Did I mention my experiences Suttons INOX HSS drill bits? [INOX = suitable for inoxidible - Austenitic steels]
• The American manufactured 10 tooth Grade 304 S/S chain pinion [
3.7465 mm chain pitch] had a #2-56 HPGS which I found with a stripped in-hex
• No problem……a Sutton INOX 2.5 diameter with quality cutting fluid dispensed with the #2-56 Grade 304 HPGS & oversize drilled for an M3 x 0.5 tapping
• This, with a new set of Sutton M3 x 0.5 HSS taps was achieved without difficulty…[actually have 2 x M3 tapping's in this chain pinion now]
• So I proceed to bore the same Grade 304 10 tooth pinion [in the ILS Myford super 7] out from the pilot bore of 1/8" to 4.0mm diameter with a Sutton INOX HSS drill bit [cost approx. $7.00] ....[~~ 1500 RPM & very low feed + the cutting fluid skimmed the stainless bore like butter & with a brilliant surface finish]
• I also bored a small brass pinion from 1/8" to 4.0mm bore at the same time
• Got back home & neither the S/S chain pinion nor the brass pinion would slide onto the engine 4.000 mm diameter shaft!
So how do you measure a 4.0 mm diameter HSS drill bit for tolerance?
After an exhaustive search of the Sutton WEB site, it appears this product is manufactured to a DIN338 Standard
After an exhaustive search of DIN338, it appears this diametrical reference is manufactured to a Class of h8
This h8 law of Engineering confirms that the said component in the size range from 3 to 4 mm diameter is to be manufactured to +0.000 to - 0.018mm
I had a
sneaking suspicion that all of the above was correct
, as both of my two components machine drilled with a 4.0 mm diameter Sutton INOX HSS drill bit did not fit onto my 4.000 diameter Saito steam engine shaft
The wonderful people at Suttons in Victoria suggested
that this was not possible & if I posted the said Suttons 4.0 INOX HSS drill bit to them by registered Post [$14.00], they would send a replacement at no charge
I have since ordered an M4 HSS parallel reamer [Class H7 +0.00 to +0.018] …yes for $1.82 from the far East…& including free postage
Has anyone encountered a similar issue?.................. Derek