Printable View
I have recently come to notice a slight concavity on the infeed table of my A3-31 jointer. The concavity is in the direction that is perpendicular to the fence.
The concavity does not seem to cause a problem in the performance of the machine.
i was told that the concavity was intentional; but, I do not understand why?
I would appreciate any comments.
I'm sure there are going to be a whole lot of people responding to this. Technically speaking, both the in-feed and out-feed tables on a jointer are suppose to be perfectly flat (I've read that the in-feed table is not as critical to be perfectly flat, but I'm not an expert here). What you have is a manufacturing flaw that is very common on the Hammer jointers. Based on my reading of manufacturing, I theorize that Felder/Hammer is not letting the cast iron settle on these items before machining the table flat (or it could be another manufacturing problem). Many people are very unhappy with this and support/replacement from Felder has been generally very poor. You can search this form for "Hammer A3" and find several comments on Hammer table flatness problems.
Here's a video showing how to determine the amount of problem you have (starting at 170 seconds into the video):
https://www.youtube.com/watch?v=F5-cjNa_yJU&t=170s
As Aaron noted this seems to be a fairly common issue. Jointer tables are meant to be flat, but how flat do they need to be? If you are getting acceptable results, don't worry about it.
A concavity on a table is not intentional.Quote:
Originally Posted by Adel Heiba
A concavity on the completed workpiece can be.
The jointers are normally set with the end of the infeed table furthest from the cutter a couple of thou lower than planar.
This produces a very slight concavity on the workpiece, resulting in a “spring” joint.
I always had my jointer set this way until I made flooring then I removed the concavity from the workpiece.
Does your jointer produce acceptable workpieces?
If yes, enjoy your machine……..Regards, Rod
The machine in the you tube is out lots. He resolved it by changing brands. Not always a guarantee. I dont know what the acceptable numbers are but my old stuff is way more true than that after 50 plus years of use.
Because the tables have the raised machining on mine they will be more prone to showing wear over time. At some point stuff being out and how is going to affect using the machine. How can you even set it up. If your outfeed to the knives is set and the table is not true where are you setting it to? the middle, out from that, or the outside edges highest point? Do you change it when you have a narrow board then a wide one?
Id set the tables co planer and if you want a spring joint then raise the outfeed a fraction. Better the leading edge of the infeed is low than high. Likely on light machines any heavy board will make it so anyway if you dont have infeed and outfeed support. Most machines will have some wear there after many years of use and friction. Fancy machines have an arm to flip to put the tables into setting for spring or. That comes along with the fancy bill.
I've searched a lot of threads on this subject. I'm not the authority, but it seems that the Felder "official/unofficial" threshold on this concavity is about 8 thou (.008"). However, their response on "official threshold" seems to be whatever concavity you are measuring. The guy in the youtube video was getting 12 or 13 thou (.013") concavity on his Hammer A3 41. I do remember him testing the Minimax FS41E and he got 2 thou across the board on that machine (.002").
got .0015 across on the outfeed leading edge and .004 for a bit on the diagonal lengthways. Its wear from 50 plus years of use. Will have to clean the table well and spend a bit of time to be accurate.
The high point machining will likely show the wear some amount visually. It would be easy to true with the ridges not having to do the whole table. Works great as it is. Thanks for putting the numbers on it
A cup in the infeed table is definitely not ideal, but if you are getting acceptable results then it's not an issue. How much are you talking about? 0.002" would be a non-issue to me, 0.010" would be huge.
John
A measurement of .0015 (which is under 2 thou) is so tiny it's not even worth mentioning, so I suspect you mean .015 (15 thou). I would assume that even 15 thou (.015") on the outfeed leading edge is not an issue since that's the first contact point for wood being moved across the table. The main table 2-3" downstream would pick up support of the wood enough.Quote:
Originally Posted by Warren Lake
I've also read that modern machines don't make their cast iron as well as the older ones (such as yours or stuff like Northfield or Oliver). Northfield still does make their original jointer machines today. I heard that they probably only sell 4-5 jointers per year.
.0015 so one and half thou. Ive been worried about it all morning :)
and .015 would make a difference, I set my knives to .0005 when I do a set up so zero chance of setting it up if the table was down .015 in the middle. Thats why I said how do you set it up, to the middle, either side or the outside edges. Good luck with that.