Thread: How much expansion do you need to allow for when a job is hot

Brendan,
PM sent

Machinery's hand book is described as the machinist's bible.
Industrial press is the company that prints it in the US, and is available small and large print as well as cd.
Category: Machinery's Handbook | Industrial Press

I just had a look where I bought mine and it has gone down to $107.50 since I bought it a year and a half ago. Over $100 is free post from this mob
28th Machinery's Handbook, Large Print Edition
The tool box edition is only $82.50 but you have to pay postage on top unless buying something else.
28th Machinery's Handbook, ToolBox Edition

The only difference in the 2 is one is small print. When I ordered it took around 6 weeks to come in.

Dave

If you are hasing a close running fit on your bush,I would allow some type of lubrication.
For the surface finish you may consider polishing with emery or buff &roll.

How many here hold the micrometer with cotton gloves when precision measuring so the micrometer does not warp from the heat of your hands?

While we all may think we are doing work to the micron level, if we actually had the capability to measure our work correctly, we would find out how ordinary it actually is.... General lathes are not good for real high precision work.... That is the realm of the cylindrical grinder..

Meanwhile back in the real world unless we are doing work for NASA what we do is good enough.. And remember there is always loctite... I like loctite

Why do you need cotton gloves RC? Unless you have a mic that doesnt have the "plastic" pieces on the bottom of the frame.

If we want to work at the micro level we have to have sub micro finishes or its a waste of time pretty much.

I thought certerless grinding was the way to go if you really wanted it spot on. Or is it just to make production easier?

Stuart

With your bush you have to allow for crush as well if u are pressing it into a hole so you would need more than the 0.02mm clearance as that would be tight as it is i would allow more than that is i was making a bush.

I would use a lathe if i had to get the size with in + or - 0.01 but anything under that you will have trouble getting the size and grinding is a better option.

With regards to how much you would leave on a shaft that is only 20mm i would leave 0.10 but on larger objects i would leave a little more especially if i had been doing heavy roughing.

Why do you need cotton gloves RC? Unless you have a mic that doesnt have the "plastic" pieces on the bottom of the frame.
Forgetting the Cotton glove part of the above it is only small Mics that may or may not have a piece of Plastic at the bottom.

Originally Posted by 19brendan81

Ha ha. The long armed branch of the sport is bad enough! One day though id be keen to get into some single action stuff.

I do long arms as well
having two more pistols built for me if the as we speak

I don't think that gloves would make much difference unless you are working to microns and have a machine shop that is stuck at 20 degrees.

Also i forgot to add run the coolant on your job for a while before meausring to take finishing cuts

0.02mm is not microns?

Us hobby guys are more than likely using the same mic and technique to measure the bore gages and the shaft to get the fit, it's not as though their going out of the shop to match a part on the other side of Aus.
I agree with you about grinders, but as for loctite, If I make something that doesn't fit, it's in the bin and I start again. It is good for locking nuts/ bolts though.

Dave

Originally Posted by .RC.

How many here hold the micrometer with cotton gloves when precision measuring so the micrometer does not warp from the heat of your hands?

While we all may think we are doing work to the micron level, if we actually had the capability to measure our work correctly, we would find out how ordinary it actually is.... General lathes are not good for real high precision work.... That is the realm of the cylindrical grinder..

Meanwhile back in the real world unless we are doing work for NASA what we do is good enough.. And remember there is always loctite... I like loctite

0.02 is 20 microns a micron is 0.001, i was talking about making things to tolerances under 0.01mm or 10 microns

I was referring to RC's post of micron level, not yours.
I think with a bit of experience, it shouldn't be to hard for someone to machine to 0.02mm in the home shop.

Dave

Should be able to machine to that aslong as there gear is good enough and setup properly

Originally Posted by 19brendan81

Cool. So I would make the shaft 19.98 and the bore 20.00 and it would fit? thats pretty tight!

could you make the shaft 20.00 and the bore 20.02 - 20.03 or is that frowned upon in the machining world?

It is usual accepted practice to apply the clearance to the bore, and not the shaft.

so stick with the 20.0 mm shaft and bore the bush slightly larger.

machinery handbook PM me if you'd like a copy..