0.475" ROD

On 1/23/2020 5:44 AM, Gunner Asch wrote: > On Wed, 22 Jan 2020 19:38:11 -0700, Bob La Londe snipped-for-privacy@none.com > wrote: >

I think I was told it was 416, but that was a very long time ago. I recall it was easily machined on the 7x10 and doesn't have the grainy finish typical of 303.

I have some TGP in a couple alloys and of course its spot on, but I have a fair amount of 303 and 304 and its pretty darned close to final dimension. Maybe I'll have to go mic a few pieces today and double check.

I think most of the 1018 and 1144 I have on hand is slightly oversized though. Very slightly.

I have noticed some types of flat bar is quite often oversized. I see it all the time in aluminum and its highly variable. From a few thousandths to 50 thousandths. The 4140 I get is pretty consistently .025 oversize. Consistent enough that for most jobs I can face off .0125 on each face and be within spec.

That doesn't make any sense. From my sources 416 is the cheaper stainless. I buy 303 for best machinability, 416 for machinable and high strength and price, and 304 if I have to have it today because that's all the local yards stock. Occasionally I'll buy 316 for special applications.

I don't know about its corrosion resistance persaye. Just that its cheaper than any of the other common stainless alloys I can buy from my regular vendors.

I always thought 316 was the most corrosion resistant of the common alloys and 303 was the least. There is also a 316L which is slightly more machinable than 316, but not as easy as 416.

They suggest 416 for pump shafts, valve components and boat shafts so maybe it's acceptable in fresh water.

A piece of 1/2" brass rod I added to an Amazon order to meet the $25 free shipping minimum measures 0.490".

Several batches of electronic components from them were out-of-spec rejects, though still usable. For example "75V" gas discharge voltage limiters conducted at either under 70V or over 80V.

Jim,

I've seen that in the UK with regards to sheet metal thickness from my local suppliers over the last decade or so. In the past when I wanted 16 swg (0.065" 1.6mm) sheet it was bang on within like 0.001", then they metricated it to 1.5mm and it was good for awhile but subsequently I've seen nominally 1.5mm sheet at 1.3mm which was unacceptable for some jobs. I guess the mills are trying to squeeze a few more sheets out to increase profitability. I've not seen bar stock like that but it isn't oversized in my experience.

I keep 4" dial calipers in the car to measure stock when I go shopping, or happen onto a useful piece. They are short enough to stay in a shirt pocket, much less likely than 6" ones to catch on a rack or machine I'm squeezing past and flip onto the floor.

They also fit under the head of the mill better to measure height.

Sometimes at an industrial supply store the reaction to the calipers is "Oh, you're an engineer", in a tone that suggests they expect I'll be demanding and difficult. When I reassure them that I'm a tech who has to build what the engineers dream up, and this is for a home project, they may offer some leftover that can be made to do the job at half price.

It is pretty close to 12mm diameter (which is really 0.4724" diameter). How precise was your original measurement (the OP's 0.475" measurement)? I get 12.065 mm from 0.475".

Some rod stock is slightly oversized, expecting turning to final dimension. It could be this way with your stainless rod.

Sounds like the rejects which are sold through some low-budget vendors.

Who is the "them" from "from them"? If a low budget vendor, it could easily be the rejects after testing and separately selling those that passed to a high-dollar vendor. :-)

Enjoy, DoN.

Them's Amazon. Radio Shack components sometimes showed a gap around the nominal value too, for instance no 10% resistor would be within 5% of nominal since those that were sold separately for more $. The measured breakdown voltage of their diodes and bridges could be anywhere from slightly below spec to far above it, but below a higher spec, ie 450V for a 50V bridge.

I only bought the brass rod to reach $25 for free shipping, as it's a size I don't have in my stock, and will be turned down smaller anyway. I need steel shafting to be correctly sized to fit bearings but for brass or aluminum that doesn't I have small 3 and 6 jaw chucks on 5C mounts that are better than collets for moving the work between lathe and mill because they stay clamped.

I have a lot of experience testing electronic components so I don't mind buying cheaper out-of spec parts and confirming they'll work for my one-off designs. I was the repair tech for the testing machines Analog Devices used to ensure their op amps meet specs.

Most DC parameters can be measured with a voltage and current limited power supply. Usually the data sheet gives everything you need to know, such as the reverse current at the breakdown voltage. High speed production testing uses brief pulses to avoid heating but you can test a few parts mounted on a heatsink.

This can measure milliAmps with a different shunt. The current trimpot range is quite wide, I set it to 199.9mA and 19.99mA with 0.5 Ohm and

5 Ohm shunts. Type T thermocouple wire is a source of Constantan for low current shunts. The exact resistance of the shunt doesn't matter as long as you can trim the reading to match a DVM in series.