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Boucher
04-17-2011, 12:49 PM
I totally screwed up the question in the other thread so I will start over. The retaining nut on my slitting saw arbor has left hand threads. The saw can be turned over to reverse the cutting direction. My understanding was that the preferred direction of cut was in the conventional direction. This means that the rotation changes with the side and direction of feed. The key keeps the saw and spacers from turning. So why did they go to the trouble to use the left hand threads?
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MichaelP
04-17-2011, 07:24 PM
I bet your arbor was made in Australia. :) Mine have right hand retention screws. And this is one of the two reasons for the chinese screw heads to break off on the first cut.

becksmachine
04-17-2011, 10:21 PM
Ok, the question makes sense now. ;)

There probably are specific situations when one way would work better than the other, but 99% of the time it makes no difference as long as you know which way to turn it to loosen it.

I think that many engineers have a large dart board on their office door to make decisions like this; right hand, left hand.

Machinists on the other hand must content themselves with a small dartboard that will fit in their tool box, to make decisions that are not covered on the print, or verbal description, or whether to follow either.

:D

Dave

JoeLee
04-18-2011, 07:36 AM
I don't understand it either......... at one time Bridgeport offered R8 stub arbors sizes 1/2" through 1 1/4" they came in either RH or LH thread. I have the old catalog to prove it. If your using the key to hold the cutter direction doesn't matter.

JL.....................

philbur
04-18-2011, 10:00 AM
Not all slitting saws have key slots.

Phil:)

MichaelP
04-18-2011, 10:53 AM
For the cases when there is a key, thread type shouldn't make a significant difference (esp., if we ignore the fact that there is always a play in the key/slot).

Many people prefer to remove the key or use an unkeyed arbor to protect the saw against fracture on binding, however. When there's no key, the retaining screw should have a right hand screw. At least, in the most common designs of the arbor. Otherwise, as soon as the saw meets a resistance, the screw will tend to unscrew. At the same time, if, for some reason, we want to run our mill in reverse while cutting (and flip the blade so it'll cut), a left hand thread will be needed.

And this is why Boucher started this thread, I assume.

Circlip
04-18-2011, 01:13 PM
Must have been made in the Southern hemisphere, it's to offset the Coriolis effect.

Regards Ian.

ftl
04-18-2011, 01:43 PM
I agree that LH vs RH often does not make any difference.

Many, many moons ago some cars came with LH wheel nuts on one side and RH on the other (I don't remember what side was what). The theory was that they were less likely to loosen with the forward rotation of the tires. That feature has clearly been dropped on passenger cars. Maybe it is still used on large trucks or some other sort of rotating application - I'd be interested to know.

JoeLee
04-18-2011, 02:04 PM
I agree that LH vs RH often does not make any difference.

Many, many moons ago some cars came with LH wheel nuts on one side and RH on the other (I don't remember what side was what). The theory was that they were less likely to loosen with the forward rotation of the tires. That feature has clearly been dropped on passenger cars. Maybe it is still used on large trucks or some other sort of rotating application - I'd be interested to know.

Chrysler had that...............

JL.................