Drill Press Quill/Spindle Bearing Installation Question

[bmwman91]

I know we have some experts in here when it comes to precision machining and machine assembly, so hopefully one of you drops in here to set me straight.

Boring backstory:
I picked up a Delta 70-200 drill press on CraigsList last week. The unit had some significant surface rust from a life in a basement in the Santa Cruz Mountains, and there was enough spindle runout that I didn't need a dial indicator to detect it...BUT, it was nothing that a couple of weekends of TLC and some new bearings couldn't fix. This was a nice but not high-end machine when it was new in the mid/late 1990's, but it is still built better than anything new I can see on the market today for under about $2000. So, as with most of the larger machines in my workshop, I figured an older unit in need of some work would end up being the better buy versus some new China-made unit even with the used one being the same cost or a little more after refurb.

I tore the machine down to the very last screw to thoroughly clean and de-rust it, and I removed all the old bearings since they were nasty. I have new FAG bearings coming this week from Motion Industries. Proper installation of radial ball bearings is fairly straightforward, but the lower bearings between the spindle and quill are of what seems to be a sort of uncommon configuration. Basically everything I can find online for consumer-level drill presses like this shows upper and lower radial bearings, but none with a thrust bearing stacked in there like mine.

The questions:
A) First, what is the right order of operations here?
My assumption is to do it in this order:
1) Press 6206 onto spindle
2) Press tighter race of 2906 onto spindle
3) Drop ball cage and loose race of 2906 onto the spindle
4) Press the spindle+bearing assembly into the quill
5) Press the 6204 in to the top by both races, supporting the assembly by the bottom of the spindle

Step 4 leads to the second question, which I think is the really important one. Also, the spindle has threads which take a locknut above the 6204, which I guess ensures that there is no axial play in the inner races after final assembly.

B) How do I set the proper pre-load on the 2906 while pressing in the 6206? Also, how to keep good concentricity between the races of the 2906?
Screwing that part of the assembly process up seems like it would make the entire effort pointless since it would either ruin the bearings immediately, or lead to a very short, hot and noisy service life. The spindle+bearing assembly has to be pressed in by the outer race of the 6206 since the tighter press fit seemed to be between its OD and the quill based on what I observed during disassembly. But, pressing it in by the outer race also means it will be easy to overload the inner race against the 2906.


I am OK with paying a competent machine shop to do this for me since I only have basic tools for pressing bearings, but I feel like that will cost me more than the drill press did lol.


Bonus question: This design seems sort of overconstrained and wonky. Is this a common setup on any other mills or drill presses?



Here is a quick diagram of the assembly I am describing. Things are to-scale in the dimensions that count.

[mrsleeve]

have you considered the freezer/oven method for helping to create clearance for getting the thrust bearing on easier. Center spindle in the freezer and tight race in oven/rosebud to see if it would just slip on with little force. The do the same thing when you go to press the assembly together and feel for when things just touch to make a tight fit, with no slack between them or just take up the slack in the bearings. I agree you are going to want to be careful of the preload, given these are smallish bearings, I still would prolly think a bit too tight is likely better than too lose, especially the precision you want from a drill press.

FWIW I would be reassembling in the same order you are planing on, just using heat and cold on appropriate parts to aid in assembly forces needed to get things back together with out too forcing things too much with limited pressing abilities

[bmwman91]

Shit, thanks man, obviously I was way over-complicating this. I totally spaced on the fact that I can use temperature for this since these are just mild press fits. I just did a quick test by tossing the old bearing into the freezer for 10 minutes and I got it halfway in just by hand. With a little more time, and heat on the quill, this should be a cakewalk.

When I put the stacked thrust+radial bearings in, I think I will stack a 45lb weight on just to provide a little pre-load and ensure that there is no gap as things cool and shrink axially. I just need to work FAAAAAST when doing this!

[Northern]

Honestly I'd probably just mark the lock nut before removal, then tighten back to where it was after the new bearings go on.

I wouldn't be surprised if 2906 is more of a relaxed fit either.

[bmwman91]

Balls, I had it apart last week and did not mark it. I do recall, in a subjective way, how tight it was on though. I was able to get it off with the tips of some needle-nosed pliers (it is a stamped nut with 4 notches) and it was maybe 3/16 of a turn past "finger tight."

