Jointer Setup - Co-Planer Trick

[kpetten]

I had trouble recently getting my jointer beds on the same plane.

I used Mark's method with the straight edge, and as he mentioned, it was taking a long time.

I had an idea to use a straight edge on each side so I could easily see how much the other side was being affected by my adjustments.

I didn't have two straight edges, so instead of buying one and waiting three plus weeks for shipping, I went to bum one from a local machine shop.

While chatting with him, he told me that they use piano wire and a paperclip. They tighten a piano wire across both beds and adjust the tables while "playing the wire" with the paperclip. When the tone of the wire changed, they where in alignment. He said I could also use feeler gauges, so thats what I did.

I thought that if a machine shop used this method, it should be more than fine for a wood shop.

Hope this tip will be useful to others.

Kirk

[JohnnyNoName]

Kirk -

That sounds like a really good idea. Do you slide the paperclip along the length of the wire? Have you tried it yet? If you haven't, do you think you could take some video or pictures as you go?

Thanks for the new technique.

Jonathan

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[kpetten]

I have used the feeler gauge, essentially using the piano wire as my straight edges.

But from his description, you use the paperclip like a violin bow.

I would like to try the paperclip method, but have my beds setup, and am reluctant to take them out again.

[Nick2cd]

this sounds really interesting to me but i don't think i completely understand. is it one wire strung across both tables? if so, wouldn't the tables both have to be at the same height for this to work? how do you verify the tables are at the exact same height? how do you secure the wire to both table ends?

[kpetten]

this sounds really interesting to me but i don't think i completely understand. is it one wire strung across both tables? if so, wouldn't the tables both have to be at the same height for this to work? how do you verify the tables are at the exact same height? how do you secure the wire to both table ends?

Yes, one string across both tables. I used two, one on each long side. you could weigh them down, or clamp them down, as long as they remain tight.

Yes, both tables are at the same hight(once adjusted) . And if you get the strings touching the tables all the way across would that not make them co-planer?

If anyone can see a problem with this technique, please let me know. I have struggled with tool setup and accuracy so much that I am ready to become a stamp collector.

[kpetten]

I will be able to provide some pics of the process sooner than I had hoped.

When doing some slot mortising(machine attachment)yesterday, and adjustment bolt came loose. Now I have to align my tables again.

There will soon be a fire sale on a garage full of misaligned tools!

[Nick2cd]

Yes, one string across both tables. I used two, one on each long side. you could weigh them down, or clamp them down, as long as they remain tight.

Yes, both tables are at the same hight(once adjusted) . And if you get the strings touching the tables all the way across would that not make them co-planer?

If anyone can see a problem with this technique, please let me know. I have struggled with tool setup and accuracy so much that I am ready to become a stamp collector.

i see now. this pretty much clears it up. my only concern is if the tables aren't at the exact same height, you may get a false reading on whether or not they are coplanar. i really need to draw out what im talking about on paper. maybe i'll do a little job in MS paint and post it this evening if i get time.

[nateswoodworks]

Very intersting, how did you attach the wire down? I was just thinking of using f style clamps and tighten one side down, pull snug and tighten the other side down. I have never been around piano wire, will that give enough tension to get a pitch sound off the wire since it is also rubbing on the jointer tables, or do you have a different idea??

Nate

[Nick2cd]

i see now. this pretty much clears it up. my only concern is if the tables aren't at the exact same height, you may get a false reading on whether or not they are coplanar. i really need to draw out what im talking about on paper. maybe i'll do a little job in MS paint and post it this evening if i get time.

this picture is obviously exagerated to illustrate what im talking about. now, the if the table on the right (infeed) was slightly lower than the table on the left (outfeed), it seems that one would see the gap near the center of the infeed table (with feeler gauges) and adjust accordingly, thus ending up with both tables touching the wire, yet obviously not coplanar. i may be looking at this completely incorrectly, so please correct me if im wrong. i hope this technique proves viable because piano wire is much cheaper than a precision ground straight edge.

[kpetten]

this picture is obviously exagerated to illustrate what im talking about. now, the if the table on the right (infeed) was slightly lower than the table on the left (outfeed), it seems that one would see the gap near the center of the infeed table (with feeler gauges) and adjust accordingly, thus ending up with both tables touching the wire, yet obviously not coplanar. i may be looking at this completely incorrectly, so please correct me if im wrong. i hope this technique proves viable because piano wire is much cheaper than a precision ground straight edge.

Nick, my tables were slopping towards the knives/ outfeed. I didn't think of(or check) if the tables sloped away from the knives/outfeed. But I think you would see that. You could raise the infeed higher and bring it down maybe?

It may not be that good a trick after all, but it did work for me. I checked with my straight edge afterwards and there were no gaps, and lowered the table for regular use and the gap was even.

Thanks for the illustration, saves me the hassle of taking/uploading pictures.

[rmac]

Here's an idea that may be worth thinking about. Instead of trying to make the piano wire just barely touch the jointer tables, put a couple of drill bits (of the same size) on both ends of the jointer and stretch the wire across them. That will elevate the ends of the wire above the tables by the diameter of the drill bits.

Then use a third drill bit (of the same size) as a "feeler gauge" to check whether the distance between the wire and the tables is the same everywhere along their entire length. From the pictures, I think the only way that can happen is if the tables coplanar and at the same height.

