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| How accurately ground is Silver Steel (aka drill rod)? |
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| awemawson:
What sort of tolerances would you expect on a run of the mill 3/8" ground Silver Steel, which I believe is called 'drill rod' over the pond ? Andrew |
| Brass_Machine:
I typically buy my drill rod from a company here called McMaster Carr. They list their O1 multipurpose tool steel as tight tolerance rods. +/- 0.0005 Not sure what other places list theirs as. Eric |
| philf:
Hi Andrew, The only reference I could find was: IMPERIAL SILVER STEEL TO BS1407 Tolerances: Up to 1.00" +/- 0.00025", Over 1.00" +/-0.0005" METRIC SILVER STEEL TO BS 1407 Tolerances: Up to 25mm +0 /- 0.015mm, Over 25mm +0 /-0.025mm From memory I thought that both imperial and metric had a +0 tolerance but it seems not. :beer: Phil. |
| awemawson:
Thanks Eric & Phil, Within 1/4 thou will do nicely if that's what turns up! I'm looking for a nice no wiggle sliding fit for a drag engraver for the CNC machine. I've made one up that works nicely from nominal 3/8" mild steel that finishes as 0.373" I'm sliding it in 3/8" sintered phosphor bronze bushes that are seemingly dead nuts on at 0.375". If the silver steel that turns up is on the high side of the tolerance I can easily lap the bushes down that much. The mild steel one works ok but the slight 2 thou wiggle annoys me and must lose accuracy when the tool changes direction so small text would look distorted. 0.002 may not sound much but it shows. As an aside I wanted a 'non rotating' tool on the CNC. The CAM program can output 0 RPM, but the TNC355 controller can't cope with that and errors. The CAM program insists on outputting an 'M03' spindle start. So as a work around I'm manually editing the code so that any 'M03' is an 'M05' (spindle stop). I suppose I should edit the Featurecam post processor to do a bit of logic along the lines of 'if RPM = 0 then M03 = M05' !!!! Andrew |
| Pete W.:
Hi there, Andrew, This might be an 'urban myth' but I was told in my formative years that silver steel, being centreless ground, can turn out to be tri-lobar (like a 50 pence piece but with three lobes rather than seven). It was said to depend upon how well the centreless grinder is set up. It'll apparently measure the same all round with a micrometer. I've never actually tried to measure a piece but I've sometimes wondered just how I'd do it. :scratch: :scratch: :scratch: I guess it would self-centre in a collet and then a dial gauge would show the variations (if any) as the collet was turned. I'm sure there are Mad Modders with experience of centreless grinding and I look forward to hearing their opinions. |
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