Skill Band Saw 3386 -1.3 Hp Treadmill Motor Retrofit

[Ulma Doctor]

Hey Guys and Gals,
i bought what i thought may be a cool little bandsaw,
a Skill 3386...

59-1/2" blades
120 VAC, 2.5 amps




it worked just fine on pine up to 3/8" and it did great on the 5mm plywood.

but it didn't like hardwoods nor did it like any thickness over 3/4" in just about any material.

i'm not a woodworker,
but if i wanna cut a small piece of 2x4, i feel a small saw should do it without too much effort.
this saw had a hard time doing a 2x4, a couple times- stopping the blade all together.
the blade popped off at the same time.
i adjusted the blade for best travel and tried again with a coarser pitched blade
it cut a bit better but it really strained to move the cellulose.

Act 1:

so, i figured before i returned the saw,
i'd modify it permanently to prevent that possibility

i let the issue go for a month or so,
and then got the inclination to retrofit a 48 frame 5.5amp 1/3 hpp 115v motor into the saw....

OH my friends, the plan was immaculate i tell you !!!!!!
i'd pop in a new motor , wire it up and badda bing, cut wood like a beaver on steroids.

Well, it didn't exactly work like that....

Here was the plan...
i'd remove the 2.5 amp 120 VAC (HA_HA_HA) motor and replace it with a (cheap) 1/3 hp motor drawing 5.5 amps @ 115 VAC.
i figured it would do much better than the anemic 2. 5 amp motor

2.5 amp motor, top 5.5 amp motor bottom


i wuzgunna' just take the motor mount and modify it to suit the 48 frame motor i intended to use.



well, i intended to use the extended length mount bolts from the 48 frame motor to mount the retrofit motor-
that wasn't gonna work, this time- the bolt circle ended up to be too close to the edge of the stock mount.
i considered making a larger mount plate.



i traced a pattern onto the old looking new steel and was gonna start cutting,

then i had another idea, use a wire ring mount.
we use these in our industry to mount 48 frame fans



this looked like it was going to be a slam dunk.....
but then reality set in.
i was going to need to make a pulley or make the spacer for the pulley to work with a .500" shaft i had.
here is the OEM pulley



i didn't want to go through all the trouble of making a simple spacer,
so i made another pulley from 6061

 

[Ulma Doctor]

ACT 2

i did some figuring and found out my new retrofit motor was a 1080 rpm motor.
the OEM motor was near 2000 rpm by ear
the original pulley od was 30.8 mm
to compensate i could go larger on my drive pulley to gain some speed
i decided to go to 35 mm,
( it's all going together perfectly i'm tellin' myself - )

After turning the od and figuring the pitch (35mm OD.100"pitch 60°tool .060" doc)



i drilled and reamed the bore to .500"

then, i used my (not so) secret weapon...

Shop Made Axa Toolpost Cross Drilling Fixture

Cross Drilling Fixture from an AXA Boring Tool Holder! i had an idea to make a cross drilling fixture for my shenwai 1236 lathes' AXA clone toolpost. i machined the shaft from 3/8" 12L14 hex shaft and single point threaded the drill chuck end to 3/8-24 to accept an old but new Jacobs short...

www.hobby-machinist.com

i used the crossdrill fixture to drill the set screw hole- works like a champion!!!

 

[Ulma Doctor]

here is the OEM and the Retrofit Motors side by side



i did the arithmetic and found out i was woefully under-speeding the blade

formula:
(Motor RPM X Motor Pulley Diameter) / (Driven Pulley Diameter X Saw Wheel Diameter X 3.14) / 12

the OEM i figure was traveling near 650 sfm - (2000 x 1.22) / (1.579 X 9 X 3.14) / 12 = 656 sfm
my new arrangement was coming in at near 390 sfm - (1080 x 1.378) / (1.579 X 9 X 3.14) / 12 = 389 sfm

so i went along my happy way.
i finished the retrofit, or so i thought


i turned the saw on and i could tell there was not enough power, even for my high expectations

i thought i could live with it, if it were not going to bog down
boy was i wrong.
it was better than oem,

but i want more!!!!!

