Do fancy spiral thicknessers just work without tearout?

[TheTiddles]

I have the same machine and I get the same problem, then I have the blades sharpened and the problem goes away. Then I forget to have them sharpened again till I get fed up with the finish again and the cycle repeats.

I’d not expect to plane any highly figured timber and not get some kind of tear out problem, by machine or by hand, but that’s what scrapers and sanders are for.

As for it being pressed steel from China, the cutter head on mine is a machined billet of steel and the beds are cast iron, not that it makes a difference to the finish.

Aidan

 

[LJM]

I used to have a Lurem former floor standing P/T, which produced good results with proper set up and sharp blades.

I found that, compared to iron or heavier weight steel bodied machines, levelling was much more critical; the body of the machine can twist if not absolutely level, and although only slight, can result in problems at table level.

So, as others have said, go back to basics. No shame in that! It can stop you chasing your tail. I got the feet absolutely level, and also filled the void at the bottom of the machine with sand. This made it appreciably quieter but also cut vibrations that could, over time, contribute to things moving out of adjustment (this also helps with balance, if you don’t want to bolt your machine down). Once I’d done that, setting the machine up accurately became quicker and simpler, I rarely needed to readjust, and quality of finish improved.

 

[Torx]

My 2p worth, the spiral blocks look like a nightmare to maintain with tiny screws and inserts stuck in place with lignin etc. I’d have a tersa block any day, double sided and a variety of different types available. I think you can even get solid carbide knives.

 

[deema]

My two penny’s worth, and I am providing popcorn!
I have tried a spiral head, I settled on a Tersa block having come form a standard bladed machine. Most professional shops seem to go for the Tersa system in my observations. But the interesting question is why do spiral blocks make the claim to be free from tear out? all system use a blade spinning around to cut the stuff, no soecial widgets or voodoo magic gizmos. So there must be some difference between the blades used.
My theory is based upon the old way you dealt with tear out. You would either scrape, or use a York pitched plane with tight mouth etc etc. for difficult timbers. The important bit is that a high pitch reduces tear out. Spiral heads use carbide blades, a very brittle substance that needs a lot of support for the cutting edge. Hence, the cutters have a high angle, I’m not sure what the angle is, but I know it’s higher than the angle sharpened in say a HSS blade. So, the only difference between different cutting actions is the ability of the bkade to break the chip before it tears out. The higher the cutting the angle, the quicker the chip breaks reducing tear out. Small cutters reduces the power requirements of the machine, a solid long carbide cutter fitted in a standard machine will need a lot more power than a spiral block that only has circa 14mm of cutter engaged at anyone time. Hence the reason they are made as a spiral, not I believe because it affects the cutt8ng action, as a by product the chips it makes are smaller which is sold as an advantage.

I use M42 cutters in my Tersa block, they have a higher angle than a HSS blade and in the main, don’t tear out irrespective of the direction of the grain. It’s not as high an angle as carbide. But, I can also put carbide cutters for my Tersa block which will I believe give me the same tear out capability as a spiral block. I can’t take as deep a cut as they are long straight cutters, and use more power.

In conclusion, the cost and convenience of a Tersa block IMO far out weighs that or a spiral block. You cannot just rotate or replace a cutter on a spiral block without generating tramways. To avoid this you have to turn or replace all the cutters. You will have to sand the tramways out. A Tersa block you can swap all the blades in less than a minute, it takes hours on a spiral block. A set of M42 blades 405mm (16”) 4 off is circa 20 for a fresh set of knives. (£40 for a the knives, 2 setups) 200+ carbide cutters......well better sit down when you need to buy them!
If the blade is inserted into a Tersa block which requires no tools to change then it’s not coming out in use, in a spiral block you have to be sure you have tightened up every single tiny torks head bolt, assuming you haven’t lost it and after cleaning all the gunk from where the cutter is seated. Not a job for an apprentice.

 

[Doug71]

Has anyone ever used knives with a slight back bevel on? It's meant to really help with tear out but I don't know of anyone who actually does it?

 

[deema]

Hi Doug, I believe the carbide cutters effectively have a back bevel.

 

[Nelly111s]

Depending on which spiral block you have, some present each cutter “straight”, others at an angle, much like you might with a hand plane. So it’s not just the angle of the cutter itself that’s at play, but the angle it’s presented to the timber.

 

[Farmer Giles]

I've got the itech 300 with spiral blades. I've been thicknessing oak burr with very little tear out.

The blades are not angled like some, but still creates a beautiful finish.

Cheers
Andy

 

[no idea]

I've got a Jet JPT310 - when it had the original head, I could not avoid tearout on maple no matter which way the board was run through or how thin the cut was. When I converted it to a helical head I had no tearout at all, either on this maple or on oak, beech, sweet chestnut, ash or walnut, regardless of which way the board is orientated. I have had this head in now for a few years and, although it is hobby use only, I have yet to rotate any of the cutters and I still get tearout free boards.

If you are looking at a conversion of a machine, it is likely to be in the £700-1000 range to do so. I was lucky because Jet produced a helical head version of my machine so after trawling through the parts manual of both machines I identified all the bits needed to do the conversion with Jet parts and managed to get them through Axminster as a special order. There is a speed difference between the two models for the thicknesser drive (the helical is slightly slower but nothing noticeable) hence the need to change pulleys etc.

Shelix and others will do a custom head for your machine if you give them the dimensions you need although there is a good chance they already have one of the same dimensions for another brand of machine that is based on the same head. The main dimensions will be the head diameter, cutter length and overall length of the head, bearing diameters and drive sprocket/pulley seat diameter.

