Craftsman 150 Drill Press Motor Bounce

[seanmnaes]

I recently picked up a Craftsman 150 drill press and overall its in great condition and works wonderfully. The belt it came with though was pretty rough, so I picked up a replacemement 44" kevlar belt. It has the swivel motor mount and a 1/2hp motor.

My problem is that the motor bounces like crazy. Check out the video to see what I mean. I read the manual and it doesn't say anything about a clip to hold it or any way to hold the plate in place after you tension it. I see that some of the later versions have a clip to prevent exactly this. Mine isn't missing any parts, according to the manual.

Any tips on how to prevent this? Right now I just use a ratchet strap to keep everything in place, but it's not a long term solution.

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-Sean

 

[BillK]

Thats pretty bad. What kind of belt did you use, it almost looks too big for the pulleys ??

Also have you looked at the top of the spindle while it is running to make sure that it isnt bent, making the driven pulleys wobble ? The motor pulley seems to be running straight so I dont think it is the problem. Has to be either the belt or the driven spindle.

 

[Davefr]

Did it bounce prior to the belt change?

Lay a straight edge across the top of both pulleys. The front and back of each pulley should all be on the same plane. Are they?

I'd also lay a spirit level across each pulley, (perpendicular to the belt), to make sure there's no motor tilt mismatch.

It also looks like the motor is pulled pretty far back from the head. Maybe one size shorter belt would be better.

 

[lafester]

Yeah the belt is too long. The bottom screw needs to go into the head which prevents bouncing.

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[FrankLee]

That is an early pivot motor mount. The stud is attached to the plate, not threaded into the head casting like later models.

The motor mount stud is too short. The bumper should contact the head frame. The weight of the motor may be too much tension.

I believe the belt length is ok. 44" is spec. Perhaps the belt was old stock and is retaining curve memory from the package sleeve. A cogged belt would likely run smoother. A Duralast 17443 (44.5") from Autozone is my preferred cogged v-belt. I just bought six of those today.

I believe the motor is vintage correct.

 

[seanmnaes]

I checked the motor spindle and it's still very true with very acceptable runout. I had also already re-mounted and tightened the pulleys so that they were parallel.

Like FrankLee said, the bottom screw doesn't go into the head. There is no hole in the head and the bolt has a rubber bumper on it. It's assembled as shown in the original manual.

The belt is stiff, so I might try a different one. I didn't try it much with the old belt as it was pretty ate up. I went with the same 1/2" belt that it came with and several other threads mention 1/2" belts.

I don't really understand how the motor can transfer any real torque to the bit if the motor mount is hinged though. As soon as you hit any resistance the belt would slip because you can never maintain tension on the belt.

-Sean

 

[FrankLee]

I checked the motor spindle and it's still very true with very acceptable runout. I had also already re-mounted and tightened the pulleys so that they were parallel.

Like FrankLee said, the bottom screw doesn't go into the head. There is no hole in the head and the bolt has a rubber bumper on it. It's assembled as shown in the original manual.

The belt is stiff, so I might try a different one. I didn't try it much with the old belt as it was pretty ate up. I went with the same 1/2" belt that it came with and several other threads mention 1/2" belts.

I don't really understand how the motor can transfer any real torque to the bit if the motor mount is hinged though. As soon as you hit any resistance the belt would slip because you can never maintain tension on the belt.

-Sean

The stiff belt is the primary cause. The stud does need to be longer though so the bumper makes minimal contact. Slippage should not be a problem.

 

[seanmnaes]

A combination of things solved the problem.

1. I ran out to AutoZone and picked up a 44" x 1/2" cogged v-belt. It is significantly more pliable and fits in the pulley better. The previous one was the same size, but much stiffer and had a cloth like exterior that I think was enabling some of the slippage I was getting.

2. I reduced the tension. Tension on this thing is counter-intuitive to me. Prior drill presses you would tension until you had specified deflection in the belt. This thing if you pinch it will always deflect because of the hinge.

3. I adjusted the stud to be more firmly in contact with the head.

All of this together fixed all of my problems. Big thanks to FrankLee and everyone else for the advise! I'll post a follow up video to show how much better it is.

-Sean