Tool post grinding

[ChinkoaParticipant @chinkoa]

Can anybody recommend what's the best grinding wheel diameter for a tool post grinding wheel on a Myford Super 7. Also motor HP/KW.?

[ChinkoaParticipant @chinkoa]

[Thor 🇳🇴Participant @thor]

Hi Colin,

Welcome to the forum. For my lathe I use a 80mm grinding wheel. I assume about 150W should be Ok, mine is smaller but then I take very small cuts.

Thor

[Chris Evans 6Participant @chrisevans6]

My tool post grinder uses a wheel of around 80mm but is has been about 15 years since it was last out of it's box and I have changed lathes since then ——–

[ChinkoaParticipant @chinkoa]

Hi Thor,

Thanks for your reply and welcome.. Re motor size, base on you comment. I have a Nutool bench grinder that I rarely use that puts out 125KW and running Running 5" grinding wheels at 2950 RPM I was thinking that this could solve a few problems re mounting. I could play with wheel size. I like you would not be doping anything excessive with it.

Colin

[John RuddParticipant @johnrudd16576]

Posted by Colin Rhodes 2 on 23/04/2017 19:19:16:

Hi Thor,

…… Re motor size, base on you comment. I have a Nutool bench grinder that I rarely use that puts out 125KW and running Running 5" grinding wheels at 2950 RPM I was thinking that this could solve a few problems re mounting. I could play with wheel size. I like you would not be doping anything excessive with it.

Colin

Wow….125KW…..!! That must be some grinder…..?

I suspect you mean 125watts…..which ought be useable…..with smaller wheels….

[Thor 🇳🇴Participant @thor]

Yes, I guess 125KW should be enough, a 5" wheel at nearly 3000rpm sounds normal, make some kind of clamping for it and try it out.

Thor

[ChinkoaParticipant @chinkoa]

Thor,

I would think that 3000 RPM would run and grind but not well. The M/S. per second is very low. . I was involved with very large Grinding wheels for many years (36" x 9" x 10" Bore. and 30" x 13" x 12" Bore). and the M/S. was checked every week and adjusted as required to maintain optimum performance as to low a M/S. made them cut soft and they would wear down quickly too fast and they would glaze over.. I have contacted Norton Abrasive for there recommendations for a 5" wheel.. I had already decide that I needed to bump up the speed to about 6000 but that is limited if I use Pillow Blocks as 6000 RPM seems to at the their top end.

I will post Nortons reply.

Colin

[Ian S CParticipant @iansc]

Maximum speed should be marked on the wheel, I think I remember some of my wheels are marked 7500rpm, don't know if that's 6" or 5". I imagine that the listed speed leaves at least 50% above that for safety.

Ian S C

[Martin ConnellyParticipant @martinconnelly55370]

Does anybody know if a Dynafile/Dynabrade type machine has ever been put to use as a tool post grinder?

Martin C

[Neil WyattModerator @neilwyatt]

As it's hard to change motor speed you can also compensate for a lower rpm by using a harder bond.

[Clive HartlandParticipant @clivehartland94829]

Most tool post grinders have a belt and opposite pulley wheels, the bigger the wheel the slower speeds should be selected. Too fast and it will break down quicker and also glaze up.

Small diameter burrs need to go faster.

Clive

[ChinkoaParticipant @chinkoa]

Neil,

I didn't intend to mount the Grinding wheel on the motor. I will put a Suitable set of Picador pulleys one on the motor and one on the grinding wheel spindle then I can get somewhere near a reasonable M/S

Colin

[Thor 🇳🇴Participant @thor]

Yes Colin,

Grinding wheels, especially smaller ones, benefit from higher RPM. I guess I should have said " a 5" wheel at nearly 3000rpm sounds normal" for a bench grinder, sorry for leaving out the last words. Using the grinder to drive a proper grinding spindle sounds like a good idea, keep us posted of your progress.

Thor

[ChinkoaParticipant @chinkoa]

Thor

Confidence in your replies are now fully restored. Norton have not replied yey?

Colin

[Ian S CParticipant @iansc]

The only reason for 3000rpm(actually 2800rpm)is the speed of a 2 pole induction motor on 50Hz, size doesn't matter whether it's 5", 6", or 8", but an 8", or 10 "grinder is always much better as the surface speed is getting nearer to the ideal speed. In the USA a 10" grinder on 60Hz runs at 3450RPM.

Ian S C

Edited By Ian S C on 26/04/2017 12:09:22

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