Contact Wheel sizes

Hi,

I'm starting my belt grinder build based on Michael Clerc's design. Now I've got a dilemma that I'd like help on.
What size contact wheels should I get?
I'd like to eventually try hollow grinding rather than just wedge type blades and I'm considering buying two - the postage is cheaper than if I were to decide to buy another in a couple of months.
Currently I'm thinking 100mm (4 inches) and 200mm (8 inches).
Should I be looking at the 150mm (6 inch) wheel instead of one of the other two or not?

I reckon that with both sizes I should be able to do just about everything I need and I'm also considering poly coated platen rollers so I'll have 2 inch (50mm) wheels to grind on as well.

For info so far I've only got the motor - 60 dollars from a fella down the road and it's a 2HP 1500 RPM model.
Gonna pick up a drill press this weekend and order some taps etc as well.

Only problem I have so far is that the motor doesn't have what I'd expect to be called a keyway, just some sort of built in key on the shaft and so I'll need to cut my own keyway on the pulley when I get it.

Thanks,

Paul

Am 8" and 4" wheel would serve you well. I would also think about getting a 2" if you want to do thin grinds,

Charlie

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Originally Posted by spazola

Am 8" and 4" wheel would serve you well. I would also think about getting a 2" if you want to do thin grinds,

Charlie

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Thanks for the info, I'll probably pick one up a little while down the line. I was considering using the platen rollers more for shaping the tang than actually hollow grinding but I can see the benefit of having a third that I can fit on as a contact wheel too.

I have a 2 inch contact wheel on the upper location on my flat platten setup. That way, I get double duty out of one setup. +1 what Charlie said.

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Originally Posted by BakerandBadger

Thanks for the info, I'll probably pick one up a little while down the line. I was considering using the platen rollers more for shaping the tang than actually hollow grinding but I can see the benefit of having a third that I can fit on as a contact wheel too.

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That is what I do, I have a 2" on one end of my platen and a 3" on the other. I just rotate the platen when I want to use either wheel alone.

Charlie

Just out of interest, below is a diagram of blade hollows along with the corresponding wheel size that was used to grind them:

Attachment 127600

They are from the notes of Ken Hawley, taken when he interviewed Bill Hukin, the man once called the Last Razor Grinder In Sheffield (he died in the mid 1990s - some say 94, some 95). At the time, Bill Hukin was working for John & William Ragg at the company's London Works in the 1970s.

The 'thin' blades (rattler, half rattler (faux frameback) and swedish rattler (frameback) had straight-ground sides, so presumably a much larger wheel was used. Other forms, like more modern double-concaved and other types of full hollow use a number of different wheels for one blade.

Regards,
Neil

Cheers Neil. So based on this you don't need bigger than a 5 inch wheel?

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Originally Posted by BakerandBadger

Cheers Neil. So based on this you don't need bigger than a 5 inch wheel?

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Paul - it depends on the width of the blade and the type of profile. For instance, if I recall correctly, for a simple concaving of a 7/8th inch wide blade a 10 inch wheel gives a wedge, an 8 inch wheel gives a quarter hollow and a 6 inch wheel gives a half hollow.

On the diagram above, I assume that the 'common hollow' means quarter hollow, that the blade width is 5/8th inches and the wheel diameter is 5 inches;
the 'middle hollow' most likely means half-hollow and the wheel diameter is 4 inches;
the 'full hollow' is what it says, and the wheel diameter is 1 and 3/4 inches.

All the above were done on stones though, stones that were regularly dressed and which decreased in diameter. Once they had got smaller they were used for smaller width razors, of for fuller hollows, so there is every likelihood that there is a fair margin on each of the given diameters. When they were too small for razors, they were passed on the knife, pocket-knife and pen-knife grinders.

Another thing to consider with the smaller diameter wheels used for full hollows in the region 3" and 2" diameter (depending on the width of the razor) is that these were not always used in conjunction with other stones. In Sheffield the tradition in hand grinding dictated the use of one stone grinding rather than the German double-grinding machine ('Hexe' - means 'witch' in german, where opposed stones were used for one part of the blade and smaller pairs of stones for other parts of the blade. This gives rise to 'walking' a narrow stone down the width of the blade - an art form in itself. Not that 'walking' the grinding stone down the blade was not practiced in Germany.

Yet another thing to consider is the bellied profile, or double-concave, which leaves a ridge of slightly thicker metal about one quarter to one third of the width of the blade above the bevel, and for which two different diameters of stone were necessary. A small one for near the spine, and an even smaller one near the bevel. At the meeting point is the belly or ridge, which acts as a stiffener. Most usually associated with double-wetstone-grinding machines, but not always so (I do mean 'wetstone' rather than 'whetstone' - water was used as a coolant).

Of course, things have changed very much over the years. In the old days an apprenticeship of seven years duration was necessary, and the art was passed on by skilled men who had learned from other skilled men. Nowadays there is not that body of skilled men left, and we usually end up teaching ourselves, and simpler grinds on larger wheels like 8 inches or so is the norm. Not that achieving a perfect grind is by any means easy.

A simple way to see what you need is to gather a few razors together which you would like to emulate, and cut card wheels of different diameters and fit them up against the hollow. With 5/8th and 6/8th razors I have found that 4 inch, 3 inch and 2 inch diameters are most common, and it is not unusual to find that none of the card circles you have made match-up perfectly with the hollow of the blade, which soon shows you how common it was to walk wheels and use wheels of different diameter on the same blade.

I restore blades rather than make them, but I only have a 4 inch and a two inch wheel contact wheels. They hardly ever fit any old blades perfectly. Contact wheels cost an arm and a leg over here, and most US makers will not ship to the UK - I know, I've asked plenty. I keep meaning to make up a series of various diameter semi-circular 'formers' if you like to be used in conjunction with a movable short platen under the belt, but never seem to have the time to get round to it.

Regards,
Neil

Wow Neil, thanks for the great info.
I know what you mean about arm and leg but i think I've found a cheaper source.
I noticed that the Alygrinder (or Maxi Grinder as it's now known) is made with wheels from Spain - so I contacted them.
For a 100mm * 50mm natural rubber wheel (no bearings) its about 55 Euros plus postage. The 200mm wheel is only 77 euros!!!! I got these prices TODAY so I'm gonna order me one of each when I get paid next week. Shipping is about 30 euros so for about 160 euros I'll have the two wheels I want and they are in 70 shore natural rubber which I've heard is better than the artificial rubber wheels for what we are doing.

Another question, as I'll be fitting these onto a threaded bar/stud which will then be fixed into a pair of pillow block bearings at the end of the tool arm. Is there a recommended size for the bar? I was originally thinking M12 (about 1/2 inch) but I'm wondering if I should go a little bigger to ensure a sturdier axle - need to make my mind up as the hole will be drilled as per my requested size.

Cheers,

Paul

I'd go with a thicker axle. 1/2 is plenty if the wheel is mounted very close to the arm. but if there is a significant spacing between the wheel and the arm, thicker is better. I'd go for 3/4 in that case.