Which bearings?

[kong]

I am converting a bench drill for milling copper, I know, I know, dangerous, stupid, waste of time, but hey, I gotta try for myself!
Anyhow, I am modifying the spindle and was wondering on the best type of bearings to replace the standard axial type in the press. Also, how many? The spindle is 5/8" dia, and the length of the quill is about 6-8", so I'm thinking either 3 bearings equally spaced, or maybe 2 top and 2 bottom. And please try not to flame me!

[CNCadmin]

Don't worry their will be no flaming here at this site .

[kong]

It's just that I've looked at other sites, and it seems that if anyone mentions drilling and milling in the same sentence gets hammered!

[castguy2003]

I would suggest a pair of bearings at the load end and a single on the pully end.

Castguy2003

[cbcnc]

Hi Kong,

I mill aluminum on my drill press and turn it on my wood lathe. It can be done. Don't expect super quality and tolerances though.
My drill press is a 1970's bench type import. CTT is the brand. I use a cheap cross slide vise and I admit that that is part of my problem with inaccuracy. The other part of the problem is in the axial endplay in the quill. I find that it works best when the quill is fully retracted and locked down. Depth of cut is changed by raising the table. You have to be careful not to move the position of the table when raising it. Also you have to be careful about how much of a cut you take or how fast you feed the part. Flex in the machine is an issue also.
When I first started the MT #2 tapered shaft would fall out if I took too much of a cut. Some gentle tapping and a rust fit seem to keep it in now.
But it has served my purposes so until I can get the metal lathe and mill that I want it will be OK.

Chris

[HuFlungDung]

/me puts away sledgehammer

How good do you want it? Angular contact bearings are what I would recommend, but depending on the design of your spindle, you may have to modify something so that you can preload them against each other. In certain sizes, you can also purchase a double row angular contact that is fairly wide, but takes care of the preloading problem since it is all internal to the bearing. List your bore and housing sizes, and the length of the existing bearing bore available, and I'll look up and see what bearing number you could adapt to it.

Metric dimension bearings are easier to come by. Your spindle may already be .6299 = 16mm, but to those not expecting it, it may appear to be 5/8" until you mic it.

[wms]

Kong,
Take a look at this site http://www.bardenbearings.com

They are the go to guys for spindle bearings. They have a spindle repair video and get a copy of the machine tool bearing catalog.
It will have lot's of info in it.

I would suggest you use a duplex pair of angular contact brgs on the tool end and a single or double deep groove radial on the pulley end.

I would use Phenolic cages, and shielded brearing. Expecially on the tool end to keep the chips out.
Class C- 7 or C- 7P are the best but cost lots more.
Also the amount of lube makes a difference, if there is to much it can generate heat. To little and you can tear up the bearing.

Hope this helps and good luck. Nothing ventured nothing gained.

[wms]

Sorry HU we posted about the same time.

[HuFlungDung]

No problem, WMS, I don't know everything and your input is certainly valuable.

I wanted to interject here that I recently converted on of my mills (Shizouka) from steel ball to ceramic Hybrid bearings. This is a retrofitted manual machine, so it was not designed for sustained moderate high speeds, meaning there is no spindle cooling. It is a simple grease packed bearing

I was getting near 200 degrees F when running steady at 5000 rpm for 5 to 12 hours. This was nasty and really made a cold tool stick hard in the spindle, enough so the toolchanger couldn't get it out. The spindle actually got the the point of jamming and scoring the spindle housing, it was so hot upon retraction. I had to insert cool down periods before I could do a tool change

Anyways, after the ceramic hybrid was put in, the same spindle runs at about 115 degrees F, no matter how long I run it. They were pricey, but I feel so much better knowing that the thing is not destroying itself when running at high speeds.

[wms]

Hu,
The ceramic bearing will run way cooler as you found out. The two drawbacks to them is that they are lot's more money and the will not take as much abuse.
You can reduce the amount of heat by the type of lube that is used in the bearing.
The best stuff I've found for "packed" bearings is Kluber Isoflex NBU-15. It is a white lube, that runs fairly cool, if you use the proper amount. As with all greases to much is not good. This is also the lube that Barden uses in their class 7 bearings.

[kong]

Wow, quick, quality replies, and no flaming! I love this site!
Anyway, I'm gonna go look at the info on the site wms suggested, and as they have UK offices too, it's a bonus! Hu, unfortunately i cannot get accurate measurements coz I have not yet removed a stubborn bearing sleeve fro mthe quill. cbcnc, i have a solid, old, Fobco star drill press, and to overcome the danger of the chuck flying off, i will be removing the jacobs taper, and getting a tool holder made to utilise the ?? thread used to hold the ejection nut. it does seem there is a lot more to bearing choice than i first thought, I'm off to do some homework!

[HuFlungDung]

Originally posted by wms Hu, The ceramic bearing will run way cooler as you found out. The two drawbacks to them is that they are lot's more money and the will not take as much abuse. You can reduce the amount of heat by the type of lube that is used in the bearing. The best stuff I've found for "packed" bearings is Kluber Isoflex NBU-15. It is a white lube, that runs fairly cool, if you use the proper amount. As with all greases to much is not good. This is also the lube that Barden uses in their class 7 bearings.

Whats this "abuse" you refer to? We're way careful over here