ball bearing retaining slug?

anchorman · Oct 31, 2018

I'm fixing a part for a saw that is no longer made, and have come against a small problem...

The main bearing had spun around in the bore in the casting, and wallowed it out, so I bored it larger, installed an aluminum sleeve with loctite 609, and then bored the sleeve to the proper size. My bearing now fits and seems concentric enough for the job. In going over the parts diagram to make sure I wasn't missing anything, I came across a part labeled "ball bearing slug", and realized that perhaps this missing part is why the bore in the housing got so sloppy in the first place.

The existing bearing is well attached to the armature of the motor, and is not making noise or seeming to have excessive play, so I wasn't going to try to pull it off and damage it in the process. The problem here is that it looks like the bearing is actually meant to be put in the housing first, since I can't see any other way to put this slug in place to keep the outer race of the bearing from spinning. I've never seen a bearing installed in this manner, and cursory googling found only other milwaukee tools put together this way.

I'm wondering if anyone has thoughts as to whether this slug is indeed meant to prevent the outer race from spinning, and whether I could get around using one by installing a small set screw through the housing to hold the bearing in place. Or maybe this part can be ignored? Please see attached pictures for details.

Thanks in advance,
jon

anchorman · Oct 31, 2018

I forgot to mention, the BB retaining slug is part 26 on this diagram. I didn't cut the hole for it all the way down, but did use a small ball burr to poke a hole between the sleeve and that channel in the housing, and could easily enough make it go the entire depth of the bore where the bearing sits as it was before I sleeved it.

HuFlungDung · Oct 31, 2018

Perhaps you mean part 62?

Did the original bearing have a lengthwise groove across the outer race for the pin to nest in?

It may have been a loose fit design, but that doesn't make it a good design. If that bearing needs to be locked, I'd apply Loctite to the race. The bearing on the other end needs to be free to float, to allow for expansion of the shaft.

BTW, I make sleeves out of steel or cast iron, because the bearings often will float in the endbell so the fit cannot be press. Assembly also requires that the bearings be a very close push fit, at the tightest. Aluminum endbells wallow out quickly, because the race cannot be tight. Most of the time, aluminum endbells actually have a steel insert cast in place and then bored for the bearing. But if you Loctite the bearing in, then aluminum is passable, I suppose. Consider when Loctiting something in, exactly how you will pull it apart next time because it can be a real bitch and a heat of 400°F will be required.

anchorman · Oct 31, 2018

yes, part 62. I'm not always dyslexic, but when I am I usually write things backwards

Loctite on the race means it's not coming out again. I'm not original caretaker of this saw, so not sure if the bearings are original. I didn't think of grove in the bearing race, but that's an interesting idea. I think I'll drill and tap for a set screw, and use some blue loctite to keep that in place. seems a safer bet than loctite on the bearing.

If I have to do one of these again, I'll make the sleeve out of steel, I guess.

Thanks!

HuFlungDung · Oct 31, 2018

I wouldn't really advise putting a setscrew against the bearing as that eggs the race out of round and/or makes a bump that the balls have to roll over. The motor rewind shops use Loctite (wisely) on many bearing applications where the fit is slightly worn and doesn't warrant a machining operation due to cost effectiveness.

I'd suggest put a single wipe of Loctite lengthwise in the housing so you've only got a narrow band of it to deal with at extraction time. No need to slather it on everywhere.

anchorman · Oct 31, 2018

Thanks for the heads up on the race bulging inside. I was thinking to grind a little flat on (or a small divot in) the bearing, and just make it snug with the screw, rather than screwing down extremely tight. sort of reproduce the effect of the pin and groove in the edge of the bearing without needing quite as much precision in my grinding. I might could grind the slot in the bearing with a chainsaw sharpening stone, and put the pin in as per original. The way the shaft and bearing go into the end housing, they are never coming out again if they have any adhesive holding them. Which may be ok, but I hate to doom this thing to the scrapyard if it needs future service.

jim rozen · Oct 31, 2018

anchorman said:
yes, part 62. I'm not always dyslexic, but when I am I usually write things backwards

Interestingly I viewed the diagram and correctly identified the part. It *said* 26 on it. Chalk one up for two
dyslexics cancelling each other out.

I suspect the assembly technique (dutchman pin) was done to reduce costs, to eliminate the need for a precision
fit between the original bore and the bearing.

anchorman · Oct 31, 2018

jim rozen said:
anchorman said:

yes, part 62. I'm not always dyslexic, but when I am I usually write things backwards

Interestingly I viewed the diagram and correctly identified the part. It *said* 26 on it. Chalk one up for two
dyslexics cancelling each other out.

I suspect the assembly technique (dutchman pin) was done to reduce costs, to eliminate the need for a precision
fit between the original bore and the bearing.

Click to expand...

Hi Jim,

Would a pin like that mate with a corresponding grove in the bearing to keep it from spinning, or just get wedged in there to take up some side to side slop? Seems like if it were just pressed in to push against the bearing that it wouldn't be doing much different than a set screw lightly pushing on the bearing. I'm probably overthinking all of this, but I like to fix things right when possible. It looks like the OEM bearing is not available anymore, so if there were a groove in the original, it's not something I could get without making myself now anyway.

-jon

John Allan · Oct 31, 2018

I have seen circular saws made with a short length of ~3/16 hard rubber to keep the outer race from spinning in an aluminum housing.

anchorman · Nov 1, 2018

that might be what that pin/slug is made out of. They don't list on the parts diagram what it's made from. Thanks for the heads up! I'll give that a shot.

anchorman · Nov 1, 2018

and wouldn't you know? A few weeks ago I threw away the used pieces of 3/16 urethane o-ring that get used as belting on some equipment at my old job... right as they would have come in handy. Typical.

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