My Jointer’s Infeed Table is not Flat
atoma
| Posted in Power Tools and Machinery on
All,
It took me a while to figure this out. At first, I couldn’t figure out why the jointer was “acting up”, where the boards would not flatten from end to end – only the front end would hit the blades and the rest of the board would float over it. Only after some investigative work I noticed that the infeed table was not 100% flat – it bowed ever so slightly in the middle. This is an older machine that has seen better days, but for old times sake, I would like to true it again. What is the best way to do this? Would simply sanding the surface work, or will this rough up the surface too much for the boards to glide across? Thanks for your input.
Replies
Someone who knows more than me will come along soon, I am sure, but I think the only way to get it really flat is to take it off the base and have it ground at a machine shop. You can probably belt-sand the high spot but I'd be worried that would cause more damage.
Most nights are crystal clear, but tonight it's like he's stuck between stations.
How much of a bow? I'm guessing you need to readjust your outfeed table relative to your jointer knives, take it down a hair.
Hi, atomo,
This can be a very frustrating experience and the solutions aren't simple. I will assume that you've taken the tables off the base, cleaned the machined surfaces of the ramps on both the base and the tables, lightly lubricated everything with wax, then put it back together being careful not to over-tighten the fastening bolts (which could introduce warp in the tables... which may be the root of the problem you're experiencing). Once you've done that, get yourself a truly straight straightedge (Lee Valley sells a 36" long one that's within .001" along its length) and using feeler gauges, find out how much it is out at its worst spot(s). If it is out by more than .008", then you should do something about it, as that's not within the allowable tolerance of most manufacturers. Once you have identified the area(s) that are high, using files or your belt sander, slowly take off material until it's as flat as you can get it. To help this out, apply blueing (a blue-tinted dye you can get from most metal-work suppliers) then scrape your straightedge along the surface and it'll remove the blueing from high spots. Keep removing material until the blueing check indicates it's level.
Wax the tables using any non-stereate furniture wax (I use Minwax's product on all my machines' exposed parts) and you'll find that boards will glide over the surface.
Another alternative to taking down the high spot(s) using files or abrasives, is to adjust the parallelism of the in and outfeed tables, such that they're coplaner along most areas as best as you can get them. This will likely require you to use metal shims under the outfeed table's ramp area. Try not to have to shim up the infeed table, as it has to slide up and down on its ramps, which can cause the shims to wear or slide out of position, rendering the unit inaccurate once again. On tables that are out be .005" or so, I have had reasonable results with this latter method, but it's not going to provide joints that are consistently accurate. Variables such as the location of your fence in relation to where the high spot on the table is, length and width of the board, how sharp your knives are, how straight the board was to begin with and such have a very great influence upon how accurate the planed surfaces are going to end out.
Good luck, for as mentioned in my opening sentence, this can be very challenging.
Marty
http://www.martyswoodworking.ca
Excellent advise. kudos
A slight bow in the table shouldn't have that much of an effect unless the stock is so short it doesn't span the dip. A hump is a problem. Once the stock has past the blades a little, you transfer pressure to the outfeed table. I suspect you may have a different problem. It could be set up or operator error. How did you set the knives in relation to the outfeed? Have you checked the tables for being coplanar? A tipped down infeed or outfeed isn't going to work.
Beat it to fit / Paint it to match
Thank you all for your feedback. From your comments, it looks like taking the jointer apart, cleaning, lubing and adjusting it should be my first steps. Any grinding and/or sanding should come after that. I suspect that there is operator/adjustment error here as well. I had adjusted the knives using a magnet to match the height of the outfeed table. Also, this problem seem to come up with long stock, not short stock. From my investigations, it looked like the infeed table has a slight bow in the middle, where the straight edge rocked ever so slightly. I also should confirm that my carpenter straight edge is true, as suggested. Again, thank you all for your valuable input. Wish me good luck. ATOMA
There's an old trick that I learned on this forum of suspending a cast-iron part between two blocks of wood and jumping on it. I did it for my jointer fence and it worked well. It went from .018" out of true to .002". Also, I wouldn't rely on a "carpenter's straightedge." If you don't want to pay for a Starrett machinist's straightedge, Lee Valley has some cheaper ones guaranteed to .003" over the length.ne sutor ultra crepidam: Disputantum Semirotten Woodworking
Sounds like a crown not a bow. A carpenters straight edge would not be considered precise. I work on machines and have machined straight edeges to calibrate such alignments. You should pick up some feeler guages. If one is talking aboput something being off it's best to use actual numbers such as it had a crown of .005" on the infeed jointer table. It gives a reference point. Also .005" would be considered acceptable for most manufacturers standpoint. Table saws can be off .015" and still be acceptable. I know that was the standard for a PM 66 when I bought mine.
