I
own a BF20 Vario mill and have—like many others—problems with the
plastic gear that transfers the momentum from the motor into the
switched gearbox. every 20-40 hours of operation, the spindle starts
rotating unevenly because the gear wears out. In my experience this
vibration has for example led to the opening of the drill chuck that
holds drill-tools and the like. Furthermore, the machine runs much louder
than with a new gear.
I
bought 3 plastic replacement gears, and I am now feeling that the last one
starts to wear out. Since I sometimes also do CNC work with this machine
I need a reliable spindle drive. I started out to find replacement gears made
of metal, but couldn't find any.
20 teeth brass gear
drill diameter 10mm
keyway 4mm
37 teeth plastic gear
drill diameter 15mm
keyway 5mm
I measured the axial distance to be about 37 mm, the gear ratio is 1.85.
These
gears appear to be imerial with a diametral pitch of DP=20, but I am
not certain of it - also because I have not found any reports on the
Internet that somebody found standard imperial
gear parts for replacement.
I have found metric Module 1 gears that at least have the same
axial distance. They have slightly different transmission ratios, so I
have decided to buy the two sets that match the ratio best. The gears
also have slanted teeth but the teeth are a bit finer.
Here
is the type numbers and where you can find them online. Not the
cheapest, but if the whole operation works they are definietely worth the
price. Make sure to get pairs of left and right rising teeth, otherwise
they will not fit together!
Mädler has an online shop for Europe where you can find these parts - they usually ship within days.
1 21435000
Stirnzahnrad aus 11SMnPb30 mit einseitiger Nabe Modul 1,0
13,10 €
1 21434000
Stirnzahnrad aus 11SMnPb30 mit einseitiger Nabe Modul 1,0
17,25 €
1 21423000
Stirnzahnrad
aus 11SMnPb30 mit einseitiger Nabe Modul 1,0
14,85 €
1 21422000
Stirnzahnrad
aus 11SMnPb30 mit einseitiger Nabe Modul 1,0
14,27 €
The two sets I bouhgt are:
20 teeth to 50 teeth resulting in a gear ratio of 2.5, or
30 teeth to 40 teeth resulting in a gear ratio of 1.33.
The
pairs have an axial distance of 37.25mm which should be possible to
adjust by tightening up the motor box of the machine to the gearbox.
Maybe I have to rework some of the holes a little bit...
One
set will make the spindle spin a little faster with less torque, the
other one slower with more torque. The gears have arrived and look very
well made. I have orderd some square HSS metal to cut the keyways on my
Sieg C2 Lathe (see this YouTube Video on how I am planning to do it).
The
next challange is to bore the holes to fit the shafts and manufacture
the keyways. I will get back to you here as soon as I have further news.
