Shaving 3/8" off all 4 sides of a 4x4

[Jeremy Johnston1]

So the new post mounts I got for my deck have an inside diameter of 3 1/4 x 3 1/4. I can purchase 40" 4x4s with the one end shaved down to fit but I need to shave down a couple 4x4 8' long. The 40" posts I bought are tapered for 11" to 3"x3".

Like this.
317525

Any suggestions on how to shave ~3/8" off of all four sides with decent accuracy to keep the post centered?

[Matt Day]

Many ways to skin the cat depending on your tools and shop setup. Radial arm saw and dado blade would be my first choice.

Router would do it too, start at the end with a big flat bottom bit and move in.

[Jeremy Johnston1]

Many ways to skin the cat depending on your tools and shop setup. Radial arm saw and dado blade would be my first choice.

Router would do it too, start at the end with a big flat bottom bit and move in.

Ahh yes, dado blade.. totally forgot about going that route. It might just be a PITA with an 8' 4x4. I have access to a nice shop setup with pretty much everything one would ever need. Sometimes the simplest way of doing things is over looked.

I'll give the dado blade a try.

[Yonak Hawkins]

I believe a jointer could be used successfully. Mount a stop on the outfeed side.

[Henry Kramer]

Unless I am missing something here, what would be wrong with setting your table saw fence at 3 1/4" and ripping the length of the 4 x 4's? You would have to cut each one twice (flipping it end for end) even with a 10" blade because you won't quite get your 3 1/4" depth.

[Mike Cutler]

Do you need to taper them, or take 3/8" off each face to a preset distance from an end?
The quickest way to do it is with a bandsaw. 8 cuts each and you're done.( As someone that has run pressure treated wood through his shop machines before, I know that I personally won't do it again. It's a mess, a big wet sticky mess.)
Another method is to set a circular saw blade depth to 3/8", and make multiple cuts, across the grain, of each side of the post from the end to a measured line representing the insertion depth. Use a wide chisel and whack out the waste. If you only have a few to do it won't take long at all. I ship lapped the top and bottom boards for a fence this way. It's a lot quicker than you think.

I guess a question I would have is, why the post mounts aren't sized to fit a nominal 4"x4" ?

[Matt Day]

I believe a jointer could be used successfully. Mount a stop on the outfeed side.

Wouldn't your jointer need to adjust to a 3/8" depth of cut? I don't think mine does that. It would also leave a radiused cut at the end.

[glenn bradley]

Jointer and planer are the duo designed for dimensioning lumber and would be my go-to.

[Joe Bradshaw]

Let me see if I understand your problem. You want to trim the 4x4's down to 3 1/4x3 1/4 to fit the holders by taking 3/8's off each side. Nominal size of 4x4's is 3 1/2x3 1/2 inches. By taking 3/8 off each side, you wind up with a final dimension of 2 3/4x2 3/4 inches. You only need to cut 3/16 off each side, which is easily done with a router and a jig.
Joe

[Matt Day]

Jointer and planer are the duo designed for dimensioning lumber and would be my go-to.
He's not dimensioning lumber though.
If I understand the OP correctly, he wants to take material off the end, 11" long not the entire length of the piece.

[Mark Stutz]

Doesn't have to be a finished surface, right? For on site work, take a circular saw set to the depth you want to remove, make a series of cuts a half inch or so apart, and pop out the waste with a chisel.



OOps. I should have read all of Mikes post before I [posted, so consider this a +1

[Greg Hines, MD]

A radial arm saw equipped with a dado blade would be the safest way to do this. If you don't have access to one, I would use a router and a jig.

Doc

[John Lanciani]

I would approach this as if I were making tenons. I would make the shoulder cut on the tablesaw using a miter gauge and having the blade height set at 3/8" and then I would cut the four cheeks on the bandsaw with the fence set appropriately for the thickness of the waste minus the thickness of the blade. In my shop I would figure the time at less than 5 minutes per post.

[Bernie May]

ditto to what John said, table saw and then bandsaw.

[Henry Kramer]

Do you need to taper them, or take 3/8" off each face to a preset distance from an end?
The quickest way to do it is with a bandsaw. 8 cuts each and you're done.( As someone that has run pressure treated wood through his shop machines before, I know that I personally won't do it again. It's a mess, a big wet sticky mess.)
Another method is to set a circular saw blade depth to 3/8", and make multiple cuts, across the grain, of each side of the post from the end to a measured line representing the insertion depth. Use a wide chisel and whack out the waste. If you only have a few to do it won't take long at all. I ship lapped the top and bottom boards for a fence this way. It's a lot quicker than you think.

