Benefits of using a smaller saw blade on a table saw?

[sploo]

I'm hopefully going to soon upgrade my little Axminster TS200 saw (205mm blades, 1.5hp) to a machine capable of taking 315mm blades (with a 2.5hp single phase motor).

I notice that the machine can actually take a blade anywhere between 245 and 315mm. Obviously if you're needing the full depth of cut then the biggest blade is a must. However, for other applications would there be any advantage (other than cost) in using smaller blades?

The machine claims 100mm max depth of cut with a 315mm blade, so I'm assuming something around 60mm with a 245mm blade. If I wanted to do a rip cut through some pretty tough 2" thick hardwood, would there be a torque advantage to using a smaller blade? I'm thinking that it'll always be the blade tips doing the cutting, so the motor will have an easier time with a smaller diameter blade when under load.

Am I thinking on the right lines, or kidding myself?

 

[mbartlett99]

I can't help but think you're overthinking it. Remember that that the tip speed on the 315mm will be significantly higher and a 2.5hp motor really shouldn't have any issues with 2" wood of any sort.

Is a 2.5 hp motor big enough for the full 4" cut in a tough hardwood - well may be if you take it sensibly. Wouldn't mind an extra 1kw for that if you had the option.

 

[sploo]

Tip speed will only be higher if the saw isn't bogging down, of course :wink:

I guess the point about 2" cuts is a good one though; with a smaller blade I'd only be able to do a 2" (or maybe 2 1/2") deep cut; and if the saw can handle a 2" cut with the larger blade there's little benefit to using a smaller blade.

As far as I understand the saw (it's a used model) comes with a 2.5hp motor; no manufacturer option for a more powerful one (in single phase anyway).

I guess if they're using a fairly standard size motor (in terms of mounting) then it may be feasible to upgrade to a 3kw (4hp) unit, as the saw is capable of running from 4 and 5hp (three phase) motors.

 

[mbartlett99]

Which saw is it anyway?

Re-wiring is not too difficult if needs must.

My 3kw Robland is running a 255mm blade which will go through 75mm of hard maple without too much bother. It is available with a 315mm blade with the same motor if that gives you an idea.

When I machine big lumps Mr Bandsaw comes to play.

 

[deema]

The idea is to use a blade as small as possible for the stuff being cut, that way the front edge that does the cutting is as vertical as possible to reduce tear out and kick back. If you use a larger blade and drop is down into the table to the proper height the leading edge will be at a a more oblique angle.

 

[memzey]

Biggest advantage is price surely? Just check what 12” blades cost compared to 8” ones.

 

[PAC1]

The problem with using smaller blades than the saw is designed for is the the peripheral speed. A 300mm blade at 3000rpm is 2828 m per minute. A 200mm blade is only 1885m per minute. You loose a 1000m per minute of cut. Also as the diameter is smaller there is more wood to cut through. Therefore you need to feed the blade much slower or risk stalling. HSE advice not to go below 60% of the design diameter personally I do not go below 80%
Also you want the bigger blade for a more vertical cut. You just raise the blade and lower the crown guard or if a modern SUVA the blade is perminantly covered anyway. You need to ensure the rip fence is set properly to reduce the risk of kick back
A 2.5hp saw might cut 100mm deep soft wood or easy hardwood but I would like to see it cut oak

 

[custard]

Another issue with smaller blades is that the riving knife and guard need adjusting. I've ended with a bunch of 300mm and 315mm blades, and it's an added faff to reposition the riving knife every time I switch from one to the other.

 

[sploo]

Biggest advantage is price surely? Just check what 12” blades cost compared to 8” ones.

True, but 245mm is ~10". so less of a cost difference (at least based on a brief look at pricing).

 

[sploo]

The idea is to use a blade as small as possible for the stuff being cut, that way the front edge that does the cutting is as vertical as possible to reduce tear out and kick back. If you use a larger blade and drop is down into the table to the proper height the leading edge will be at a a more oblique angle.

I've not come across that thinking before; in fact I understood it's generally a good idea to keep the blade as low as possible (with the bottom of the blade gullets just above the stock). The gist as I understand it is to have the maximum number of teeth doing the cutting.

 

[sploo]

The problem with using smaller blades than the saw is designed for is the the peripheral speed. A 300mm blade at 3000rpm is 2828 m per minute. A 200mm blade is only 1885m per minute. You loose a 1000m per minute of cut. Also as the diameter is smaller there is more wood to cut through. Therefore you need to feed the blade much slower or risk stalling. HSE advice not to go below 60% of the design diameter personally I do not go below 80%
Also you want the bigger blade for a more vertical cut. You just raise the blade and lower the crown guard or if a modern SUVA the blade is perminantly covered anyway. You need to ensure the rip fence is set properly to reduce the risk of kick back
A 2.5hp saw might cut 100mm deep soft wood or easy hardwood but I would like to see it cut oak

315mm down to 245mm (the range for that saw) is about 77%, so not too bad.

