saw shaft for dado blade

[terry fitzpatrick]

 I have a sears craftsman cabinet saw read in woodworkin mag some time back that you could get a longer shaft to use dado blades with.Having a hard time finding one.Any Ideas?I contacted sears and they said duh .

[John Schaben]

You don't even need two threads exposed. Once all the threads on the nut are fully engaged, anything sticking out beyond the nut isn't doing anything anyway.

I would like to hear back from the OP.. I think the saw referenced would take at least a 3/4 stack if not more. Hmm, suppose he read the manual???

 

[Rick]

My dado is an adjustable type, not a stackable, which makes the problem worse I think.

Who reads manuals?  I can't read Spanish.  I took Latin in school.

[John Schaben]

Hi Rick - A couple of different types of adjustable dado's. Some don't change the amount of arbor required. Biggest thing about the adjustable is they don't leave all that flat a bottom. The blade(s) essentiall wobble around in a fixed area. I, personally don't think a glass flat bottom dado is all that important unless you are making a sliding dado for some reason. A little texture leaves some tooth for the glue. If I want a dead flat dado I'll go with the router.

Rick said:

My dado is an adjustable type, not a stackable, which makes the problem worse I think.

Who reads manuals?  I can't read Spanish.  I took Latin in school.

[Hugh Clare]

I think the idea of exposed threads comes from self-locking nuts (the kind with nylon inserts). The first couple of threads on the typical bolt are slightly smaller in diameter. The exposed threads insure that all of the threads in the nylon insert are full diameter. It's actually an inspection item on aircraft. :) I agree that any threads not actively involved in "gripping" are wasted.

[Rick]

You familiar with aircraft fasteners?  Perhaps I should wire my arbor nut on!  LOL

.

But ... any reminders about safety are appreciated.  Thanks

Hugh Clare said:

I think the idea of exposed threads comes from self-locking nuts (the kind with nylon inserts). The first couple of threads on the typical bolt are slightly smaller in diameter. The exposed threads insure that all of the threads in the nylon insert are full diameter. It's actually an inspection item on aircraft. :) I agree that any threads not actively involved in "gripping" are wasted.

[Rick]

John, you are right about the sloppy bottoms from my Craftsman adjustable dado.  I bought it almost 20 years ago, and haven't used it until the other day building a bunch of large drawer boxes.  It really was designed for those saws with a longer arbor.  I cut a dado for the bottoms and a shallow rabbet for the sides.

John Schaben said:

Hi Rick - A couple of different types of adjustable dado's. Some don't change the amount of arbor required. Biggest thing about the adjustable is they don't leave all that flat a bottom. The blade(s) essentialy wobble around in a fixed area. I, personally don't think a glass flat bottom dado is all that important unless you are making a sliding dado for some reason. A little texture leaves some tooth for the glue. If I want a dead flat dado I'll go with the router.

[Jay Boutwell]

A few years ago I went to using a dado that is adjustable and the reason I did this was due to the under sized plywood that are common today.  This allowed me the  ability to adjust the cut to fit the plywood.  I have set aside the other dado blades that I owned for this reason.  It may not leave a totally flat bottom but a couple strokes with a sharp chisel fines that problem.

I am in agreement with the others about the exposed threads.  If you have one or two threads exposed you are save using the dado on the arbor providing that it does not over power the saw.  In purchasing a saw it is good practice to make sure it is powerful enough to run dado blades and other attachment other that a saw blade.

I would not settle for one that does not have at least a 1 &  3/8 inch long arbor.  Any add on shaft extensions is asking for danger.

 

 

[Ken Darga]

re ''Effective Thread Engagement''---

Threads in the nut and screw/bolt are not complete to the end.

  There are ''chamfers'', (bevels on the edges/ends), that will not result in intimate contact with adjoining threaded mating surfaces.

  If a nut is only engaged so that it is flush with the screw end, there will be a couple of threads that are not fully engaged.

  Threads that are not ''effectively engaged'', do not have adequate holding power for its size and thread pitch.

Hence, a ''rule of thumb''---a minimum of two threads exposed beyond the nut face, to ensure effective thread engagement.

Some better made saws, feature ''acme'' or ''square'' threads, for better holding power and increased torque.

[terry fitzpatrick]

 Wow this is incredible cant believe all the good feedback i recieved.Thank you all.Since that worked out so well got another one.I have a grizzley 6 inch jointer ihave checked it several times for flatness blade height and the whole 9 yards but apparentley im doing something wrong my boards come out bowed when i try to glue them up.I know other people with the same problem.I hate to see them just gathering dust.

[Hugh Clare]

I agree the rule of thumb is a good one. In my case, I would have to choose between two threads with no washer and flush with washer. As my arbor shaft has acme threads, I don't believe the two-thread rule is of any benefit, at least not enough to justify leaving the washer out. I don't remember ever seeing a table saw arbor that didn't have acme threads. I certainly would not consider any kind of extension on the arbor shaft. My gut tells me that's a recipe for disaster.

Ken Darga said:

re ''Effective Thread Engagement''---

Threads in the nut and screw/bolt are not complete to the end.

  There are ''chamfers'', (bevels on the edges/ends), that will not result in intimate contact with adjoining threaded mating surfaces.

  If a nut is only engaged so that it is flush with the screw end, there will be a couple of threads that are not fully engaged.

  Threads that are not ''effectively engaged'', do not have adequate holding power for its size and thread pitch.

Hence, a ''rule of thumb''---a minimum of two threads exposed beyond the nut face, to ensure effective thread engagement.

Some better made saws, feature ''acme'' or ''square'' threads, for better holding power and increased torque.

[Ken Darga]

ps---''acme'' threads have greater holding power over ''square'' threads.

Ken Darga said:

re ''Effective Thread Engagement''---

Threads in the nut and screw/bolt are not complete to the end.

  There are ''chamfers'', (bevels on the edges/ends), that will not result in intimate contact with adjoining threaded mating surfaces.

  If a nut is only engaged so that it is flush with the screw end, there will be a couple of threads that are not fully engaged.

  Threads that are not ''effectively engaged'', do not have adequate holding power for its size and thread pitch.

Hence, a ''rule of thumb''---a minimum of two threads exposed beyond the nut face, to ensure effective thread engagement.

Some better made saws, feature ''acme'' or ''square'' threads, for better holding power and increased torque.

[Ken Darga]

ps---Saw arbors, that have short shafts, Are Not for use with Dado Blades---are not designed to accept wide Dado Blades.  

Ken Darga said:

re ''Effective Thread Engagement''---

Threads in the nut and screw/bolt are not complete to the end.

  There are ''chamfers'', (bevels on the edges/ends), that will not result in intimate contact with adjoining threaded mating surfaces.

  If a nut is only engaged so that it is flush with the screw end, there will be a couple of threads that are not fully engaged.

  Threads that are not ''effectively engaged'', do not have adequate holding power for its size and thread pitch.

Hence, a ''rule of thumb''---a minimum of two threads exposed beyond the nut face, to ensure effective thread engagement.

Some better made saws, feature ''acme'' or ''square'' threads, for better holding power and increased torque.