More on the Jet 310P/T

[ivan]

Some further notes on the Jet 310 'lift together tables' P/T:

The P/T continues to please with value for money. Although the tables ar not perfectly flat (about +/- 1.5 thou) when set up with engineers' straight edge happily plane to the same degree of accuracy. However a few easily corrected faults have come to light.

Table droop
- there is a small amont of backlash in the infeed / outfeed table rise and fall mechanism. Both tables should be set by raising into their final position, or you'll get a significant table droop, and an unexpectedly concave cut.

Cutter block belt drive
- to provide clearance at the back of the cutter block, a very small diameter pulley is used, smaller that the reccomended minimum diameter for an "A" section V belt. Partly because of this and poor Chinese belt quality (not unusual) the belt has shredded covering the hidden works with copious fine black powder. This probably contans carbon in some form, but not a lubricating one like graphite, so it had to be cleaned off.

The soution is to fit an "AX" belt - same cross section, but cogged (like most fan belts) to allow it to flex round smaller pulleys (min dia 64mm). Correct belt is AX 1194. The proper design solution would have been a poly-V belt, which easily flexes round smaller pulleys)

NB Following the manual instruction on belt change will result in an over slack belt and misaligned pulleys. Belt should be tight enough not to thrash about whist running, and both pulleys should be in the same plane.


Thicknesser drive
- The thicknesser "Z" section drive belt also runs over a very small pulley and would be beter specified as "ZX" ground and cogged type, although you may find slightly stiffer "XPZ" equivalent easier to find. Correct belt is ZX 770, (or XPZ 800).

Whislt cleaning off (see above) I discovered a couple of loose parts, bearing shaft 248 and cam wheel shaft 224, which had insufficient thread to allow the fixing nuts to full tighten. Easily rectified with a die or by fitting thicker washers. The Chinese washers on the machine are of variable thickness, and these parts may have just got a thin washer.

 

[wizer]

Well you lost me after Table Droop. I do pull the infeed table back up to set on my JPT-260. Sadly the outfeed is fixed on the 260.

 

[Maverick.uk]

Ivan

Some good comments on this P/T.

Incidentally when i was an apprentice engineer we were always taught that if yu went passed your sent point on the approach on any machinary, lathe, mill etc you should always back of and try again, go round for another landing so to speak. Adjustments like this would always make sure backlash never caused a problem.

Cheers

Kevin

 

[Nick.]

Hi Ivan - your comments will be forwarded direct to Jet's chief engineer in Switzerland

Mark's comments a few years ago on this forum resulted in Jet machining the face edge of the fence - I'm not aware anyone other manufacturers have ever gone that extra distance

any feedback on how Jet can improve is warmly welcomed

I'll post Jet's reply back - thanks for the feedback - are you a retired engineer?

As has been mentioned, backlash can occur in £15,000 plus machines too - always raise rather than lower if you need it that accurate - I will check to make sure this is mentioned in the manuals.

The P/T continues to please with value for money

Thank you Ivan

Best regards
Nick
Brimarc Tools and Machinery

 

[deano]

i have just bought this machine and had a new 16amp breaker fitted for it but when i start the machine it instantly trips the breaker ??? anyone else found this ?
i didnt want to up the breaker incase i would do damage in the long run

 

[wizer]

I had an electrician put my 260 in and IIRC it tripped the 16A breaker so he put in a 32A, but maybe I'm remembering that wrong? I'll have a look later.

 

[DaveL]

You should have a 16A 'C' rated breaker to cope with the starting surge that the motor will pull.

 

[pryally]

mine was fine with a 16 amp breaker to start with and now it keeps tripping (in winter)

i have tried a type c breaker - still trips though!

jet have sent me a replacement motor to try - could this just be damp, pretty damp garage? don't want to change the motor if it's damp...

sorry for the hijack - i want my machine working again

 

[DaveL]

mine was fine with a 16 amp breaker to start with and now it keeps tripping (in winter)

The cold does make a difference, the oil/grease in the bearings is more sticky, the bearings will be tighter and the so will the belt. All of these things added together can cause the starting current to be higher and the breaker jumps out.

