MIMF

Several years ago my local HD had a sale on for a 13" thkness planner ($149)
Used it a few times but on stock that is 1/8" that you want to take down to 1/10" its not good as its too violent.
What i really needed was a thickness sander.
Looked at plans and considered building one for some time but in a moment of desparation, decided to see if conversion was possible.
The blades of my planner are wedged into a 1/2" wide by 1/2" deep trough with a bar that has small bolts. You drop in the blade, then the bar, back out the bolts, to tightly wedge the "blade/bar" into position.
There are two blades on opposite sides of a 3" diameter roller.
I bought a 36" x 4" sanding belt (80 grit) and cut the diagonal joint leaving me a strip with this 45 degree angle. I then cut my 4" wide piece into two 2" pieces.
Using the ready made angle drop the end into the trough, i then used some scraps of wood made several "suger cube" size blocks and hammerd them into the trough to jam in the sandpaper. The next step is to carefully wind the paper on the roller, should all be flat with no overlap. When you get to the end trim and jam the other end with your sugar cube.
I then used a tough tape on each end to carefully and neatly cover the sugar cubes and hold the sandpaer firmly in place.
I lost two inches of usable width but the result is just great.
Two important hints, 1) install carefully and tightly, and 2) when sanding drop your depth in very small increments.
Lastly, its still a planner no permanent changes were made.

Yikes, doesn't a planer spin a LOT faster than a drum sander?

I applaud the ingenuity, but yikes + 1.

The drum sanders I've had (Griz & Performax) run around 2300 sfm (surface feet/min).

Assuming a 10,000 rpm planer and a 3" drum, that works out to 7850 sfm and a 20,000 rpm planer would be twice that.

I don't know how well those planers grab the wood, but it seems things could go very wrong very quickly. Even with light cuts, I'd think burning the wood would be a problem?

Sounds as if you're using your planner in a way it wasn't planed for.

Yes i agree it is high speed, but dropping in very small increments is the key. No burning.
The first three pieces of sandpaper were destroyed until i got the installation right.
The 80 grit was also the optimum.
tip - with unit shut off, feed the piece in and drop the drum until it sticks, raise a hair to remove and put the entire piece through to make sure you you have set to the highest spot. Make your first pass at that setting then begin.
I made a lot of passes, easy does it as i find this piece of machinery intimidating. Also i wore heavy gloves and safety glasses.

I could be wrong, but I believe 80 grit is way too course to go to final thickness, especially on top wood.
I also doubt you could make this work with anything much finer than 80 grit.
I suspect that using sandpaper instead of planer knives allows you to go a little thinner, especially on figured wood, but not very much thinner.

Wonder if a router speed control could help?

80 grit is the finest I use.... The wood gets the scraper after that.

Anything finer on a thickness sander is a waste of time and money.

Mario Proulx wrote:80 grit is the finest I use.... The wood gets the scraper after that.

Anything finer on a thickness sander is a waste of time and money.

my experience is that is true except with 120

120 is special?

<g>

I've found that 120 is a good grit to take something to on a wide belt, easier to take over from there with another surfacing tool than 80 grit, while 150 grit on our machine usually necessitates going back down to 120 with a RO to get rid of chatter marks from the belt seam.

John Sonksen wrote:I've found that 120 is a good grit to take something to on a wide belt, easier to take over from there with another surfacing tool than 80 grit, while 150 grit on our machine usually necessitates going back down to 120 with a RO to get rid of chatter marks from the belt seam.

Also I usually go from 80 straight to 120 as the 100 grit belt just slows you down

So far, so good, I guess. But I'd be mighty worried about the tough tape/sugar cubes coming loose. Would it be possible to adapt the original blade clamping scheme to lock in the paper?

Also, can you tell if hammering in the sugar cubes distorted or damaged the knifehead?

I can't remember what kind of motor is on those portable planers. Could a HF Router speed controller be used to slow it down? Could a variac be used to slow the motor down? (Are variacs still around?)

I think most tabletop planers use brush motors (router motors) so I would think a router speed controller would work. they usually have smaller diameter cutter heads,(1 1/2 - 2 inches??) so the FPM might not be too bad.
Interesting idea!

Just make sure your pulse width modulator speed controller can handle the voltage*amperage with some room to spare.

The knife blades and the bar that holds them are removed. This leaves a trough 1/2" deep x 1/2" wide. My "sugar cubes" (1/2 x 1/2) are of spruce and are hammered in flush jaming the sandpaper tight. The tape is covering the sugar cubes, make sure the tape gets 1 1/2 revolutions and the final bit is pressed nice and smooth. I installed the tape in both directions and didn't get better results one way or the other, as long as the tape is well stuck.

I tried to use the bar to hold the sand paper but this was quite tricky because you need to tighten the sand paper one end at a time. It can be done that way, you need a piece of wood same thickness as the knife blade.

Re: speed control

While rummaging the Harbor Freight website, I looked up the Router Speed Control. The manual says that it will handle 15A, and the motor plate on the Delta 12" 22-540 planer reads 15A too. I'm a bit skeptical about the accuracy of either of these specs, but I'm thinking this idea over. I wonder how much the torque would be reduced at lower speed.

If I do it, I think that I will make hardwood shims that replace the blade. I thought about grinding the edge off an old blade, but I'd think that over for a long time first. I wouldn't want a thin piece of HSS loose in the machine (or me especially). I would definitely stand to the side of the machine during all operations.

I'm just curious:
Has anyone ever used toothed or serrated planer blades?
Let's say you took a set of knives and ground a series of notches 3mm apart, sharpened
and offset them on the cutter-head.
Do you think that would allow you to thickness down to .1"-3mm or so?
Would you dare try such a thing?

Hi Tom,
With the table top planers I've used (DeWalt , Delta) planing to 1/10th of an inch is no problem. The smaller cutterheads allow the rollers to be closer together so there is less chance of the wood wrapping around the cutterhead and blowing out the dust chute.