[Artie F. Emm]

I'm learning some basic lathe operations, making guide wheels for use on a belt grinder. Think of a skateboard wheel and you'll have the picture. I turned some aluminum stock to outside diameter, faced the sides, and drilled a hole for the axle.

Now I want to create an opening for a bearing. The outside diameter of the bearing is 1-1/8" x 3/8" wide. How much additional OD do I provide so the bearing will press in and out easily enough?

Thanks!
Dave

[exnailpounder]

A good fit would require you to press the bearing in and drive it out. I would stay as close to your dimensions as you can. I'm kinda new to the lathe too but you're going to find out that there is nothing really hard about it, plus it's fun. Good fit up is the mark of a craftsman but a couple thousandths bigger won't hurt anything and allow you to remove the bearing without too much pain as long as some slop isn't going to cause you any problems.

[Farmwelding]

Yep as tight as you can get it. All I know is that any bearing flying out of anything is never a good time. Give yourself a tolerance of like .010 and you will probably get it tight enough

[Erich]

.010 interference will ruin a ball bearing in short order.
There are lots of bearing catalogs that specify the exact interference but 0.001 inch should work.
You want a press fit on the ring of the bearing that is rotating, and clearance on the non rotating.
Turn it a thou or two under size and then use some abrasive paper to smooth the surface finish and bring the size in.
If you do over shoot and endup with slop you can use Green Loctite stud and bearing mount.

A skateboard wheel would be press on OD and slip fit on ID.

A shaft spinning in bearings would be Press on the ID.

[electrode]

For a press fit or interference fit I would go .0005 to .001 and would get there by using a reamer. Then I would heat the piece with a hot air gun and tap the bearing in. If you go too loose you can always add some green loctite 640 to fix that. So machine the hole for your 1.125 OD bearing to 1.1240 or 1.1245 and polish it to fit if you don't use a reamer. You are looking for an interference fit of .0005 to .001 for best results and loctite if you go too loose.

Info on different loctite products from web:

271, Red: High strength threadlocker for larger diameter hardware.

262, Red: High strength threadlocker for for hardware smaller than that which uses 271 (more like heli parts). Either does a good job for our stuff, however. I see 271 most commonly in auto parts stores.

609, Green: Retaining compound, high strength, for mounting slip fit bearings to shafts. An appropriate product for tail boxes.

603, Green: Retaining compound, high strength, similar to 609 but good where the parts may be a little oily. Good for mounting oilite bushings in housings, BTW.

640: Green: Retaining compound, high strength. Similar to 609 and 603. Lacks the oil tolerance of 603. I use it where I might have trouble with adjacent bearing contamination with the product, such as start shaft bearing blocks, since it has a little greater viscosity than 603.

638, Green, rather thick: Ultra strong retaining compound for assemblies with a marked amount of slop in the fit, min 0.004". Don't try to use this stuff for our normal bearings on healthy shafts. It sets almost immediately in the tight gap, and you'll never have the chance to get the bearing into place.

290, Green: Wicking product for thread locking AFTER assembly. Medium strength, much stronger than 242 blue in my experience. Not the correct choice per loctite for bearing mounting.

242, 243 Blue: Classic medium strength threadlocker for most of our threadlocking applications. 243 is the oil tolerant version.

222MS, Purple: Low strength threadlocker for small diameter or otherwise delicate fasteners.

Bottom line:
NEVER choose a loctite product by color alone.

You can build a really good model with 242 for thread locking parts you'll need to remove, 271/262 for screws you really don't want to ever move on their own, and 609/603 for fixturing bearings to shafts. 290 is great for set screws which needed to be tweaked for ideal postition of the part on a shaft (like a bevel gear) and which you don't want to have to go back and remove the screw to apply the loctite.

I know guys use other products for these tasks, but these recs are based on the specs and technical data sheets published by Loctite.

Ben Minor

[exnailpounder]

You machinists I love the fact that you guys are so precise! I never met a machinist that never said " I could do that better" when you look at something

[Farmwelding]

Well when you learn machining or do a machining project you have to be precise because two parts off .010" in both directions doesn't work. It's withing tolerance sometimes but it doesn't mean it is going to work.

