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- Apr 30, 2015
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What's a magneto bearing? What's a magneto? Just kidding I know what a magneto is.
Mark S.
Mark S.
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Spindle bearings
- Thread starter NGillem
- Start date
You have a 6204ZZ bearing with phenolic cage. Ill look thru my stock tomorrow and see if i have any. Do the end caps press againgst the inner or outer race?
Is the any room behind the race that is stuck in the housing?
Where are you located? I may be able to remove the old races and install the new ones for you.
Is the any room behind the race that is stuck in the housing?
Where are you located? I may be able to remove the old races and install the new ones for you.
- Joined
- Jan 29, 2017
- Messages
- 311
I reckon they are L20 bearings, 6204's are normal deep groove ball brgs, they dont dismantle like magneto or angular contacts. Being deep groove there is no adjustment to minimise clearances which means any tightening of the spindle nut will force the inner races towards each other with catastrophic results. Any machine spindle of such precision will have angular contact bearings and is adjusted accordingly.
My FAG bearing book lists a B7204E.T.P4S.UL as the correct brg to use, good for 30000 rpm with grease or 45000 with oil. Dimensions are 20 x 47 x 15mm in metric.
SKF list a 7204BECBP in their book. SKF rate theirs at 18000 rpm but don't mention lubrication.
The only difference is the SKF brg is 14mm max width while the FAG goes to 15mm.
I had a good look at your pictures and noticed how there is a step behind the innermost brg races. I had a similar situation on my G0602 headstock and not having the correct puller to extract them I ground out two opposing recesses in the casting to get some purchase with a pin punch. After the shells were out I filed them larger and dressed them for future access. You may be able to do the same. I think your shells are not fitted with much of an interference, more a nice hand press fit if anything.
Good Luck.
My FAG bearing book lists a B7204E.T.P4S.UL as the correct brg to use, good for 30000 rpm with grease or 45000 with oil. Dimensions are 20 x 47 x 15mm in metric.
SKF list a 7204BECBP in their book. SKF rate theirs at 18000 rpm but don't mention lubrication.
The only difference is the SKF brg is 14mm max width while the FAG goes to 15mm.
I had a good look at your pictures and noticed how there is a step behind the innermost brg races. I had a similar situation on my G0602 headstock and not having the correct puller to extract them I ground out two opposing recesses in the casting to get some purchase with a pin punch. After the shells were out I filed them larger and dressed them for future access. You may be able to do the same. I think your shells are not fitted with much of an interference, more a nice hand press fit if anything.
Good Luck.
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There is a spacer that pushes against the inner race on the right hand side off the top pic... the other larger pieces are end caps that keep out debris from what I can tell. There is no room to get behind them, in the second pic you can see shims behind the race I'm assuming to set bearing preload those shims can be rotated but no other movement to speak of So no real room to get behind.
Thanks again for all the help
Thanks again for all the help
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- Jul 2, 2014
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Those are not 6204ZZ bearings...
- Joined
- Jan 29, 2017
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NG, that's correct, those shims are for setting preload, same for any other machine spindle. Considering the bearings you removed are either magneto or angular contacts, thats all I would be searching for to replace the originals with.
I wouldn't want you to destroy your grinder because someone recommends changing them to another format. I like the fact you're not scared to take on a job like this because in reality it is simple, its the bearing adjustments that cause the most grief.
cheers
I wouldn't want you to destroy your grinder because someone recommends changing them to another format. I like the fact you're not scared to take on a job like this because in reality it is simple, its the bearing adjustments that cause the most grief.
cheers
- Joined
- Jan 29, 2017
- Messages
- 311
NG, I noticed in your last post that you said "the shims can be rotated". That seems to tell me that there was excess clearance in the assembly, or that particular shell has moved somehow. Indicating that there is a minimum amount of interference holding the shell in. Maybe your ultrasonic cleaner started walking it out.
For purely radial loads such as a surface grinder, properly pre-loaded deep groove bearings will work just as well as angular contact bearings at a much lower cost. For hobby level the cost difference can mean a lot. For a mill spindle angular contact duplexed bearing are a requirement, due to the thrust loading.
Nate can decide which route he wants to go. I am suggesting an affordable solution. Worst case, he can replace them later with the more expensive angular contact bearings.
Nate, keep in mind whichever bearings you decide on, the shims will have to be adjusted for proper pre-load. Adjusting the pre-load to run properly at operating temperature can be difficult to set. If you don't have enough clearance when cold the bearings may seize at temp.
Nate can decide which route he wants to go. I am suggesting an affordable solution. Worst case, he can replace them later with the more expensive angular contact bearings.
Nate, keep in mind whichever bearings you decide on, the shims will have to be adjusted for proper pre-load. Adjusting the pre-load to run properly at operating temperature can be difficult to set. If you don't have enough clearance when cold the bearings may seize at temp.