Planer Knife Protrusion/Stickout

[Matt Culik]

Hi. I just purchased a circa-1994 Powermatic Model 15 planer that needs a basic tune up. This is my first planer. It didn't come with the knife-setting jig, so I've decided to 3D-print my own. I took some rough measurements today and modeled the cutterhead in CAD. The cutterhead itself is 2.875" in diameter, and I read in several places that having the knives protrude 1/16" beyond the cutterhead is good. 1/16" protrusion makes the overall cutterhead diameter 3", which is what I modeled.

Looking at my model, which probably isn't super-accurate, but isn't bad either, it looks like the tips of the knives protrude beyond the gibs just .009" (red arrow distance in the attached detail pic). The blue dot distance in the pic is .074", so just a bit over 1/16".

Does this look right? I'm concerned that .009" isn't "enough tip," and that I'll be constantly adjusting the blades to keep enough edge past the cutterhead. On the other hand, I've read a few posts saying the "less tip" the better.

I can certainly move the blades out (limited by the amount of lateral clearance to the chipbreaker), but I'm not sure this is the right thing to do, and it changes the cutting angle (although I don't know how sensitive these machines are to changes like that).

Thoughts? Also, thoughts on the knife-setting jig shown in the overall pic?

Thanks!

https://i.ibb.co/sQY3Cb0/Planer-Cutterhead-Overall.png
https://i.ibb.co/XXYjhXw/Plane-Cutterhead-Detail-2.jpg

[Mel Fulks]

I put the sharp edge almost an 1/8 th inch past the edge of the gib

[Brian Runau]

Suggest you ask PM. Brian

[Mel Fulks]

Just make sure the gib edge is entirely on flat surface . Not into the grind

[Bill Dufour]

Make sure the bottom of the knife is at or below the bottom of the gib. If it is not it is too worn and needs to be replaced as a balanced set.
Bill D

[Warren Lake]

Do you have a manual?

You make the table parallel to the head first. Then you decide your knife projection. Some manuals will tell you. I tried some different numbers and .050 above the head works well on my machines. Its one rotation of my dial so makes it easy.

You are making a cutting circle. With your bed parallel to the head make all your knife projections the same above the head. On the SCM stuff with the .050 I use ive never had to adjust the rollers and not even checked them as its always works well with the same knife projection used each time.

You might have to set the rollers and pressure bars and all depending if it was set to some other number a fair bit different than what you are going to use. Most manuals have a sectional side view and give you the heights of all that stuff.

Not so common but machines with knife grinders they set the knives higher as they expect you to get 5 of 6 hones out of them before pulling the knives up again.

[Kevin Jenness]

Ask the manufacturer/ see if you can find a manual online. If the knives are in the head now and the machine feeds ok it is probably safe to copy the existing knife projection. If they are too far out of spec you may find it impossible to adjust the chipbreaker, feed rollers and pressure bar properly.

[Robert Engel]

About 1/8" proud of the cutter head.

I suggest you check the table for parallel before using a jig.

I adjust mine off the table b/c I've never been able to get the table perfectly parallel. But that's a 20" planer.

On mine the rollers and pressure bar are set relative to the knives.

Definitely get the manual!!

[Jared Sankovich]

Definitely get the manual!!

Just download a grizzly/shopfox/jet/delta (any 15" 4 post) manual. They are all identical.

[Matt Culik]

Thanks, everyone. For those saying get the manual, I've reviewed several, including the Grizzly, the new Powermatic and the correct manual for this machine. They all provide specs for roller and chipbreaker heights relative to the cutterhead, but as far as knife protrusion goes, they all say to use the jig. For whatever it's worth, the Grizzly manual did say the cutterhead diameter is 3". My understanding is all these machines have a cutterhead diameter of 2.875" WITHOUT knife protrusion, so I'll take that as I'm headed in the right direction with my 3" approach.

I was out in the shop last night looking at it, and it's also possible the gib in my model is wrong. It doesn't appear to extend past the cutterhead nearly as much in real life as it does in the pics above. I re-measured and am not sure where I'm wrong, but maybe...

Anyway, 3D printing is cheap, fast and easy, so I'm going to print my jigs as designed and see how it goes.

Again, thanks for the help! Will let you know how it goes.

[Warren Lake]

You answered your question with your numbers your knife projection is 1/16" .0625 above the head. Id still get the manual for roller, pressure bar etc set up numbers. If you look at 3 or 4 different 24" planers the set up numbers for each are different.

[Kevin Jenness]

A somewhat more sensitive gauge can be made with a button tipped dial indicator held in a wood block that straddles the knife pocket. Here's an excellent primer on adjusting traditional planers with shop made gauges by Bob Vaughan of sainted memory https://www.bing.com/videos/search?q=planer+knife+setting+gauge+vaughan&view=detail&mid=8B3CE7C3E05864DC25AD8B3CE7C3E05864DC25AD&FORM=VIRE The gauge can be seen in use at around 7:00 in.

[Gregory King]

I put the sharp edge almost an 1/8 th inch past the edge of the gib


I did too Mel. I have a General 130 with the same 3" diameter- 3 knife head. The specs call for 1/16 " protrusion as well. I installed new knives after I bought it. So. I moved it out to the !/8 "+ if anything. Works well.