[cj737]

Instead of heat, you can also throw both pieces in the freezer. They will each shrink slightly allowing a simple press fit, that after they warm, will be very snug. The tolerances advised are exactly what I would use too.

[bruce991]

Best to sneak up on it and get it right than not be a craftsman and scrap the part. .002 press maximum on most of my machining jobs. Most accurate final size on a shaft would be done on a centerless grinder, and a ID with a reaming, or ID grinder.

[Rupes]

You machinists I love the fact that you guys are so precise!

They just don't have big enough hammers....


Besides if you overshoot just tig it up and have another go


Theres a channel on youtube called "Make it extreme" He made a belt grinder. I was intrigued but I wondered after looking at some other model if the wheels shouldn't be crowned like bandsaw wheels for keeping the belt centered. I did find plenty of wheel kits around though that I thought of buying and just making up the rest.

So how you do you machine up an accurate crown on an alloy wheel on a lathe

[kiwi2wheels]

With an interference fit on the OD, go for a bearing with a C 3 tolerance.

Even if you use a slip fit inner/outer, the C 3 will give better life.

[Artie F. Emm]

Wow! Thanks for responses. At the risk of exposing my ignorance... I'm glad I posted this question. The lathe work is something I've always wanted to try, and I'm finding it interesting and fun- and gaining more and more respect for the people that do it well.

These wheels are part of a 2x72 belt grinder build, and since I've seen 1616zz bearings in use on other machines it seemed reasonable to use them. The bearings accommodate a 1/2" axle so I plan to use a 1/2" bolt; I drilled a 9/16" hole through the wheel so contact would only occur between the bearing and the bolt. The "well" for the bearing will center around the axle hole, and I thought I would leave a raised ridge around the axle hole so that surface of the wheel would contact only the inner ring of the bearing. Is that a good idea, or is it better to use a spacer on the bolt?

[bruce991]

Hope your looking at 10.9 grade shoulder bolts and not soft hardware grade bolts or you will buying bolts by the pack.

[electrode]

So how you do you machine up an accurate crown on an alloy wheel on a lathe

Use the compound or a taper attachment if your lathe has one and a good tool bit.

[electrode]

Wow! Thanks for responses. At the risk of exposing my ignorance... I'm glad I posted this question. The lathe work is something I've always wanted to try, and I'm finding it interesting and fun- and gaining more and more respect for the people that do it well.

These wheels are part of a 2x72 belt grinder build, and since I've seen 1616zz bearings in use on other machines it seemed reasonable to use them. The bearings accommodate a 1/2" axle so I plan to use a 1/2" bolt; I drilled a 9/16" hole through the wheel so contact would only occur between the bearing and the bolt. The "well" for the bearing will center around the axle hole, and I thought I would leave a raised ridge around the axle hole so that surface of the wheel would contact only the inner ring of the bearing. Is that a good idea, or is it better to use a spacer on the bolt?

I don't understand the 9/16" hole part on the wheel. Do you have any pics? I would have left it at 1/2" and put the bolt through the bearing ID.

grinder wheels.jpg (18 KiB) Viewed 997 times

[Artie F. Emm]

I don't understand the 9/16" hole part on the wheel. Do you have any pics? I would have left it at 1/2" and put the bolt through the bearing ID.

My thinking for the 9/16" hole was to avoid contact friction between the axle and the wheel. That way the axle will only touch the bearing ID. To me that makes intuitive sense, but please let me know if that's wrong, or a recipe for failure. I've only drilled one wheel so far, happy to pivot and make the others right.

[Rupes]

Id of the bearing is 1/2, so slightly larger bore through the rest of the wheel for axle clearance. You're putting a bearing on each side yeah like on a skateboard wheel? Some of the ones I've seen just had a single bearing but it seems like a good way to chew it out.

Can't really tighten them up either, well the drive wheel and one of the wheels you can but the others will have to have a bit of play so they can find their center on the belt?

[Artie F. Emm]

You got it, a bearing on each side of the wheels, much like a skateboard wheel.

