By Jim Frye
A lot of times you see people extolling the sound virtues of the induction motor and in the same breath stating that the universal motor is too loud. You almost always see this in relation to the BT3000 (BT3K), which has a universal motor. It’s funny that you don’t hear people complain that their router or circular saw is too loud, but then no one makes a router or circular saw with an induction motor. You probably couldn’t lift one if they did. Only once have I seen, in print, any comparison of the BT3K’s noise level with other table saws. A couple of years ago, Fine Woodworking Magazine (FWW), did a comparison test of the contractor type saws on the market, including the BT3K. The noise levels for the contractor saws ranged from a low of 80 decibels to a high of 90 decibels. The BT3K tested at 93 decibels. By comparison, my QSP industrial ShopVac measures 93 decibels when it is connected to the BT3K. The nosiest contractor saw was the Grizzly G1022 at 90 decibels. So, a stock BT3K is 3 decibels noisier than the saw that is usually touted as being a better buy than the BT3K. By the way, it is a bit difficult to discern a 3 decibel difference with the human ear.
The U. S. Department of Labor has published regulations concerning noise in the workplace and a review of the numbers should help the reader understand noise measurements. Because the human ear can hear a vast range of sound levels, the Decibel Scale was created to make it easier to classify sound levels. The scale is logirithimetric so 90 dB is 10 times louder than 80 dB. The decibel scale starts at 0 which is considered to be the Threshold of Hearing and 130 is considered to be the Threshold of Pain. The Other levels of relevance here are:
65 | Normal conversation |
75 | Average factory |
80 | Loud music |
90 | Beginning of unsafe levels |
110 | Amplified rock music |
120 | Jet airplane taking off |
150 | Immediate hearing loss |
Decibel Level | Maximum Time per Day |
90 | 8 hours |
92 | 6 hours |
95 | 4 hours |
97 | 3 hours |
100 | 2 hours |
102 | 1 1/2 hours |
105 | 1 hour |
110 | 30 minutes |
115 | Less than 30 minutes |
Delta 6” bench top jointer, 6,000 rpm | 86 dB |
Delta 6” bench top jointer, 11,000 rpm | 96 dB |
Dremel 10” bench top band saw, 970 sfpm | 68 dB |
Dremel 10” bench top band saw, 2,900 sfpm | 86 dB |
Delta 12” bench top drill press, 620 rpm | 71 dB |
Delta 12” bench top drill press, 3,100 rpm | 74 dB |
Shop Vac QSP industrial vac | 93 dB |
Bosch 2 hp router, 8,000 rpm | 70 dB |
Bosch 2 hp router, 25,000 rpm | 102 dB |
Ryobi 3 hp plunge router, 10,000 rpm | 92 dB |
Ryobi 3 hp plunge router, 28,000 rpm | 103 dB |
Makita 1/2” corded drill | 102 dB |
Bosch random orbit sander, setting 1 | 87 dB |
Bosch random orbit sander, setting 6 | 98 dB |
Black & Decker jig saw | 97 dB |
DeWalt biscuit joiner | 106 dB |
Black & Decker 1/4 sheet sander | 102 dB |
Black & Decker 7 1/4” circular saw | 109 dB |
As an additional comparison, I measured a PowerMatic model 66 table saw. These saws are considered to be the best 10” table saw in the business and I thought it would be interesting to compare it with my BT3000. I have a relative who has a PM66 and his workshop is nearly identical to mine. Both shops are in the basement with open joists above. Both shops have two concrete walls and two wood stud walls. Both shops are 12’ x 12’ in size. Both saws sit on rubber wheeled stands. I measured both table saws running in the middle of the shop floor with the meter at my ear level standing in front of the saw. The PM66 measured 86 dB and the BT3K measured 87 dB!
The obvious point here is that it is extremely important that you use proper hearing protection when working with power tools in your shop. I have a set of ear muffs that are rated at 29 dB reduction. These muffs will make even my worst noisemaker quiet enough to fall below the federal exposure guidelines.
I have been working on several noise and dust collection projects for the BT3K over the years and they have reduced the noise level of my BT3K to put it in the same noise range as the contractor saws. The modifications I made to my saw were rather simple and inexpensive. They are as follows:
- The interior of the saw cabinet was covered with 1/4” thick by 2” diameter disks of clear silicone sealer to quell noise from vibration. Cost $5.00. Other BT3K users have lined the saw cabinet with sound deadening foam to reduce interior noise of the BT3K.
- The bottom of the saw cabinet was closed off with a dust collection pan to keep stray sawdust out of the area inside of the stand. Cost $4.00 for the hot melt glue sticks used to glue the corrugated cardboard parts of the pan together and a can of silver spray paint.
- The triangular openings at the top front and rear of the cabinet were closed off with duct tape, but scrap wood would work just as well. Cost $0.00.
- The vent slots at the left side of the cabinet were closed off with duct tape also. Cost $0.00.
- The rear dust port opening in the cabinet was closed off with an articulated cover. Cost $2.00 for a piece of 1/4” plywood.
- The stand was modified to sit on three rubber tired casters. I used two Ryobi BT3K casters at one end and a swiveling, locking castor at the other end. Cost $25.00.
This leaves only the motor vent slots on the right side of the cabinet open, along with the tilt/elevation hand wheel slot on the front and the blade slot in the throat plate for noise to escape from the cabinet. Total cost for noise reduction on my BT3K was $36.00. I am in the process of enclosing the metal saw stand with a cabinet made from 3/4” plywood. The mass and sound deadening characteristics of this enclosed cabinet should reduce the noise level of my saw even further.
Original PDF Document:
bt3knoise.pdf