Asking for comments regarding installation issues of angular contact vs tapered roller bearings.

[Richard King 2]

I didn't read all the posts. I did want to say I stopped hammering or pressing on bearings several years ago. I made a cone bearing heater. I used a 4" diameter x 8" shaft of aluminum and turned a taper on it from my lathe compound - over approx 6" I went from 3" to 1/4" taper. Then flipped it around and drilled / bored a 1/2" clearance hole in about 6" long. Ordered a 110 v heat sink from Grainger and slid it in the hole, locking it in there with a plate. I set the bearing on it, plug it in and use a infrared heat gun to test the temp and when the temp raises the to 140 F which takes about 5 minutes. Then using a channel lock drop the bearing on the shaft. The heater expands the inner race a few thousands and it slips on , slicker then shise. You can but them for under $1000.00, but I made mine. It works super. I can go and take a few pictures if needed. It's out in my shop. I've never tried this, but a customer of mine used to lay the bearing on a cookie sheet and heated the bearing up in their cafeteria gas stove oven to 140 degs. They had a rolling work bench with a vise they rolled into the cafeteria....lol....That worked too...

 

[addertooth]

For those not following, the purpose of the KEYED spacer is to make sure the spindle gear aligns with the tumbler gears.
The upgraded tapered bearings are thicker, so this forces the spacer to be Thinner to keep the gear on the spindle aligned with the
tumbler gears.

A note of warning, the original spacer is made of plastic, and it's Internal diameter is sloppy-loose. Measure the spindle on the lathe
and cut a clearance hole in your new spacer or it will have too much slop. As long as things are properly tightened down, it shouldn't
flop, but I know how machinists can be about dimensions. Then you need to cut/file/shape a keyway on the internal diameter of the
spacer.

Here is a picture of the spindle-gear/tumbler engagement. Also, a picture of the spacers after they are keyed.
Only one was needed, but I made two of different thicknesses so I could play with ideal gear alignment.

 

[homebrewed]

Wow, that is a really bad way to have angular contacts without a center spacer.

Any way, I see some of the problems. The spindle shaft should not have to press on (or beat like ToT). You know from the bearings the od of the shaft. Make or buy an OD brass lap and get some diamond lapping paste.

Suburban tool lapping video

Another really good video on bore lapping

To drive the part for lapping it really doesn't have to be that accurate(on center). So rig something up or go to a friends house and use their lathe.
Any way you want a light interferance fit. Literally only .0002" interferance and its almost impossible to get a fit like this on lathe but easy (but time consuming) to lap in. With it very clean an Lap, clean, and measure. It goes slow so you shouldn't overshoot if you use fine paste. Laps keep things on concentric(if they were to begin with) were polish paper will not.

Get some dry ice from town, cool your outer races and warm the housing with a heat gun. The outer races should fall in. Let temps equalize. Heat the inner cone to 225-250 degrees and it should slide on. If you don't want to use your wife's oven, either get a small convection oven from a garage sale or buy the correct tempil stick and use a hot air gun. The tempil stick will melt at its rated temp.

Also ToT showed horrible practice with bearings. Don't set them on an abrasive scotch bright pad, cleanliness is paramount in bearings. We rebuild tools in clean rooms and filter solvent to 2 microns and then do a final rinse of parts with canned brake cleaner.

Thanks for the reminder about laps. I have a small mill that can be used to drive a lapping tool, although I'm not sure how well ID lapping will work with regard to a pocket. I'm thinking it may be difficult to lap the ID near the bottom of the pocket (the bottom corner of the lap will quickly wear away). Maybe cut a small over-ID relief at the bottom? I doubt that a little relief groove will materially affect the stability of the bearing once it's installed.

Regarding preexisting procedures/usages of bearings on these machines, you have to keep in mind that they are mostly designed to be cheap hobbyist-level tools. A new 7x14 lathe only costs about $1100 from Grizzly so the manufacturing costs have to be kept pretty low. When I pulled the old bearings off the spindle, I noted that it still had obvious turning marks so it wasn't ground to tolerance. About the only part of the lathe that IS ground is the top surface of the bed.

 

[Firebrick43]

Thanks for the reminder about laps. I have a small mill that can be used to drive a lapping tool, although I'm not sure how well ID lapping will work with regard to a pocket. I'm thinking it may be difficult to lap the ID near the bottom of the pocket (the bottom corner of the lap will quickly wear away). Maybe cut a small over-ID relief at the bottom? I doubt that a little relief groove will materially affect the stability of the bearing once it's installed.

Regarding preexisting procedures/usages of bearings on these machines, you have to keep in mind that they are mostly designed to be cheap hobbyist-level tools. A new 7x14 lathe only costs about $1100 from Grizzly so the manufacturing costs have to be kept pretty low. When I pulled the old bearings off the spindle, I noted that it still had obvious turning marks so it wasn't ground to tolerance. About the only part of the lathe that IS ground is the top surface of the bed.

If using tapered rollers I wouldn't lap the pockets. Just freeze with dry ice the cups(outer race) and they should fall in, and expand as they warm. If using angular contacts, then yes, use either a boring head and cut a light recess if it will fit on your mill. The bearings do have a radius so its not to critical. I personally wouldn't use angular contacts here, even though in most situations I think they are worth the cost.

I would just lap the OD of the spindle shaft.

I am trying to keep that in mind the original quality/use, but those are the very issues that are causing problems. And therefore I recommended lapping as one can make their own lap out of scrap cheaply(only purchasing the compound) and have excellent results with little money in exchange for ones time. You learn new skills along the way.

 

[Kukulski]

Article on installing angular contact bearings…

https://www.arceurotrade.co.uk/machineguides/Mini-Lathe-Angular-Contact-Bearing-Change-Guide.pdf