AC Needed in Machine Shop cutting Hard Bearings and holding +.0000 / -.0002" ?

RocknRonF · Aug 17, 2018

HI Guys,

We machine existing ball and roller bearings that have already been heat treated to 62-65Rc. We do grooving, chamfering, facing, etc.. and have to hold tolerances like +.0000 / -.0002". and currently is mostly dry cutting on a manual lathe and mill.

We are expanding the machine shop and adding CNC's, a VF3 and CNC Lathe and increasing the size of the shop. We are trying to decide if we need Air Conditioning in our machine shop in order to hold these tolerances. The warehouse can get from 50-90 degrees inside. I have had difficulty holding these tolerances when its too cold or hot in the warehouse/machine shop from my experiences here.

What do you guys think? Do we need AC in our machine shop trying to hold these tolerances??

I really needs your advise
Thank you
Ron

tdmidget · Aug 17, 2018

Absolutely yes. A 2 inch od bearing would grow over .0005 in that kind of temperature swing.

Zahnrad Kopf · Aug 17, 2018

You could simply figure it out for yourself by taking measurements at your 50°F, repeat the process at 90°F, and record the measurements. You should arrive at your answer fairly quickly,if not immediately.

Seriously? You're trolling. Right? Looking to evoke a few laughs. ( ? )

Any actual machinist I have ever known in my lifetime has been keenly aware of how temperature affects part sizes.

AARONT · Aug 17, 2018

Industry standard is 68°F or 20°C. So yes, you need it to be climate controlled when working to those tolerances. If you're not, you're going to have a whole lot of bad parts coming back from your customers.

https://nvlpubs.nist.gov/nistpubs/jres/112/1/V112.N01.A01.pdf

RocknRonF · Aug 17, 2018

Zahnrad Kopf said:
You could simply figure it out for yourself by taking measurements at your 50°F, repeat the process at 90°F, and record the measurements. You should arrive at your answer fairly quickly,if not immediately.

Seriously? You're trolling. Right? Looking to evoke a few laughs. ( ? )

Any actual machinist I have ever known in my lifetime has been keenly aware of how temperature affects part sizes.

LOL! No. I'm a beginner. I'm the Director of Quality and Operations at my company and they wanted to do bearing modifications in house so I took a basic machining class for 3 months, bought a lathe, mill, surface grinder and set up a shop. I was able to generate $200k of revenue in the fist 60 days so now we are expanding now. I am a skilled Mechanical Application Engineer over 36 years, but only been machining for 2 years on manual machines with only a basic machining class. I use expandable collets that we machine to size from Rovi Products to hold all the bearings. I had planned AC the whole time but I recently hired a skilled machinist to run my shop and he is the one that didn't think AC was necessary. So I had to come here to get advise from the experts! Sorry, I know this question is extremely lame.

Thank you for your feedback. Any advise or insight is greatly appreciated.
Ron Foster

Mike1974 · Aug 17, 2018

Zahnrad Kopf said:
You could simply figure it out for yourself by taking measurements at your 50°F, repeat the process at 90°F, and record the measurements. You should arrive at your answer fairly quickly,if not immediately.

Seriously? You're trolling. Right? Looking to evoke a few laughs. ( ? )

Any actual machinist I have ever known in my lifetime has been keenly aware of how temperature affects part sizes.

Machinist yes, manager no. Depends on why/who is asking.

Zahnrad Kopf · Aug 17, 2018

RocknRonF said:
LOL! No. I'm a beginner. I'm the Director of Quality and Operations at my company and they wanted to do bearing modifications in house so I took a basic machining class for 3 months, bought a lathe, mill, surface grinder and set up a shop. I was able to generate $200k of revenue in the fist 60 days so now we are expanding now. I am a skilled Mechanical Application Engineer over 36 years, but only been machining for 2 years on manual machines with only a basic machining class. I use expandable collets that we machine to size from Rovi Products to hold all the bearings. I had planned AC the whole time but I recently hired a skilled machinist to run my shop and he is the one that didn't think AC was necessary. So I had to come here to get advise from the experts! Sorry, I know this question is extremely lame.

Thank you for your feedback. Any advise or insight is greatly appreciated.
Ron Foster

Ron, do yourself a favor and read the publication that AARONT linked. In short, yes. You most assuredly need climate control if you desire to do good work and be allowed the opportunity to continue doing more good work.

My own recent post might help - https://www.practicalmachinist.com/...vant-shop-use-353761-post3222181/#post3222181

JCByrd24 · Aug 17, 2018

Zahnrad Kopf said:
Any actual machinist I have ever known in my lifetime has been keenly aware of how temperature affects part sizes.

This thread and response is a great example of the seemingly age old "trade x" vs "trade y" vs "management" debate/finger pointing/bashing, whatever. I'm assuming by "any actual" you mean any decent machinist. But certainly there are actual machinists that don't understand or apply everything a decent/good machinist does, perhaps this example being one. That's what separates the upper from the lower echelon in any trade. The same applies for engineers, and managers. Good ones in any category avoid generalizations about the others and respectfully learn the capabilities of the other, and aren't offended when the same is done to them in return.

