Planer/Thicknesser slightly bowing stock

[YorkshireMartin]

Hi guys.

Sorry for the long post, it's just not easy for me to explain as I don't know all the terminology. I appreciate your patience.

The last time I used my planer everything it churned out was dead flat. For reference, I was planing 100x100 redwood at that time.

Today, I came to plane down some walnut and oak and I've come across a bit of a strange problem. Whatever I put through it seems to be coming out bowed along the length, except, the bow is on the lower side. It's very slight, only 0.5mm, but still annoying and I'm not sure what could cause it.

At first I thought user error, so I had a play around with technique (particularly pressure) and ended up with the exact same result across multiple boards.

Usually, when I introduce a bowed board to the planer, I place it ends down. With the correct transference of pressure from infeed to outfeed, you whittle away at the bow progressively at each end, until finally you are planing the entire length and then you know the board is flat. In theory.

What is happening here, is that the planer appears (also sounds) to be taking wood equally across the length and width of the stock, yet leaving a slight bow.

I've heard many times of bows due to incorrect application of pressure on the infeed. But I've done tests with no pressure at all applied (push stick only) and the result is the same. I've also never heard of bowing happening this way up. It's always been "ends up" as far as I've read.

The stock is 2" walnut x 9inch wide in 5ft lengths. The oak was 1" thick by 7.5" wide in 2.5ft lengths. There is a bow of the same amount in all the stock.

PT is a Sedgwick PT255, so not particularly wide beds, but not narrow either.

I hope this makes sense. Perhaps I'm expecting too much out of the planer?

Can anyone offer some insight as to what might be causing this? The only difference I can think of between the redwood I planed and the oak/walnut is that the hardwoods are, well, hardwoods, and they are wider.

Thank you.

 

[Zeddedhed]

Try another 2.5 ft length and see what happens.

 

[YorkshireMartin]

Try another 2.5 ft length and see what happens.

I have tried 4 lengths of walnut and 4 of oak. All the exact same bow amount, regardless of the length of stock. Also turned around the stock after a pass, same result.

I took a twist out of the same oak successfully (verified by doing light passes and observing where material was taken), only to find this bow was happening to everything.

It's only very very slight. Perhaps 0.5mm was an exaggeration, it's more like 0.25mm at the high point I guess.

 

[James-1986]

In my experience planing thicker stock is easier than thinner stock. Simply because the pressure you put on the timber will force it against the bed, it then springs back. Wearing grippy gloves and using lubricant will help, as you can use smaller amounts of pressure to pass the timber over the machine.

Sedgwick machines are fairly well made, so it would be unusual for it to suddenly be inaccurate. It will be worth checking the knives, you may find they are a little low on the outfeed, which will cause all sorts of problems.

 

[YorkshireMartin]

In my experience planing thicker stock is easier than thinner stock. Simply because the pressure you put on the timber will force it against the bed, it then springs back. Wearing grippy gloves and using lubricant will help, as you can use smaller amounts of pressure to pass the timber over the machine.

Sedgwick machines are fairly well made, so it would be unusual for it to suddenly be inaccurate. It will be worth checking the knives, you may find they are a little low on the outfeed, which will cause all sorts of problems.

I'll check the knives for sure. Need to find a jig to do it.

The tables are lubricated with liquid wax, I forget the brand but it's common and purpose made for the job. I reapplied it just to be sure but no dice.

As you know, the outfeed on a sedgwick isn't adjustable. What I thought was, that the additional width of the stock over what I'd planed before might be causing it? I just can't imagine what would need to be out of alignment for this to happen. It's precisely the opposite of what a planer should be doing theoretically, assuming pressure is applied on the outfeed, anyway.

 

[James-1986]

You don't need a jig to check. Take a 1' piece of wood with a straight edge, hold it down on the out feed and spin the block. The knives should brush the piece of timber or perhaps carry it forward a little, if the knives miss they are too low. Check the knives on both edges and in the middle, you will be able to gauge if the knives are cutting equally across the block. If the knives are a little high the planer will snipe the end, if they are low you will never plane anything straight.

Does the planer have a standard or Tersa block? If standard and the bed is fixed, I'd assume they have some springs under the knife to set the height.

Sedgwick are very helpful and will offer very good technical advice over the phone.

If your machine puts out 100mm square redwood accurately then it may just be worth accepting what it is doing with the thinner stock. 0.25mm bowed over that length in thinnish stock isn't bad. If you level out the beds and push that board down with your finger it takes very little pressure to take that bow out. With a big very accurate machine the weight of the timber is usually enough, with planers that have shorter beds you have no choice but to apply pressure on the out feed.

