I have commented that I replaced all the bearings in my square dial 10EE. That wasn't quite true, the large bearing pair in my reduction gearbox seemed good so did not replace it, but in using my lathe there was a slight kerklunk noise from the reduction gearbox so I decided to replace the bearing pair.
The bearing pair is a New Departure 20209DTL 15 degree angular contact pair. The DT means universal ground for any mounting configuration and the L is light preload, and no number after the DTL means ABEC 1. The problem is the front bearing has a snap ring, which for New Departure is a 4 prefix, so the front bearing is 420209DTL.
LocateBB on Ebay does not show any 420209 bearings. They do have a H420209 and a corresponding H20209, the H meaning 25 degree contact angle.
Modern designation angular contact is 7000 series, and for a snap ring bearing the suffix is NR. LocateBB had an NTN 7209NR and equivalent 7209, but the standard NTN contact angle is 30 degrees. I purchased this set because it was significantly less expensive than the New Departure set, and neither of these sets matched the original contact angle.
If there had been an issue with the higher contact angle, I think my next attempt would have been to get a normal 20209 or 7209 pair and simply loctite 290 the outer races in the casting. This option provides lots of choices, for example on Ebay right now there is a set of 4 20209DTL7 bearings, brand new for only $65. DTL7 bearings are of the same precision as the spindle bearings, ABEC 7, which is not needed for the gearbox, but it is an example of the low price for even very high quality bearings when there is no snap ring. The fit of the bearings in the casting is so tight that I do not think there would be an issue with no loctite, but with the large contact surface, Loctite 290 would probably secure the bearing so well it would probably be very difficult to remove.
As it is the NTN bearings are in fact quieter than the bearings I removed and there doesn't seem to be any ill effects of the 30 degree contact angle. If anyone is considering replacing the bearings, I bought the only NTN 7209 NR that LocateBB had, but the H20209 pairs are available and the Loctite method is always available.
The bearing pair is a New Departure 20209DTL 15 degree angular contact pair. The DT means universal ground for any mounting configuration and the L is light preload, and no number after the DTL means ABEC 1. The problem is the front bearing has a snap ring, which for New Departure is a 4 prefix, so the front bearing is 420209DTL.
LocateBB on Ebay does not show any 420209 bearings. They do have a H420209 and a corresponding H20209, the H meaning 25 degree contact angle.
Modern designation angular contact is 7000 series, and for a snap ring bearing the suffix is NR. LocateBB had an NTN 7209NR and equivalent 7209, but the standard NTN contact angle is 30 degrees. I purchased this set because it was significantly less expensive than the New Departure set, and neither of these sets matched the original contact angle.
If there had been an issue with the higher contact angle, I think my next attempt would have been to get a normal 20209 or 7209 pair and simply loctite 290 the outer races in the casting. This option provides lots of choices, for example on Ebay right now there is a set of 4 20209DTL7 bearings, brand new for only $65. DTL7 bearings are of the same precision as the spindle bearings, ABEC 7, which is not needed for the gearbox, but it is an example of the low price for even very high quality bearings when there is no snap ring. The fit of the bearings in the casting is so tight that I do not think there would be an issue with no loctite, but with the large contact surface, Loctite 290 would probably secure the bearing so well it would probably be very difficult to remove.
As it is the NTN bearings are in fact quieter than the bearings I removed and there doesn't seem to be any ill effects of the 30 degree contact angle. If anyone is considering replacing the bearings, I bought the only NTN 7209 NR that LocateBB had, but the H20209 pairs are available and the Loctite method is always available.