Many years ago I worked in a small timber yard and in winter we used to take the belt off the planer and spin the motor with a bit of string as the power was applied, if this was not done the fuse would blow. After the motor was warm the belt was put back on. Of course H&S would have been down on us like a ton of bricks now. :roll:

 

[pryally]

mine was fine with a 16 amp breaker to start with and now it keeps tripping (in winter)

The cold does make a difference, the oil/grease in the bearings is more sticky, the bearings will be tighter and the so will the belt. All of these things added together can cause the starting current to be higher and the breaker jumps out.

Many years ago I worked in a small timber yard and in winter we used to take the belt off the planer and spin the motor with a bit of string as the power was applied, if this was not done the fuse would blow. After the motor was warm the belt was put back on. Of course H&S would have been down on us like a ton of bricks now. :roll:

thanks for the info - think i'll give the string trick a miss though....

 

[dicktimber]

Maybe I missed something but why are we working to 1.5 thousandth ?????

Has the plot been lost altogether?

Mike

 

[ivan]

Working to a thou, Mike?
As the customer, I don't really know quite what degree of tolerance in P/T table flatness is regarded as acceptable for cabinet making. You might expect a £5000 Felder or £10,000 Martin to be more accurately ground, from more thoroughly relieved castings that a £1000 Jet, but they don't say either! I thought the figures might interest other purchasers of more modest stuff, especially as my test piece happened to plane flatter than the tables! This does have some effect, as the handplane which touches the stuff next is taking off between 1 and 2 thou a shaving. When the accuracy is reapeatable you can machine nearer the finished size, saving a bit of timber and work. And, to be honest, I was quite impressed!

I think the backlash is a feature of the design, Jetman, and thanks for your interest and follow up. In mine it's in the linkage between the two eccentrics which rotate to raise the table, but the washers/thread length and V belt matters are a Q issue. Possibly also the domed adjustable table height bolts I posted about earlier (very soft) A ground, cogged AX V belt (no lumps and vibration!) about 6 or 7 quid extra retail would have been a nice touch, though. I don't have a formal eng. background, it's agriculture, but I'm used to machines and workshops (tractors and hydraulics) and amateur machining. Belt / pully info posted was obtained from belt mfrs. catalogues, and the quoted belts are now on my P/T.

 

[dicktimber]

Never the less 0.001" or mill or whatever, is irrelavent whatever is used to thickness timber, given that we work with a material that is so unstable that moving it from part of one country to another can end up destroying your prized piece by distortion and movement.

One thing that does surprise me is that sometimes designs of machines are changed from a proven design concept, that works.
For instance, look at the sedgwick range of P/T. Fixed planer tables, cast iron, and cast iron fences. Flat single bed.
It works, full stop.
The new generation P/T have for some reason opted for throw out of the way tables, either both or a single end.
And they are supposed to go exactly back in the same position every time?. The more moving parts, the more chance of the tables being out.
Aluminium fences....god who ever thought of that one as a design cost cutting plus?

So why change? Accessability, Ease of use, cost reduction?

But then this is what it's all about.
One is priced at double the other and one at half the price.
One is in my price range...the other just out.........
ahhhh if life could be easier?

Mike

 

[ivan]

I agree entirely, Mike. Nevertheless, I would preferr to have stuff leave the planer requiring just 2 or 3 handplane passes on each face, and that's about 3 or 4 thou (each face). Checking the table alignment with a staight edge now and then is part of the price I paid for the convenience of lifting tables. The double lift/tilt is a design shared by the Felder, incidentally, although the cutting height is set differently. Provided you lower the tables without carelessly dropping them onto the stops, they reposition accurately.

Edit:
Just did a check with my (Felder) extension tables fitted (to the Jet P/T), makes tables 2.9M overall, and edgeplaned 2.4M lengths of softwood are coming off with an approx 2 thou hollow according to my 2M eng. straight edge. Well done Jet!

Re the backlash, you could align the tables including the backlash induced droop, and then remember to set the cut by always lowering into position - just be consistent!

 

[dicktimber]

Iva...
We reached common ground...

Good speaking with you

Mike