In this example the engineer gives the benefit of the doubt to the experienced machinist, but enlists a "trust but verify" approach, which isn't a bad thing. And in this case has learned something about his experienced machinist. The follow on conversation with the machinist would be interesting, and probably more would be learned.

ewlsey · Aug 17, 2018

The company I used to work for got a contract to cast and machine aluminum hemispheres. Big ones. Up to 5 feet in diameter.

Part of the contract was that they had to be machined in a climate controlled shop. So, they bought an adjacent building, tore out the whole 6" concrete floor and poured 10" floors (probably 50,000 square feet), upgraded all the electrical, put in a few poured foundations for a broach and two CMM machines, and hired riggers and electricians to move the whole machine shop to the new building.

A few months in the management decided the AC was just too expensive. They turned it off and went back to machining things like they used to. No worries.

Customer finds out about the decision and pulls all casting and machining work full stop.

I hate to think how many $ million they spent on this project. And how many $ millions they lost in future work on the contract.

hanermo · Aug 17, 2018

What types or sizes of bearings are You modifying ?

Zahnrad Kopf · Aug 17, 2018

JCByrd24 said:
This thread and response is a great example of the seemingly age old "trade x" vs "trade y" vs "management" debate/finger pointing/bashing, whatever. I'm assuming by "any actual" you mean any decent machinist. But certainly there are actual machinists that don't understand or apply everything a decent/good machinist does, perhaps this example being one. That's what separates the upper from the lower echelon in any trade. The same applies for engineers, and managers. Good ones in any category avoid generalizations about the others and respectfully learn the capabilities of the other, and aren't offended when the same is done to them in return.

In this example the engineer gives the benefit of the doubt to the experienced machinist, but enlists a "trust but verify" approach, which isn't a bad thing. And in this case has learned something about his experienced machinist. The follow on conversation with the machinist would be interesting, and probably more would be learned.

Speaking generally, it is not a good idea to assume things. Speaking specifically, it is never a good idea to assume things with regard to me. Period. By "actual" machinist, I meant ( and continue to mean ) any person ACTUALLY employed in the profession that has attained enough of a skill set over time to withstand scrutiny by peers of the same profession enough to be considered generally worthy of the title of "Machinist", as it has been traditionally understood. Not a tinkerer. Not a "maker". Not a maintenance man that once saw a mill turned on. In other words - Someone with enough skills and the experience using them to have experienced exactly why temperature is an important consideration in the quest for quality.

Not quite what you took it to mean. Hey?

Mtndew · Aug 17, 2018

RocknRonF said:
We are trying to decide if we need Air Conditioning in our machine shop in order to hold these tolerances.

Is this even a real question?
:confused:

thermite · Aug 17, 2018

RocknRonF said:
HI Guys,

We machine existing ball and roller bearings that have already been heat treated to 62-65Rc. We do grooving, chamfering, facing, etc.. and have to hold tolerances like +.0000 / -.0002". and currently is mostly dry cutting on a manual lathe and mill.

We are expanding the machine shop and adding CNC's, a VF3 and CNC Lathe and increasing the size of the shop. We are trying to decide if we need Air Conditioning in our machine shop in order to hold these tolerances. The warehouse can get from 50-90 degrees inside. I have had difficulty holding these tolerances when its too cold or hot in the warehouse/machine shop from my experiences here.

What do you guys think? Do we need AC in our machine shop trying to hold these tolerances??

I really needs your advise
Thank you
Ron

No. Not exactly.

What you NEED is a bit more complex. Costs according.

You need full "environmental" control.

Temperature is only the obvious one.

Humidity, airborne corrosives, gas and solvents, and particulate control, less obvious, but every bit as essential if your speciality is bearings.

They are expected to preserve what their maker - who has ALL these things, plus the monitoring and logging of their effectiveness 24 X 7 X 365 - shipped them with. Essential, not optional if they are to LAST worth a damn for YOUR customers in-use.

Y'see.. it's like a fetus. This part of their "life" bearings are vulnerable to harm they can resist well-enough once out in the world ,"grown up", and safely installed in their housings. Sealed, hopefully. Fed only CLEAN lubricants. Known to not last "forever", but to have earned their cost, not failed "early".

Whilst still "naked", they need better care.

Dry cutting and grinding of bearings on manual lathe mill, and grinder?

Pilgrim? That easy 200 large may have carried the time-bomb of commercial destruction out the door with it already in impaired bearings with shortened lives.

"Luck" is serious hard to quantify.

Best I can do for now for my own "luck" is to blacklist all of California to make sure I'm not the one to get buggered bearings, yah?

JCByrd24 · Aug 17, 2018

Zahnrad Kopf said:
Speaking generally, it is not a good idea to assume things. Speaking specifically, it is never a good idea to assume things with regard to me. Period. By "actual" machinist, I meant ( and continue to mean ) any person ACTUALLY employed in the profession that has attained enough of a skill set over time to withstand scrutiny by peers of the same profession enough to be considered generally worthy of the title of "Machinist", as it has been traditionally understood. Not a tinkerer. Not a "maker". Not a maintenance man that once saw a mill turned on. In other words - Someone with enough skills and the experience using them to have experienced exactly why temperature is an important consideration in the quest for quality.