[Gregory King]

Matt, on another setting as I just finished adjustments today, the table rollers call for .010 " above the table. I'm probably at .011". Book says that anything over .010 could result in snipe on both ends. No snipe yet. Got to tinker the adjustments is my best advice. Greg

[Holmes Anderson]

That drawing must be inaccurate because the gibs should not protrude as shown in the drawing. The protrusion of the knives beyond the cutterhead is not limited to a single exact distance as far as I know, i.e., it doesn't have to be exactly 1/8, 3/16, or whatever. You can probably just set the back of the knife bevel about even with or slightly above the cutterhead provided the knives don't bottom out. What is critical is that the knives are parallel with the table and that the infeed roller, outfeed roller, chipbreaker, and pressure bar are all set relative to the height of the knives. This may help you with a full tuneup http://wiki.vintagemachinery.org/Getting%20Peak%20Planer%20Performance.ashx . The 3D printed gauge will not be user friendly. Do yourself a favor and buy magnetic jigs to hold the knives and a precision gauge to set all heights (and remove the springs under the knives if they are there because they will lift the magnetic jigs off the cutterhead).

[Andrew Hughes]

I will add to this thread. I set my knives approx 1/32 out instead of the 1/16 showing in the pic.
I also grind the bevel at 42 because the head has a 38 degree hook . That leaves 10 for clearance.
If I had a knife grinder I would stick them further as mentioned up thread.
Good Luck

[Warren Lake]

I know you know high speed steel.

I measure to the tip of the knife as that is what is cutting. ive had a dial on enough heads to see some have a dip on the head as you approach the knife opening. I zero on the head then as rotating sometimes see a dip maybe .004 as im close to the opening.

What is your knife projection from the head being zero to the tip of the knife? I figured I pushed it low enough at .050 as i set up now, at some point there will not be enough projection, im sure im still fine as never any issues and it cuts cleaner than when i started high and worked down. If you have a few minutes at some point will you check that number.

and

now thinking what about Tersa and all the spiral stuff projections over the head. Do they all have the same feed rate capability or what if not?

[Will Boulware]

I'd second the recommendation that the OP spend some time with the Bob Vaughan video on knife setting. It goes through a cutterhead diagram that will answer a lot of the questions that have been asked, and it explains a lot about planer setup that you'll need to know to get the rest of the machine dialed in.

Skip the knife setting jig and get an inexpensive dial indicator with a magnetic base.

[Dan Hahr]

I probably just got very lucky but here's my only experience. I bought a Delta X5 15" planer that was rusted all over. This was probably around 2010. I disassembled it and cleaned it up. I put it back together and set the rollers and chipbreakers as close as I could with shop made blocks and a cheap dial indicator. I set the knives after I honed them by sight alone. I set the bottom of the bevel about 1/32" above the cutterhead and set it as parallel as I could. I figured that it would work okay, but once I got a good dial indicator, I'd set it up right. I ran some boards through it and was very happy with the surface quality. I measured the thickness at both sides and was within a few thousandths.

Well, that was the last time I touched it. Now, I have a Dewalt 735 that I do most of my finish sanding with but I use the bigger planer for rough planing. It really needs new knives as some of the nicks are fairly deep. I am not sure it is worth setting the knives perfectly if I can eyeball them to this level of quality. I am going to swap them out with new ones soon. I guess I will find out if my first results were repeatable.

Dan

[Andrew Hughes]

I know you know high speed steel.

I measure to the tip of the knife as that is what is cutting. ive had a dial on enough heads to see some have a dip on the head as you approach the knife opening. I zero on the head then as rotating sometimes see a dip maybe .004 as im close to the opening.

What is your knife projection from the head being zero to the tip of the knife? I figured I pushed it low enough at .050 as i set up now, at some point there will not be enough projection, im sure im still fine as never any issues and it cuts cleaner than when i started high and worked down. If you have a few minutes at some point will you check that number.

and

now thinking what about Tersa and all the spiral stuff projections over the head. Do they all have the same feed rate capability or what if not?
Here’s a look how my knives sit right now. If I move them down 1/32 I’d right at 1/16 th projection.
The cutting circle is 5inches for Oliver. What’s your new machine just curious

[Warren Lake]

Do you know what the tip is over the head? I know im asking you a different way than you measure. Machine is a Wadkin BAJ. Just a lump right now busy with other things. I did email Tersa and had an issue with some emails. They have just rewired from the block to my office with Cat 5 so hope its okay now. This is the Tersa Info.

472275

[Andrew Hughes]

I see what you looking at. As my knives sit the they are 44 thousands above the body of the head converted its 1.1 mm.
My manual says to set the face of the knife out 1/16 from the lip of the gibs or breaker. I bet that would put them out 1 mm from the head.
I just remembered something I was going to share. I bought another set of t1 from Amana 12x1.25x1/8 they came perfectly in balance each weighed the same and same thickness. Somebody’s got their head screwed back on straight.
The grind on the back is a little rough compared to American National knifes blades. I paid less then 30$ a knife so I’m happy.
I have 3 sets of t1 and one set of m2
Good Luck Warren

[Mel Fulks]

I’ve noticed with T-1 and REAL M2 ,that when the knives are all exactly the same length, they are balanced . With the
cheap steel ,after balancing , some knives are over 1/8th inch different.

[Andrew Hughes]

Yes that’s true Mel. I wore down a set of Amana t1 made in Germany one thing I noticed as they got smaller and smaller they developed lots of warping.
Thats when I decided to start looking closely at news stock. Even new sets had a crown to them but what really confused me was one knife was much heavier. It turned out to be thicker I don’t remember how much because I sent the set back.
I went back and forth until I found a set acceptable.