Planer bed has a dip in the middle

[Mark Gibney]

I'm restoring an old planer, a PM 100.
The bed dips 6 thousandths in the middle. Is this a big enough dip that it warrants having the table ground flat?
The table is 12" x 24".

thanks, Mark

[Patrick Walsh]

Hmm there are a few here that could tell you. I can’t tell you with certainty.

I do think many manufactures specs are like 4-10 thousandths.

My Felder jointer has a did of 4 thousands just after the cutter head on one section of the outfeed table. It does matter if you edge joint right there. The tables are also out about the same 4 thou regarding coplanar. I notice it but it doesn’t affect my work for the most part.

[David Kumm]

Unless you can get it done really cheap, probably not. The planer at 12" allows only one board at a time and you can learn to place various widths to negate the dip. Plan B might be to watch for a parts machine and swap beds if you find you can't live with the hassle. Old planers tend to have wear in the middle so always check the chipbreaker and bed for excess wear in the middle. Dave

[Robert Engel]

I doubt it will be an issue with fairly thick wood.

Thinner lumber you could use a sled.

[David Sochar]

A 12" planer is a bit small to be reworking like it is a 1942 Rockwell. If there is a dip in the bed, then there is also a worn hollow in the pressure bar. Either one could give you fits, but both together will interfere with feeding.

[Mark Gibney]

Thanks for the feedback guys, I'll see if I can get it done for a reasonable price, and I'll check the pressure bar.
And welcome to the neighborhood David.

[johnny means]

So that would translate, theoretically, to a .006" discrepancy in anything coming off of it. Would that have an adverse effect on any of your work? Could you even measure it if you tried? I can't imagine you'd gain any functionality or performance from machining.

[Bradley Gray]

Doesn't the planer have bed rollers?

[David Sochar]

So that would translate, theoretically, to a .006" discrepancy in anything coming off of it. Would that have an adverse effect on any of your work? Could you even measure it if you tried? I can't imagine you'd gain any functionality or performance from machining.

Well, I think the wood would not necessarily conform to the dip in every case. A piece of 8/4 Oak will not deform .006. But a 1/2" Cedar strip might. In between, you will get a flutter on the top side of the board. Nothing that would not clean up in subsequent operations - scraping, sanding, etc.

Rhythmic defects are common in molders with harmonic disturbances being the chief cause. These can be just a few 10/1,000", but they still show up. I have spent days chasing down ripples in 7" wide crown molding.

[Mark Wooden]

The PM 100 has edges on both sides of the bed, you'll probably lose those if you can find someone to grind it. If you're using the bed rollers that much of a dip probably won't show in any appreciable way.

[Derek Arita]

This planer has an indeed side and an outfeed side, right? Are there no table adjustments available?