I just went through some issues with my jointer and it sounds like the outfeed table may be a bit too high, lower it a ahir then check the results.
mousejockey
It sounds to me like the infeed table needs to be realigned with the outfeed table. There should be adjusments underneath each table. I've had a similar problem and the realignment fixed it fine. The blades are aligned with the outfeed table
papa
How could you speculate such a thing. He never said what kind of jointer it was and only a parallelogram jointer has such adjustements under each table. Atoma really didn't post any details to diagnose the problem.
Thank you Papa53921 and RickL for your input. I am sorry did not provide enough information. This is a Summit 6" Jointer Model T8155. Built in 1990. I could not find adjustment screws on the bottom of the infeed table, but it has the two screws on the side to cinch it down. Thanks.
Seriously, drop your outfeed table a hair. There are many articles/posts on how to set up your jointer. The method I used when I had the same problem you describe was to take a flat stick (about a foot long is what I had at hand) set it on the outfeed table with the stick overhanging the blades by an inch or two (again I'm sure this is described in detail somewhere else) and I rotated the blade drum toward the infeed table. The blade should slightly catch on the stick so as to propel it forward (backward?) an inch or two. All the blades should react about the same.If you think about it, if your outfeed table is too high, the stock will make contact with the blades first, removing some material, then it rides up on the outfeed table bringing the stock out of reach of the blades for the rest of the pass, never allowing you to true the board.I too thought that there was a problem with my jointer, after all it's a cheap chinese piece of slag with some machined surfaces, almost certainly machined without proper aging of the iron (so that it warps a bit later), but it does the job and it's WOOD that it's working. When I break out the feeler guages and micrometers it all looks pretty bad but at this point I am generally satisfied with the results.
bh
"The method I used when I had the same problem you describe was to take a flat stick (about a foot long is what I had at hand) set it on the outfeed table with the stick overhanging the blades by an inch or two"
Just chiming in here-that caught my eye-and I don't want to get into whether Chinese machines are good, bad or ugly, or how to deal with perceived out of straight tables.
That stick method is a well known method that use to be taught in the trade. Don't underestimate how accurate and quick it can be. The "stick" needs to be heavy, long enough and straight- needs hand planing (;).A small equal forward movement is wanted-not an inch or two. Something like 3 or 4mm is right.Philip Marcou
Philip, thanks for the clarification!
bob
I thing this is whole message board is about suggestions.......I'm a do-it-yourselfer like most on here.
Hi,
I would highly recommend you find a copy of John White's book "Care and Repair of Shop Machines". In it he gives some down and dirty details about the adjustment and testing of jointers. He also details some simple and VERY ACCURATE, user made replacements for the very expensive straight edge required to test jointer tables.
It's a very good book!! I can't say enough good things about it. Suffice to say that I have dozens of WW'ing books and that one is one of only two that stay in the shop.
No, I'm not getting a kick back! LOL Seriously, this book will pay for itself the first time you refer to it.
Regards,
Mack
"WISH IN ONE HAND, S--T IN THE OTHER AND SEE WHICH FILLS UP FIRST"
I also recommend that book. It helped me get my jointer working after it developed a twist in the outfeed table. If you get the long straightedge from Lee Valley, be sure to test it. I found out mine had a bow of .004 on one end.
TW
I made the test set that John White detailed in his book. So simple, so cheap and so incredibly accurate! I could not believe it until I put them to use! I don't know what a 4' - 5' machined straight edge cost but I'd be willing to bet it's a HELL of a lot more than a few pieces of MDF and some drywall screws!!!
Regards,
Mack"WISH IN ONE HAND, S--T IN THE OTHER AND SEE WHICH FILLS UP FIRST"
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