Planer Thicknesser Knives advice please

[tony.w]

I bought a used Mini Max FS31 rebuilt and set up and i'm very impressed with it (abeit its heavy to move about on wheels on a cushioned floor), I would like to either replace or sharpen the knives. The Knives are 310mm long 20mm width and 3.2mm thick i have found Axminster APPT310 HSS blades on ebay which for £37 for 3 didn't seem bad however they are 3mm rather than 3.2mm and not sure the blade retainer will make up the difference.

Last or one of the owners left a etched date and some other wording almost 20 years ago

I have the manual but its not much use to be fair but it does quote 000605065 as a part number for them

 

[Malc2098]

I had my previous P/T blades sharpened at this company. EPS Services.

Might be worth a call.

 

[Trevanion]

Sounds more like an Imperial knife, which would surprise me on Minimax as the European stuff is usually Metric but they do also sell them in the USA so perhaps more aimed for that market. In that case, it would be 12 1/4" x 1" x 1/8" which is a common size.

https://www.ebay.co.uk/itm/282534186005

 

[Mike G]

If your planer is like mine, you screw machine screws through the block and the knife/ blade/ iron into a backing plate, which clamps the knife tight against the back (as it rotates) edge of the slot in the block. There is always a small gap between the backing plate and the other side of the slot in the block, and it won't make any difference if this gap is 0.2mm wide than previously.

If you have diamond plates it is pretty easy to sharpen your own knives. I haven't paid for mine to be ground for 5 years or more, I reckon.

 

[Cabinetman]

Sounds more like an Imperial knife, which would surprise me on Minimax as the European stuff is usually Metric but they do also sell them in the USA so perhaps more aimed for that market. In that case, it would be 12 1/4" x 1" x 1/8" which is a common size.

https://www.ebay.co.uk/itm/282534186005

No sorry, SCM Minimax stuff over here is all metric.
I would try a Diamond plate as Mike said. Not much different to sharpening a plane blade really, but leave in the mc to do it.
Ian

 

[Mike G]

Not much different to sharpening a plane blade really, but leave in the mc to do it.

I take mine out and clamp them in a home made jig, and then rub them on the coarse diamond plate.

 

[Steve Maskery]

3mm or 3.2mm will make no difference.
What does make a difference is the quality of the grind. Not just the bevel, but the back of the knife. A sharp edge has to have 2 flat edges, not just one.
I have a couple of sets of knives from a well-known UK supplier. They are mediocre, not because of the quality of the steel, but because of the quality of the face grind.
However, with a couple of jigs, it is easy to turn a sow's ear into a silk purse. I do it like this:

Last week, my friend Bob was helping me to pass a rather large beam (200mm x 200mm x 1.5m) over my P/T. He accidentally leant on the blade guard and all hell broke loose. No blood, fortunately. But the guard was a mess which I have had to beat back into shape and the knives need rather more than a tickle. Fortunately I've found a sharpening service only about half an hour away, so I shall give them a try.

 

[tony.w]

Thankyou for the very informative information i would love to sharpen what i have but my wife was expecting at least one new window by now so i think i will look to machine shop to get them done or as 0.2 shouldn't be a issue i will purchase a new set of three blades.
Thanks again everyone for your comments

 

[meccarroll]

I used to take my planer blades to a saw service in Horsford (Norwich UK) but they came back concave and burnt the saw blades I had sharpened there also came back untrue so I decided to have a go at sharpening my own planer blades.

I just put an angled piece of wood on my bench grinder and guide the planer knives by eye. I lightly move the knives from side to side to side checking them with a flat bar to make sure I am keeping them true.


The wheel is quite fine and wide which helps when running the knives past.


Very simple but so long as you only take light passes and check on a regular basis you can't go wrong.



A close up of the finished knife and no it's not burnt at the end it's just the lighting.




And the finished knife from a distance.



You can buy diamond coated wheels as in the picture below. The one below is a 120 grit which is a bit coarse. I purchased the dimond wheel so I could sharpen some tungsten cutters I have (I need a less course wheel though).




The only reason I sharpen my own knives is due to the poor experience I had with the saw service and it works out quicker time wise to sharpen them myself than taking them to be sharpened. It takes me about one hour to sharpen three knives.