drill press restoration question

[metalmagpie]

I'm refurbishing another old drill press just for fun and because the Taiwan DPs from the '70s and '80s were so much better than the stuff I see sold today. The one I'm doing now is a benchtop, but it has the familiar import drill press design features. Key among those is the rack and pinion table height adjust mechanism. The one on this press (a Jet 13R) appears to be slightly differently designed than what I think of as the standard design.

Here's a picture taken from a recent rebuild of a Foremost 20" machine:



If you look closely at the rack, you can see that it is beveled at the top and bottom. The very top surface of the casting which bolts to the machine base is machined with a matching bevel, as is a top ring. The whole rack is free to rotate around the column along with the table. The rack is prevented from moving in the vertical direction by the beveled castings. Also, the top ring is adjusted so there is a close fit which keeps the rack from canting off from the vertical.

So the little Jet bench unit I am working on is similar. The base casting is beveled, as is the bottom of the rack. However, when I got the machine there was no top ring. Looking closely at the markings on the column, I suspect there never was one. The top of the rack is not beveled - it has a step machined into it. This step does not mate with any part that I have. Yet, the thing still works. The rack stays vertical, the table goes easily up and down, and the rack never pulls very far away from the column at the top. Here is a picture:



(Note, I haven't cleaned the rack yet!)

The head of the benchtop drill press sits right down by the top of the rack. If you look at the marks on the column, you can see the column where it was covered by the head casting. I can't see any sign of a top ring ever being installed there.

So now I need to decide whether to make a top ring or not. I can't find a picture of another one without this ring (which some manufacturers call a 'rack collar').

What do you think the function of that top ring (collar) is? Should I shorten my rack a little and make a ring?

metalmagpie

[J Tiers]

The collar keeps the rack from flapping around if you lower the table way down.

Obviously the head kept the rack from rising. Possibly it was intended to have the ring integral with the head, but that feature wasn't machined-in. or, maybe it was supposed to have a ring, which may have functioned as a stop to allow turning the head without having it slide down.

You could make a ring, sure. And are you certain you would need to shorten the rack? Is the head position that critical?

[JoeLee]

That rack gear has to flop all over without the top ring. My Delta drill press is the exact same design, there is a lot of play where the rack goes through the crank casting. I was never impressed by it.
Sometimes when I swing the table the rack doesn't want to move in the bottom groove and I have to help it along by hand.
It's worse when I add the weight of my cross slide table to it. When I rebuilt the head I cleaned up the groove which was gummed up with dust and dried oil but it didn't make much difference. I had some brief thoughts of coming up with some kind of a mod for the groove like a modified bearing or something but that's as far as it went. I rarely swing my table much.




JL...................

[djc]

So now I need to decide whether to make a top ring or not. I can't find a picture of another one without this ring (which some manufacturers call a 'rack collar').

What do you think the function of that top ring (collar) is? Should I shorten my rack a little and make a ring?

The shape of the rack is similar to that on a Startrite EFI drill (also sold as a Rockwell 70-100). Make a ring. On this machine the collar stops you winding up the table too far and off the top of the rack. On the machine mentioned, the column has three shallow holes in it into which dog point screws locate and secure the collar. If you don't want to drill your column, put brass pads into the holes and just do the screws up tight.

[dave_r]

On my drill press, with the same setup, I just noticed today (as I happened to be cranking it down a fair amount), that the top ring is present, but it is just sitting way too high (like up near where the drill heat mounts to the column). It still works fine, and I only noticed it because the platform stuck on something on the column a bit, and the crank pulled the rack up a little bit. But pushing down on the platform, it went back to working ok. It's stiff enough to not flop around (at least on mine) or get jammed at an angle by rotating the platform on the column.

I'll probably eventually move the ring to the correct position...just another thing on the ToDo list that is already way too long...

[Arcane]

.............. Should I shorten my rack a little and make a ring?

metalmagpie

You already answered that question when you said:

Yet, the thing still works. The rack stays vertical, the table goes easily up and down, and the rack never pulls very far away from the column at the top.

metalmagpie