Mandrel Center Hole Size

[TriHonu]

I purchased a set of expanding mandrels (0.5 - 1.0 inch). The center holes are only 1/8in in diameter.



Riten has a document on their site titled Center Hole Specifications. ( https://www.riten.com/wp-content/upl...nter-specs.pdf )
According to that document these mandrels are limited to parts weighing less that 1 lb.

They are listed as Lathe Mandrels, are they actually grinding mandrels?

I am concerned that they would only be suitable for holding bushings.

[wierdscience]

Grinding and light lathe work, turning down bushings and that sort of thing, the same as solid lathe mandrels.

[TriHonu]

I can see the reason for the hole size on the small end of the 1/2" mandrel, but the entire set has 1/8" center holes.

[JRouche]

Bushings for sure. Just dont ask more from the tool than it is built for. Look like a nice set. JR

[J Tiers]

If you do a little math, you will rapidly determine that ther is no consistency to the numbers. Slightly larger actual areas are allowed considerably larger pressures, NOT in proportion.

Between 1 lb and 500 lb allowable, there is a 500:1 difference. The area difference is 19:1. The "stress on E" is 26:1. The shear stress is 32:1 Not a linear relation at all.

If you use a solid center, use their numbers. If you use a rotating center, you can easily move up an entry, to 10 lb. I have a similar set, and have had no issues at the higher numbers. I use a rotating (ball bearing) center.

[JRouche]

If you do a little math, you will rapidly determine that ther is no consistency to the numbers. Slightly larger actual areas are allowed considerably larger pressures, NOT in proportion.

Between 1 lb and 500 lb allowable, there is a 500:1 difference. The area difference is 19:1. The "stress on E" is 26:1. The shear stress is 32:1 Not a linear relation at all.

If you use a solid center, use their numbers. If you use a rotating center, you can easily move up an entry, to 10 lb. I have a similar set, and have had no issues at the higher numbers. I use a rotating (ball bearing) center.

Now how come phukin drunk Poulice dont come after you? Hahaaa

Haa, kidding. I like!!! JR

[TriHonu]

If you use a solid center, use their numbers. If you use a rotating center, you can easily move up an entry, to 10 lb. I have a similar set, and have had no issues at the higher numbers. I use a rotating (ball bearing) center.

Thanks for that information. I have a couple of rotating centers and will make sure to use them on larger parts. I considered opening up the center holes and decided it would be difficult keep them as concentric as they are now without regrinding the shaft.