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Bench Grinders & Lathe Tools.

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Pete W.:
I referred in a previous thread to the subject of HSS lathe tools.  That thread was intended to be humorous but I also indicated that I had some questions about the grinding of HSS lathe tools that I would raise in a separate thread - well, here it is.

First of all, a bit of background.  I've always kept my grinding machine in a separate building away from my lathe & drill-press.  This involves running out an extension power lead and also temporarily moving some other 'stuff' out of that shed to make room to access the grinder.  I'm enthusiastic but I don't achieve as many workshop hours per year as most of you guys!  The net result of this is that, despite running my lathe since about 1970, I've done very little grinding of HSS tool blanks.  I've managed quite well with a selection of Cintride brazed carbide tools of various shapes.  These only require an occasional quick kiss with a carborundum slip stone or a DMT diamond hone.

Now, in this post, I'd like to get Modders' opinions and comments on a couple of grinding machine and grindstone topics.  Please note that I am concerned with the common double-ended bench grinder, not the more exotic 'tool & cutter grinders'.

The first topic is bizarre.  I recently visited the local branch of a national chain of tool merchants.  I have been dissatisfied for some time with my tool grinding facilities so I asked the staff member what sort of range of grinding wheels they kept in stock.  He replied that they kept none in-branch 'because they have a 12 month shelf-life' so I would have to order from their Head Office via their web-site.  To say that his reply surprised me would be a huge understatement!  To explore its implications, it's reasonable to assume that a grinding wheel in use on a machine can't have a 'shelf life' longer than if it were on the shelf but I know of bench grinders whose wheels haven't been changed in decades!  How about that?

My second topic concerns the presentation of tool blanks to the grinding wheel.  The conventional wisdom is that the tool blank should only be presented to the rim of the wheel, never to its flat sides.  I recently bought a second double-ended bench grinding machine and its User Instructions echo this restriction.  However, in grinding a lathe tool, the major part of the job is to form a prism shape with plane faces, not concave faces.  Furthermore, Harold Hill's book on tool sharpening has illustrations clearly showing tools being presented to the side of the wheel.  I look forward to your comments. 

DMIOM:
Pete,

I can't offer any definitive advice, but I have previously found the UK HSE's "Safety in the use of Abrasive Wheels" useful, you can buy the hardcopy, but it is also available as a free PDF download. I'd suggest you might have a look yourself; on a quick read the only pertinent reference I can spot is "....All organic bonded wheels for hand-held applications will bear a use-by date of three years from the date of manufacture....."

Dave

PekkaNF:
Yesh...organically bonded wheels have expiry date and that is pretty common on cut out wheels, they don't mature that well

http://www.highspeedtraining.co.uk/hub/grinding-wheel-marking-system/

The expiry date if it’s an organic bonded wheel (this will be 3 years from the date of manufacture).

This marking is often on steel cap/hub, often sample discs that come with grinder are allready expired.

Short dig from the garage revealed this:

Pekka

gerritv:
If I recall correctly, Harold shows the tool being presented to the corner of the wheel, not the full side?

The exception is drill grinding where there is very little pressure.
The only sure way to get a flat side is to use a cup type wheel, where you are grinding on the side :-)

Gerrit

chipenter:
Using the side of the can generate heat , and iff used for long periods may crack the wheel , but only iff hard pressure is used and the tool is red hot .

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