Civil Engineering Reference
In-Depth Information
Fig. 11.17. A hand reamer has a tapered lead to the cutting edges.
Using a reamer
When preparing a hole for reaming you should use the two-hole drilling meth-
od.
You need to drill a decent size hole prior to reaming. For small reamers up
to
3
⁄
8
in (10mm) leave about 0.012in (0.3mm) for the reamer to remove. For
reamersupto
3
⁄
4
in(19mm)leave0.016in(0.4mm)andover
3
⁄
4
in(19mm)leave
0.020in (0.5mm).
For reaming speeds use about
1
⁄
3
to
1
⁄
2
of the drilling speed for the same
diameter. Feeds should be from 0.002 to 0.004in (0.05 to 0.1mm) per tooth
per rev. Multiply the feed per tooth by the number of teeth to give the feed per
revolution. When you are feeding the reamer you will probably feel it if you
are pushing the reamer too fast as it will start to bind up.
Use plenty of neat cutting oil for steel, brass, bronze, gunmetal and cast
iron, but for aluminium paraffin should be used. For any type of plastic you
should not use oil as a cutting lubricant as it can attack and/or degrade the
plastic; instead compressed air or plain water should be used.
DRILLING ADVICE
Drilling 90-degree cross holes
You can drill 90-degree cross holes through a bar by using a bar through the
first hole resting on two parallels or clocked true with a test indicator. You
could also drill cross holes using a dividing head.
