.0035 press fit for a 3/16 dowel?

RJT · Sep 1, 2015

Brilliant engineer has designed a part 3/4 thick hard A-2 58-60 R/C that a 3/16 dowel has to be pressed through and stick out 1/4 inch. Hole dimension is .1840 - .1842". Even freezing one and heating the other, I don't see this happening. Maybe in aluminum or soft steel. Just shake my hear and politely tell them (my customer) what the hole size should really be. :wall:

Milland · Sep 1, 2015

Allow ~.0005 for interference, that should be more than enough.

grbl · Sep 1, 2015

When I see a problem on a customer's print, I just suggest changes. Does everyone immediately assume the engineer is an idiot, not that they've found a mistake? They say to never attribute to malice what is adequately explained by stupidity, but I say never attribute to stupidity what is adequately explained by laziness.

Cole2534 · Sep 1, 2015

grbl said:
When I see a problem on a customer's print, I just suggest changes. Does everyone immediately assume the engineer is an idiot, not that they've found a mistake? They say to never attribute to malice what is adequately explained by stupidity, but I say never attribute to stupidity what is adequately explained by laziness.

Yes. It makes for better internet bitching.

Milland · Sep 1, 2015

grbl said:
When I see a problem on a customer's print, I just suggest changes. Does everyone immediately assume the engineer is an idiot, not that they've found a mistake? They say to never attribute to malice what is adequately explained by stupidity, but I say never attribute to stupidity what is adequately explained by laziness.

If the engineer is that "lazy", I'd suggest he find an occupation that is more amenable to lack of effort...

Zahnrad Kopf · Sep 1, 2015

RJT said:
Brilliant engineer has designed a part 3/4 thick hard A-2 58-60 R/C that a 3/16 dowel has to be pressed through and stick out 1/4 inch. Hole dimension is .1840 - .1842". Even freezing one and heating the other, I don't see this happening. Maybe in aluminum or soft steel. Just shake my hear and politely tell them (my customer) what the hole size should really be.

That would be fun to watch though. :popcorn:

D Dubeau · Sep 1, 2015

About the only thing I know that loosens up fit's that tight is Gin.

Philabuster · Sep 1, 2015

Zahnrad Kopf said:
That would be fun to watch though.

Just need a bigger hammer.

paracongo308 · Sep 1, 2015

We used .002 interference fit on 6" inch pilot pins in very large stamping dies. Never heard of one coming loose even after hundreds of thousands of hits. Hope he stays away from designing large tooling.

Milland · Sep 1, 2015

paracongo308 said:
We used .002 interference fit on 6" inch pilot pins in very large stamping dies. Never heard of one coming loose even after hundreds of thousands of hits. Hope he stays away from designing large tooling.

What, 1/32" interference is too much? Just throw the pin in the freezer, it'll fall right in...

sable · Sep 1, 2015

I can beat that one ,I had a 10mm pin with an interference of 0.5mm ,luckily I couldn't meet the timescale constraints on that project.

specfab · Sep 1, 2015

sable said:
I can beat that one ,I had a 10mm pin with an interference of 0.5mm ,luckily I couldn't meet the timescale constraints on that project.

I can see your problem. 6 month leadtime on the press for the pin installation...

HuFlungDung · Sep 1, 2015

RJT said:
Brilliant engineer has designed a part 3/4 thick hard A-2 58-60 R/C that a 3/16 dowel has to be pressed through and stick out 1/4 inch. Hole dimension is .1840 - .1842". Even freezing one and heating the other, I don't see this happening. Maybe in aluminum or soft steel. Just shake my hear and politely tell them (my customer) what the hole size should really be.

Common occurrence when a 'designer' has never attempted to make and assemble real parts in the real world. There's just something about actually fitting two parts together with your own efforts, (or taking them apart) to drive home a few lessons that one tends to remember far better than 'book learnin' '.

extropic · Sep 1, 2015

RJT said:
Brilliant engineer has designed a part 3/4 thick hard A-2 58-60 R/C that a 3/16 dowel has to be pressed through and stick out 1/4 inch. Hole dimension is .1840 - .1842". Even freezing one and heating the other, I don't see this happening. Maybe in aluminum or soft steel. Just shake my hear and politely tell them (my customer) what the hole size should really be.

Your story is unique and new in the annals of machine shop lore.

Did you report your concerns to your boss, or just choose to bitch here?

Trying to decide which is the larger PITA, you or your customer.

Big B · Sep 1, 2015

As long as this doesn't go in a space vehicle I would suggest to the customer that the hole be spec'd as "Press fit for 3/16 dowel pin".

Porschefix · Sep 1, 2015

Sounds like a decimal point mistake to me. Of course I've never made a mistake like that (cough, cough)

paracongo308 · Sep 1, 2015

Milland said:
What, 1/32" interference is too much? Just throw the pin in the freezer, it'll fall right in...

We used liquid nitrogen, then later we switched to dry ice & alcohol to freeze them in. The most I ever seen for press fit was trunions for the double action toggles on a large Toledo press. That was a 8 inch pin that required .007 press fit in cast iron frame. Used Alcohol & dry ice.

Cole2534 · Sep 1, 2015

extropic said:
Your story is unique and new in the annals of machine shop lore.

Did you report your concerns to your boss, or just choose to bitch here?

Trying to decide which is the larger PITA, you or your customer.

Lol

John Welden · Sep 1, 2015

I don't even drill a hole when I want to press fit a pin. Hit it hard enough, it'll go.

Big B · Sep 1, 2015

I doubt that I have a .1840-.1842 reamer. Sounds like what the member is complaining about in the tolerance thread.

.0035 press fit for a 3/16 dowel?

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