Thread: Making a Cylindrical Square.

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Originally Posted by simonl

My son has autism. He does more than look at his toes.

Simon

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Simon you are trying to distort what i was saying, if you dont understand... the point is the pure and utter rudeness of forum members in here not replying to posts.
Actually I can also include you as one of those rude people, here is the last time you ignored me when I tried to help you.
https://metalworkforums.com/f65/t204...74#post1957874
Last time m8 as I am pulling my head in and not gunna bother anymore, there is a handful of good people in here so apologies to those of you.

see ya later alligators

Hi shed,

Yes you are correct. I didn't reply or thank you or give further feedback. That's my fault and I apologise. I read it and watched the video but for whatever reason I totally forgot to reply.

Sorry mate, No excuse given the effort you went to in order to help me out.

Let's put it behind us and move on.

Simon

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Originally Posted by shedhappens

Yes RC, that material is not good enough dimensionaly as it comes for the intended use, here are the specs https://www.voestalpine.com/highperf...Chrome-bar.pdf
I was more concerned about the stability of the linear rail, I dont think that it is quality stuff and I would not like to go to
the effort of making a precision cylindrical square with it only to find that it wiggles around with temperature change later on.

I still think cast iron is ideal for a home shop made one. The problem I have with the options given is firstly you are going to need a really really well centred centre hole at both ends.

You will need a tapped hole away from the centre hole to drive the workpiece, it the bar is through hardened, it complicates things. If you are going to grind them, grinding is really really slow if you have a large amount of material to remove. For home shop use I think just plain cast iron is going to be quite suitable.

Originally Posted by shedhappens

... the point is the pure and utter rudeness of forum members in here not replying to posts.
...

I'm assuming you're including me in that category Shed, since I haven't replied to your post regarding doing a batch on the Churchill.
When you posted that I was about half way through a 21hr breakdown stint at work, and your post the next morning about nobody replying was probably made while I was picking up gear at the start of next one.
Sorry if you felt I was ignoring you.

I'm not sure why you think that linear shaft might be less dimensionally stable than the chrome bar. Both are 4140 and induction hardened to similar hardness. The chrome bar just has the addition of the chrome plating, and is produced to broader diameter tolerances. I'm not sure what pricing is like for chrome bar, but unless it was significantly cheaper than linear shaft I can't see any advantage in using it.
I haven't priced a short piece of new linear shaft, but I had found a couple of metres of NOS 60mm for around $400 delivered. Hence my earlier suggestion and rough cost if a few people were interested.

My thinking around using the linear shaft was that its probably OK to use without touching the diameter. Given the -19uM is a maximum tolerance, I'd expect that any diameter variation over the short length required for a CS is likely to be MUCH less and likely to be a tiny taper rather than a corrugation. By the time you halve the dimension (assuming the axis of the square is perpendicular to the end face) I expect it would be in the category of "I probably can't measure it in my workshop".
I'd expect that anyone who was considering making a CS on their lathe would be able to set up a piece of shaft so it was parallel with the spindle axis. Doesn't even need to be running perfectly true to recess and square the end - just parallel. The machining method for squaring would depend on what an individual had available to them, but the recessing shouldn't be an issue as the shaft is only case hardened.
I could be talking out a hole in my bum, but that was my thinking

Steve

Hi Guys,

FWIW, Has anybody bothered checking their local scrappy ?

I've just been in mine, he has some scrap hydraulic rams that look to be around 75 mm in diameter and around 5 foot long. I can't even lift one, let alone get one home ! If I asked nicely I know he would cut a piece off for me. He wants £35.00 for one, which I think is cheap, particularly compared to the cost of making them.

Hi Baron,

I've got a single acting hydraulic ram that I bought about a year ago. It needs new seals but the rod itself looks immaculate. In fact it's hard to contemplate that the ram would not have significant wear given the seals are flogged. I'm not even sure I have the capability to measure the rod but I may have a look tomorrow.

If it's any good I'm happy to come to some arrangement to cut it up in 100 - 150mm lengths and distribute. I really don't think I have the capability to machine a piece into a cylindrical square but I'd be keen to somehow supply the material (pending it being suitable) and in return receive a cylindrical square out of it!

Simon



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Ok. Well turns out that things may look in good nic..... until you approach with a micrometer!

It does show considerable wear along it's length when measured. I suspect that you would need to grind back a considerable amount of chrome to get it within acceptable limits.

Probably be alright with new seals as a ram but no good as a square.

Simon

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Chrome Plated bar is not a good choice for making one of these anyway, the thickness of chrome is only a couple of thou at the most and it would be hard to set up and grind the O/D without breaking through. Grinding hard chrome also has it's own challenges.

I managed to get a bit done on the pins today, honed the bores to straighten them out a bit, made a mandrel and ground the O/D of one. I checked the hardness at just on 60Hrc which is quite hard.

Gudgeon Pin..JPG

IMG_1618.JPG

I can confirm that a large gudgeon pin will make very good cylindrical square, provided that you have access to a cylindrical grinder to machine it.

This is now my favorite C/S as it is longer and larger in diameter than the others that I have.

volvo.JPG