Building the Worden Grinder - the unexpurgated version

Some while ago, MEW printed my articles on building the Worden grinder; the article was serialised over issues 174 through 176. For reasons that still escape me, the text was heavily edited in the introductory sections, and the bits that were edited out made their way into a letter from me in the Scribe a Line page of issue 175.

I have just finished adding the article to my website in its original form, so you can now read it as it was originally intended:

**LINK**

Regards,

Tony

Quote " For reasons that still escape me, the text was heavily edited in the introductory sections, and the bits that were edited out made their way into a letter from me in the Scribe a Line page of issue 175."

Tony,

Whippets are a protected species in certain parts of the country.

With respect to all the kit suppliers out there, I just cannot see £400 worth of bits here, even with the motor.

The only reason I have not bought a tool and cutter grinder kit, is the price. Instead I have bought a couple of dismantled lathes (complete with DRO's in one instance) for less than half the cost of this particular kit, with which to build a tool and cutter grinder.

Then I found someone who is happy to regrind my cutters at very, very reasonable cost so the pile of bits have found their way into the "not urgent" pile

graham.

Graham;

I debated for years, then Neil Hemingway was in il-health, and I thought I had missed an opportunity.

Finally, about a year ago I purchased a kit, had it sent overseas (including metric frame 220v motor) and think it's great.

Is it worth it? Is the brass for my Ivatt 2-6-0 cab worth it?

I ponder the costs so much that my wife just says "life is too short, just buy it"

Current project is doing the Thomas Rolls from Hemingway; nice to have all the bits in one box, as (for me) purchasing materials is long-winded and expensive proposition.

I do have some bits on the Worden on my web site: http://cnc-for-model-engineers.blogspot.com

Just my boxing-day opinion;

Another Johns.

I feel you are missing the point.

It's not just £400 worth of bits.

It's the cost of buying in material, stocking it, cutting it to length for far more choice than just this one kit.

Sourcing, buying and stocking all the ready made ancillary parts.

Then packing and shipping and getting a fair return so you can be around to supply other kits to other people in the future.

True you look thru a packing list and think "I can buy this for £x and this for £y so why are they charging £X+Y+ ? " But you never regard your time, labour as part of the equation and that is a very big part.

Looking at it logically. if it was that profitable there would be plenty of people doing just this.

many on this board are retired so time isn't an issue. My advise is to go for it and make a fortune.

Whippet in, whippet out, and wipe it.

Dennis

I would like to jump in here, regarding the Alu. carrier for the grinding wheels. they have a reduced dia. screw that slides in the slot in the motor shaft and a brass pressure pad opposite retained by a grub screw. I find that they come loose ever

y time I use the wheel. Any one have an answer to this?

Clive

Clive,

If I understand correctly what you describe ... this can only give support along two diametrically opposed lines.

If there were two pressure pads (say 30° to 60° apart), then there would be three-line support, and therefore much better stability.

Note: This may be bonkers, if I have misinterpreted your description!

MichaelG.

I've had a Worden for several years and never had this problem until a recent wheel carrier I made, the threads for the screws were just a little bit loose, solved the problem with a bit of PTFE tape round the grub screws, you could also try a dab of thread sealing compound, I've used this in the past to 'firm up' a screw that will be loosened and tightened occasionally.

John, with respect, having been self employed as both a wholesale supplier and a retailer for more years than I care to remember I don't think I am missing the point.

I just think that this - for me - is not a value for money package. I would certainly encourage somebody to "go for it" as competition is a terrific thing for the consumer but it is not something I could do right now as I am quite busy thankfully. It is certainly something that is an opportunity though.

The model engineering community is often thought of as a bit of a "target audience" but look at the size of the attendance to the shows, these people could easily be customers. And God knows I think we could all use a drill sharpener that a) works and b) is affordable.

graham.

Thank you MichaelG, that does make sense. I followed the drawing and fully expected it all to work but it is disconcerting to find the wheel moving when sharpening. It not only moves back but can wobble a bit.

