Stainless steel block needed... urgent!

[Wedg1e]

I know, I know... daft o'clock and almost time for Santa to appear but we've just had an urgent enquiry in from a client who wants a reference block making in 316 ASAP (as in, delivered the day we come back after xmas!).
Not sure of overal dimensions yet but probably needs to be 100 x 150mm minimum - and 200mm thick!
Our local machine shops have all bu993r3d off to the pub for the duration so I'm stuck with Google - and you lot!
Any ideas who might have lumps that sort of size...?

 

[F.J.]

Blimey, nowt like last minute. Sorry I cant help you. Ive just had a call to go to Birmingham tomorrow but I finish in exactly 1 hour from now so they can bu993r off themselves

 

[Maker]

I can't help you but I have to ask; What's a reference block?

 

[BrokenBiker]

I can't help you but I have to ask; What's a reference block?

i would assume it is a block machined to specific dimensions to use as a reference as to what size a part should be...we used to have various blocks and bars that we would set the verniers at zero with and then we could see exactly how far out of tolerance we were without having to work things out, just add or minus the number on the vernier and it comes back into spec

 

[gordon stephenson]

Sorry can't help Ian, but if you do find a piece, Don't drop it on your foot.

 

[Paul.]

A block that size is going to weigh around 24kg, and would take some sourcing at any time of year let alone Christmas, When I've made largish setting blocks in the past we usually fabricate a box from 8 or 10mm plate or bar then get it machined to size,
And no I'm not offering, I'm doing absolutely nothing welding or engineering related now until next year.

 

[Spark plug]

the best I can think of this time of year would be metal supermarkets, but make sure your sitting down!

 

[gordon stephenson]

It might not be just a matter of being the right size it may have to be solid for ultra sonic NDT type testing

 

[Wedg1e]

It might not be just a matter of being the right size it may have to be solid for ultra sonic NDT type testing

Absolutely right: dimensions within +0.1/ -0.0mm, with flat-bottomed holes drilled and reamed to silly tolerances. The holes will be 3mm diameter and probably have depths of 25 to 175mm in 25mm steps.

Paul's right as well, it will weigh a bit; smaller blocks tend to have a number of small diameter (typically 1.2 to 3mm) holes of different depths but the spacing between them is relative to the thickness of the material and the beam-spread of the ultrasonic probe, so for 200mm thick the holes would have to be so far apart the block would need to be the size of a milling machine bed - and 8" thick. Plan is to have one hole per block, 8 holes required... someone's going to be giving their tooling some hammer in the new year

Expecting a call back from a well known metals supplier up in Newcastle, watch this space...

 

[Wedg1e]

I can't help you but I have to ask; What's a reference block?

Google image search for 'Ultrasonic calibration block' will tell all

Give your engineering head a workout and see if you can figure out how some of those shapes/features are made - OK so a CNC will do it now but most of the designs used to be produced on manual machines...

 

[BrokenBiker]

most of the shapes that come up in that search could be done on a manual mill with a rotary table/dividing head by the looks of it...wouldnt wire erosion be more accurate though? the stuff we used to knock out in the tool room on the wire eroders was always spot on although it was painfully slow. obviously couldnt do the holes with it though

 

[Wedg1e]

most of the shapes that come up in that search could be done on a manual mill with a rotary table/dividing head by the looks of it...wouldnt wire erosion be more accurate though? the stuff we used to knock out in the tool room on the wire eroders was always spot on although it was painfully slow. obviously couldnt do the holes with it though

Well yes and no to the wire erosion; under high magnification it leaves a surface like the backside of the moon. Also some features are so small, bizarrely (and a bit like Willard whassname) they're better done mechanically. For example, a lot of spark erosion machines can only go down to a 0.1mm diameter wire and there is an inherent gap created around it owing to the jumping sparks (if you will), so you can't claim better than 0.2mm width of a slot. You can however buy a 0.15mm slitting saw which makes a cleaner slot with a nicer internal finish... if you have an operator who can make best use of it! There were a few crossed fingers and held breaths when we first watched that being used.

The holes can have some silly accuracy requirements (see ASME 5)... centre location, distance from block edge or other holes, concentricity, perpendicularity measured in seconds of arc, straightness... you can't even measure most of them using x-ray. Oh and if not a through hole they have to have flat bottoms so it acts as a better reflector than the cone-shaped bottom of a typical drilled hole.
A couple of suppliers got caught out when we proved they were drilling them with standard drills and not flat-bottoming them as requested - quite easy to detect using a drill bit and height gauge.

Finally, in most cases every surface is required to be surface ground to 0.4u, tight enough on a flat surface but on a radius that also has to end up at finished size +/- 0.05mm...

 

[MattH]

That all makes my efforts on my old Bridgeport the equivalent of me say "I managed to put my pants on".