 

[YorkshireMartin]

Thanks James. It's a standard block.

I don't yet own a quality straight edge of sufficient length so thats the first thing I'm going to address next week.

I'lll have to look into setting knives. It was a reconditioned machine and I haven't set it up again since I got it. I didn't need to as previously I'd had great results but now I think I'll have to look again.

 

[custard]

When was the last time you sharpened the knives?

Incidentally, a 0.25mm-0.50mm concavity on a 5' length isn't terrible, I realise you can do better (I target, and consistently achieve, 0.1-0.2mm concavity on a 2m length) but I've known plenty of workshops that would regard your planer as spot on!

 

[YorkshireMartin]

When was the last time you sharpened the knives?

Incidentally, a 0.25mm-0.50mm concavity on a 5' length isn't terrible, I realise you can do better (I target, and consistently achieve, 0.1-0.2mm concavity on a 2m length) but I've known plenty of workshops that would regard your planer as spot on!

I haven't sharpened them yet, it was on my to-do list. All they tackled prior to today was about hmm, 20 linear meters of redwood. I wouldn't have imagined that would tax them too much. It's certainly something to consider though, at this juncture. I have to admit though, I don't see how blunt blades could cause this?

The 0.25mm concavity is on, seemingly, any length. The 2.5ft lengths of oak are exactly the same in concavity (at the high point) as the 5ft lengths if walnut. Thats what has me stumped. I can't see the logic in that at all.

What I am dreading, is buying a good long straight edge and finding out the outfeed tables outer end is higher. In other words, some muppet has lifted the planer by it's table. That's my nightmare scenario. Then again, on longer stock, the concavity would be more pronounced wouldn't it?

If I have to deal with this concavity, my new favourite word by the way....what is the best way to deal with it? I'm making a table, so the top does have to be flat. Am I looking at sanding or planing to flatten?

I'm so sorry fellas, I always seem to be here asking something. I really do appreciate all the advice and try to help out where I can.

 

[James-1986]

0.5mm on a 5' tabletop? Pretty good going. I'd just pull the pipper down onto the base and collect my cheque :lol:

 

[malky boi]

Hi, I had a similar problem on my sedgick MB planer.

The out feed table is slightly adjustable by the way of shims. If you loosen the fixing bolts that hold down the table to the body you can insert shims to adjust it all ways. I got the shims from sedgwick direct and they are ultra thin!! You will see what I mean when you look at the table, all I know is that using the shims solved my problem. Oh, and if you haven't set the blades in a sedgwick before, they are a pain.

 

[YorkshireMartin]

Hi, I had a similar problem on my sedgick MB planer.

The out feed table is slightly adjustable by the way of shims. If you loosen the fixing bolts that hold down the table to the body you can insert shims to adjust it all ways. I got the shims from sedgwick direct and they are ultra thin!! You will see what I mean when you look at the table, all I know is that using the shims solved my problem. Oh, and if you haven't set the blades in a sedgwick before, they are a pain.

Thanks malky. I'll know more once I purchase a longer straight edge. In terms of blade setting, do you have a jig for doing so or some other method?

 

[malky boi]

I don't have jig, but there are a few on the market. I think Veritas do a planer jig but don't know anything about them.

The 2 small allen screws used to raise the blades up and down on the MB are the problem. When you put in fresh blades and just nip up the lock screws, you then put the allen key in to adjust the blade height. The problem with mine was that the allen key was tight up against the blade and you can't turn it. Sedgwick sent me some more adjusting screws but with a smaller allen screw welded into the standard size, so you can turn the smaller key and adjust blades easily. But they tend to break off after a while. So it's really trial and error. Hope this helps!!

If any one else has a foolproof way of adjusting sedgwick planer blades, I would love to know!!

 

[dzj]

Do you get this concavity when edge planing also?

 

[custard]

When was the last time you sharpened the knives?

Incidentally, a 0.25mm-0.50mm concavity on a 5' length isn't terrible, I realise you can do better (I target, and consistently achieve, 0.1-0.2mm concavity on a 2m length) but I've known plenty of workshops that would regard your planer as spot on!

I haven't sharpened them yet, it was on my to-do list. All they tackled prior to today was about hmm, 20 linear meters of redwood. I wouldn't have imagined that would tax them too much. It's certainly something to consider though, at this juncture. I have to admit though, I don't see how blunt blades could cause this?

Blunt knives (and even moderately unsharp knives) are the biggest single cause of planer problems. Put another way, with really sharp, well set knives you can get away with all sorts of other issues! It's entirely possible that blunt knives are lifting the workpiece when it first enters and finally exits the cutter block, and only taking a full bite in the central section. That would explain why you're getting the same concavity on different length workpieces.