I will re-appraise the set up and let you know once I have tried it. I may need a bit of time for this though.

Clive

Clive,

Not built a Worden or used one or even studied the drawings but i do have a good grasp of modern electric motors and the way they are built up today isn't conductive to a precision grinding technique.

For a start modern motors have very loose bearing fits by engineering standards. When I strip a motor down for mods it's very common to just be able to pull the rotor with bearings on out of the end shields.

Also to aid manufacture and tolerances there is rarely any method of controlling end float, the usual way is a wavy washer at the non business end.

This means any axial load on the shaft will push the rotor backwards.

If I was using one of these modern motors for this application I would secure the front bearing into it's housing with a keep plate such as older motors used to fit.

Failing this I would secure the rear bearing into it's housing with a bad of loctite and relocate the wavy washer to the front housing, basically pushing the rotor back as far as possible from the start.

I think Harold Hall's idea of using a cheap bench grinder is a good one, By machining the ends of the shaft while it is running in its own bearings ensures it is true and machined to a good finish and accurate (If non standard )size. Together with John's suggestion about dealing with end float you finish up with a quit useable motor at a lower price. One extra step would to be to balance the rotor while it is out. Harold Hall's wheel mounting method also ensures the wheel runs true. The only thing I would add to Harold's design is to key the hub to the shaft so it is safe to run the motor in either direction. One thing I found with the bench grinder I used on my cross vice tool grinder was that one bearing was loctited to both the shaft and the housing. this resulted in me damaging that bearing in removing it. Replacing the bearings anyway with good quality bearings is probably a good idea. The motor will probably need to be dismantled anyway to access the ends of the windings to make it reversible.

Les..

For a start modern motors have very loose bearing fits by engineering standards. When I strip a motor down for mods it's very common to just be able to pull the rotor with bearings on out of the end shields.

Also to aid manufacture and tolerances there is rarely any method of controlling end float, the usual way is a wavy washer at the non business end.

The whole idea of the wave washer is to put a controlled axial preload on the bearings. As the force exerted by the washer is not very large, the bearing next to it (normally the non-drive end) has to be a sliding fit in it's housing.

The reason for the axial preload is to ensure that the bearing balls rotate & don't skid when the motor is run unloaded. This has been standard electric motor design for many decades.

I can't recall the motor shaft on my early Wordon moving under load, but I will check next time I use it. I think that mine has an East German motor fitted. It came "finished" from a Myford open day sale - IIRC I paid £75 for it. Whoever had built it obviously wanted to use it quickly - no paint & rather rough & ready worlkmanship all round. A query on a forum (can't recall which now) brought forth a set of the original drawings, which show that the original builder modified the machine from the published design.

The original design has the bearing block & guide rail next to the grinding wheel, where it picks up grit and gets stiff very quickly. I have only used iy to finish turning tools, as I have no confidence that i could control the table feed accurately enough to try thr ends of end mills. On the "jobs to do" list is to replace the plain cast iron bearing block with a linear ball bushing and design a stop arrangement (the original builder's modification to the angle setting arrangement removed the "as designed" stops).

Nigel B,

John -

I believe there are parts of the country where they are bred for the table...although I would have thought a breed with more flesh on the bones would have been preferable!

Regards,

Tony

Edited By Tony Jeffree on 27/12/2013 15:12:20

Not if you want spare ribs!

Wippets don't have spare ribs.

Everything inside the fur is needed...............

Good read

Thank you

> I think Harold Hall's idea of using a cheap bench grinder is a good one, By machining the ends of the shaft while it is running in its own bearings ensures it is true and machined to a good finish and accurate (If non standard )size.

For my grinder I used a cheap machine mart grinder, but rather than using Harold's approach, I fitted an aluminium alloy spacer for a diamond wheel which I turned with the grinder shaft between the pre drilled centres in it on the lathe. The end result is that I can gently touch the diamond wheel with a fingertip when running and feel no vibration at all.

Neil

" The end result is that I can gently touch the diamond wheel with a fingertip when running and feel no vibration at all."

Just the smell of burning flesh

Martin P