true and flat. Then I rolled it over and cut the base. From
there it was the same procedure! Bill in Boulder
My thoughts: If the base is milled flat, this should be done first so that subsequent milling is parallel to the base. If the ways are seriously out of parallel with the base, then this should be compensated for when milling the base.