In the picture that Electrode added, the largest wheel is the drive wheel, mounted on the motor shaft. The mid-size wheel is a tracking/idler wheel, which has a side-to-side tracking adjustment and is mounted on a spring arm to take up slack in the belt. In the aluminum version of these wheels, the drive and idler wheels are domed with a peak in the center of the tracking surface that keeps the belt running true. The two smallest wheels are guide wheels and are flat, not peaked. Overall tracking also requires the wheels to be mounted on the same plane.

[electrode]

Id of the bearing is 1/2, so slightly larger bore through the rest of the wheel for axle clearance. You're putting a bearing on each side yeah like on a skateboard wheel? Some of the ones I've seen just had a single bearing but it seems like a good way to chew it out.

Can't really tighten them up either, well the drive wheel and one of the wheels you can but the others will have to have a bit of play so they can find their center on the belt?

I think I understand now. Do the wheels come with a hole in the center that is 1/2" and you need to machine the wheel for the bearings to press into? Then the center is drilled slightly larger for clearance like you said to keep the axle (bolt) from rubbing on it? Makes sense to me. I would have thought if you bought the wheels they would have the bearings already in them. But I looked back at the first post and realized you are making the wheels. Carry on...sounds good to me. As long as the ID of the bearing is pressed against the inner part of the wheel you will be fine.

[Erich]

I would make some spacers to fit between the two bearings.
Use 5/8 od 1/16 wall tubing. Open the id so the bolt fits thru.
Press the bearings in with the spacer between the inner rings.
Now you can install the 1/2 inch bolt and tighten the daylights out of it and it won't put any undue stress on the bearings.
Another spacer on the outside will set the location of the wheel relative to the main structural plate.

[electrode]

I would make some spacers to fit between the two bearings.
Use 5/8 od 1/16 wall tubing. Open the id so the bolt fits thru.
Press the bearings in with the spacer between the inner rings.
Now you can install the 1/2 inch bolt and tighten the daylights out of it and it won't put any undue stress on the bearings.
Another spacer on the outside will set the location of the wheel relative to the main structural plate.

I was starting to post that same thing in my last remarks but if he does it correctly the inner race could be on solid meat just like a spacer would be. I was thinking on the lines of a motorcycle wheel how there is a spacer tube between the bearings for the same reason.

[Artie F. Emm]

The width of the bearing is 3/8. My plan is to cut the bearing opening to that 3/8 depth in a ring that will touch only the inner bearing ring, and cut the rest of the opening a touch deeper. That should provide that same compressibility of the tube idea.

[electrode]

The width of the bearing is 3/8. My plan is to cut the bearing opening to that 3/8 depth in a ring that will touch only the inner bearing ring, and cut the rest of the opening a touch deeper. That should provide that same compressibility of the tube idea.

You got it. The tube on a motorcycle wheel for example is precisely machined to allow the axle nut to be torqued while keeping the bearing from any unwanted lateral force which would greatly shorten the life of the bearing. But you got that figured out so go for it.

[Rupes]

Used to tick me off as a kid with roller skates, when you hold the center of the bearing the outer spins just fine. When you install and have two bearings on that axle because they didnt have spacers in between when tightened it up it would put lateral force on the bearing and bind it up and so you'd have to back off the nut. Always seemed a dumb design to me. It basically means the bearings inner race can rotate on the axle. I'm pretty sure they're still like that. I think its just the weight of the rider that forces the axle down on the inner race and the bearing takes the line of least resistance and works normally rather than spinning on the axle.

As for the grinder, what would be its primary use? I had something very similar in mind but with a removable front end that could be swapped out for an attachment like this. Having the entire unit mounted to a 6 or 8 inch square post concreted in the ground would be great especially if you wanted to hinge it so it could be rotated to a horizontal plane. I was thinking along the lines of knife making and general purpose

http://www.ebay.com.au/itm/231429758787 ... EBIDX%3AIT

[Artie F. Emm]

I'm thinking of general fabrication use. For knife makers a machine like this is a must have, but i'm not a knife maker... yet, at least. Swapping ends out and using rollers like the ones in your link, rotating 90* for grinding on a long edge- it's a very versatile machine. This link shows the machine in use and swapping ends out, and shows it quickly and easily fishmouthing pipes for welding, which is an eye opener!

https://m.youtube.com/watch?v=BYllaxuzMk0