Band saw

[Howard LewisParticipant @howardlewis46836]

Out of the box, the generoc saw worked reasonably well.(It worked even better after it had been fettled and adjusted)

The only reason for changing the bearings was that the incredibly skinny bearing spacer failed, and ruined the lower bearing and oil seal, so my hand was forced.

“As received”, careful alignment and adjustment should result in a quite useable machine.

Setting the blade tension correctly will greatly extend blade life.

Howard

[JasonBModerator @jasonb]

Just measured my Femi holding the phone at head height.

82dB on slow and 86dB on fast. so about half the noise level of what yours is making.

[Adam HarrisParticipant @adamharris13683]

I have removed the blade and the dB sound level is the same – ie it is the motor and nothing to do with the blade wheels or guides

[Adam HarrisParticipant @adamharris13683]

Jason, very interesting and thank you so much for the effort in measuring yours. As it is purely the motor creating this noise (maybe a reduction gearbox too through which the motor spindle drives the wheel?), it is difficult to know what to do next. I will disassemble the motor and see if I can improve the spindle bearings or at least check the grease levels

[Adam HarrisParticipant @adamharris13683]

I have checked with Chester and they have just tested some other 85M machines/motors in stock and found them all similarly very very loud (ie 92dB or more at min revs), and since the motors and machines are all the same as the generic chinese BS-85 one can only assume that the official documentation stating these BS-85 bandsaws produce sound levels of 82dB at min revs is simply a load of hogwash, probably a pretence in order to compete with the Femi. I’m going to pull the motor apart and see what the issue is and if any mods can reduce the noise.

[MacolmParticipant @macolm]

I assume all the band saws we are considering have universal (commutator) motors. My quite old Femi certainly does. The main noise, therefore, most likely comes from the armature fan. This is present both for cooling the windings but also to present a rising load characteristic with increasing speed in order to limit the maximum speed on light load.

On my Femi, a slotted end cover limits the fan airflow. With this removed, the noise is greatly increased, so it is presumably there to manage the noise level. Do the Far East saws have anything similar?

[Adam HarrisParticipant @adamharris13683]

Hi Malcolm, spot on! I have removed the motor and the noise only drops by 2-3dB so the gearbox is not the culprit. It is a regular commutator motor, bearings appear smooth so I also suspect the fan as it cannot really be anything else. So I have flattened the vanes somewhat in the hope of reducing noise but have yet to get it back in between the pair of sprung carbon brushes! I am looking for some long steel shim strips gone missing and will revert. Many thanks

[MacolmParticipant @macolm]

If the brushes have spiral “snail shape” springs, you can sometimes offset them to bear against the side of the brushes so as to hold them clear. Then pry them to the proper position once assembled. May need some bent wire manipulation.

[Adam HarrisParticipant @adamharris13683]

A decent length of shim steel works well with carbon brushes. Anyway, I flattened the vanes to 50% of their angle and got a 2dB improvement, then flattened them further until hardly any angle and got a further 2dB improvement at max speed and no further improvement at min speed. Still decent airflow. So now I am at 90 dB min speed and 94dB max speed. Quite a noticeable improvement and better harmonics to my ears. If I put a sound canopy over the slotted end cover where the air intake occurs, leaving a gap of 5-10mm I do get a further 2dB reduction both at min and at max speed so I think that is worth doing as a future project . However I think the fan design is the real issue and  I will look for a better designed and smaller fan, maybe try to buy the Femi fan as a Femi spares part, or maybe the whole motor if cheap enough and can be fitted to my gearbox! I attach a photo of the innards for any who are interested. Very many thanks Malcolm and Jason for your contributions.

[Adam HarrisParticipant @adamharris13683]

[Adam HarrisParticipant @adamharris13683]

[Adam HarrisParticipant @adamharris13683]

Very many thanks Malcolm and Jason for your contributions.

[Adam HarrisParticipant @adamharris13683]

Maybe I should feather the edges of those fan blades with a dremel

[Adam HarrisParticipant @adamharris13683]

Malcolm the problem you alluded to is that having reduced the air resistance (and noise)  of the fan , the motor now runs too fast such that min blade speed is now 90 mpm (ie double the original) and max is 130 mpm (about 50% increase). Maybe not much of a problem for cutting aluminium but a problem for cutting steel.

[JasonBModerator @jasonb]

I’m sure once the blade is cutting that will offer a lot more resistance than the fan blades and bring the speed back down. Just watch the temperature if using for a prolonged time.

[Adam HarrisParticipant @adamharris13683]

Thanks Jason

[Adrian R2Participant @adrianr2]

Interesting discussion, I’d always thought it was the gearbox of my cheapo portable bandsaw that made all the noise but wrongly it seems. Fan for Femi shown here – different design, and by the look of it part of the speed controller.

https://www.bricoutensili.com/en/femi-spare-parts/6542-fan-motor-with-magnetic-core-for-band-saws-femi.html

[Adam HarrisParticipant @adamharris13683]

I saw that Adrian and the Femi 782 XL motor is available separately for £170 in UK from SawsDirect, very likely would fit the generic chinese BS-85, but too steep for me.  I think this Chester 85M is impressively accurate with a smooth finish to the cut. After putting a strip of 0.4mm shim steel under the outer length of the vice I am now getting a vertical 0.13mm thickness variance across a 55mm diameter aluminium bar. No shim and the variance was 0.45mm so if I had a slightly thicker strip of shim than 0.4mm which I don’t (yet)  I think I could get the vertical variance closer to 0.

[Adam HarrisParticipant @adamharris13683]

Adrian I’m not sure that Femi fan design would work in the position of the BS-85 fan but likely the same outer diameter – might be worth a shot.

[Adam HarrisParticipant @adamharris13683]

I have read somehwere, maybe on another forum or maybe on this forum under a separate topic heading, that using stick wax on the bandsaw blade for aluminium is a good idea. It most certainly is NOT a good idea on these little BS-85 bandsaws. After trying to put only a very little along the teeth edge of the blade, after only a few cuts I found waxy balls of aluminium chips all over the inside and on the rubber of the blade wheels and the blade going around bumpety bumpety bump. After removing the blade and cleaning it all out (much less easy than hoovering up dry chips)  we are thankfully back to smooth running. These BS-85 bandsaws are strictly dry cutting only. So if anyone wants a barely used stick of Trend saw blade wax let me know….

[Chris KaminskiParticipant @chriskaminski64716]

For those with small budgets and tiny workshops… one of these might do.

Only £179 (delivery included) and quite capable out of the box.

I don’t like the vice (especially for sketchy setups like in the first pic)

but it went through 150mm dia lump of EN8 like through butter

 

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