drill precise 1.124" diameter hole in 12L14 Carbon Steel 1

[rmarcus999]

I need to drill a hole which will house a ball bearing in a piece of 12L14 steel. I would like the hole to be 1.124" +0 -.0005. I usually use a reamer for a precise hole, but I didn't find a reamer that large and anyway large reamers are very expensive. The only way I can think to do this is with a boring head. But, I don't have an inside micrometer and can't find gage pins the right size. I thought of using 2 gage pins next to each other whose diameters add to 1.124". I also thought about making a gage pin. Any suggestions would be appreciated.

 

[MikeHalloran]

You know how small threading dies are almost split, and fitted with a tangential screw that can spread them just a tick? Make something like that, and use it like an inside mike.



Mike Halloran
Pembroke Pines, FL, USA

 

[dvd]

1. Decide what temperature that you want the hole to meet tolerance.

2. If your hole is that important you might want to pay someone to bore it.

 

[Metalfixer]

Measure with a telescope gage and 1"-2"outside micrometer.

 

[btrueblood]

You should be able to get a reamer in the correct size for under $100.

Measuring to <.0005" with a telescope gage can be tough.

 

[looslib]

Measuring to <.0005" with any hand-held device will be tough.
Use a CMM, but this may be overkill.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[unclesyd]

As posted above measuring to 0.000%" is big problem.
At a minimum it would normally take a 3-point micrometer to measure and check circularity, taper, etc.
You can forget about drilling with that accuracy as the old probable hole size rule will get you unless you drill and ream..

Another option would be to jig grind the old drilled hole.
Another possible option might be to take the precision out of mounting the bearing by using Tolerance Rings.

http://www.usatolerancerings.com/

 

[juergenwt]

rmarcus - holding 1.124 +0, -0.0005 with a boring head should not be a problem if you are skilled. First make a plug gage. 1.1235 on one side (GO) and 1.124 on the "NO GO" side. 12L14 should cut very nice. Make the boring tool with a small radius (stone it!) in front and work with a good caliper until you get close. Than add slowly, go about 1/8 deep - check with "Go" side. Lubricate. Good luck.
For some help in checking with the plug gage you can put a 1/8 lead 1.123 in front to help you get started, but than you need to go deeper than 1/8 in order to check.

 

[engineer4fun]

I agree with looslib is really hard to measure <.0005 but the CMM would be the best choice for the job.

Designer and <a href="

http://www.coilingtech.com/compression-springs.html">compressing

springs</a> enthusiast