Planer knives

[Chipwrights]

I recently bought a set of tct planer knives from Axminster, they worked well and lasted 5 months working mainly with Sapele, when they got tired I sent them off to be re-sharpened, a couple of months later I re-fitted them to the machine and a few weeks later they were getting tired again, a bit strange I thought, they should last a lot longer than that. On investigation I found that when resharpened they had changed the angle from 35° to 45°, so meaning a much finer angle which isn’t going to last as long, does anyone on here have any thoughts on what honing angles should be? I’ve taken it up with the sharpening people but they’re not being very helpful, the cynic in me says a finer angle means much more work for them on a more regular basis, ie every month rather than every 5 months. Larger workshops probably wouldn’t notice this. I emailed Axminster and they were adamant that the new knives left them with a 35° angle, any views?

 

[Cabinetman]

Hello and welcome, I can’t help on the angles I’m afraid, I use Tersa, certainly the sharpening co I use would do them to whatever angle I asked and I would be more than a little bit annoyed at having my new blades messed about with/spoiled. Ian

 

[eribaMotters]

45 degrees is wrong, although it does give a stronger edge and would be less susceptible to chips. Mine are 30/35 degrees and cut fine. As soon as I detect a less keen cut I give a light hone with a diamond stone whilst they are in the block. Because of that more acute angle this is easy to do and brings the irons back to original performance.
At the same time, if I've found a nick then I stagger the knives in the block to offset the nick that may appear to a lesser extent in the next knife.

Colin

 

[TRITON]

I have to keep adjusting the fence to find a section that is clean mine have the appearance of a serrated bread knife.
I've even got a machine capable of resharpening them. Just lazy I guess.

 

[Jones]

I gave up on normal blades and went for disposable as you get two sharp edges for not much more than one resharpened one. Also don't need to reset the holders.

 

[Spectric]

I gave up on normal blades and went for disposable

Same here, but maybe not out of choice! I had issues with a Record Pt107 and could not get a decent setup with all three knives, I actually could get a better finish using just two and ended up buying the Esta system from ESTA Knife System and now the blades are cheaper, two cutting edges for less than one original and they just fit with no setting up.

Another bonus is that because they are cheaper and easier to fit you have no excuse to be lazy and if nicked or knackered then change them.

 

[johnnyb]

the angle your refering to is the clearance on normal knives ie the rake angle is determined by the block. so yes changing the angle has effectively weakened the edge hugely in a very brittle product to begin with with no change of effective angle. clearance is solely to stop rubbing behind the knife.

 

[Doug71]

Does a grinding angle of 45 degrees not give a stronger edge than 35 degrees? Think 40 degrees is about standard.

Some people put a slight back bevel on for hardwood to give more of a scraping action and reduce tear out.

Some good info here which might be useful from @Peter Sefton

https://www.peterseftonfurnituresch...terseftonmakingthemostofyourplanerarticle.pdf

 

[johnnyb]

dougs possibly right if its more acute its weaker basically. I just pictured 35 degrees then made it 10 degrees sharper.

 

[Doug71]

dougs possibly right if its more acute its weaker basically. I just pictured 35 degrees then made it 10 degrees sharper.

The confusion could be that @Chipwrights might be taking the angle from the perpendicular where I normally think of it from the flat of the blade (don't know which way is correct with planer blades).

I am told 40 degrees is standard on HSS but 55 degrees could be expected on TCT as it is quite brittle, this would account for the 35 degrees Chipwrights quoted if measured from the vertical?

So as others have said if your blades have been made 10 degrees sharper yes the edge will be weaker.

Maybe the sharpening place just does them all at 45 degrees as a bit of a compromise and nobody has ever questioned before

 

[ivan]

The angle on my 310 Jet PT knives is about 35 deg - if it was a plane blade you'd be sharpening at 35 deg. New blades the same angle. Probably chosen for softwood? Cuts hardwood better but slower with a backbevel of about 10deg, with less chipping out of difficult grain.

 

[RobinBHM]

Same here, but maybe not out of choice! I had issues with a Record Pt107 and could not get a decent setup with all three knives, I actually could get a better finish using just two and ended up buying the Esta system from ESTA Knife System and now the blades are cheaper, two cutting edges for less than one original and they just fit with no setting up.

Another bonus is that because they are cheaper and easier to fit you have no excuse to be lazy and if nicked or knackered then change them.

That’s a good system - it just fits in the original block.

I have an old surface planer with 2 knife block - I shall have a think about this.

how did you get on with fitting it etc?

 

[Spectric]

how did you get on with fitting it etc?

It was very easy, you locate the knives on the carriers and then just drop into the drum and tighten using the original nuts. Because the carriers locate on the drum there is no setup, all blades sit at the same height and then you adjust the outfeed table. It made my PT107 usable and now cheaper for blades.

 

[Doug71]

That’s a good system - it just fits in the original block.

I have an old surface planer with 2 knife block - I shall have a think about this.

how did you get on with fitting it etc?

I have an old Sedgwick MB which I changed to the ESTA knife system, as Spectric says it's very easy to use. Really modernised my old machine.

 

[Dlyxover]

Dose the ESTA knife system do away with need to realign the blades each time you fit new blades?

 

[Jones]

With the etsa knives you don't need to reset in practice but it's worth checking in case you do . It's not the same as tersa which are self setting.

 

[RobinBHM]

It was very easy, you locate the knives on the carriers and then just drop into the drum and tighten using the original nuts. Because the carriers locate on the drum there is no setup, all blades sit at the same height and then you adjust the outfeed table. It made my PT107 usable and now cheaper for blades.

I have an old Sedgwick MB which I changed to the ESTA knife system, as Spectric says it's very easy to use. Really modernised my old machine.

many thanks for that advice, that’s really useful.

It seems a great compromise, not as good as TERSA perhaps but still pretty easy to do.

 

[Spectric]

What it delivers is an easy no setup system, with all the knives set the same then you only need to worry about the outfeed table height. What I find strange is that the OEM's are still selling machines with what I would class as an outdated method of fitting and then having to adjust blades, had I known of the issues it would cause me then I would never have entertained such a machine as the Record PT107, and even the Startrite SD31 has the same system although easier to change from planing to thicknessing but at £600 more. In hindsight I would have probably gone for an Axminster AT260 which has a three knife cutter block with quick change HSS knives which are self setting.