The test is to run the workpiece through the thicknesser, which of course holds it firmly against the pressure and feed rollers with no possibility of flutter or lift, and see if the problem is repeated.

In any event you'll have to tackle the knife sharpening/setting issue sooner or later so it might as well be now. If you haven't done it before I guarantee there'll be moments of bleak despair and helpless frustration! But persevere and if necessary repeat the entire process two or three times. You'll find you get better and faster each time. Where I see many hobbyists go wrong with their P/T's is that they run the knives way past the sensible sharpening date (go into any hobbyist's workshop and ask to plane something and I can almost guarantee the owner will apologetically mumble something about the knives being a bit blunt!), the problem becomes self perpetuating as if you don't sharpen and set regularly you don't get the practise to do it quickly, accurately and efficiently.

New, non-disposable knives are rarely sharp enough. So if your P/T is new you'd expect to see performance deterioration very quickly. If it's second hand there's every chance the previous owner just gave them a quick hone in situ, so again they'll soon need some attention.

Good luck!

 

[YorkshireMartin]

Do you get this concavity when edge planing also?

After checking in better light this morning, yes, it's happening on edges also.

 

[YorkshireMartin]

When was the last time you sharpened the knives?

Incidentally, a 0.25mm-0.50mm concavity on a 5' length isn't terrible, I realise you can do better (I target, and consistently achieve, 0.1-0.2mm concavity on a 2m length) but I've known plenty of workshops that would regard your planer as spot on!

I haven't sharpened them yet, it was on my to-do list. All they tackled prior to today was about hmm, 20 linear meters of redwood. I wouldn't have imagined that would tax them too much. It's certainly something to consider though, at this juncture. I have to admit though, I don't see how blunt blades could cause this?

Blunt knives (and even moderately unsharp knives) are the biggest single cause of planer problems. Put another way, with really sharp, well set knives you can get away with all sorts of other issues! It's entirely possible that blunt knives are lifting the workpiece when it first enters and finally exits the cutter block, and only taking a full bite in the central section. That would explain why you're getting the same concavity on different length workpieces.

The test is to run the workpiece through the thicknesser, which of course holds it firmly against the pressure and feed rollers with no possibility of flutter or lift, and see if the problem is repeated.

In any event you'll have to tackle the knife sharpening/setting issue sooner or later so it might as well be now. If you haven't done it before I guarantee there'll be moments of bleak despair and helpless frustration! But persevere and if necessary repeat the entire process two or three times. You'll find you get better and faster each time. Where I see many hobbyists go wrong with their P/T's is that they run the knives way past the sensible sharpening date (go into any hobbyist's workshop and ask to plane something and I can almost guarantee the owner will apologetically mumble something about the knives being a bit blunt!), the problem becomes self perpetuating as if you don't sharpen and set regularly you don't get the practise to do it quickly, accurately and efficiently.

New, non-disposable knives are rarely sharp enough. So if your P/T is new you'd expect to see performance deterioration very quickly. If it's second hand there's every chance the previous owner just gave them a quick hone in situ, so again they'll soon need some attention.

Good luck!

Thanks custard.

Is this possible to do myself or should I be looking at sending them away? I don't have a means of sharpening other than diamond stones and these are only 2 inches wide by 8 inches long.

 

[custard]

Is this possible to do myself or should I be looking at sending them away? I don't have a means of sharpening other than diamond stones and these are only 2 inches wide by 8 inches long.

You can hone planer knives yourself, either in situ in the machine, or in a simple wooden jig on the bench. But grinding yourself with diamond stones, although theoretically possible, would be pretty arduous and skilful in practise.

At the early stages you need to remove as many quality variables as possible, so I'd send them away. You'd be better really focussing your efforts on learning how to set the knives.

It's a good idea to have a second set of knives that have been freshly sharpened, thus taking away one of the more popular (and feeble) excuses for running blunt knives, namely "I don't change the knives because I need the machine right now so can't send them away for grinding"!

Good luck

 

[harvestbarn]

You might find my post of use see setting-spring-supported-planer-blades-with-axminster-jig-t92745.html I have no experience of your machine but suspect it is not so different.

 

[YorkshireMartin]

You might find my post of use see setting-spring-supported-planer-blades-with-axminster-jig-t92745.html I have no experience of your machine but suspect it is not so different.

I dont think the Sedgwick PT has springs.

After quite a lot of digging I have just found a manual for it. If anyone wants a copy, PM me your email address and I'll send a PDF. In conjunction with all the help I've received here, I think I can tackle it.

I just hope it's nothing more serious. Time to get a proper long straight edge anyway, been putting it off for a while.