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Fitting a 5/8" bush to a 16mm arbour?

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Deadeye

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I want to fit a CBN wheel to the grinder.
Record Power decidedly unhelpful ("you'll invalidate your warranty").
The manual said arbour 12.7mm; got bushing from Axminster (reduces from 32mm). No fit - measured again - 16mm. Assumed this must be 5/8" and me being hurried as the manual is imperial and Axminster do a 5/8" but not a 16mm.
5/8" too small - definitely 16mm.
So I'm 0.125mm too tight.
Anyone able to take .0625 off the inside radius of two bushes for me?
Or do I need to start again?
Or can I with household implements only take that off the arbour?

Grumpy.
 

TFrench

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If you post them to me I can turn them out to 16mm.

Sent from my SM-G973F using Tapatalk
 

AES

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Under NO circumstances should you try ANY DIY mods to a grinding wheel bush unless you have a lathe (at least). And though you haven't said what material the bushes are, that includes NO use of heat!

At risk of preaching, NEVER underestimate the "capacity" of a grinding wheel to explode and do extensive damage - at least to the surroundings if not to yourself as well.

Sorry to sound fierce, but as part of my apprenticeship I saw a small grinding wheel explode ("only" on a training film) and believe me it was frightening. I saw that film over 50 years ago now and today I still treat all grinding wheels (and related bushes) with GREAT respect.

You are absolutely correct to be biting TFrench's hand off to modify/make new bushes. Nice gesture from him.

Sorry, "lecture" over now ;-)
 

CHJ

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AES":1igxt1md said:
…….
At risk of preaching, NEVER underestimate the "capacity" of a grinding wheel to explode and do extensive damage - at least to the surroundings if not to yourself as well...….
That includes the temptation to "Do a quick test" without the containment guards in place.

As an aside I once witnessed a 4 foot diameter grinding 'tyre' let go at a bearing manufactures , it was contained by the guards but I didn't fancy the job of the tool setter sorting that out.
 

AES

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Yup, thanks for that reminder too CHJ. Getting the (steel) guards back onto even a small workshop bench grinder can be a bit of a PITA sometimes, but just as you say, do NOT be tempted folks.

We often see items able table saw safety on here (I have no experience whatsoever of those things) but sometimes "we" forget about "simple" little bench grinders. No need to be "scared", but "handle with respect"? Oh Yes, always.
 

Inspector

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AES in this case the wheel is a CBN wheel, either solid steel or aluminium. They don't fly apart like an abrasive wheel does and in most cases are not used with guards. They are even sold without them here when equipped with CBN wheels as a woodturning sharpening package. Having some guarding is a good idea to keep from getting tangled up in any spinning machine however. They can't be dressed like a grinding wheel to true it up though so metal bushings rather than a plastic are better to keep things concentric. The one thing that I see as a potential issue is the 12.7mm shaft suggests it is a small grinder and the motor may not be able to handle the weight of the wheel, at some point failing electrically. Likely why Record says it will invalidate the warranty.

Pete
 

AES

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Ah, OK, thanks Inspector. I thought the "CBN" was just a brand name or something.

Apologies for my earlier warning Deadeye, but the warning stands for any wheel that consists of "just bits of stone glued together", which even with modern processes is what grit-type grinding wheels are (simply said).
 

Sideways

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For your reference, take a quick look at this thread.
post1280119.html#p1280119
I bought a 200mm CBN wheel off Axminster, the 40mm wide one, not the 32mm ones they sell which fits their own 200mm trade grinder, eventually I bought the latest model Record 8" grinder with 20 or 25mm wheel and a 40mm.
That record grinder definately has 5/8" dia spindles and I bought the Axminster bushes to fit their wheel to the machine.
My thread was about chasing down some slight sloppiness and manufacturing eccentricity in the CBN wheel and bushes.
I got lucky and in the end I was able to orient the installation of the wheel to offset the imbalance and it now runs a treat.
I should say that this was in no way a dangerous level of imbalance, but a CBN wheel should be able to spin super smoothly. At first fit it didn't but eventually I got it in a state I was happy with.
Record were the same with me by the way - it's quite a powerful machine but they don't recommend this grinder for CBN wheels. The only reason I can imagine is that these wheels have huge inertia and take a lot of starting. The startup current in the motor is probably higher and lasts longer than a machine used with ordinary wheels. I tend to start the wheel spinning by hand before I press the on switch, that should help take the edge off the startup surge, and in any case, you don't start and stop these often considering it takes a few minutes for them to spin down.
 

Robbo3

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Mike Waldt & the Gosforth Handyman have fitted CBN (Cubic Boron Nitride) wheels to their Record grinders
- https://www.youtube.com/watch?v=zeWJl3DRxDw
- https://www.youtube.com/watch?v=T-iXS7DnZEM

I had to fettle Axminster's CBN wheels to fit their own slow speed grinder. One is Imperial & the other metric although both are stated to be metric. Luckily I have a lathe & the judicious use of emery cloth on the bushes got them down to a press fit.
Axminster didn't want to know - not even to get the sizes quoted correctly.
 

Deadeye

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Ach. Further troubles. I had for convenience (where the machine is) taken off the narrow, coarse wheel guard. I'd assumed (and I'm s low learner still to be doing that) that the arbour on the other side would be longer for the 40mm fine wheel there - after all, I'm just swapping a 40mm wheel for another 40mm wheel, right?
Well, no. The fine wheel is cut away and there is only 25mm of arbour (which is 16mm despite what RP say/have on other machines) so there's no way the new wheel (40mm thick at the bore) plus bushes will fit.
So options now seem to be to find a different wheel, with a reduced thickness at the bore, or buy a new grinder!
 

Sideways

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Aaah, you're suffering some of my troubles. The big 200x40mm wheel I bought was full width at the centre. The bushes add more width 5mm ish each inside and outside, So that called for a long shaft on the grinder. Not so many of those about. I can tell you the bigger model record just fits with a full set of threads through the nut (on it's 40mm side). The narrow wheel side has a shorter spindle and both sides are 5/8" dia.
You don't have room for, or need in my opinion, the washers intended for use with a ceramic wheel when you fit a CBN.
Good luck in your hunt and check if you are still within the time limit to return the wheel if it's all too much bother.
 

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