Thread: Jet Jpt310hh - tables not quite flat

Originally Posted by elanjacobs

Here it is: https://www.woodworkforums.com/f155/j...ml#post1744735

I could see for myself in the end that the table flatness did not seem to have an impact on performance once the coplanar adjustment was accurately done. The problem with the machine is repeatability and its inability to stay coplanar during use or following table adjustments for depth of cut. This was a fundamental flaw in my opinion.

I believe the people that rave about this model are either seeking to justify their investment or have a much lower perception quality and accuracy than I do.

I paid $3k for a 3-phase, standard cutterhead JPT-310 about 5 years ago.

I spent some time setting it up properly, and learning how to use it.

The tables are slightly dished, but that's from wear.

It still machines boards repeatably to within 0.1mm thickness, with no discernable curvature.

Wood isn't a stable medium - it moves. Machining a moving material to better than 0.1-0.2mm precision is a waste of time and effort.

The equivalent Hammer machine now costs over $6K delivered, but may better meet your exacting standards.

Originally Posted by Mr Brush

I paid $3k for a 3-phase, standard cutterhead JPT-310 about 5 years ago.

I spent some time setting it up properly, and learning how to use it.

The tables are slightly dished, but that's from wear.

It still machines boards repeatably to within 0.1mm thickness, with no discernable curvature.

Wood isn't a stable medium - it moves. Machining a moving material to better than 0.1-0.2mm precision is a waste of time and effort.

The equivalent Hammer machine now costs over $6K delivered, but may better meet your exacting standards.

Like I said the machine can get accurate results but the machine I had did not have repeatable accuracy. 0.1mm is pretty good I agree but you need to know you are going to get this all the time and not have to spend hours setting up the machine every time you use it.

Can I ask do you test your results after you use it to verify? Do your projects come together with acceptable tolerances?

Here is test: check you machine for coplanar. Once confirmed to acceptable tolerances (i.e. within 0.05mm or .002 inches) unlock your infeed table and adjust the height up and down a few times. Now check it again and what do you get? If your machine is still coplanar I am a jealous man. This is the method I used: https://www.youtube.com/watch?v=gO74...e_gdata_player

No offence to you and the success you have had with your machine by the way.

I have used Wood Whisperers videos to set up several machines, including the JPT-310. In fact, I bought some setup gear precisely because he used it.

Note that in the video you linked, the Powermatic machine has a ground surface on the tables. The JET JPT-310, in common with many cheaper machines, has a ribbed surface on the cast top. The tops of the ribs wear much more unevenly than a ground top. This means that when taking local measurements with a (steel) straightedge and feeler gauges, I can get quite a bit a variation depending on exactly where I take the measurement. I setup coplanar when I bought the machine (which took a whole day....), and never had any need to recheck this during several years use. When I did finally get bored and recheck it (4 years later), I ended up adjusting the infeed table by the tiniest amount to return to coplanar, and that's it. I'm sure I could find an error greater than 0.1mm across the full diagonal of the infeed and outfeed tables if I looked, but that has no practical effect on the performance of the machine at all. I could induce more error in the jointing process simply by incorrect technique, i.e. applying the wrong pressure to the board in the wrong place at the wrong time as it passes the cutterhead.

At no time did I notice any difference in the accuracy of the results obtained, and I seriously doubt that the adjustment I performed made the slightest bit of difference to be honest. I was just changing the blades, and got a bit carried away.

I alternate between jointer and thicknesser mode all the time, and this doesn't have any effect on the accuracy of the machine. I use a domino machine for a lot of joinery, and one thing this needs for good results is precisely machined stock. In fact, that's the reason I upgraded to a JPT-310.

I'm just concerned that you are unlikely to find a (hobbyist) machine that you will find satisfactory. Hammer is still only a hobbyist machine, albeit much more expensive. There are numerous threads on here about people having quality/setup problems with assorted Hammer gear (e.g bandsaws). I'm sure a Felder machine would give you the precision you crave, but for the price it damned well should.

I say again. It's wood, it moves, just accept it. If you want to machine something to sub 0.1mm tolerances, and have it stay there, I think you should consider metalwork !

Sorry for the rant. I just realised that you are probably just a forum troll, and I've simply been feeding you. Over and out.

Originally Posted by Mr Brush

I have used Wood Whisperers videos to set up several machines, including the JPT-310. In fact, I bought some setup gear precisely because he used it.

Note that in the video you linked, the Powermatic machine has a ground surface on the tables. The JET JPT-310, in common with many cheaper machines, has a ribbed surface on the cast top. The tops of the ribs wear much more unevenly than a ground top. This means that when taking local measurements with a (steel) straightedge and feeler gauges, I can get quite a bit a variation depending on exactly where I take the measurement. I setup coplanar when I bought the machine (which took a whole day....), and never had any need to recheck this during several years use. When I did finally get bored and recheck it (4 years later), I ended up adjusting the infeed table by the tiniest amount to return to coplanar, and that's it. I'm sure I could find an error greater than 0.1mm across the full diagonal of the infeed and outfeed tables if I looked, but that has no practical effect on the performance of the machine at all. I could induce more error in the jointing process simply by incorrect technique, i.e. applying the wrong pressure to the board in the wrong place at the wrong time as it passes the cutterhead.

At no time did I notice any difference in the accuracy of the results obtained, and I seriously doubt that the adjustment I performed made the slightest bit of difference to be honest. I was just changing the blades, and got a bit carried away.

I alternate between jointer and thicknesser mode all the time, and this doesn't have any effect on the accuracy of the machine. I use a domino machine for a lot of joinery, and one thing this needs for good results is precisely machined stock. In fact, that's the reason I upgraded to a JPT-310.

I'm just concerned that you are unlikely to find a (hobbyist) machine that you will find satisfactory. Hammer is still only a hobbyist machine, albeit much more expensive. There are numerous threads on here about people having quality/setup problems with assorted Hammer gear (e.g bandsaws). I'm sure a Felder machine would give you the precision you crave, but for the price it damned well should.

I say again. It's wood, it moves, just accept it. If you want to machine something to sub 0.1mm tolerances, and have it stay there, I think you should consider metalwork !

Sorry for the rant. I just realised that you are probably just a forum troll, and I've simply been feeding you. Over and out.

Not really necessary to call me a forum troll simply for explaining my experiences that were different to yours.

There is a difference between the machine set up tolerances needed for accurate work (i.e. very fine e.g .05mm) and the tolerances expected on the machined timber (e.g. 0.1 mm you noted).

There must have been an issue with my machine because I could set it up dead-on coplanar and got good results and if I adjusted the depth of cut it went out of coplanar and produced terrible results.