Accu-finish sharpener

RC99 · Dec 15, 2014

I was thinking of making something like the Glendo Accu-Finish grinder..

I have this geared motor on hand... It runs at 145rpm

If I attach an 8" 600 grit diamond lapping wheel US 200mm 8" Diamond Flat LAP Wheel Grit 600 Lapidary Jewelry Grinding Polishing | eBay to it along with a rest... I think it should work OK..

tdmidget · Dec 15, 2014

That is a grinding wheel not a lap. Three things to worry about here.
1. They don't know lapping from grinding
2. The diamond concentration is "perfectly high". That's not exactly an industry standard term.
3. There is no recourse on a chinese manufacturer.

CBlair · Dec 15, 2014

I doubt that motor will handle the load once you put a tool to it....but if it does work then hop to it!!!

Charles

RC99 · Dec 15, 2014

tdmidget said:
That is a grinding wheel not a lap. Three things to worry about here.
1. They don't know lapping from grinding
2. The diamond concentration is "perfectly high". That's not exactly an industry standard term.
3. There is no recourse on a chinese manufacturer.

1. I am not really sure there is a difference.. AFAIK lapping just means low speed grinding with very fine abrasives.. it is still a grinding process..

2. For the price I doubt there is a massive concentration of diamond material, but enough for limited use.. Thick diamond wheels from moretrusted manufacturers are big $$$.. but proce of diamond has obviously dropped a lot over the years as synthetic diamonds become easier to make..

CBlair said:
I doubt that motor will handle the load once you put a tool to it....but if it does work then hop to it!!!

Charles

The motor is 260 watts or 1/3hp @ 145rpm... Big enough for a lap.. The motor/gearbox is US built out of a microfiche machine..

Pete F · Dec 16, 2014

Sweet as Bro!

I thought 600 might be a too coarse for lapping. I have a wheel, but I'm not sure what grit it is off the top of my head, not what I'd think was coarse anyway, and it just eats carbide! Could you try it with a cast iron on other sort of lap with impregnated diamonds from paste?

Richard King · Dec 16, 2014

Bob the host of the Kansas City class bought a set of those types of wheels. 200, 600, 1200 and i think 2000 grit for $65.00 on ebay or something like that and he bought a Chinese slow speed grinder from the green bear store. It had a lightweight wheel on it and he put the lapping disk up against the side of it and it worked slick. That little motor does look a bit small, but hell nothing ventured nothing gained. in the Swedish class we made an arbor and put a Glendo 1200 grit wheel in his lathe and made a wood block cut at a 5 deg angle. I lousy picture but it's attached to the right side of the green machine and has a round tool rest. ( having a hard time seeing the pictures as I had one eye fixed and one eye is getting fixed next Monday (Cataracts). Rich

TGTool · Dec 16, 2014

I've got the motor base from an otherwise worn out food processor I've been saving for just such an experiment. It's relatively low speed - I think I clocked it at roughly 600 rpm and by weight seems hefty enough. I have some friends who are interested in scraping but are retired on disability and low incomes so if there are low cost ways to help them get useable tool sharpeners it's a good contribution.

Richard King · Dec 16, 2014

Good Idea TG...I bet one could find one of those old 2 beater cake mixers at a Salvation Army store or Good Will and buy a slow motor for cheap and rig up something...:-)

Scottl · Dec 16, 2014

Please post pictures of the finished rig and some feedback as to how well it works.

Mcgyver · Dec 16, 2014

RC99 said:
1. I am not really sure there is a difference.. AFAIK lapping just means low speed grinding with very fine abrasives.. it is still a grinding process..

they're quite different. Lapping is abrasive cutting where the grit is embedded in a non-sacrificial material - ie cast iron - and very often of the geometrical accuracy of the lap is important in determining the out come. For example a lapping plate or cylindrical internal lap. Grinding on the other had has the abrasive bonded together and is sacrificial.

viewing the action in the context of sharpening the end of the scraper, I can see how the ops might look similar so it might seem like splitting hairs, but both processes get used so many different ways, it would be a mistake to start thinking of them as the same.

since its posted in scraping, the intended use is carbide scraper sharpening? what do you see as the advantage of the slow rpm?

