Think if I found all my raw stock was undersize by the same amount I'd be checking the calibration of the measuring device first before coming to any conclusions.

What are the tolerances on sizes for bright bar – or any other bar for that matter? I'd have thought that selling bar under stated size might just fall foul of trading laws unless made very clear that size is nominal and by how much under it might be.

2 thou clearance on 1/2in. is definitely in the "large clearance" range as defined in Tubal Cains Model Engineers Handbook. How much better is that fit than the old knocking version – do you need it to be a better fit – too good a fit and you might get binding from other tolerances and inaccuracies in the mechanism.

If you check the tolerance put out by the various steel companies you will find they are all in this same ball park.

Trying to hold dead size over a continuous run of many tens of thousands of feet , travelling at about 30 mph off the rollers, is impossible.

It's a question of scale, you are only interested in 2" long being to size, they are interested in metric tonnes.

I'll join in the festival!

You should celebrate Fizzy, you are not going crazy and all your bar is well within BS spec.

What is important is the bar must NOT be oversize and between 6 and 18mm diameter it can be up to 0.07mm (nearly 3 thou) undersize.

Bright bar is not intended as being a bearing surface as supplied and the biggest likely problem is if it won't fit in a hole.

You may be surprised just how much undersize it can be:

**LINK**

Compare with silver steel:

Neil

I was close to Southampton one day and so popped into the metal Wharehouse to buy some 16mm square bar by about 14" long. when I got home I found that the bar was 5/8" (15.825mm). It would have been a 60 mile return trip to exchange it, so I bit the bullet and used it. Moral, take your mic when buying stock!!

Frank

Nothing at all to do with this but- Last week I wanted some 3/8" bsw cup-square bolts for a special job. Dropped in at local garage on the off chance, man said "we only do metric now, have some 10mm over there", so picked up the box and they were 3/8" bsw.

Fizzy,

It depends on the application but my ME Handbook (Tubal Cain) suggests a clearance of 1 thou plus 1.5 thou per inch diameter for a "normal running fit" so you're not that far out.

Russell.

Not enough room! A quick count reached 30+ micrometers, and that's only the external ones. They'd just be more things to trip over, and after recent events I'm thinking "safety" in the workshop. It would be really dumb to trip over something and grab hold of a rotating machine. A guide might help put things in context:

Garage = workshop

Dining room = Tool room, cutter store and measurement area

Lounge = 3D printing and technical library

Kitchen = Casting aging, work in progress and assembly hall

Study = Drawing office

Actually, the kitchen is dual purpose, and I am about to prove that by knocking up a curry for supper this evening.

Regards,

Andrew