-- Russ

[Nick2cd]

Nick, my tables were slopping towards the knives/ outfeed. I didn't think of(or check) if the tables sloped away from the knives/outfeed. But I think you would see that. You could raise the infeed higher and bring it down maybe?

It may not be that good a trick after all, but it did work for me. I checked with my straight edge afterwards and there were no gaps, and lowered the table for regular use and the gap was even.

Thanks for the illustration, saves me the hassle of taking/uploading pictures.

kpetten,

don't get me wrong, i think this is a great trick and im going to try it myself. i just want to be sure we have analyzed it from all angles before i employ it. i have a habbit of tuning my tools beyond repair.

[kpetten]

kpetten,

don't get me wrong, i think this is a great trick and im going to try it myself. i just want to be sure we have analyzed it from all angles before i employ it. i have a habbit of tuning my tools beyond repair.

I know the feeling, but that drill bit idea should solve the problem of the bed sloping away from the outfeed table. 2 pieces of wire and 5 drill bits still cheaper than 2 long straight edges.

[Beechwood Chip]

The drill bit / piano wire technique assumes that the shanks of the drill bits have the same diameter to within a few thousandths of an inch.

[rmac]

The drill bit / piano wire technique assumes that the shanks of the drill bits have the same diameter to within a few thousandths of an inch.

True enough! I've always assumed that drill bits were made to pretty tight tolerances, but I don't have anything to back that up. And, after some Googling I still don't have anything to back that up. But my dad's an amateur machinist. He'll either know or have some reference book that tells. I'll report back after I've picked his brain.

In the meantime, as Mr. Chip says, what really matters is that the thicknesses of the two wire supports and the thing you use as a feeler should all be as close to identical as you can manage.

-- Russ

[kpetten]

The drill bit / piano wire technique assumes that the shanks of the drill bits have the same diameter to within a few thousandths of an inch.

You could use drill rod, key stock, or tool steel. All of which are machined to tight tolerances.

Besides a straight edge could be out .0001" per foot. This would be potentially be .0004" on a 4'. My beds span a distance of almost 6' combined. The 2 drill bits would need a be potentially out more than .0006" to equal the accuracy straight edge.

This is wood that we are working with, not machining engine parts. How accurate do we have to be?

[Dan S]

But my dad's an amateur machinist. He'll either know or have some reference book that tells. I'll report back after I've picked his brain.

-- Russ

Metalworking, is one of my other hobbies, and that is where this method was more common. I say was, because laser are used now instead. Getting the ways of a metal lathe co-planer are very important, and in most cases a machinist level (not a cheap tool) is used to ensure this. So I don't get flamed by any fellow machinists let me be 100% clear, the ways aren't being leveled, they are being made co-planer by using level as a reference. This method works great in most cases, but it breaks down where level isn't possible. A good example of this, is on board a ship, this is where the wire method comes in.

As a side note, a good drill bit should be within 2 tenths (0.0002") of its stated diameter.

[rmac]

He'll either know or have some reference book that tells. I'll report back after I've picked his brain.

Well, I was wrong. He didn't know and he didn't have a book. So no help here. Looks like Dan S has us covered, however.

-- Russ

[Kerry]

You could use drill rod, key stock, or tool steel. All of which are machined to tight tolerances.

Besides a straight edge could be out .0001" per foot. This would be potentially be .0004" on a 4'. My beds span a distance of almost 6' combined. The 2 drill bits would need a be potentially out more than .0006" to equal the accuracy straight edge.

This is wood that we are working with, not machining engine parts. How accurate do we have to be?

Most straightedges that I have seen are usually only ground to be accurate to .001" per foot, Though it's possible to make them as accurate as you state I doubt most of us would care to pay the price they would command. Lee Valley's steel straightedges are only ground to .001" for their 12" and 24" and .0015 (that's read 1 and 1/2 thousandths not 15 ten-thousandths usually) for their 36" version. Their aluminum ones are spec'd at .003". Yes they say that's the deviation for the full length but they tell you nothing about the sag factor nor provide for it's correction. Starrett's straightedges are spec'd to .001 per foot, and I would trust them to be more correct in their accuracy listing due to the fact that they are used by machinists who work to much tighter tolerances. They do warn (and provide measures to compensate for it) that their 36" and up straightedges need to be supported to correct for deviation in their length due to sag, because of their length. Yet somehow Lee Valley's aluminum 72" straightedge is accurate to .003" for the entire length. I doubt that highly. They sell good straightedges, don't get me wrong, but I doubt they are as accurate as that in use.

You are right though. How accurate do you need to be? Considering wood moves MUCH more than metal I doubt any of what I mentioned matters truly, but I thought I just throw that out there.

BTW the piano wire thing is/was also used by Millwrights to align turbine rotor shafts to within .002" for reinsertion in generators. That is all the slop they can tolerate and still be able to get the shaft in, so the method can be very accurate if done correctly.

Good tip rmac with the drill bit thing. It could work though I'd check the drill bits with a dial caliper at the least just to be sure they are close. That would also at least give you an idea of how much error you could have using that method. I'd still use feeler gauges if I had them though.

Hope you don't take any of what I wrote as a criticism kpetten.