 

[Ulma Doctor]

ACT 3
DC Treadmill motor Retrofit

after having difficulties mounting and belt adjustment on the ac motor side of things,
i made considerations for using a 1.3 hp @95VDC treadmill motor and a KBMM-118 controller i had lying around instead



i tuned the KBMM-118 to a nice no load speed and decided not to use the P3 high speed pot tab on the board.
the reason,
is that with the P3 enabled, the blade speed would reach dangerous over-speeds



i clamped, then drilled & tapped my proprietary eyeballed 3 lug pattern on the flange the OEM motor mount to accept the DC motor assembly
and cut the stub threaded end from the motor and then mounted er' up





since i already had a pulley made, i just had to punch the bore out to 17 mm
i didn't have a 17 mm reamer, so i drilled to 41/64 then bored to a 17.01 mm finished size.

i hacked the crap out of the main housing to create clearance for the treadmill motor.
a necessity beyond my control.
i was in too deep and not going back

i was concerned about dust control so i made use of an under utilized recyclable,
milk jug plastic

i mocked up a simple dust shield for goofs and expanded on the idea



after a couple attempts, i made good templates
from these templates i made some respectable dust shields
there is 2 layers, with a floater in between to try to keep the dust away from the dc motor



i did final fitting of the motor and did the pulley alignment and locked er down.

i have about .100" clearance between the pulley and the saw wheel,
but it runs without interference ( sorry poor picture below)


(if clearance becomes an issue, i can easily remove and shave down the pulley)

 

[Ulma Doctor]

Act 4

I added the control board and connected the wiring in the OEM saw controls
and took it for a test run
the speed was too fast so i turned the KBMM-118 down to acceptable levels

here is a couple shots of the 10k potentiometer i used



here is the diagram fro the KBMM-225- it wires up similar to the KBMM-118


note :Max hp is 1.5 on 115vac control with heat sink
external cooling recommended



i have yet to mount the KBMM-118 , the potentiometer, or the enclosure.

i gotta leave something for act 5

 

[dlane]

Hi Mike, it’s been a while. I thought you had a band saw already. Anyhow good luck with it.

 

[brino]

then, i used my (not so) secret weapon...
i used the crossdrill fixture to drill the set screw hole- works like a champion!!!

Yep the secret is out!
I used mine (a shameless copy of yours!) just yesterday to drill two set-screw holes in a shaft coupler for my farther-in-law.

and took it for a test run
the speed was too fast so i turned the KBMM-118 down to acceptable levels
........i gotta leave something for act 5

Well does it work?

You're just a Cut Tease!

-brino

 

[markba633csi]

Hi Mike- I have a Skil belt sander of that series/vintage and it's a piece of c**p too.
A heroic effort on your part tho, slow it down even more and you can cut metal
Mark

 

[Ulma Doctor]

Hi Mike, it’s been a while. I thought you had a band saw already. Anyhow good luck with it.

Hi Derrick, i hope all is well- it has been a while !
i have meat cutting saws at the shop i can use, but this is my only bandsaw at home

Yep the secret is out!
I used mine (a shameless copy of yours!) just yesterday to drill two set-screw holes in a shaft coupler for my farther-in-law.
Well does it work?
You're just a Cut Tease!
-brino

nice to know that my projects give other's ideas for doing stuff!

yes sir, the saw works!
i'm gonna make a short video and let the peanut gallery see!

Hi Mike- I have a Skil belt sander of that series/vintage and it's a piece of c**p too.
A heroic effort on your part tho, slow it down even more and you can cut metal
Mark

Thank you very much Mark!
i just hate it when you have (realistic) expectations and the product falls short.
thanks for the idea in regards to the metal cutting!

 

[Ulma Doctor]

Well does it work?

You're just a Cut Tease!

-brino

well, since you asked...