Knife Gib Rant

[Tom Esh]

Jointer mechanics, how do keep the blasted knife gibs from walking (and taking the knives with them) when you tighten the bolts? I just spent the better part of a day getting all the knives aligned - or within .002 anyway. At one point I was considering using a hammer - but couldn't decide whether to use it on the jointer or myself for not buying it with the Byrd head.:)

[Peter Quinn]

I loosen all the gib screws on one knife (the machine is manually disconnected of course), remove the knife, remove the gib, clean everything with compressed air and nylon brush to start.

I have numbers I drew on the head with a sharpie so I don't inadvertently change a knife twice! My knives are sharpened/jointed by a professional knife grinder so they are very flat and very sharp. I always keep them together as sets throughout their life.

I replace the gib and a fresh knife, lower the height set screws to place the knife just below where I want it, then GENTLY snug the two outer most gib screws just enough so I can still manipulate the height. Then I play soft, soothing music for 20 min to put that gremlin in the head to sleep.

With the two jib screws just almost barely kinda snug, I raise the knife height incrementally until turning the head (always turning the head backwards into the straightedge to avoid damaging the cutting edge) pushes a straight edge 1/8" backward. I do this on the outer edge of each knife.

Then I GENTLY snug each of the inner gib screws, then I start from one side and torque all gib screws to proper tightness. Then I recheck my height. Repeat for the other two knives, always changing one knife at a time, knver pulling all three knives then replacing all three.

I have done a knife change this way in 10 minutes with very good results. On less focused days I don't do knife changes at all!

[Jim Davenport]

Another thing I've done is to stone the side of the gibbs that face the cutter head. On my jet they were quite rough. Removing the burrs, and roughness makes the changing blades a lot smoother (pun intended).

[Tom Esh]

...then GENTLY snug the two outer most gib screws just enough so I can still manipulate the height. Then I play soft, soothing music for 20 min to put that gremlin in the head to sleep.

With the two jib screws just almost barely kinda snug, I raise the knife height incrementally until turning the head (always turning the head backwards into the straightedge to avoid damaging the cutting edge) pushes a straight edge 1/8" backward. I do this on the outer edge of each knife.

Then I GENTLY snug each of the inner gib screws...

Good advice! That's pretty much my method except I torqued them starting with the inner bolts. (Shame on me for reading the manual:)) In one case I swapped bolt positions which seemed to help a little. Test run today. Hopefully I won't have to fool with this again until the next knife change.

[Mark Rios]

Exactly why I bought a jointer with a spiral head. I'll never buy another without one.

[Gary Keedwell]

Reading a thread like this one reminds me how much I'm looking forward to my carbide indexable head when I retire.:rolleyes:;) (I hope to buy one before that, though)
Gary

[Tom Esh]

Another thing I've done is to stone the side of the gibbs that face the cutter head. On my jet they were quite rough. Removing the burrs, and roughness makes the changing blades a lot smoother (pun intended).

The gibs are actually coated / enameled - presumably for corrosion resistance, but I think I'll remove it before next time.

[Tom Esh]

Exactly why I bought a jointer with a spiral head. I'll never buy another without one.

Yep. I'll probably give it one more knife change, but the slippery slope is definitely facing that direction for me too.:)

[Mark Rios]

Don't fight it, Tom. Just let it happen. Don't fight it. It will be okay.




:D

[Pete Bradley]

I hold the knife down with the end grain of a block of hardwood.

Pete

[Gary Herrmann]

I'm also very glad I upgraded to a spiral head on my jointer and planer. If I'm lucky, I'll forget how to change traditional knives out.

[Tom Esh]

WooHoo! Fired up for a test run and it's beautiful. Replacing / setting the knives was actually just the last (and by far most frustrating) step in a complete re-tweaking from the factory settings. Tables were just a scootch out of parallel. Not so much I couldn't get a good flat surface, but I was getting a slight lateral taper which often resulted in one edge being uncomfortably close to the target thickness. So to make a long story short, I ended up learing more about parallelagram jointers sooner than I thought I'd have to, but at least it has a happy ending.:)

[Tom Esh]

I hold the knife down with the end grain of a block of hardwood.

Pete

Yep, I tried that but with one particularly troublesome bolt there was no way I could apply enough force to stop it. I swear the thing was acting like another jackscrew. I ended up swaping bolts around on the gib till I got lucky.