Jet P/Ts with lift-together tables - useful info.

[ivan]

Mine was supplied with the table locking handles adjusted to lock sloping forward at about 45 deg. This is a bad idea.

The tables are easier to adjust and examine if the coupling piece with the lifting handle is removed. Remember that the l/h table is now free to fall down if you raise it up!

The action of the locking device is now in view, and it will be seen that with handes set in this position, locking the tables down distorts the cast iron table support sideways, scrubbing it over the Tower Bolt head under locking pressure.

The Tower Bolts (the downloaded US manual calls them Temple Bolts) sit opposite the table hinge, and have a domed head, which sets the exact table alignment. I recently discovered* that they are made from Chinese cheese, so it's not surprising that the scrub-when-you lock action was causing the tables to require frequent tweaking to keep them planing flat. The US manual also states, but doesn't explain why, that the handles should be set to lock in a vertical position. If you do set them thus, the scrubbing action virtually disappears, and so wear on the bolts is much reduced.

* table adjustment described in the US manual requires a lot of tweaking of these bolts and the thread proved very soft... replacements can be readily made from HT setcrews, rounding the heads with a Bob Wearing lathe (drill and file) and finishing on abrasive. I used the original tower bolt head to burn a matching hollow in endgrain, and used that under the cloth abrasive in the drill press to finish.

 

[RichardC]

Ivan

I came across this problem with the locking handles by accident. I noticed that after levelling the infeed table (I have a PT260) and locking it down it was no longer co-planar with the outfeed table. I discovered the problem lay with the locking mechanism pulling the table down very slightly from its position in the unlocked position. Like you, I now lock the tables with the handles in the vertical position.

Re the temple bolts, I can't find a reference to then in the UK or US manuals. I presume you are referring to the 2 x 2 bolts on the "handle" side upon which the tables rest. On my machine these are hex headed bolts. When I came to replace them with set screws, I noticed that the originals were not tapped square into the steel support. Not a lot I can do but the set screws do allow a much finer adjustment.


Richard

 

[ivan]

On my 310 they sit either side of the rather car bonnet like "bolt" that the locking handle traps. They have a domed head - a hex bolt with a dome machined on top of the head. They support and align the tables on the operator side, opposite the lifting hinge.There are usually some characters on a plain, standard head- 8 8 (and maybe maker) is common - don't they interfere with adjustment?

 

[RichardC]

Ivan

We are clearly talking about the same bolts except that mine did not have domed heads. I tried filing the tops flat to match the underside of the tables but with little success as the bolts were not tapped in perpendicular to the table. I replaced them with set screws, mainly because I could achieve a more sensitive adjustment of each bolt using a hex wrench even though the table doesn't make total contact with the top of each screw.

As an aside, have you ever checked the flatness of the table surfaces? I laid a straight edge across mine and could get a .003 inch feeler guage under the centre section. This caused me some concern but as the P/T produces square edge timber and the .003 inches/.08 mm is the machined tolerance of the straight edge, I have not bothered too much about this observation. When I contacted Jet UK about the machined tolerances of the tables, all I got back was a copy of the manual!!

Richard