Straight Edge recommendations

[Prashun Patel]

Thanks. I have a Hammer A3-41 (a JP combo, 36" infeed and outfeed respectively). I am trying to joint 9' boards, so I have constructed 48" outfeed and infeed extensions. This is where the issue is. I am having trouble getting the extensions perfectly level.

After adjusting the knives and shimming the extensions, I am still getting a slightly convex (sprung) joint. It's about 1/16" over 9 feet. The boards are between 6"and 10" wide.

In fact, I am able to clamp the joints shut easily enough - even before some final passes with the jointer plane.

At this point it's a personal challenge to get a perfect joint off the machine. My definition of this is that there is no visible space when the boards are brought together by hand. I will see if the 50" straight edge

[Patrick Walsh]

This setup will work on your machine. The infeed is a Felder unit. Outfeed is aigner but on a Felder bracket. Table is modified to fit the Felder bracket. I use the largest Stabilia R beam level to set it up. I made the bench in the background with this setup along with a number of dinning tables at this point. I struggled previous as you are with the exaggerated spring joint.

Set the level on the infeed and adjust to the extension table. Same on outfeed and your done. Just have to set cut depth prior and not move it. The long level really helps as it’s long enough to be to long so you know what you got the full length. Think the level was like $300. I still want a 72” Starrett but this is working for this purpose.

Sorry no picture of level but I promise it’s what I use. Zero spring joint just a perfect jointed edge off the machine and no helper.
5E827CD7-74CC-4D3E-A6B1-C7A5BCC34A22.jpg

Thanks. I have a Hammer A3-41 (a JP combo, 36" infeed and outfeed respectively). I am trying to joint 9' boards, so I have constructed 48" outfeed and infeed extensions. This is where the issue is. I am having trouble getting the extensions perfectly level.

After adjusting the knives and shimming the extensions, I am still getting a slightly convex (sprung) joint. It's about 1/16" over 9 feet. The boards are between 6"and 10" wide.

In fact, I am able to clamp the joints shut easily enough - even before some final passes with the jointer plane.

At this point it's a personal challenge to get a perfect joint off the machine. My definition of this is that there is no visible space when the boards are brought together by hand. I will see if the 50" straight edge

[Andrew Hughes]

I would like to suggest you focus on the outfeed side long and flat is the key.
My jointer is 99 inches over all length. I set the beds up with a suburban tools straight edge.
This is a 11 ft white pine that was faced and jointed without extensions. I wouldn’t mind have one that Oliver offered back in the day.

Good Luck

[Dennis Yamamoto]

See John White's book, " Care and Repair of Shop Machines". In Chapter 2 on Jointers, he shows how to make a master bar for checking jointer tables. It's as economical as MDF and drywall screws.

Looking for a reliable straight edge between 72" and 96" long. Any recommendations on something economical?

I'd be using this for setting jointer table outfeed and checking jointed edges and tops for tables for flat.

[Carl Crout]

My Festool tracks do double duty as tracks for the track saw and straight edges.
My Makita tracks - sort of...

What does that mean? The Makita track isn't straight or just not convenient to use as a straight edge?

[Jim Becker]

I have several long carpenter's levels, but none match each other. So when I recently went to check / buy an 8" jointer, I purchased the Lee Valley 50" aluminum straight edge.
It's great for the money, but it doesn't balance itself on the tables, which is a minor inconvenience.

Take one or two blocks of wood and put a slot in them that's a hair wider than the thickness of the straight edge and a hair deeper than the height. Slip it/them over the top of the straight edge as you have it on the surface you're testing. It/they will hold the straight edge up without binding it so your hands are freed to do what needs done.

[Jim Becker]

I would like to suggest you focus on the outfeed side long and flat is the key.

I agree with this...support on the finished side is more important to get dead on than on the infeed side, in my experience.

