Arbor Setscrews

[DLB]

In another thread, JPG said:
"I recently purchased a 'bag' of round point set screws.(ball shaped end) I consider them correct for non slanted arbors on the tapered flat. I consider the slanted arbors need a flat point set screw. Flat pointed set screws are easily made using the ss tool kit, miter gauge, and sanding disc."

I found that intriguing. The flat on the SS main (quill) spindle is tapered (about 3 degrees IIRC). Same for the upper aux spindle. The lower aux spindle does not appeared to be tapered, nor does the optional spindle adapter that goes into the tail stock. Some arbors have a matching offset ('slanted arbors') and others do not. Couplers do not. But all seem to come with flat setscrews.

So I understand the objection to the combo of flat setscrew, tapered flat, and non-slated arbors. But I'm not understanding the solution/recommendation. And part of me is not understanding why we have non-slanted arbors/couplers.

I'm relatively new to the PowerPro. I've never really had an issue with setscrews but I know several PowerPro users have, and I'm always conscious of the possibility.

- David

[JPG]

First, the quill shaft ... has always been both tapered and truncated before reaching the end of the shaft.

Early arbors etc. were NOT biased, but straight.

The biased arbors began(our discovery) with a certain chuck which had came with a redesigned ss adapter.(the redeisgn added the bias) Since then other arbors etc. have been observed to have that bias that matches the taper angle.

Now with a tapered flat AND a biased set screw thread, the flat pointed set screw contacts the shaft evenly across the flat point. With a tapered flat AND a straight(non biased) set screw thread a flat pointed set screw contacts the shaft flat at an angle that causes only one edge/side of the set screw point to contact the shaft flat. Wear reveals this uneven seating.

With a ball/round/oval point screw, the contact will be tangent to the setscrew 'point regardless of whether the set screw threads match the flat taper. However the contact area is less that that obtained with a flat point set screw 'attacking' from a right angle so biased/tapered/flat point is a better arrangement.

IMO the ball/oval/whatever is preferable to a flat point that contacts the shaft at only one edge.

Sorta nit picky - yes.

This is our conclusions - no one from SS has expressed anything different.

[jsburger]

First, the quill shaft ... has always been both tapered and truncated before reaching the end of the shaft.

Early arbors etc. were NOT biased, but straight.

The biased arbors began(our discovery) with a certain chuck which had came with a redesigned ss adapter.(the redeisgn added the bias) Since then other arbors etc. have been observed to have that bias that matches the taper angle.

Now with a tapered flat AND a biased set screw thread, the flat pointed set screw contacts the shaft evenly across the flat point. With a tapered flat AND a straight(non biased) set screw thread a flat pointed set screw contacts the shaft flat at an angle that causes only one edge/side of the set screw point to contact the shaft flat. Wear reveals this uneven seating.

With a ball/round/oval point screw, the contact will be tangent to the setscrew 'point regardless of whether the set screw threads match the flat taper. However the contact area is less that that obtained with a flat point set screw 'attacking' from a right angle so biased/tapered/flat point is a better arrangement.

IMO the ball/oval/whatever is preferable to a flat point that contacts the shaft at only one edge.

Sorta nit picky - yes.

This is our conclusions - no one from SS has expressed anything different.

That is why you see some shafts dimpled with a half moon.

[chapmanruss]

I remember we had the discussion before about the angled (off from 90 degrees) set screw holes in arbors. I wish I could remember which one had the angle and which ones didn't. I do remember checking each one of the different arbors, spindles, chucks, etc. I have but only posted those findings in that previous thread. A quick check just now of a few arbors shows that originally they were not angled to the reverse taper of the quill's spindle. I checked an early (1960's) 1-1/4" Saw Blade Arbor P/N 505511 and a later (Shopsmith Inc. but unknown year) one and neither have an angled set screw hole. Some Spindle Mount Accessories apparently never had angled set screws. I have an early machined aluminum 3" long Drum Sander (1947-48 vintage) and my newest, a 6" long Drum Sander and neither are angled. The 6" long Drum Sander uses the same ends as the 3" long one with an additional 3" spacer, longer bolt and second rubber sleeve. Both an old 3326 Jacobs Drill Chuck or one of my current style Drill Chucks have non angled set screws. That may explain the reason the Tailstock Chuck Arbor is flat not tapered for the set screw.

With what JPG said on spindle mount accessories, those with an angle to the spindle's reverse taper a set screw with a flat would be best. For those not angled maybe we should consider an oval set screw for best contact. In any case avoid cone shaped set screws since they will do the most damage to the spindle. They are best used for parts not regularly coming apart like holding way tubes to the base/arm and tie bar castings. As always check to make sure the set screw is centered on the flat.