How-To:
Jet 6" Jointer - Infeed Depth Adjustment
Mechanism Repair
There’s something about putting your hand on the infeed adjustment wheel on your jointer and discovering that you can no longer raise the table. When it’s an important tool in your work habits, it really brings things to a stop. In late April of 2002, this happened to me and what was interesting was discovering the cause to be a simple safety device that all jointers must have when shipped and sold.
Jointers,
due to their nature, are rarely used for cuts greater than 1/8" and most
woodworkers take only 1/32" to 1/16" in normal situations. The exception
is when using the jointer to make rabbits along the edge of a board and even
then, the depth is gradually increased over multiple passes. For this reason,
jointers are equipped with a special “stop” mechanism that prohibits
the infeed table from being lowered more than 1/8" without knowingly
releasing the device.
The device works by having a spring-loaded pin engage a hole when the depth is cranked down to 1/8". Unfortunately, once the pin is engaged, the user must release it to raise or lower the infeed table...and that’s the rub...many folks don't realize that the pin has been triggered and when they try to force the table up (or down) a small casting called a “ball crank” can be broken. While the manual mentions the safety device, many folks apparently do not realize the implications. The screw assembly that is used to raise and lower the table can exert a huge amount of force, regardless of whether you resemble Popeye or a young child.
A dealer that I spoke with indicated that the device has often caused problems with jointers on display in tool retailer showrooms--so much so, that many dealers remove the safety mechanism from machines on static display to insure that browsing customers don’t have the opportunity to prove how strong they are by breaking the a ball crank.
Please note that Jet, your dealer and I do not advocate or suggest removal of any safety device from your tools. If you choose to do so, be aware of the increased danger, take caution accordingly and understand that you are responsible for any injury to you or others that may result.
The
picture on the right shows both the broken unit and the replacement. As you
can wee, the finger(s) that are easily broken when the height adjustment is
force with the lock engages are not large. Fortunately, replacing the ball
crank is a relatively easy task. You do need to disassemble the jointer, however
and may need assistance in lifting the tool off the base cabinet as well as
turning it over. I have to give kudos to Jet, too. They were called on a Monday
afternoon, and had the new part in my dealer’s hands by Wednesday afternoon,
and that involved a shipment from Tennessee to Pennsylvania.
To
replace the ball crank, remove the jointer from the base by reversing the
assembly process as described in the manual. Be sure to use some tape to hold
the cutter head so that the knives are not exposed while you work on the repair.
Do not make any changes to the outfeed table or knife adjustments as they
are not affected by this repair. Once you have the tool free of the base,
place it inverted on an appropriate surface--I used a Workmate® for this
operation with the spilt tables spread wide. Vacuum any “resident sawdust”
before you start the replacement procedure.
The
first step is to remove the adjusting screw mechanism so that the ball crank
(#25 on the Jet diagram) will be able to be removed and replaced. To do this,
remove the crank knob by loosening the sew screw. Tap out the retainer pin
that keeps the screw in the infeed casting. Be sure that you don't loose the
brass washers as they not only provide spacing, but also act as a simple bearing.
there are three such washers...one on the outside and two on the inside. Once
the “front” side is free, rotate the screw using the rear knob
while holding the adjusting nut. (#19 on the Jet diagram)
Loosen
and remove the pivot pin (#12 on the Jet diagram) that holds the ball crank
in the jointer. This is a metric bolt that is just slightly over 1"...I
carefully used a 1 1/16" socket as I did not have any metric sockets
that large. Be careful not to strip the bolt head! When you remove this bolt,
you will be able to remove the broken ball crank from the machine and install
the replacement. The fingers of the new ball crank need to surround the shoulder
pin (#9 on the Jet diagram) before you replace and tighten the the pivot pin.
When
the pivot pin is reinstalled, the the assembly should look like what you see
in the picture to the right. Reinstall the adjusting screw from the rear by
holding the adjusting nut in the ball crank’s fingers and threading
it through. Be sure to replace the brass washers in the same orientation and
position as they were originally. Secure the adjusting screw mechanism by
replacing the pin through the shaft and reinstall the adjusting crank. Be
sure to tighten the set screw.
Your
jointer should now look like the picture at the left. Check that all fasteners
are secure before you reassemble the tool on it’s base. Before you reinstall
the fence, consider doing some maintenance to your table surfaces by cleaning
them with mineral sprits, removing any surface rust and applying a good coat
of quality past wax. The fence surface should be cleaned and waxed, too. Zero
out the infeed table and then recalibrate the depth indicator by making test
cuts.
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