Author Topic: strange observation  (Read 2635 times)

Offline Twinsquirrel

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strange observation
« on: February 12, 2009, 05:03:31 AM »
My mini lathe hasn't been used for about 4 months but before it was left I made sure it was well oiled up and properly adjusted (a daily task).

When I came back to it yesterday the cross slide gibs were very very loose, and took almost a full turn on each grub screw to remove the play, strangley the compound slides' gibs were also out of adjustment but in the other direction i.e. too tight?

So, some wooly thinking brought me to the conclusion that it must be the change in temperature that was causing it.... On went the heater to bring the temperature up to 20 degrees C. The heater is directly under the bench where the lathe is and it was left on all day while I was at work. Wierdly, when I came back it was still exactly the same?

Any ideas whats going on here? I'm not too worried about it as it's a simple adjustment job to sort it out but I'm just interested to see what you think is happening.

Cheers

David
So many ideas, so little skill

Offline Darren

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Re: strange observation
« Reply #1 on: February 12, 2009, 05:10:07 AM »
Could it be changes in oil thickness after leaving for so long?
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Offline Twinsquirrel

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Re: strange observation
« Reply #2 on: February 12, 2009, 09:35:37 AM »
good thought Darren but.....

I disassembled the slides and cleaned the running surfaces without moving the adjustment grub screws and it all seems the same. I've readjusted it now and all seems to be well.... strange.... :scratch: :scratch:

On another note it seems that my lathe has a similar problem to yours mini Darren in that the carraige is slightly tighter at both ends of its travel, not much and I dont have any finish problems that I am aware of so its not causing me any problems at the moment.

Cheers

David
So many ideas, so little skill

bogstandard

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Re: strange observation
« Reply #3 on: February 12, 2009, 10:22:30 AM »
David,

It can take a long time for a machine to start expanding or contracting due to ambient temperature, due to it's mass.

I put an oil filled rad in my shop, and it is on permanently to raise the ambient temperature. It took a couple of weeks before the machines stopped feeling like a block of ice, they still feel cold compared to smaller tooling even now, and that is after six weeks. I suppose the same thing would happen if I turned the rad off, the machines would work like storage radiators for quite a while.

John

Offline cedge

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Re: strange observation
« Reply #4 on: February 12, 2009, 10:59:17 AM »
David
A man using Uncle Fester as an avatar should be more than just passingly familiar with the phenomenon known as Shop Gremlins....LOL  Something like Trunk Monkeys but much smaller and a lot harder to get rid of.

Steve

Offline memerson1

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Re: strange observation
« Reply #5 on: February 14, 2009, 09:09:19 PM »
I am new to this forum - just joined tonight - and looked at this post first.
I have had similar "loose bolts" in my combat robots when they sit idle in the shop for months.
FL winters have days when the temperature swings 60 F or more from morning to night.
After several moths I have found every cap screw in a bot in need of 1/4 - 1/2 turn to get it tight.
I suspect the rise and fall of the mercury causes the screws to back out - most of the frames are AL
and the cap screws are steel alloy so these metals have very different expansion characteristics so the effect
is more dramatic - but I would think the same thing has happened with your lathe.
I agree with the earlier post that keeping your shop at a constant temp. will help keep your tools tight.

my 2-cents.

Offline SPiN Racing

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Re: strange observation
« Reply #6 on: February 15, 2009, 03:44:34 AM »
Hi Michael  :wave:

Nice to see you on the forum!  Did Norm give you the link? I had heard you did the robots.. but never actually got a chance to say Hi.

Yes Im the one with the RX-7s across from David, and working nights. :)


I have not really run into looseness in the garage.. but when its as cold as it ha been here in the last month or so.. I stay in the house. LOL

Scott
SPiN Racing

Offline Bernd

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Re: strange observation
« Reply #7 on: February 15, 2009, 10:11:21 AM »
Hi Michael.  :wave:

Glad you joined. I think you'll like it here. :thumbup:

If you would please put a short post in the Intro section about yourself and interests. ::)

I know my interests are piqud when I read "robot". I have a passing interset in them. Got any good links. There was one I found but just can't seem to find it again no matter how long I look. All I can remember from the website is they guy has a very complete metal shop for build his bots.

Again, welcome to the collective. :borg: Oh and  :mmr: and after a few reads you'll get  :proj:, YA,  :ddb:  :ddb:  :ddb:  :ddb:

Reagards,
Bernd
You can't fix "STUPID".