[Alan Ing]

As others have mentioned, an oversized reamer is a great way to go. You can definitely bore precise holes using a boring bar, but using a reamer is a bit faster.

I would suggest you get an over / undersized chucking reamer set. Enco's cheapest set is currently $59.95 (china's finest, prefer american, but these have served us well for 6 years). These sets come with 14 reamers (reamers are .001" + and - of standard chucking reamers centered on 1/8" - 1/2" sizes by 1/16th increments)

.124"
.126"
.1874
.1876
.249
.251
.3115
.3135
.374
.376
.4365
.4385
.499
.501

The great thing about an over/under size set, is that you can use the undersize reamers for pressing fitting pins and shafts (some bearings) and use the oversize ones for slip fits.

Also get a standard size reaming set from 1/8" to 1/2".

While we are talking about reamers, other useful reamers that we use for FRC include .874", .875", 1.124" and 1.125" which really help if you want to install 3/8" and 1/2" ID flanged bearings like the ones used in Andymark gear boxes. We use these all the time and make life a whole lot easier. Since these reamers are on the large size, we have had to turn down the shafts so a standard 1/2" chuck or a 3/4" collet could fit them.

I think we also have a .315" reamer which we use if we are installing custom gears to a CIM motor. remember, the shaft on a CIM is metric 8mm (.315) not 5/16" (3.125). Probably would be better if we had a .316" reamer.

Remember, these reamers can be used in a lathe or a mill.

Typically we bore or drill hole sizes about 1/64th" smaller and then ream them to fit. Do not run the reamer at typical drill speeds. Run them much much slower and with lubricant for best results.