Press fitting a Ball plunger
Press fitting a Ball plunger
(OP)
Hello,
I'm calculating the hole dimensions to press fit a 0.38" OD x 0.865" SST Ball Spring Plunger (http://www.mcmaster.com/#standard-spring-plungers/...) Part number 8262A17.
If I go with FN2 fit, i get the Hole Dia to be 0.38060 Max and 0.3800 Mins as per the calculator at Link
Is 0.38060 be machined and inspected? Isn't 6/10000" too small of a interference?
Please excuse my inexperience.
Thank you all
I'm calculating the hole dimensions to press fit a 0.38" OD x 0.865" SST Ball Spring Plunger (http://www.mcmaster.com/#standard-spring-plungers/...) Part number 8262A17.
If I go with FN2 fit, i get the Hole Dia to be 0.38060 Max and 0.3800 Mins as per the calculator at Link
Is 0.38060 be machined and inspected? Isn't 6/10000" too small of a interference?
Please excuse my inexperience.
Thank you all





RE: Press fitting a Ball plunger
Frankly who knows how good their 0.38 dimension is. Maybe it's really 0.375. They don't give you any tolerance. Get one in your hands and mic it, but the purpose of the knurl is to make it less sensitive to needing the perfect interference fit. It'll kinda broach itself into things.
Just by feel I'd throw 3-7 tenths interference in steel and 5-10 in aluminum. You never say what material you're smashing these things into.
RE: Press fitting a Ball plunger
Your .38" diameter is knurled. Interference fit calculations require an accurate, documented tolerance. You have neither. If they do not have a recommended hole diameter for this thing, I recommend you find another vendor and catalogue.
--
JHG
RE: Press fitting a Ball plunger
They have always been very helpful and forthcoming with just exactly that type of info for me in the past.
RE: Press fitting a Ball plunger
drawoh, I wish I could switch suppliers but unfortunately that's not an option
Tmoose, great idea. I'll send them a request for more detailed info.
RE: Press fitting a Ball plunger
RE: Press fitting a Ball plunger
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Press fitting a Ball plunger
I'd double check with the manufacturer.
RE: Press fitting a Ball plunger
NOT 17-4PH.
The axial knurl will probably peel right off.
You need a different part.
The ball plungers normally used in hard material have threaded ODs and a wrenching slot, which allows them to be threaded into a blind hole, with the possibility of deforming the gozinta with a prick punch for retention, or buying the plunger with a plastic locking pellet in the thread.
I know, the design is already cast in concrete.
It's going to be a problem.
Send up a flare now, or prepare to be stuck answering the phone for the product's service life, or until the sh!tstorm comes.
Mike Halloran
Pembroke Pines, FL, USA
RE: Press fitting a Ball plunger
So, I got back in touch with McMaster telling them that hole tol of +/- 0.01" is not right and they responded that they actual hole dimension is 0.375" +0.002"/-0.
This is the REAL dimension for the hole I believe. Please let me know your thoughts on it.
And thank you for all your valuable feedback and suggestions.
RE: Press fitting a Ball plunger
Mike Halloran
Pembroke Pines, FL, USA
RE: Press fitting a Ball plunger
RE: Press fitting a Ball plunger
The knurl will be shaved off, and is not likely to retain the part,
AS IS CLEARLY STATED IN MACARCO'S CATALOG PAGE LISTING THE IDEAL SUBSTRATES.
If failure of the ball plunger or its assembly puts you in court, YOU WILL LOSE, since you or your company seem determined to use the part in an unapproved and unintended way.
If there's no possible way for this design undecision to land you in court, well, you haven't thought about it enough.
Mike Halloran
Pembroke Pines, FL, USA
RE: Press fitting a Ball plunger
RE: Press fitting a Ball plunger
I've used both items, threaded and pressed, but never would dream of using that pressed plunger in metals. Threaded are a pretty good no-brainer piece of hardware, and can be quite adequately locked in place with appropriate goop or by just getting the nylon stud type.
_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5
RE: Press fitting a Ball plunger
One issue with using these ball spring plungers for detent mechanisms is ensuring a consistent force at each installation. This is one reason why adjustable threaded bodies are often used. The self-locking types seem to perform quite well.
RE: Press fitting a Ball plunger