Startrite 275 table saw riving knife dimensions

[Pooky]

I have just bought a Startrite 275 table saw which I am very pleased with but it has no riving knife. I have the manual but it has no dimensions.

I am thinking of making my own. Does anyone have the dimensions for it that I could use please?

Thank you.

 

[LJM]

You can derive your own pattern, based on the position of the mount (for the knife) relative to the blade and the appropriate gap (if I recall Startrite say max 12mm; don’t know if that’s standard or correct, but the manual will guide you).

you also need to factor in the required position of your crown guard.

 

[LJM]

I’ll likely make a pattern for mine in due course, and get one laser cut, as I’ve done in the past for other saws; I’ll share the drawing when I get that done

 

[Pooky]

Great. Thank you.

 

[eribaMotters]

Pattern covered as above. but what about the thickness? Aim for something just over plate thickness of the blade but no greater than the kerf or cut it makes.

Colin

 

[LJM]

The pattern isn’t all that well covered by the manual; it only gives an oblique view, not to scale, if memory serves; You can derive the dimensions by making a pattern and using the dimensions that you do know, ie a radius that will clear your saw blade (up to 305mm+ clearance). I don’t have it to hand, but it gave the riving knife thickness in the manual for my Startrite saw. But it needs to be between the blade thickness and the kerf.

 

[NetBlindPaul]

HSE offer some guidance for the correct use of riving knives in the link.
I have based the design of replacement knives for customers on that when they have not been available.
Use saw blade steel or “gauge” plate though.

https://www.hse.gov.uk/pubns/wis16.pdf

 

[sploo]

I have that saw. When I can next get into the garage I'll see if I can get you some numbers.

For the thickness however - my original riving knife is "wrong"; in the sense that I suspect it's sized for older HSS blades rather than modern carbide tipped blades. As such it's too thin and I really should make a new one.

The thickness of a riving knife needs to be thicker than the thickness of the saw plate, but thinner than the saw kerf (the width of the slot cut by the teeth). This is to ensure that if timber tries to "clamp" onto the blade due to stresses in the wood the riving knife will still allow the blade to cut, but it won't allow the timber to grab onto the saw plate (which is usually a first class ticket to having your stock delivered straight to your gentleman's area).

 

[eribaMotters]

Pooky,
you might find the picture below of use. It is of the riving knife on my Startrite TA175 that was I believe the original fitted to the TA275 I used at work. The two saws share the same components. My saw runs blades up to 305mm.
The large grids are 50mm so if you scale it you should have a perfect fit. I would make one in thin mdf first to put your mind at ease.
The plate is 2.1mm thick. 2.5mm would probably be better. I run thin kerf blades to reduce the load on the motor, as my saw started life as a 175 the motor is smaller than that on the 275.

Colin

 

[sploo]

Colin's done exactly what I was going to do (overlay the knife on a grid); so no need for me to pull the one from my saw now

 

[sploo]

as my saw started life as a 175 the motor is smaller than that on the 275.

FYI I once asked a former Startrite guy what the differences were between the 175 and 275 (because other than the supplied blade and range of motor HP options I couldn't see anything from the components list) - the answer is: there isn't any. It makes some sense, as the riving knife can be moved back and forth to be in the right place for different sized blades.

Point being: you can install a 3hp motor on a 175 and run 12" blades with no issues at all.

 

[eribaMotters]

I have found with the existing 1.5hp single phase motor I can happily rip 3" hardwoods with a a 12" 24T fine kerf blade.
Occasionally the saw will trip, but is usually cool and runs again fine after a few minutes. It's given me 20+ years of service like this.

Colin

Just had another thought. Swap the belts over to the toothed type and tension correctly by moving the motor on its mounts and you will also benefit from a sub 10 second stop of the blade.

 

[Pooky]

Excellent Colin, that’s just what I needed.

Thank you for all the other info...

 

[JimmyStartrite]

I work for whats left of Startrite, I was a service engineer and now sell the spares for the legacy machines

the difference between a 175 and a 275 is motor power, the 275 having a higher spec motor and the ability to have a bigger blade without overloading

belt profiles have little impact on transmission, never over tension a belt, it should have around 1/2" of play, over tensioning can cause a myriad of problems

we manufacture and stock most the internal assembly for TA175/275 and everything else Startrite produced from the original drawings and using the original tooling, our riving knives are laser cut and far superior to the original and sometimes now illegal and dangerous original open end types that are still out there


head over to Machine Spares Ltd

Wont let me post a link for some reason!