Also, I think that I just needed to do a decent cleaning of the bores in the quill. I hit them with a fine wire brush in my drill to remove the light surface rust that had formed in the last week as well as any burrs from smacking out the old bearings, and I can just manage to get the (old) bearings in by hand...it's a tight slip fit. I guess that this is all dead-typical...looser fit on the stationary part, tighter fit on the rotating part (spindle).

The diagram is not 100% accurate either. The bore for the 6204 in the quill is actually ~2mm deeper than the bearing's thickness. This makes it easy to deal with the axial thermal expansion/contraction if I cool/heat things for assembly.


Follow-up question:
Do you guys lube the bore and/or shaft prior to bearing installation? If so, what do you use? Since I do not plan to actually press anything in, but rather use heat & cold, is it still advisable to lube? I find a lot of conflicting information about this online...it seems like a religious topic!



Just for fun, when I am all done later this week, I'll post a cheesy "build" thread for this rebuild, with pictures and colorful commentary!

[IceWhite]

Sorry I can offer no help, but this is interesting, will be looking forward to the cheesy build thread too!

[ahlem]

Since you got it in the Santa Cruz Mountains, I would use either squashed banana slugs, surfboard wax or STP as a lubricant when you reassemble. Probably stick with the STP.
We rebuilt a couple older drill presses at work and my suggestion would be to use the nut on top to establish a good pre-load after the assembly is all together and use a feeler gauge between the back of the chuck and the body of the spindle to minimize the slop to a couple thousandths.

[bmwman91]

STP? Bruh, that is not a locally-sourced, organic, artisanal lubricant from a 51% woman-owned company. Putting that on a tool from Santa Cruz would be a micro-aggression against its gender identity.

Crushed banana slugs on the other hand.....

[Northern]

lube wouldn't hurt, just a matter of if the lube would be considered contamination after the fact (like if it were to be painted) - and of course simply not being too lazy to lube it before assembly.

[mrsleeve]

A light coating of your favorite light oil would be more than sufficient I would think. Motor oil or even a bit of 3in1 would just aid in assembly and not be a big deal since a good drill press would be exposed to such things in normal operation from cutting oil splash and spray occasionally

[bmwman91]

Cool, I will use some of the Mobil 1 5W-20 I have for my wife's car to lightly coat the mating surfaces.

Any suggestions for grease to use on the 2906 thrust bearing? It is a separable type that doesn't come with lube. This is not exactly a super demanding application or anything. I have some Molykote BR2 left from a clutch / flywheel job, as well as a can of MIL-25537 prop shaft grease from 1961 (random "gift" from an older neighbor). The MIL stuff is a bit thicker, and pink/clear, so I am inclined to go with that simply to avoid having black grease (Molykote) making a mess.

[Northern]

I would run a bearing grease of some sort, BR2 is a spline grease and has molybdenum disulfide which is good for sliding surfaces, but not for something like a bearing. MIL-G-25537 is listed as an Oscillating (Spherical) Bearing Grease, which might be fine (and I'd probably use it). If you're worried, a cheap tube of wheel grease from a parts store would be fine too.

[bmwman91]

OK cool. I'll hit the auto parts store on the way home and get a little tube of wheel bearing grease.

Thanks!

[mrsleeve]

I would run a bearing grease of some sort, BR2 is a spline grease and has molybdenum disulfide which is good for sliding surfaces, but not for something like a bearing. MIL-G-25537 is listed as an Oscillating (Spherical) Bearing Grease, which might be fine (and I'd probably use it). If you're worried, a cheap tube of wheel grease from a parts store would be fine too.

Molly is fine in bearings, just not high speed bearings, other wise toyota would not spec very high molly content grease for birfield joint services. Just needs to be a relatively low pressure, low speed low temp bearing which in the world of bearings this application would qualify as.

[Northern]

I've always been told that the bearing will pick up the moly as it rolls and will foul.
Maybe I've been misinformed.

MoS2 is an anti-fretting ingredient, so it seems weird for it to not be in a high pressure/sliding surface scenario