[Mark Gibney]

I like your idea of using the wood blocks Jim. I use a 72" carpet layers straight edge from Crain tools and your idea will help.
I think I paid $70 or so for the straight edge.

https://www.craintools.com/carpet-other/straight-edges

[Prashun Patel]

That's a great idea.

[Randy Heinemann]

I may get some disagreement but I don't think you need a straight edge that long to make sure the two surfaces of a jointer are in alignment. The total length of the table on my Jet 8" is 72" and I feel I get a good read on flatness with a 36" Woodpeckers straight edge. I don't feel I need to have a straight edge that extends the entire length of the tables. I think it would be obvious if they weren't co-planer with the 36" straight edge. At least my jointer yields edges and faces that are smooth and straight for the purposes of gluing and building furniture or cabinets, so I think it's working. I'm sure there are other ways to check flatness of table tops; like winding sticks. A 36" straight edge and either purchased or home made winding sticks would probably be a lot cheaper and more likely to be reliable than a 72" average priced straight edge.

[Alex Zeller]

Seams like there's more than one topic being discussed here. They are similar but not quite the same. A straight edge for woodworking can have many functions with each requiring a different level of accuracy. If you are trying to check the flatness of a cast iron table or set a table up to a blade on a machine then you will want very accurate. If you are looking to set up an outfeed table then +/- .0005 is overkill. Even on outfeed tables there's two kinds. Those who have a large shop where machines and tables don't move so they can be fine tuned and then there's the kind that are used in a small shop where the outfeed table is moved all the time and is used with multiple pieces of equipment.

For my outfeed table I use a glass straightedge. It's an 8' wooden Lufkin and has a slight bow to it of about 1/32" of an inch. But it does well for what I use it for. It was free to me but if buying one I would most likely opt for a phenolic version. They make them up to 12' long (maybe more), aren't too heavy, and don't move like wood does. But if you want one 8' or longer shipping is an issue since UPS doesn't like things 8' long.

[Brian Holcombe]

+/- .0005” per foot is .003” over 6’.

[Patrick Walsh]

You act like that’s significant

Ok I won’t screw this thread up anymore than it already is.

But in all seriousness what has kept me from splurging on. A sub tool or sterrett 72” edge is it has to get shipped to me. And then I’ll need someplace to check it. I tried calling Sterrett in athol and they do not sell direct.

I have been working with a machine shop local to me “just there this morning” and I’m sure they have a large plate being a 35k sq ft facility with like 6 zillion machines and 40 employees. Place is just unreal actually but that’s another thread.

I see a use for both edge and level. My complaint about the level is they are so sensitive. If “And I do” pair a machine level with my Stabillia levels like four stabillia all working off and with each other making a box around my table and x through the middle I can get the stabillia levels all reading exactly the same. Put the dam machinist level up there and set it match one side. Move it to the other side and the bubble disappears not just moves. It’s enough to make you want buck yourself off a building into moving traffic.

So what does that say about the accuracy of a standard high quality level?

That’s a question and observation not starting a argument.

+/- .0005” per foot is .003” over 6’.

[Jacob Reverb]

+/- .0005” per foot is .003” over 6’.

Angstroms, puh-leaze.

Better yet, quark-diameters. (I use quarter-sawn.)

[Edwin Santos]

I don't know if this helps but here goes - I have had good experience with the telephone support from the Felder/Hammer techs in Delaware. They seem to be big fans of the Oneway gauge. This is a $99 dial indicator in a unique cast iron housing. With it you can check both tables for flat and planarity, both in relation to each other and in relation to the cutterhead. Once you have done this, use the same gauge and the same procedure at the junction between machine and your auxiliary tables at both the infeed and outfeed side.
Personally I think a Oneway is a more accurate and controlled process than a super long straightedge and feeler gauges plus it can do other things like measure fences for square or tune other machines.

If I understand your post and you are getting a convex cut, then I would say you have a valley condition where one or both tables (or aux tables) are kicked up slightly on the end.
Maybe try giving Felder's techs a call and see if the feedback you get is similar to mine.