advice on purchase of bench grinder full price or offer grinder

[Brian Deakin]

Which bench grinder would you buy

Model	AT8SRG2
Nett Weight	30kg
Power	900W (230V)
Rating	Trade
Speed	1,425rpm
Voltage	230V
Wheel Diameter	200mm
Wheel Width	32mm
Bore Size	1.1/4"

for $225

or


Model - RBG150D
Rating - Engineer
Power - 375W 230V 1ph
Voltage - 230V
Speed - 2,900rpm
Wheel Diameter - 150mm
Wheel Width - 40mm
Bore - 32mm
Weight - 18kg


half price at $100

I intend to use the grinder primarilary to sharpen turning tools

[John Hart]

I would buy the cheaper one....not because it's cheaper but because I like higher speeds, the wheel is wider, and it consumes less power.

Cheaper is just a bonus

[Reed Gray]

For me, the more heavy duty the better. Speed really isn't much of a factor. You may have problems finding wheels with a 1 1/4 inch bore though.
robo hippy

[Dane Riley]

6 inch diameter is on the small side for sharpening turning tools. Why such a large bore?

[Bill Boehme]

Definitely the larger one. The smaller one wouldn't be able to handle CBN wheels. The slower speed of the larger one is just fine. It is a four pole motor and the other is two pole. Four pole motors run smoother because of less torque ripple.

[Clint Bach]

Have you considered none of the above? The six inch wheels eliminate the six inch one for me. The large shafts limit the wheels available. Do these even come with wheels? If not that is an additional expense.

C

[Olaf Vogel]

Four pole motors run smoother because of less torque ripple.

Interesting...I had to Wiki that one.

I experimented with various motors on my lathe (since it takes a generic 3 phase motor mount).
A few surprises came out of these experiments.

A 10 hp 2 pole motor, is (roughly) the same size/weight as a 7.5 hp 4 pole, and smaller than the 5 hp 8 pole.
I finally settled on the 5 hp, 880 RPM one. Mostly because it needed less mechanical gear reduction to get down to my speeds.

Very smooth (as you say), will run as slow as I want, and has a ton of torque. (I've named it the e-Hemi!)
Plus I can double the RPMs via the VFD if I want higher RPM.

But I'd never heard of torque ripple - thanks!

[Leo Van Der Loo]

For me, the more heavy duty the better. Speed really isn't much of a factor. You may have problems finding wheels with a 1 1/4 inch bore though.
robo hippy

32 mm or 1.25 inch bore is an industrial standard bore size, (and larger) CBN wheels are sold with that size bore as well.

http://solutions.3m.com/wps/portal/3...=7582983&rt=r3

[Brian Deakin]

Thank you to everyone for your posts and the points raized eg bore size and availabiity of stones and cost I have done some research and think this may be an option

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£117.55 Inc. VAT £97.96 Exc. VAT ✔ Available Qty Follow Product Code: BG200WL

Standard Delivery - 1-3 Working Days or Less* (*Subject to stock availability, Next Working Day option available on selected items at checkout)

Product Features & Specification

High power induction motor suitable for workshop use. Fitted with aluminous oxide grinding wheels which are suitable for general sharpening and grinding applications. Includes water tray for cooling hot materials. Features built-in wheel dresser for cleaning, sharpening and trueing grinding wheel surfaces. Equipped with fully CE approved safety guards and wheel location flanges to meet current EU abrasive wheel regulations. Motor and switch gear meet CE low voltage and EMC directives. Fitted with a BS approved safety plug. Pivotal work light for added visibility in poorly illuminated areas. 550W/230V High power induction motor. Suitable for general grinding and sharpening operations. Includes water tray for cooling hot materials. Features built-in wheel dresser for cleaning, sharpening and trueing grinding wheel surfaces. Supplied with one coarse and one fine wheel. Supplied with eyeshields. Pivotal work light for added visibility in poorly illuminated areas. Model No. BG200WL High power induction motor suitable for workshop use. Fitted with aluminous oxide grinding wheels which are suitable for general sharpening and grinding applications. Includes water tray for cooling hot materials. Features built-in wheel dresser for cleaning, sharpening and trueing grinding wheel surfaces. Equipped with fully CE approved safety guards and wheel location flanges to meet current EU abrasive wheel regulations. Motor and switch gear meet CE low voltage and EMC directives. Fitted with a BS approved safety plug. Pivotal work light for added visibility in poorly illuminated areas.

my thoughts were to use to tke my time and regulary quench the tool

[Paul Gilbert]

I thought that you weren't supposed to quench HSS tools. I have never done that to my Thompson's either. At any rate the only time that the tool should get really hot is when you are regrinding the shape. Touch up grinding should be done frequently and gently.