P/T Broken

[wobblycogs]

My P/T (Jet JPT 260) has just broken down and I thought I'd let everyone know how so that hopefully you can avoid what I'm sure will turn out to be a very costly mistake.

I was starting thicknessing up a bit of oak. I measured one end at 24mm, set the table to a 23.5mm and started feeding the piece in. I was greeted by the P/T's usual happy wood munching sounds right up to the point where the wood stopped moving. I immediately spotted the problem, hit the power button and lowered the table to recover my now slightly mangled piece of wood.

I'm sure all you seasoned veterans have spotted my mistake already - the wood got thicker towards the bottom end and had jammed against the kick back fingers.

So what broke I hear you ask? There is a large white plastic (yes, plastic) sprocket that makes up part of the drive train for the feed rollers. About a down teeth on that sprocket have sheared off. Oddly enough it didn't fail straight away I was able to put about 20m more wood through before I noticed any problem.

What I assume happened was when the wood jammed the feed rollers kept going and sufficient force was placed on the plastic sprocket to deform the teeth. Then, a little while later, they just gave up. To be honest I'm really surprised the belt didn't slip as it's fairly loose but looks like the sprocket lost the battle.

Will be looking up replacement parts in the morning, might need an engineer though as it looks tricky to replace.

 

[9fingers]

The sprocket is made of plastic deliberately to protect everything else when a snarl-up occurs.You should be able to get spares through Brimarc/axminster

Bob

 

[wobblycogs]

Ok, that makes sense, cheers.

I'm amazed now much power a relatively small (10mm maybe) flat belt can deliver though. I would have put money on the belt slipping first. As an aside: on the sander I made of Christmas I've been worried that the belt wasn't big enough to deliver all the power but I'll stop worrying now as clearly it will be able to delivery more than enough power.

On the plus side the Jet has the ability to disengage the feed rollers (maybe all do?) so I think tomorrow I'll get LOML down in the workshop and finish of this batch of thinknessing by pushing it though by hand.

 

[Oryxdesign]

Did it look like this?

 

[wobblycogs]

Pretty much, I've lost a bit more off the teeth - enough for them to skip on the smaller cog and make a terrible banging noise.

 

[Oryxdesign]

Ah yes that banging noise.

 

[wobblycogs]

Well the plot thickens as it seems there's more wrong than I thought. I tried disengaging the feed rollers and pushing some wood through by hand but I got no joy - the wood wouldn't pass the in-feed roller.

So, I've took off both back access panels and removed the feed roller pulley assembly so that I could get to the large plastic sprocket. My guess was that the feed roller power train was binding up on the broken teeth and so removing the pulley would allow everything to rotate freely. This wasn't the case, even with the pulley removed the feed rollers wouldn't turn so I then removed the shaft that holds the plastic sprocket along with the rest of the roller disengaging mechanism (annoyingly the lock nut on the back of that shaft is 16mm which is about the only size spanner I don't own!) so that I could slacken off the drive chain.

Once I had the drive chain slackened off I tried rotating the feed roller sprockets individually. The out feed roller rotates quite easily by hand but the in feed roller is seized up tight - no way I could turn it by hand. I'm guessing it should be like the out feed and rotate fairly freely?

Before I go pulling apart the in feed roller mechanism which looks fairly complex does this sound like the right diagnosis? If so what could possibly have gone wrong, I'm guessing the bearings must have seized but this machine has seen hardly any use. Although I got it second hand it can't have done more than a dozen boards worth of wood in it's life.

Cheers

 

[9fingers]

I'm sure that it is this machine that at least one other user has posted about with seized feed rollers

If you have a search of the archive you should find it. Proceed with your dismantling carefully but don't forget to take some pictures to help re-assembly.

Bob

 

[beech1948]

wobblycogs,
Sorry to hear of your problem. Assuming you get the spare part then you should:-
1_ Take photos from all angles at each step in disassembly. You might want to try to find a parts diagram before starting so that you can see the relationship of many parts

2 Get a 100 self close plastic bags in at least 6x8 inch size to keep the parts in. Label them well with a black felt tip PERMANENT marker. eg Left side input roller screws. Keep units together and handed.

3 Consider any rust on the rollers or components and consider of you need a liquid wrench. If so try brake fluid and acetone and keep applying in small amounts for 48 hrs.

4 Have the proper size spanners and toolsready don't make do and mend

5 Have some light machine oil available to re-lubricate and do so sparingly

6 If metal then wax input rollers, bed and output rollers

7 P/T look complex but arn't. Learn as you go and apply learning as you reassemble. You can do it and will learn the feel of the machine as you do.

best of luck and all success.
Alan

 

[wobblycogs]

Thanks for the tips / advice. Fortunately I'd already got a parts diagram as I'd downloaded and printed off the American manual which is passable on the quality front. It looks like the machine is fairly modular which is good to see but I think I'm going to have to take apart the whole of the cutter block assembly to replace the offending bearings. Can't say I'm really looking forward to that - the first switch-on after reassembly will be a scary ordeal .

Cheers, Graham