Not quite what you took it to mean. Hey?

You just proved my assumption... and when someone states their assumptions up front to make it clear what they are responding too, you could lighten up a little about it. Plenty of machinists out there with little experience or just not stellar at what they're doing...just read this forum...

thermite · Aug 17, 2018

JCByrd24 said:
You just proved my assumption... and when someone states their assumptions up front to make it clear what they are responding too, you could lighten up a little about it. Plenty of machinists out there with little experience or just not stellar at what they're doing...just read this forum...

C'mon. Thermal coeefficients of expansion and "STP" Standard Temperature and Pressure, were covered at school somewhere between 8th and 10th grade basic science class, yah?

Any "machinist" who has somehow MISSED it on the shop-floor need only to be able to draw breath or own a motorcar or a cookstove.

This was a serious dumb - or serious OPTIMISTIC more likely - question.

Hoping for some sort of "magic shortcuts" known only to the secret brotherhood of wizards so the spend could be avoided.

Zahnrad Kopf · Aug 17, 2018

JCByrd24 said:
You just proved my assumption... and when someone states their assumptions up front to make it clear what they are responding too, you could lighten up a little about it. Plenty of machinists out there with little experience or just not stellar at what they're doing...just read this forum...

We'll agree to disagree without my going into why, as it isn't germane to the topic. Start a new one and I'll contribute to it there. Too, my reply is plenty light, bearing no intended weight or negative intonation. Again, don't assume. I simply pick my words purposely. Trust me on this. ( Or not. Es macht nichts. )

9100 · Aug 17, 2018

Temperature control is only the beginning because the part heats up from cutting. I know one shop that has a pause in a CNC lathe program for the operator to measure the part's temperature with an infra red heat gun and input a correction to the program.

Also, the temperature must be maintained all the time. Back in the 70s when energy saving was big, the accountant in a company turned off the AC on Friday night without telling anyone. Monday morning the prototype maker threw a monumental tantrum and wouldn't do anything but rough out parts for several days. He was the best machinist I have worked with and routinely worked to tenth tolerances. Different parts of a machine heat and cool at different rates so until everything reaches equilibrium it will be shifting in unpredictable ways and I considered his objection completely justified.

Bill

Milland · Aug 17, 2018

The point on temperature control is that it's much easier to do "tenths" work accurately, but it's certainly possible to get good parts when actual temp is known and corrected for by CTE calculation and diameter adjustment.

This presumes good temp readings, machines at uniform temperature, ditto parts and measuring tooling (generally also steel of similar CTE).

That said, it's much easier to work in a temperature controlled shop, and frankly, the machinists will be more efficient with less time wasted due to heat or cold effects (extra water breaks, hindered thinking due to cold, etc.). Just good human resources to keep reasonable temperatures.

But it sounds like you're cutting "non-rolling" feature modifications, not recutting races or resizing rolling elements. So actual size control isn't so critical (.0002" sucks for precision rolling elements). And doing this currently on manual machines means less than optimal control of cutting tools anyway, due to V-way defection, Acme screw driven axis, etc.

So I think you'll do better with decent CNC machines installed, but it'll lower mistakes and measurement corrections if the shop is temp controlled. I'd push for it...

carbonbl · Aug 17, 2018

Maybe this machinist who said A/C was not necessary was assuming that the temperature could be controlled only at the inspection stage and any adjustments required could then be relayed back to the uncontrolled shop floor. Knowing the coefficient of expansion and the measured error at inspection temp a correction factor could be figured out for a particular shop temperature? Or plain-old sneak-up-on-it-til-it's-good (with frequent pauses to let parts come to temperature in the inspection room)? While that seems like a horribly inefficient process for any volume it kinda sounds like something that might have been in place from the days when one machinist was doing a few modifications with manual machines. So maybe it is a challenge of changing ingrained habits that will never work for higher production while still valuing your machinists' experience.

Its interesting to see how decisions get made when shops expand and add processes, what good habits are established and what bad habits remain along for the ride. While I don't work to these kinds of tolerances that decision-making process is one I think about a lot (even in relation to non-machining things), so these threads are an interesting read.

thermite · Aug 17, 2018

Milland said:
The point on temperature control is that it's much easier to do "tenths" work accurately,
.
.
it'll lower mistakes and measurement corrections if the shop is temp controlled. I'd push for it...

One ole "Day Job" also found that air-con for the whole plant gave them tens of years at being able to hire and keep staff at more economic wages.

When they started with it, prior to 1950, not many folk had air-con in their own residences or automobiles. Putting in a day at "the plant" was more comfortable than most any other option, competitor's plants or even staying at home included.

Where MOST shops, even today, fall-down is failure to INSULATE well and make provision for some sort of restriction or even "airlocking" of roll-up doors and loading docks.

AC costs a lot of money when you try to do the whole damned county.

AC Needed in Machine Shop cutting Hard Bearings and holding +.0000 / -.0002" ?

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