tailieunhanh - Handbook Of Shaft Alignment Episode 2 Part 2

Tham khảo tài liệu 'handbook of shaft alignment episode 2 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 300 Shaft Alignment Handbook Third Edition refer to as oversized slot shims. If it is necessary to install a shim spacer thicker than 125 mils it is recommended that carbon or stainless steel plate be used and that the plate be surface ground on both sides to insure parallel surfaces within 1 mil over a 6 in. distance. The spacer should have 125 rms surface finish or better after grinding. The precut U-shaped shims mentioned above are typically made from stainless steel which is the recommended material to use to prevent oxidation or corrosion that could occur with carbon steel shims. Brass shims work well unless there is ammonia present. Carbon steel is usually acceptable if you have to make a plate over 125 mils thick. The precut U-shaped shim sizes A through D were meant for use on NEMA motor frame sizes 100 through 400 series. These shims can obviously be used on other machines besides motors. These standard shim sizes work on about 70 of the machinery in industry but they do not work on everything particularly larger machinery so it is not uncommon to fabricate custom shims to work in many situations. The rule of thumb is to provide at least 80 contact between each machine foot and its point of contact on a baseplate frame or soleplate. Often I have found C-sized shims sitting under a machine foot whose footprint is 6 in. X 9 in. Just because the shim slot fits the hold down bolt diameter does not necessarily mean that is the right shim for the job. Therefore in many cases special shims need to be fabricated. Shim stock can also be purchased in 6 in. wide rolls in 100 in. and 180 in. lengths and can be aluminum brass carbon steel and stainless steel in usually the following thickness 1 2 3 4 5 6 7 8 10 12 15 20 25 and 31 mils. To fabricate shims over these thickness you need to use sheet metal that can be purchased in the following gauges Gauge Thickness in. 28 26 24 22 20 19 18 16 14 13 12