Thread: Slitting saw keys

All my milling slitting saws are keyed.

All my arbors for securing the slitting saws have either a hex ,flats or square machined on to the arbor to aid in the tightening of the nut.(Vertical or Horizontal)

I have never had any cutters cause damage to my key/s.

The only time I have ever seen damage to a key is if the saw is not secured correctly (loose) or if there has been a major jam up.

The fact that the arbor is bent should really have no part in the problem.

Is there any reason why you haven't made a replacement for the bent arbor.

How are you holding the arbor when securing the saw.

I've had that problem - I solved it by not using keys on thin slitting saws and just relying on friction to clamp the blade. The previous mill didn't have a keyway so that was the standard method.
With regards to the bent arbor, it depends on how much bend you have. I would think (broad generalisation coming up) that almost all arbors have some sort of bend in them - it just depends on whether it is measured in microns or mm. Personally I can live with 0.1 of bend, especially if the alternative is turning a metre of diameter 75 stock down to make another. If you did the maths you'd probably find that the ripple you'd get on the bottom of a cut with a small bend would be negligible.

Michael

Additional thought: Having now looked at what you were doing it looked like about 1/5th of the saw would have been in contact with the job. That would go a way towards evening out the chip loading on the blade.

Thanks Peter and Michael,

Peter, No jams or anything, this is the first time i have used the arbor so i didn't know it was *bent* (more in a bit) It is a NT40 500mm long horizontal arbor so not something that can just be replaced easily. I have tightened the nut with the spindle brake on and in the gear i'm using (about 50rpm) so i have gotten it plenty tight.

Michael, i'll try without the key.

It turns out the arbor is not actually bent. There must have been a tiny chip or something in between 2 of the washers/collars(?) which bent the arbor when i tightened the whole lot up. Its cutting true now.

The arbor its self is not a very hard item to make at all if you use a nt40 side lock arbor,only requires a thread for the arbor nut,a key way for cutters and 2 flats for the locking screws.

Material would be centreless ground 4140 of the correct OD.

Originally Posted by Ueee

Michael, i'll try without the key.

It turns out the arbor is not actually bent. There must have been a tiny chip or something in between 2 of the washers/collars(?) which bent the arbor when i tightened the whole lot up. Its cutting true now.

Hi Ewan, Here is a link from Ramsays Yahoo Groups site for K&T Milwaukee. It is for K&T arbors, and the first pages have a list of tips for taking good care of them. Although I have seen recommendations not to use a key for saws, just to clamp them between the spacers, it is not what K&T said. They do repeatedly say though in their operating manuals and also in this list of correct procedures in using arbors, that they need to be scrupulously clean, and free from burrs and nicks. They also say to hand tighten until all the arbor supports are clamped in place, and only then to use a spanner to tighten the end nut, so as not to spring the arbor.
Great work on your beautiful mill, you have a real gem there.
Regards,
Rob

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Thanks Peter and Rob,
I had not thought of making an arbor like that Peter, my biggest problem is getting suitable steel, i cannot get it locally, i guess Bohler would have it?