Yet another finger engine

[SmoggyTurnip]

I started to build a finger engine similar to Bogs.
This is what my large standards look like so far:

I got a bunch of bearings at a local hobbie shop and a pirated copy of Bogs CAD software.

The numbers shown are the best measurements I could take with the tools shown. There are 2 sizes of bearings. I am guessing that they are metric bearings - the box they came in did not give any measurments.

If i convert my measurements to SI I get
Large bearing OD = 10.988 mm
Small bearing OD = 7.98 mm
Both ID = 5.0038

Now I need to decide what size hole to make for them. And how to make the hole.
I do not have a boring head for my mill but I am considering making one, I do have a 4 jaw chuck for the lathe.

What size hole should I be trying to make? How accurate does it have to be.

Sounds like such a simple thing - make 2 holes for the bearings, but I have been thinking about it for a couple of weeks and I am still not sure which way to go. Any advice would be appriciated.

 

[kf2qd]

Looks like the bearings are 11mm & 8mm easiest way to make the holes is with a reamer.

 

[CrewCab]

and a pirated copy of Bogs CAD software.

............. : .......... ;D ........... your not alone ST :big:

CC

 

[Mcgyver]

There are 2 sizes of bearings. I am guessing that they are metric bearings - the box they came in did not give any measurments.

the vast majority of bearings that are out there are metric; even in imperial machines. you can get imperial sizes, but they are not as common so most things are made with metric bearings because they're the most widely available. it shouldn't;t matter - you machine to .4330 (11mm) instead of some nominal imperial number. btw, are you using the ratchet to tighten up that mic? it should have read .4330 instead of .4326 which says it either needs some adjustment you are using a heavy hand. Its tough to work to better than a thou when you are starting half a thou out.

Fitting roller bearings is some of the most demand work a machinists can be called up to do - they should be a specified press fit and the tolerances are in tenths. too far one way and its loose, too far the other and its applying too much force on the bearing its holding. While this is true, we can put aside these exacting standards until we're making say, a spindle. For now be as accurate as you can, better than a thou and use cylindrical loctite or other retaining compound to seat them

don't worry about not having a boring head, it is best to bore them in the lathe anyway.