8" Jointer blades

[Chance Raser]

So i bought a used 8" PM M60 Jointer. I have been reading and watching alot of videos while fixing it up (its my first jointer). All in all, i have successfully gotten the tables co-planer. Based on some forum searches i ordered some blades grom global tooling.

I began to install the blades, got both ends zeroed out and then for good measure i checked the center. It was .004" - .005" lower in the center than on the two ends. I was totally confused. After checking everything 3 times, i pulled the blade off and put it on my veritas straight edge that is within .003 over the 38". I moved the blade all over the straight edge and this was the consistent result.

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Two of the blades are .004 out of flat. So my question is, did i buy shitty cheap blades and that is the issue, or is this something that i should have expected and i need to "Joint the blades" as shown in the PM60 manual with a 10" sharpening stone on the jointer?

Honestly i hope its just the blades, i would spend more on blades if someone has a good suggestion for nice straight flat blades. The process of "jointing the blades" as shown in the manual kinda scares me.

Suggestions? comments?

http://www.globaltooling.net/ZSigZ/
8" x 3/4" x 1/8" V2-HSS Planer Knife Set of 3
Smooth Back, Bevel Edge - 8" Length x 3/4" Width x 1/8" Thick - Set of 3 Knives. Fits Jet JJ-8 jointer, Powermatic 60, Pryor, Sunhill.

[Ric Flanders]

My guess is that the blades were not made properly. What you do next is your call... You could easily make a sharpening jig that could get the blades you bought straight. Or you could just return them. I.M.E. Infinity Tools makes nice planer and jointer knives.

[M Toupin]

All blades will flex some, when installing blades start from one side and work your way to the other.

Here's an oldie but goody video (https://www.youtube.com/watch?v=VRnrWOwun68)showing the proper method.

Mike

[Frank Drew]

Chance, I've never heard of Global Tooling and maybe I'm being unfair but it sounds like the manufacturer of the kind of stuff you'd find in a discount store's bargain bin. Send them back and buy some quality blades. Good blades might need honing but should arrive straight.

[Ronald Blue]

Did you contact them? Honestly that should be the very first step before coming on here. I see nothing on their website to make me think they won't stand behind their products. You posted here apparently before contacting them. If they refuse to stand behind their product then you have a beef. Just saying. I think they should be better than .004 but I am not sure you would know the difference if you didn't check them either. You are after all working with wood which moves plenty.

[Bill Space]

OK, so the question is, is 0.004 or 0.005 inch over an 8" jointer blade an issue or not.

For me it would be, since it is not consistent over the width of the jointer blade. Perhaps for others it's not an issue?

It's hard for me to accept that a straight 8 inch knife should be 0.004 inch outside flat across its width.

This is not something that fits within my experience! In free air the cutting edge should be VERY close to perfectly flat in my experience.

Bill

[Ronald Blue]

OK, so the question is, is 0.004 or 0.005 inch over an 8" jointer blade an issue or not.

For me it would be, since it is not consistent over the width of the jointer blade. Perhaps for others it's not an issue?

It's hard for me to accept that a straight 8 inch knife should be 0.004 inch outside flat across its width.

This is not something that fits within my experience! In free air the cutting edge should be VERY close to perfectly flat in my experience.

Bill

I don't disagree that is more than it should be. However I stand by my statement to give them a chance to make it right rather than coming here first. I understand wanting confirmation that they shouldn't be that far off. If you check their website they don't appear to be a shady operation. I think they deserve a chance to rectify it.

[Chris Fournier]

You really need to do some research about tolerances and how to deal with them. In one breath you talk about your straight edge that is .003" over 38" (by no means a great straight edge as far as straight goes, claimed straight that is, great value and accuracy for woodwork for sure) and in the next you are complaining about your blades being out .004" over 8". You can turn perfectly straight blades into spaghetti and .004" out blades into perfectly straight with installation technique or a lack there of. And big picture is that .004" over 8" of wood is nothing. Most folks can't even feel that and you will be cleaning it up...

[Bill Space]

You really need to do some research about tolerances and how to deal with them. In one breath you talk about your straight edge that is .003" over 38" (by no means a great straight edge as far as straight goes, claimed straight that is, great value and accuracy for woodwork for sure) and in the next you are complaining about your blades being out .004" over 8". You can turn perfectly straight blades into spaghetti and .004" out blades into perfectly straight with installation technique or a lack there of. And big picture is that .004" over 8" of wood is nothing. Most folks can't even feel that and you will be cleaning it up...

