User should be careful not to drag file across work on back stroke as with any filing operation. Files shall be kept clean
and free of rust. Clogged files can be cleaned by wire brushing. The use of chalk or talc on file will help prevent
3-201. Machine filing using rotary files (miniature milling cutters having spiralled sharp teeth with smooth deeply cut
flutes) are operated at high speed. The rotary files are operated up to 10,000 RPM for small diameter and to 2,000
m2Yimum peripheral feet/min for the larger diameter. The teeth should be coarse (about 14 teeth per inch) with deep
polished flute and spiral notched design.
Wear goggles or face shield when filing with rotary files to protect eyes.
3-202. REAMING. Generally most of the different type reamers may be used for aluminum, but for best results the
spiral fluted reamers are recommended solid, expansion or adjustable. The spiral should be opposite to the rotation to
prevent reamer from feeding and hogging into the hole. Holes to be finished by reaming should be drilled sufficiently
wider-size to assure positive cutting rather than scraping and swedging (indication of oversize drilled holes and improper
feed is the projection of a lip around hole diameter after the reaming operation is accomplished). Finish reamers should
be maintained with exceptionally keen cutting edges and highly polished flutes for smooth work.
3-203. The following procedures and tools are recommended for reaming aluminum alloys:
Tool material: High carbon steel for general use; high speed steel/or carbide tipped for durability and continued
Tool type: Straight/spiral with 100 spiral flute and solid teeth.
Clearance and rake angles: Top rake 50 to 80; clearance angle primary 4° to 7, secondary angle 15 to 20;
cutting angle 84° to 90°.
Machine speed and hole reaming allowance: Cutting speeds up to 400 it/min for straight
holes, tapered hole
should be somewhat slower about 300 350. The desired feed in inches/revolution is 0.003 to 0.010. Hole to be reamed
should be undersize 0.005 0.015 inch diameter (reaming allowance).
Cutting fluids: Soluble oil/mixture of kerosene and lard oil, light weight machine oil.
3-204. SAWING. It should be emphasized that the same principles which govern the shape of cutting tools for
aluminum should be applied, as far as practicable to saws for aluminum.
3-205. Band Saws. Band saw blades of spring temper steel having a tooth spacing of from 4 to 11 teeth per inch and
with amply radiused gullets are recommended for 21lmlinum alloys. Curved or copying cuts are made with band saws.
In any type of work, high blade speeds are desirable with a speed range from 1,500 to 5,000 feet per minute. For heavy
sections the saw teeth should be fairly coarse with a slight set and a slight amount of front rake, the restricted chip space
requires the use of coarser tooth spacing of about four teeth per inch to avoid clogging and binding. Also the flexible
back type of saw with teeth hardened to the bottom of the gullet is used for heavy work. Blades having as many as 14
teeth per inch are satisfactory for thin materials. A good and simple general rule to follow when sawing aluminum is that
the spacing of the teeth on band saws for 2hlminum should be as coarse as is consistent with the thickness of the
material being sawed. The softer alloys require appreciably more blade set than do the harder, heat treated alloys.
Usually an alternate side rake of about 15 and a top rake or "hook" of 10 to 20° proves quite satisfactory. This amount
of hook, however, requires a power feed and securely clamped work. For hand feeds the top rake must be reduced
considerably to avoid overfeeding.
3-206. The band saw blades must be well supported by side rollers and back support both immediately below the saw
table and about 2 or 3 inches above the work. The top blade supports are placed slightly in advance of those below the
tables and the blade should be allowed to vibrate freely to elimin9te excessive saw breakage. As a general rule, a noisy
band saw is cutting more efficiently than the saw that cuts quietly. Quiet smooth cutting band saws usually produce
smooth burnished surfaces accompanied by excessive heat and consequently decreased blade life.
3-207. Hack Saws. Hack saw blades of the wavy-set type are well suited for cutting aluminum by hand. The wavy set
type of blade having 5 to 15 teeth per inch has sufficient chip space to avoid clogging and binding on aluminum alloys.
For extremely fine work a jewelers blade may be used.
3-208. Special routing machines are available which cut varied profiles from aluminum sheet or plate rapidly and
3-209. Lubricants and coolants. Power hacksaws and hand saws require a cutting lubricant for most operations
involving thick sections. Soluble oil cutting compounds and neutral mineral-base lubricating oil applied to the sides of the
blade aid in minimizing friction and gullet clogging. Light applications of heavy grease or paraffin wax will provide ample
lubrication for some work. A wide selection of lubricants exists, ranging from tallow or grease stick to kerosene-thinned
mineral base lubricating oil. Stick type lubricants should be applied very frequently.