Table Saw Refurbish, Arbor Size Reduction

[Steve Neumann]

Hi Folks. Good Day to anyone reading this. I am updating an older saw. It is a Boice-Crane Model. The numbers 400 are on the bottom of the cast top along with the brand name. I have removed the arbor with the intent of replacing the bearings (which I have already purchased) and to update the saw to be a more usable form for me I am going to have the 3/4" arbor turned down to 5/8". I have secured a machinist to do the turning for a minimal cost. Now, here is my dilemma. As I am not a machinist I don't understand the variations in thread styles and pitches.
The thread that was used on this arbor originaly looks to be of a standard inch style thread. I have read plenty that says an ACME style thread is common for table saws. In a post that I cannot find back, one of Sawmill Creeks moderators suggested not to use a standard thread nut on said arbor. Why not use standard thread, and am I better off with a fine or coarse thread of whatever thread used. Last portion of query. are there many places that are able to apply this ACME type thread to an arbor or is it something from the past?
I live in Buffalo, Minnesota, USA
This project is dragging on too long but I don't want to make a hard to live with mistake.
Thanks much for your consideration of this query.
Steve

[Dick Brown]

Steve,
I had the arbor on my Clausing turned from 3/4 to 5/8 also. Went to a local supplier and bought a 5/8 Acme nut, took it to my local machine shop, $20 later was headed home with a usable, standard size for a 10" saw arbor. Fortunately, my saw is left tilt so arbor threads are right hand. If your saw is right tilt, you need left hand thread or your blade will more than likely loosen up or even the nut come off and you could have a many toothed projectile loose in your shop.

[Bruce Page]

Steve, the ACME thread profile is more durable and more accurate than a common 29° thread. The ACME thread major diameter (largest diameter) is tightly controlled and has a flat crown (see pic) as opposed to the common sharp ΛΛΛΛ thread. The flat crown is required for location concentricity between the bore of the table saw blade and the arbor. Imagine mounting a dado stack without an accurate diameter to locate it.
As Dick pointed out, your Boice-Crane likely has a left handed thread. Your machinist should be able to verify right hand or left hand. It is critical that the arbor modification is machined with the same handed thread.
If your machinist balks at the ACME thread or chasing a left handed thread, you should find another machinist.

[Tony Pisano]

Acme threads are usually beefier than standard threads and better for dirty dusty conditions and have a faster pitch. (think c-clamps, bench vises, lead screws on lathes) you should find them at McMaster Carr or MSC Industrial supply

[David Kumm]

A left hand acme thread and nut will be quite a bit more expensive to machine than a standard and with a 5/8" arbor I'm not sure you get that much bang for the buck. Fine threads are stronger than coarse but you have to be more careful. The arbor transition from 3/4 to 5/8 might be the weak point rather than the threads but way above my pay grade to know. A stepped inner flange ( part bored to 5/8 and part to 3/4 ) would help that. A good machinist will know. Dave

[Bob Vaughan]

I recommend you consider the 5/8-12 LH square thread as used on the Delta Unisaw. The outstanding feature of this is that the tops of the threads are close together and flat. Washers and shims don't slide down in like they do with some acme threads and its even worse on standard V-threads. The Unisaw arbor takes dado sets and cutters far easier. I really prefer that thread. Also, the rather expensive nut is somewhat thin so a dado set can be a little bigger rather than trying to fight some huge glob of steel that comes in the form of a off-the-shelf acme nut. I've got acme threads on my current table saw, but one of these days, I'm going to make an arbor that has those wonderfully designed Unisaw type threads.

Unisaw - 1.jpg

[Chris Fournier]

I'm with Bob on this one and I do all of my own machining. Acme is great for withstanding clamping forces but yo don't need this in this application and the Acme will actually be a pain to use with dados and shims.

[Myk Rian]

None of these suggestions are going to do any good until OP tells us if it's left or right tilt.

[Bruce Page]

I'm with Bob on this one and I do all of my own machining. Acme is great for withstanding clamping forces but yo don't need this in this application and the Acme will actually be a pain to use with dados and shims.

Both an ACME or square thread will do the job, the main point I was trying to make above was not to use a V thread. My reading of the OP's post was that he didn't see the need and wanted to use a standard 29* thread - which he will regret later.

[Lee Schierer]

A left hand acme thread and nut will be quite a bit more expensive to machine than a standard and with a 5/8" arbor I'm not sure you get that much bang for the buck.

A 5/8-6 or 5/8 - 8 left hand acme nut is $3.05 from McMaster Carr.

[David Kumm]

Lee, you are correct. It was the acme die I was remembering. I'm not good enough to cut acme threads and my machinist figured the die was worth it. Mine was bigger though. Dave

[Frank Pratt]

I never had a clue that this was even a thing. I knew about v-threads & Acme threads, but not those. My saw has Acme & the dado shims do get caught in them if I'm not careful. Thanks for sharing this.

I recommend you consider the 5/8-12 LH square thread as used on the Delta Unisaw. The outstanding feature of this is that the tops of the threads are close together and flat. Washers and shims don't slide down in like they do with some acme threads and its even worse on standard V-threads. The Unisaw arbor takes dado sets and cutters far easier. I really prefer that thread. Also, the rather expensive nut is somewhat thin so a dado set can be a little bigger rather than trying to fight some huge glob of steel that comes in the form of a off-the-shelf acme nut. I've got acme threads on my current table saw, but one of these days, I'm going to make an arbor that has those wonderfully designed Unisaw type threads.

Unisaw - 1.jpg

[Ruperto Mendiones]

Possibly not practical...but...instead of modifying the arbor, get the blades custom bored to the arbor diameter.

[David Kumm]

Not a big deal to have blades rebored. I have 5/8, .73. 1", 30mm, 1 1/8 and 11/4" so having a guy to bore is necessary. A good blade that can be resharpened a half dozen times lasts me a lifetime and two or three blades per saw is all that are needed. Dave

[Steve Neumann]

Hi Folks. Just replied to all your wonderful posts but wasn't signed in, lost that letter. spent 3 hours on the phone trying to find a nut for the saw. Lost too much time today, must go to work. I'll update later if I remember to sign in.
Steve Neumann.
P.. What's OP? Thanks