 

[julianf]

I contacted shelix.

They knew exactly the machine (of course the same machine is sold under other brands also) and were able to quote from stock.

The price was over double what I paid for the machine in the first place. Which is fair enough, but if I'm going to spend that sort of money, I'd rather swap the base machine for somthing nicer first.

Shelix were very nice and I basically said this to them, and they agreed. I can't remember what the exact wording was without checking but the gist was "yeah, the Axminster is entry level, get an old wadkin or somthing and we will do you a head for that"

Axminster do the 206 now that has the helical head. I had alreaddy started wondering how similar they may be.

But beyond a (fairly low) price point, I'd still flog the Axminster and buy some old British cast.

 

[thikone]

Could you perhaps measure the cutting angle? Because given this:

As an example quite a few years ago a friend with a four knife block Felder was having problems with tear out on cladding he was making we ran it through my thicknesser & came up with a finish he was perfectly happy with, but I’m guessing it’s bound to be due to the different geometry of the blocks, the tips are taking a smaller shaving & are presented to the timber at a shearing angle rather than straight on.

and this

Its (more or less) fine on softwood, or, for instance, straight grained hardwood, but figured hardwood, even even stuff like oak with non-straight grain, and its not good.

It might be that straight knifes have smaller cutting angle. Therefore, good for softwood but not so good for hardwood.

And spiral segmented knifes have bigger cutting angle. Which makes them better on hardwood but would probably be not so glossy on softwood.

 

[Peter Sefton]

Has anyone ever used knives with a slight back bevel on? It's meant to really help with tear out but I don't know of anyone who actually does it?

Yes, it does help and strengthen the cutting edge, I wrote an article including this technique a few years ago.

https://www.peterseftonfurnituresch...terseftonmakingthemostofyourplanerarticle.pdf
I have used a few planers over the years and have a spiral block one on order, I like the finish it gives.

Cheers

Peter

 

[wallace]

Wadkins 24"RM has a skewed head, one portion is best for soft woods and the geometry of the other half is suited to hard wood. But who has room for a 24" planer. I might be doing an 18" FM for a guy in Australia and he has expressed an interest in changing the head. I've not done it before so should be fun

 

[thikone]

Ah, I found the video where I saw the difference:

So, it is indeed a different cutting angle. About 45° for straight knifes and about 65° for segmented knifes. The drawback is that it is harder to push wood over such cutter. And no tearout on hardwood but not smooth surface on softwood.

Thanks Peter for back bevel article! Now it all comes together and looks pretty much the same as with hand planes. Till now I only used hand planes and recently ordered Hammer A3 with spiral cutter and I have to learn how to use that this year...

Picture taken from here:

(sorry, it is in Russian)

 

[julianf]

I'm still on this one...

There did not really seem much point in getting a spiral head for my existing Axminster, so it's looking like I may be on the way to a BAO/S (with some table issues, but it's likely the thickenesser side of it is fine)

I did spot a hammer A3 on the used market which was a consideration also, but that opportunity quickly passed, and I have a liking of old British cast anyway.

So far as I know, the companies offering retrofit spiral heads are 'just' buying them from firms in China anyway, so I contacted one of them directly and I suspect the price may not be quite as fearful, but I don't know with certainty yet.

Am also looking for a rotary phase converter. From speaking with other people, with more knowledge than myself, it seems that the bao/s can be run from an inverter for the main motor and then the right size cap for the feed motor, so long as the 2speed function is dropped. And the cost, likely under £100 (so much cheaper than the rotary converter but not as conveniant)

Or, as it's just two blade, maybe I'll give the esta system a go first. Noone seems to list 12" blades in carbide though, so maybe I need to actually call up for them (I'm away at present and will not do so until I return)

So, yes, still working on this one. Will see what happens...

Thank you.

 

[julianf]

Solution -

and -

The BAO/S is not yet running, but the drum sander, even though you shouldn't use it as a thicknesser, has made a massive amount of difference to what i can and can not do.

Im aware wide belt sanders are more sensible, but i dont have the amps for one of them, so drum sander it is.

 

[johnnyb]

I've had the axi 12inch spiral jobbing for 4 years about. Great machine tbh. certainly not faultless but very very good finish(still needs belt sanding etc)
it has some teeth that stop it taking more than 2mm off. sensible on wide boards but a pain on joinery items( I might grind a mil off the teeth one day)
in four years off full time professional use I've only swapped the cutting edges 3 times! although they are due but it still cuts really well. I take them out clean the head and cutters etc hone them on a diamond stone and put them back on. takes 2 or 21/2 hrs. I've also found a strong extractor makes a big difference to so much(finish feed )
until I had this machine I couldn't properly utilise my other machines to the same level as four square and flat was hard to achieve. a tersa block is a fine choice as well but I would not swap unless the base machine was a heavier more industrial affair like an scm or felder.

 

[D_W]

I'd imagine the spiral head makers have made a lot on people who don't read their manual to understand setting the back knife (chipbreaker) on heads that have an adjustable chipbreaker.

The reason pro shops use tersa instead of spiral is because the blades are standard, and the machines are more efficient power-wise than a carbide spiral head.

The original machine referenced here looks like it may just be a standard single knife older head style, but if it's not, mind how the chipbreaker is set and then the knives won't tear out no matter how dull they get.

I've got a friend here with a DC580 delta planer that he just hated until he put a spiral head on it. I'd bet he never read the manual about setting the original head and the change-over cost something like $1300. big penalty for not reading a manual.