TGTool · Dec 16, 2014

The hook I've always had for distinguishing grinding and lapping is that lapping uses a free abrasive. The most dramatic mental pictures are the free abrasive machining (FAM) setups with a large rotating plate, several smaller rings holding a group of parts, and pressure platse on top of the the parts in the restraining rings. My sense was that the abrasive slurry was constantly recirculated as it worked its way out and was slung off the edge of the plate.

The claims for the process are interesting too. They can produce very flat surfaces (if the lower plate is maintained) and very parallel surfaces between the top and bottom if desired. To get all the parts in the ring parallel, they're just randomly rearranged a time or two so the net effect is like surface plate flattening by successive comparisons and rotation. You can imagine that with random errors in thickness initially, the pressure plate over the whole group will wind up producing a wedge shaped assembly. By moving individual parts around, tall and short get averaged out to parallel.

Mcgyver · Dec 16, 2014

TGTool said:
The hook I've always had for distinguishing grinding and lapping is that lapping uses a free abrasive. The most dramatic mental pictures are the free abrasive machining (FAM) setups with a large rotating plate, several smaller rings holding a group of parts, and pressure platse on top of the the parts in the restraining rings. My sense was that the abrasive slurry was constantly recirculated as it worked its way out and was slung off the edge of the plate.

free abrasive lapping is a subset, cutting can be by both embedded abrasive and rolling abrasive....buts a just a (smallish?) subset. Lapping as you use for sharpening a scraper has the abrasive embedded in the lap (which becomes the cutting tool) The lap itself remains largely untouched (unlike with the free abrasive use you described).

I don't mean to sound like gods gift to lapping, I've done some done flat and and a bunch of internal cylindrical, but the greater part of my knowledge comes from "Handbook of lapping polishing"...I'm quite prepared to be wrong in the face of superior knowledge

Scottl · Dec 16, 2014

Quite a few decades back I worked at a company that made equipment for spraying hot melt glue. The gear type pumps used all metal to metal seals. The pump parts were all surface ground as matched sets and then hand lapped using a cast iron lap. The rotating parts were lapped just a little bit more time than the pump body for clearance.

Pressures were extremely high as the molten glue was pumped through steel braided hose to the nozzles. When new hoses were required we crimped the fittings on with 4 segment tapered dies using a rig with a bottle jack for power. The worst part of a rebuild was removing the hardened and baked on glue.

RC99 · Dec 16, 2014

This feels like the Spanish Inquisition at times..

TGTool · Dec 16, 2014

I don't expect anyone here intends to be abrasive but we've all been lapping up bits of knowledge for so long we're anxious to polish any bits we think we have. The adamantine opinions may come across a little rough but after a series of posts it usually sorts to the nitty gritty.

I will stick to my loose abrasive opinion though, whether it's embedded first or simply embeds itself in the process of introducing the lap, the workpiece, and the abrasive to each other. Even when not intentionally embedded first the usual advice has been to use a softer material for the lap so that the abrasive embeds there and scours the workpiece. Finished size and shape may be a function of both the lap's accuracy and/or of the action between the lap and workpiece if they're stroked as one might in honing. So one case might be a shape used to lap a mold cavity where the shape of the lap is transferred to the work. Another might be the small hole laps such as these just down the page here where only a portion of the lap is the desired size of the hole and it must be worked along the length of the workpiece.

And also it may be a matter of nomenclature getting us confused or of course I could simply be wrong about all of this.

JST · Dec 16, 2014

Dunno about the semantics.....

But the original Accu-Finish works extremely well. If the shop-made one is anything lik it, it will work very well also.

The combination of slow speed and water-coolant makes the diamond wheels OK for steel as well as carbide.

aerodark · Dec 17, 2014

Partial Gratuitous Thread Hijack Warning!

Is the secret formula that they sell for making coolant hooey? Can kerosene, synthetic coolant, other be used more economically with good results?

JST · Dec 17, 2014

aerodark said:
Partial Gratuitous Thread Hijack Warning!

Is the secret formula that they sell for making coolant hooey? Can kerosene, synthetic coolant, other be used more economically with good results?

I just put a tiny amount of detergent in water and go with it. Been doing that for years, and it works fine. No magic. The water has to "wet" the wheel, which the detergent makes happen.

Mcgyver · