Loud bang when starting Jet planer

That’s very much how my powermatic planer starts. Single phase motor.
Sometimes it’s really soft sometimes hard.
Mine sits on a very uneven floor so I have wood shims under all four corners lifting it up slightly. Helps a little.
Good luck

-- Aj

Those belts seem to really be flopping around quite a bit. Is it possible they need to be re-tensioned? Are the pulleys tight on the shaft? Motor mounts secure?

-- "You know, I'm such a great driver, it's incomprehensible that they took my license away." --Vince Ricardo

Those belts seem to really be flopping around quite a bit. Is it possible they need to be re-tensioned? Are the pulleys tight on the shaft? Motor mounts secure?
- Ripper70

+1 Check pulleys, motor mounting bolts and belt tension;
AKA = remove the belts and checking EVERYTHING.

They look too loose, but can be other issues?
My Jet 20” belts don’t move that much, but they do flex on start up.

Rubber residue from belts is normal sign of wear. Significant amounts of dust means significant belt wear. Could be due misalignment (most common), loose/damaged pulley, or improper tension. Have seen cases where loose set screw in pulley groove was protruding into belt and abrading the inner edge. Could also have bad bearings requiring excess force to get cutter head moving?

Investigation of wear on belts and shiny wear spots on pulley often explains exactly what is wrong. Helps to have a fresh belt for comparison if you don’t mess with belt power transmission often?

A bang at start up is often referred to as ‘belt slap’. Usually means not enough tension, or need new belts as they are de-laminating between plys. Note that as belts age, they stretch and wear on bearing surfaces. This means occasional re-tension is required between replacements.

PS – Always set tension on cold belts. Warm/hot belts are expanded, and shrink when cold; creating excess tension. Belt tension is almost an art form, especially when comparing long or short belts? There are a ton of references online if you don’t want to use the Jet owner’s manual recommendation for belt tension.

https://www.bestorq.com/library/techinfo/whytension.pdf

http://www.powerdrive.com/Downloads/ECatalogs/VBeltDrive/Belt%20Tension%20Checker%20Instruction%20Sheet%20..pdf

https://www.skf.com/binary/49-66598/12419-V-Belt-replacement-work-instructions_EN.pdf

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

+1 on checking the belt tension. Be sure to check the set screws for the pulleys, A loose screw will present with a thunk when the pulley slips and finally catches where the set screw contacts the key or flat on the shaft.

I’ll check the tension and set screws. Other info I should have mentioned: the planer is now 2 years old, but only used maybe 30 min total run time, ever.

I’ll post another video after adjusting the screws and tension for those interested in the results.

Other info I should have mentioned: the planer is now 2 years old, but only used maybe 30 min total run time, ever.

- Newbie17

In that case, replace the belts. Lack of use can cause the belts to conform to the curves of the pulleys affect their flexibility. Age may also may also explain the excessive rubber dust.

-- "You know, I'm such a great driver, it's incomprehensible that they took my license away." --Vince Ricardo

Other info I should have mentioned: the planer is now 2 years old, but only used maybe 30 min total run time, ever.
- Newbie17

Whoa!
30 minutes of run time, should generate a minuscule amount of rubber dust. If you have excess rubber dust with light usage, suggest your pulley alignment is off, and/or belt tension is WAY TOO low.

+1 Long storage is hard on belts.
They take a set due tension stretch around pulley. It can take 15+ minutes for belt to warm up, and lose the deformation from being stored. As belt ages, it loses flexibility and may never remove the deformation in belt shape. When this happens, belt gets noisy, and is hard to set proper tension. Replacement is only solution.

PS – When you replace belts on tool with multiple belts, try to get belts all made from mfg lot; as they tend to be better matched in length. That or order expensive (matched length) sets from OEM. If belts are not same length, each has different tension. BTW – Your video shows one belt appears longer than the rest.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

Alright, now to find appropriate replacements belts

Edit: I was reading through the document on how to check and adjust various parts of the machine and it seems that almost every part (cutters, rollers, belt tension, motor pulley alignment relative to cutter pulley…) needs adjustment. There’s evidence of misalignment of all the parts according to the manual. It’s going to be a long weekend.