100mm cut in "hard" hardwood is probably not that likely for me I guess, but having come from a decade of using bandsaws (before I used my first table saw) I really do like the finish that can be achieved straight off a TS (as well as the accuracy) - i.e. I'd prefer to do cuts with the TS if I can. The Axminster TS200 can begin to struggle a bit with 50mm deep rips in decent pine, so a saw that comfortably handled 75mm rips in pine would be nice.

 

[sploo]

Another issue with smaller blades is that the riving knife and guard need adjusting. I've ended with a bunch of 300mm and 315mm blades, and it's an added faff to reposition the riving knife every time I switch from one to the other.

Yea, that is a good point. Changing the riving knife in the TS200 is a PITA (I have a few 185, 190, and 205mm blades). The saw I'm looking at has a sliding table, so access should be a bit easier.

I guess the answer is: just suck it up and buy a few good quality 315mm blades :wink:

 

[MusicMan]

I manage very well with three blades: a Freud thin cut ripping; a combo general use; and an 80 tooth for fine cross-cutting and laminate work.

I have heard two schools of thought on the height/angle of the blade. At school, we were taught that the blade should only just protrude over the work, so that the teeth cut almost horizontally and gave a much better finish. More recently I have heard the argument that the more vertical the cut, the better, as it pulls the wood down onto the table, which as safer.

Could we have some views from experienced professionals, please?

Keith

 

[custard]

Could we have some views from experienced professionals, please?

You'll hear exactly the same debate in professional workshops! However, H&S are pretty clear, smaller blades lower peripheral speed which increases kick back risk, and the blade should be raised so that the entire tooth is exposed...but no more.

There's also debate about the benefit of pushing the workpiece down against the table, some sawyers prefer the sliding table to be about a quarter of a mill above the saw table with minimal downward pressure from the saw blade, so that sheet goods glide easier; others think the opposite. Personally I like my sliding table virtually flush with the saw table and the saw blade raised minimally. That doesn't make me right, but it's what I prefer, and in my workshop it's my rules!

 

[stuartpaul]

......
A 2.5hp saw might cut 100mm deep soft wood or easy hardwood but I would like to see it cut oak

This one https://www.axminster.co.uk/axminster-i ... h-ax649822 is about 2.9hp if my conversion is right (2.2kw) and it happily cuts 100mm oak.

I've never even thought of running a smaller blade and have to say that I don't find blades that expensive but sharpening isn't cheap (around here anyhow!). I'm soon to try sharpening myself which could prove to be interesting.

 

[deema]

Large professional saws have speed adjustment to allow the peripheral speed to be adjusted to the size of blade. I have the option to select for instance three speeds. HSE are also very clear, use the smallest blade possible within the limitations of the Saw and stuff being cut. All saws will specify the smallest blade that can be used. So, for example a 12” Saw will usually have a limit of a 10” blade if it’s fixed speed.

The smaller the diameter of the blade with it set at the right height for the stuff being cut the reduces the area of blade within the wood, reducing the risk of kick back not increasing it.

A smaller diameter blade, with the right number of teeth with always give a cleaner cut than a larger blade again with both set at the correct height, I.e. the gullet level with the top of the stuff being cut.

A good Saw will enable the riving knife to be easily and quickly adjusted in both height and horizontal distance from the blade.

 

[no idea]

A smaller blade will stop quicker if the motor is braked and will put less start up load on the motor than a larger motor. Neither are really a benefit if the saw is already compliant with stopping time requirements and it doesn't trip the breaker on start up with a larger blade.

 

[MusicMan]

Could we have some views from experienced professionals, please?

You'll hear exactly the same debate in professional workshops! However, H&S are pretty clear, smaller blades lower peripheral speed which increases kick back risk, and the blade should be raised so that the entire tooth is exposed...but no more.

There's also debate about the benefit of pushing the workpiece down against the table, some sawyers prefer the sliding table to be about a quarter of a mill above the saw table with minimal downward pressure from the saw blade, so that sheet goods glide easier; others think the opposite. Personally I like my sliding table virtually flush with the saw table and the saw blade raised minimally. That doesn't make me right, but it's what I prefer, and in my workshop it's my rules!

Thanks Custard, that is very helpful.
Keith

 

[sploo]

Well, sadly the deal fell through. It was an eBay auction (that for long-winded reasons I thought would go within my budget - it didn't). Shame really as the seller seemed like a good guy. Back to the drawing board (I can't stretch to a brand new Hammer K3! :| )

 

[OscarG]

...and the blade should be raised so that the entire tooth is exposed...but no more.

Cheers, I've often wondered how much of the blade should be exposed. I thought people only had a little bit of the blade peeping out for safety reasons but it actually cuts better that way?