Drill press belt deflection and speed

[JHZR2]

How much deflection of a v belt on a drill press is correct? My 1950's drill press is smooth and completely vibration free if I leave it loose, like as in 1.5" deflection... I set the ruler so the outer edge of the belt was at 3" exactly before I pressed on the belt. It has worked just fine for soft and hardwood and the brass doorknob job I posted about last week. I could tension it a lot more, but then it's louder. Still smooth and for the most part vibration free (the motor can vibrate a bit but it doesn't really translate much to the body or spindle), but makes a lot more noise. Bearings on the motor are tight and smooth. I figure light belt tension is good for this too, but what's the compromise? Belt slippage? Seizure? The way the motor is mounted and adjusted leaves for some play even if the belt is really tight, so the tighter the belt, the more those forces can come into play and make motion and noise. Also, my setup only goes to 610 rpm or so. For bigger cuts or metal, lower speeds seem to be recommended. That said, what's the issue if instead of a super low speed (seem lots of recommendations for 250rpm), I just reduced the duty cycle? That is, ensure the same number of cutting feet or contact rotations per minute as if working at 250, just shorter and lighter contact running at 610? What issues would I need to be concerned with? I'm not planning to cut with huge forstners or hole saws in metal, but for general knowledge, this would be helpful. I suppose a different pulley on the motor would always be viable - essentially just a ring around the shaft diameter to get maximum ratio. Thanks!

 

[Tman220]

If its not slipping, I don't see a downside to leaving it a little on the loose side. Another plus to the belt being loose is that if you are ever drilling something tougher than wood with a large drill bit and the bit grabs, I would much rather the belt slip and smoke than spinning the piece into me!!

 

[pkunk]

Originally Posted By: Tman220

If its not slipping, I don't see a downside to leaving it a little on the loose side. Another plus to the belt being loose is that if you are ever drilling something tougher than wood with a large drill bit and the bit grabs, I would much rather the belt slip and smoke than spinning the piece into me!!

I just turned a belt inside out running a 35mm plug cutter. Had to order new belts. If you're drilling something tough, use a clamp. The flesh injuries are painful and last a long time.

 

[Linctex]

Originally Posted By: JHZR2

I could tension it a lot more, but then it's louder.

Bearings are going out. No other reason for that.

 

[maxdustington]

Originally Posted By: JHZR2

How much deflection of a v belt on a drill press is correct? My 1950's drill press is smooth and completely vibration free if I leave it loose, like as in 1.5" deflection... I set the ruler so the outer edge of the belt was at 3" exactly before I pressed on the belt. It has worked just fine for soft and hardwood and the brass doorknob job I posted about last week. I could tension it a lot more, but then it's louder. Still smooth and for the most part vibration free (the motor can vibrate a bit but it doesn't really translate much to the body or spindle), but makes a lot more noise. Bearings on the motor are tight and smooth. I figure light belt tension is good for this too, but what's the compromise? Belt slippage? Seizure? The way the motor is mounted and adjusted leaves for some play even if the belt is really tight, so the tighter the belt, the more those forces can come into play and make motion and noise. Also, my setup only goes to 610 rpm or so. For bigger cuts or metal, lower speeds seem to be recommended. That said, what's the issue if instead of a super low speed (seem lots of recommendations for 250rpm), I just reduced the duty cycle? That is, ensure the same number of cutting feet or contact rotations per minute as if working at 250, just shorter and lighter contact running at 610? What issues would I need to be concerned with? I'm not planning to cut with huge forstners or hole saws in metal, but for general knowledge, this would be helpful. I suppose a different pulley on the motor would always be viable - essentially just a ring around the shaft diameter to get maximum ratio. Thanks!

What DP is it? I have a 50s era Craftsman King Seely model that I bought awhile back and am going to be setting it up soon. I think you need an intermediate pulley to get slower speeds, as that is how it was done back in the day. You might be able to find a factory slow speed pulley assembly but they are going to to be pricey as there were more DPs made without them than there were with them and everyone buys old DPs and wants to drill metal with them. I just watched a video on youtube by AvE that discussed using VFDs on a 3 phase motor to control the Hz of the motor to slow it down or speed it up no matter what the pulley ratios. I assume you are on single phase, but I think this is the route I would go, because finding or making an intermediate pulley is going to be difficult or expensive.

 

[JHZR2]

Originally Posted By: Linctex

Originally Posted By: JHZR2

I could tension it a lot more, but then it's louder.

Bearings are going out. No other reason for that.

Maybe they are - its a 1950s motor. I did just re wire the main cord, and when doing that, I tried real hard to assess play and smoothness, which were excellent, but it is old... That said, the noise Ive assessed to be motion-related, like how the motor mounts to the frame, which mounts to the main body. Multiple points of movement and vibration.

 

[mk378]

There's a pulley bearing as well as the spindle bearings. Take the belt off and check the pulley for wobbling or bearing noise. You're always going to hear some noise from the spindle splines rattling in the pulley hole, especially with no load, this was never intended to be silent.

 

[Linctex]

Originally Posted By: mk378

There's a pulley bearing as well as the spindle bearings. Take the belt off and check the pulley for wobbling or bearing noise. You're always going to hear some noise from the spindle splines rattling in the pulley hole, especially with no load, this was never intended to be silent.

Yes, correct. I think this is the worn bearing.... not the motor bearings.

 

[JHZR2]

Spindle is smooth as can be. Ive verified the noise to be where the motor mounts to the plate that connects it to the rest of the press. It is not the spindle or either pulley. Obviously if the belt is too loose it flaps around. If I tension it too much, it transfers vibration and operating noise through the mounting point, which is dissipated silently otherwise somehow...

 

[andyd]

The belt runs between 2 sets of pulleys for variable speeds ? The slack is there to accommodate differnt speeds is my guess. If the press works as it should why fix it?

 

[JHZR2]

No my press only has one set of pulleys. I don't know how much deflection is enough or too much. Not clear the same rules as for auto v belts apply...