I don't have a clue why this thread caught my attention. But I would say that 0.003" inch over 38 inches is reduced to much less than 0.001 inch over 8 inches, without question. IF the original measurements can be accepted.

Let's not lose track of the fact that the original poster stated that the blades were four thousands of an inch, or more, out of flat when checked while in free space.

It is difficult for me to imagine any reason why I would accept an 8 inch long piece of metal that is supposed to be flat, when in the end it's 0.004 inch (or worse) out of flat when hanging in free space.

Granted we can only go by what the original poster has stated.

[Chris Fournier]

I don't have a clue why this thread caught my attention. But I would say that 0.003" inch over 38 inches is reduced to much less than 0.001 inch over 8 inches, without question. IF the original measurements can be accepted.

Let's not lose track of the fact that the original poster stated that the blades were four thousands of an inch, or more, out of flat when checked while in free space.

It is difficult for me to imagine any reason why I would accept an 8 inch long piece of metal that is supposed to be flat, when in the end it's 0.004 inch (or worse) out of flat when hanging in free space.

Granted we can only go by what the original poster has stated.

True enough! Leaving the tolerances behind I would cling firmly to the fact that installation of said knives will have more to do with how straight they are in the head than how straight they are lying on a table top.

[Chance Raser]

Ok, there are a lot of questions and comments above that I don't feel like using the quote system with.

So, first and foremost to get it out of the way, I did contact the seller at the same time as i posted here. They were pretty quick to respond.

My main question (having never owned a jointer) was is .004 too much in an 8" blade. The consensus was that yes it is. This was confirmed by the seller, they said there is no reason their blades shouldn't be perfectly straight.

They offered to replace them or refund out right. They said they would check a fresh set of blades on their granite slab before putting it in the mail for me. The blades are on the way.

Chris, I feel like .003 in 38" is a pretty tight tolerance for hobby woodworking, and I don't see the need to spend the extra $100 to get .001 in 38”. I while I think the .003 in 38" is acceptable, I do strive to get as close to perfect as my tools allow.

With that in mind, .004 over 8" is 6x worse than .003 over 38" and beyond what I would have ever expected. Be moving the blade all over the straight edge and coming up with consistent readings I was confirming that it wasn't just a bad reading on one spot of a bad straight edge.

As for installation being the main fault, I will accept a fair amount of responsibility due to lack of experience. However I will also stand firmly that I watched numerous videos, read a few articles and none of them mention blades being out of flat. I tried to set up the blades 3 times, starting from one side of the blade and moving across just like in Bob Vaughn's video. The problem showed up when I had to raise the center of the blade by lifting one side. By the time I got to the other end and both ends were correct the middle was always low. That's when I took the blades back out and checked against my straight edge.

I'm not saying it's impossible, but I find it difficult to think that I can get the .004 belly out of a 3/4" wide x 1/8" thick piece of HSS while only holding it snuggly with five screws. The jointer only has two lifter plugs per blade, one on each end. Maybe if it had a center lifter plug, but I would still doubt it. But... This could all be chalked up to inexperience, idk.

Thanks for all the comments and help

[Mel Fulks]

Having used jointers that I added a calibration scale to, I found that wear of a little less than 2 thousandths on the knives translated to to making the out feed table "too high" and cause the material to "climb" requiring the outfeed table to need lowering. So I have to believe that the knives are not accectable as is. We had a top notch sharpener of all types of saws ,knives, drills, router bits ,etc. who bought a new extremely expensive machine knife grinder when some of his customers started to complain that the knives were not ground straight. He did not try to tell them that a few thou didn't matter.

[Andrew Hughes]

I grind my own knives on my tormek with the jig that's sold for the tormek. It did take some tuning to get the knives clamped flat.
So that they are ground straight.
I enjoy setting jointer knives but I do own one of the finest jointers ever make.It has a 5 inch diameter head with a 38 degree hook angle so I grind my t1 Hss knives @ 42 degrees.
When they are new and set right they will make a very pleasant buzz thru anything even figured woods.
I used to have a jointer with a Bryd head and it was a joke.
Ok I'm done bragging.;)

[Mel Fulks]

Andrew, thanks. That is valuable info,not bragging. Needs to be heard more. But next time mention how much wood it will remove in one pass! They can stand in as straight line saw.