how are ball detents seated? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: January 21, 2025, 06:07:40 am
content: How do they seat a detent ball on something like a screw driver bit?It looks solid.Do they just deform it using a press? I mean to prevent the ball from falling out.

author: ataradov
author_rank: Super Contributor
timestamp: January 21, 2025, 07:13:07 am
content: Just deformation. On bigger sizes you can often see a stamped ring around the ball. That's a leftover from the deformation punch.

author: coppercone2
author_rank: Super Contributor
timestamp: January 21, 2025, 07:19:51 am
content: is there a special insert for this purpose?

author: Psi
author_rank: Super Contributor
timestamp: January 21, 2025, 07:32:33 am
content: Maybe the ball is not a sphere to start with but after it's pushed in they push further to crush it into a sphere.I doubt heating/cooling is involved, as that would add quite a bit of cost and reduce speed

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 21, 2025, 07:41:32 am
content: Quote from: coppercone2 on January 21, 2025, 07:19:51 amYep, made in the toolshop of the factory making the parts that have the ball detent.It wouldn't be much more than a tubular shape made of tool steel of appropriate dimensions in a press.

author: thm_w
author_rank: Super Contributor
timestamp: January 21, 2025, 09:57:36 pm
content: https://www.reddit.com/r/whatisthisthing/comments/g9eavl/what_is_the_ball_thingy_called_in_these/You can see here they pressed off to the side.Quote from: Psi on January 21, 2025, 07:32:33 amIts probably hardened ball bearing so won't deform.

author: Psi
author_rank: Super Contributor
timestamp: January 21, 2025, 10:29:58 pm
content: ah, of course, they press the outer ring around the hole to reduce the hole size after installing the ball.Yeah, that makes the most sense.Quote from: thm_w on January 21, 2025, 09:57:36 pmDoesn't need to be hardened steel for the application, but yeah you're probably right since small ball bearings are already mass produced.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 22, 2025, 02:15:53 am
content: I believe the correct term for how the metal is deformed at the top of the hole drilled to capture the detent ball is "upset".

author: coppercone2
author_rank: Super Contributor
timestamp: January 22, 2025, 03:59:41 am
content: I thought a way to do it DIY would be to use a tiny chisel to make a crown around the ball, similar to holding diamonds in rings

author: ataradov
author_rank: Super Contributor
timestamp: January 22, 2025, 04:06:49 am
content: For DIY just a couple dimples with a center punch would be enough. The fit of the ball and the hole is really tight. Even minor upset is enough.

author: coppercone2
author_rank: Super Contributor
timestamp: January 22, 2025, 04:38:44 am
content: How much clearance do you need for it to be reliable from getting jammed up ?The thing that concerns me is that if you make it a shoddy seal, diy, it might tend to let stuff in.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 22, 2025, 04:55:14 am
content: Most smaller and less expensive equipment has the ball detent held through an upset. You do find other techniques on larger and more expensive gear.Stuff does get into these, regardless of the fit. Keeping tools in shape, or restoring old tools you have found often involves cleaning, a non-trivial task.It is surprising how complex the design is. I am sure most people have had tools where the detent spring was too strong and it was virtually impossible to remove the tool. There is a trade between the spring rate of the spring and the tolerancing of ball size and the upset parameters. These in turn affect how sensitive the detent action is to the tolerances on the mating tool. It would be ideal if none of the operating loads of the tool were transferred to the ball. But I have had several occasions where this is not true and the detent mechanism is damaged. Fault could lie on either side of the interface.

author: ataradov
author_rank: Super Contributor
timestamp: January 22, 2025, 05:01:55 am
content: I don't know the exact numbers, but it should not jam with reasonable clearances. You don't need extremely precision fit, those things are mass produced really cheap. You want it to be close so that it does not let the stuff in and so that you don't have to displace a lot of material.But the displacement itself is not going to affect the seal, since it is not engaged when the tool is in use, so you have to rely on the ball fit.Here is a video that shows repair using a punchat around 3:30 mark you can see the result. It is pretty poorly done, but I can't find a better video. He made 5 marks and he really did not need 2 of them and the rest did not need to be so deep.Also, for bigger stuff they sell pre-made assemblies that just screw in with the ball already in place. All you need is a tapped hole.