Alright, now to find appropriate replacements belts

Edit: I was reading through the document on how to check and adjust various parts of the machine and it seems that almost every part (cutters, rollers, belt tension, motor pulley alignment relative to cutter pulley…) needs adjustment. There’s evidence of misalignment of all the parts according to the manual. It’s going to be a long weekend.

- Newbie17

HaHa, must be your 1st time using a commercial sized planer?

Large industrial wood working tools have maintenance schedules in regular shop using tools everyday. Completely normal to have: weekly oiling and cutter checks, monthly belt tension and gear box oil checks, annual gear box oil changes, etc. After you figure it all out, it’s a 5 minute job each week, maybe 15 minutes each month, unless something needs fixing/adjusting.

Won’t BS you: 1st time setup on new/rebuilt machine can be daunting. I spent an entire 8 hour day getting my first rebuilt machine setup per manual. Have now rebuilt 4 different 15”/20” planers. Only takes me 2-4 hours to check and adjust all rollers, cutter head knives, and drive train; having done it a couple times.

Checking belt alignment is easy:
1) Check motor mounting bolts are snug.
2) Remove belts, and check pulleys for unusual wear or loose set screws.
3) Use a straight edge between pulleys to get them in same plane.
Adjust the motor position on mounting plate, the pulley position on shaft(s) as necessary to gain alignment.
4) Put belts back on, make sure all bolts are snug, and apply proper tension.
5) Check belts are aligned and machine is operating properly.

easy peasy lemon squeezy :-)

It takes longer to remove/replace the covers on enclosed cabinets, then perform the actual belt alignment. Should take 15-20 minutes at most to adjust belts?

Suggest you attempt belt adjustment on the machine before buying new belts. Will help you learn what is wrong, and if you really need new belts. Unless Jet shipped cheap nasty old belts with machine, would think they should last longer than 2 years; just run a little noisy due storage deformation?
I only use my planer 1-2 times a month, and have constant issues with belt noise due being idle. But I don’t need to change belts more than once every 7-10 years, even in my dry AZ climate. YMMV

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

Sounds like the motor is jumping on start up, due to loose tentioner which will cause the loose belts scene in the video.

-- Colombia Custom Woodworking

CaptainKlutz, I did all the adjustments you mentioned and followed the manufacturer’s instructions on how to do them for my machine. The pulley alignment wasn’t as easy as I thought it would be since the pulleys were tipped toward each other, so using a straight edge couldn’t work. That was frustrating. If you want to see what I did and the end result, here is a video below. Compare it to the first video and hopefully I did a good enough job to use the machine without problems. If you notice anything else, please let me know.

https://www.youtube.com/watch?v=5T6gJpTMXP8

Also, I checked the cutterhead parallelism relative to the table and the table rollers relative to the table and all of them were perfect. The infeed roller next to the cutter is out of position by 0.02”, it should be 0.004” height difference relative to the cutterhead, but it is 0.024”. I’ve been getting indentions on boards that needed only little planing. I’m working on this adjustment now.

1) Looks like lack of tension was source of bang noise, and it’s fixed? The operation looks normal to me.

2) The lower pulley misalignment will be a source of belt wear. How much wear happens over time .vs. time to fix it; is the only belt question left.
Since the motor is mounted to a plate pivoting on welded mounts; only way to adjust shaft position is add shims between plate and motor. A few strategically placed washers could be added if belt wear is shredding lots of rubber after a short time. If don’t see a pile of rubber dust after couple hours run time, I’d leave it alone.

3) Might want to search forums for discussion on 15” & 20” planer issues regarding leaving marks on wood; due segmented in-feed rollers when taking light cuts. Common issue on these planers, since Delta made the 13” machine they cloned. Worse, OEM manuals are horrible at explaining that these factory adjustments are only a starting point. Not going to re-post all information in this thread, since it already exists on LJ. Only add that setting the in/out feed roller heights (and in-table rollers) should be adjusted based on types of material you run.

FWIW – Different OEM specify different feed roller heights, with a range of 0.020 to 0.040 being common recommendation. It’s a funny specification when compared between OEM; since most all the 15/20” Taiwan made planers come from same factory?
My current 20” is set to ~0.025” from cutter head, as it was optimum trade off between consistent feeding, and smallest marking on light cuts for my work. My previous 15” planer run best with 0.030” difference.
YMMV

Cheers!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!