I guess a question I would have is, why the post mounts aren't sized to fit a nominal 4"x4" ?

If these 4 x 4's only need to be reduced at the end I agree with the bandsaw method. It was my understanding that they needed to be cut 3/8" less on all 4 sides the entire length of the 4 x 4 when I suggested the table saw.

[John Hubbs]

Wouldn't your jointer need to adjust to a 3/8" depth of cut? I don't think mine does that. It would also leave a radiused cut at the end.
I would do it with my jointer. Depth of cut would be 3/16" and would be run for 11" on all four sides to get the results requested. Piece of cake for a decent jointer...

[Ryan Mooney]

Doesn't have to be a finished surface, right? For on site work, take a circular saw set to the depth you want to remove, make a series of cuts a half inch or so apart, and pop out the waste with a chisel.

I see someone has done a bit of construction :D This does indeed work remarkably well and is the way I'd go as well given the material and use.

Somewhere not to far behind would be using a router to shave the material off. Just behind that would be to just use a large chisel to hog the material off.

[Mark Stutz]

I see someone has done a bit of construction :D This does indeed work remarkably well and is the way I'd go as well given the material and use.

Somewhere not to far behind would be using a router to shave the material off. Just behind that would be to just use a large chisel to hog the material off.

Have seen it done more than I've done it with a circular saw, but have done it with a backsaw:D. I just know that I would not have a way to support an 8 foot 4X4 to run it thru my tablesaw, bandsaw or jointer.

[Mike Cozad]

+1 on either RAS with dado or circular saw and chisel.

[Jim Dwight]

Just to throw another tool into the mix, my track saw would make nice straight cuts 2 inches deep on each face. One of the many challenges of working with 4x4 PT is that it is often not square, however. So cutting from two sides will not necessarily result in a flat surface. Since a circular saw wouldn't do the whole cut, in any event, I would finish with a hand ripping saw or a jigsaw. If the cut quality is not an issue, my Bosch can and has done ripping duty on PT wood this thick before. Surface would be a bit rough, about like using a hand ripping saw, but for many things it would be good enough and it could be cleaned up. Jig saw could do both cuts, long one and short one, just fine.

[Tom M King]

Doesn't have to be a finished surface, right? For on site work, take a circular saw set to the depth you want to remove, make a series of cuts a half inch or so apart, and pop out the waste with a chisel.



OOps. I should have read all of Mikes post before I [posted, so consider this a +1

That's the way I'd do it, but why in the world would they sell 3-1/4" post mounts????

[Dan Hahr]

Why don't you just cut the shoulders with a speed square and a circular saw set for the depth and finish up with a flat bottomed straight bit in router. Start at the end and work up to the cut.

Dan

[Jeremy Johnston1]

I just realized that I never followed up on this. I actually went a really easy route. Set up a 2x4 on each side of the 4x4 with the router bit set to the desired depth. Then used a piece of plexiglass as the guide so it would extend out over both of the 2x4s.

Worked out pretty good.

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[Peter Quinn]

Never caught this the first time. I'm amazed nobody mentioned the bandsaw, its sort of built for this sort of thing. Minimal dust, very fast, very accurate, even a 14" saw can make the shoulder cuts with a quick adjustable stand or saw horse out rigger to hold the weight, then push them in up to the shoulders....I'm guessing less than 2 minutes per stick all in? I have done something similar for a neighbor doing some fence repairs. He was breaking his but with a sawzall trying to trim 8' posts. Too painful to watch, . Looks like you got it done, I for one would not like to route all that PT lumber. Nice thing about the bandsaw, set the fence once....all four sides...as many posts as you want...done.

[Myk Rian]

Looks like you needed a "Tenon", instead of a "Taper".

[Dan Hahr]

There's nothing wrong with doing it that way, but by resting half of the router on the factory face and starting at the end, you could just remove a bit at a time and work back to the 11" mark. Always referencing off the factory dimensions, you will be reducing it by the same proportional amount per side. No need for the giant base or rails, just keep some weight on the back side of the router. Matt nailed it in the first post, too...

Dan

[lowell holmes]

My band saw tracks straight. I would start with that and finish with my #7 hand plane.