Setting Jointer Knives - intimidated

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Forum topic by camps764 posted 10-26-2013 12:05 PM 1699 views 1 time favorited 11 replies Add to Favorites Watch
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867 posts in 2383 days

10-26-2013 12:05 PM

I recently bought a used Powermatic 50 jointer. All three knives were shot. After reading online, I tried to sharpen the knives in place – no luck. So I built a small sharpening jig that I found on LJ’s. The jig is sweet, and would work really well, but the last owner, (maybe the owner before that) tried to regrind two of the knives and ruined them.

I ordered a new set – no big deal.

After reading the zillion and a half articles online about setting and replacing jointer knives I’m a little intimidated on the process. This is definitely a case of information overload. Some say they need to be exactly the same height as the outfeed table. Some recommend a few thousands proud of the outfeed table. Some reference the distance between the bevel and the cutter head. All agree that precision is absolutely critical to a functioning machine.

Here’s how I understand/plan to approach it:

1. I set the infeed table to the zero position – and made sure I got any sag out using a nice straight edge. I now have less then .0015 clearance at any point on the straight edge across the length of the tables – per the manufacturer’s instructions

2. Find top dead center on the cutter head using a dial indicator on a magnetic stand. The Garage Woodworks guy (thanks!) has a video showing this. According the video I put the magnetic base on the infeed table and locate top dead center on the portion of the cutter head that does not have a knife slot. Top dead center is the highest point in the arc of the cutter head.

3. Mark Top Dead Center on the fence as a reference point.

Here’s where I get fuzzy on the process.

4. Insert new blade so that it rests on the jack screws and tighten the gib screws very lightly.

5. Place the magnetic blade lifters (small jigs I made using magnets and pieces of flat steel) on the outfeed table. Position the cutter head so the blade is on the Top Dead Center mark on the fence and move the magnetic jig to the blade so that it lifts it up, even with the outfeed table.

6. Tighten down gib screws.

Move on to the next one.

So, my question for the wise masses on LJ’s: Does this sound like a reasonable process? Is it accurate enough? Am I missing something? Is there something that would simplify the process?

Thanks in advance folks!

-- Steve

11 replies so far

View cutworm's profile


1075 posts in 2817 days

#1 posted 10-26-2013 12:27 PM

I don’t see anything about locking down the knives.
Other that that I did it pretty much the same way last week.
After I lock the knives I back the jack screws out against the knife bottom just for good measure.
I then zero my dial indicator on the outfeed table and check the knife with it to make sure it’s close to zero about .001” or less.

I have found it gets easier each time.

-- Steve - "Never Give Up"

View camps764's profile


867 posts in 2383 days

#2 posted 10-26-2013 12:35 PM

Thanks for the quick response cutworm, and the confirmation that the process is right.

that’s a good suggestion, thank you.

It feels like a really simple procedure, so maybe I am just making a mountain out of mole hill in my head. After reading/watching all the videos and seeing posts that describe it as difficult and tedious and whatever else, I was assuming that it was a miserable process.

-- Steve

View Don W's profile

Don W

18754 posts in 2591 days

#3 posted 10-26-2013 12:41 PM

as long as thy are tight, the worst that’ll happen is a wavy piece of wood and you’ll start over. If the blades are consistent with the head, the gauge will be off. I measure mine anyhow.

-- - Collecting is an investment in the past, and the future.

View DeLayne Peck's profile

DeLayne Peck

545 posts in 2225 days

#4 posted 10-26-2013 12:56 PM

You’re on the right track with the magnets setting the blades to the heigth of the outfeed. Here’s a post by GaryK That seems to be standard procedure.

The proof is in the pudding. I like to run checks on scrap wood before and after planing on my table saw top.

-- DJ Peck, Lincoln Nebraska. Lord, keep your arm around my shoulder and your hand over my mouth.

View camps764's profile


867 posts in 2383 days

#5 posted 10-26-2013 01:00 PM

Thanks for the confirmation and suggestions guys. I’m going to give it a shot this AM and report back now that I’ve got some confirmation that I wasn’t missing anything.

-- Steve

View MedicKen's profile


1615 posts in 3486 days

#6 posted 10-26-2013 02:04 PM

-- My job is to give my kids things to discuss with their

View 404 - Not Found's profile

404 - Not Found

2544 posts in 2993 days

#7 posted 10-26-2013 04:41 PM

There is a more low tech way of doing it for anyone without a dial indicator
Infeed table is wound up to same height as outfeed, then a small flat stick with two pencil marks 1/8 apart is placed over the cutter block with the front mark level with edge of the outfeed table. Turn the cutter block so the knife catches the stick and lifts it onto the infeed table. Adjust the height of the knife until the stick only travels between the front mark and the back mark. Do this at each edge and the middle of each knife.

View hydro's profile


208 posts in 1775 days

#8 posted 10-26-2013 07:10 PM

Renners has the right idea. That’s how I do it and it is simple and effective. Don’t overthink this and make it more difficult than need be.

-- Minnesota Woodworkers Guild, Past President, Lifetime member.

View gfadvm's profile


14940 posts in 2713 days

#9 posted 10-27-2013 01:11 AM

I basically used Renners’ method but used a steel rule instead of the “small flat stick”. The most tedious part of mine was getting the knives all level across the width of the table. I think those magnetic jigs address this problem.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View pintodeluxe's profile


5702 posts in 2837 days

#10 posted 10-27-2013 05:34 AM

1+ Renners method for those that don’t own a dial indicator.
As long as the blades are flush with the outfeed table, you should get good results.
The part about tightening the blade screws gradually is important so the blade setting doesn’t shift.
Remember, it feels like you are loosening the blade bolts to tighten them.
People make it sound like a difficult procedure, but with a little patients and the right tools it becomes a simple task.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View camps764's profile


867 posts in 2383 days

#11 posted 10-27-2013 10:11 AM

That’s a great suggestion Renners.

It’s all done. It took about 1 hour total – which isn’t bad IMO. I was expecting 2+ for my first try.
It was a fairly painless procedure overall.

Just like Pinto said – as long as you have patience it wasn’t bad at all.

I pretty much followed the procedure I listed above. I had to fiddle with the knives/jack screws a little bit. But using the dial indicator on the base, and the jack screws for micro adjusting, it was pretty easy to get it set to wherever I wanted it.

The magnetic jigs were a life saver. I think it would have been a tremendous pain to do it without them. They held the blade where I wanted it, and locked the cutter head, but still allowed me to wiggle it back and forth enough to make sure I was top dead center.

The first cuts with fresh blades were AWESOME! I can’t believe I’ve gone this long without one of these things.

Thanks again everyone!

-- Steve

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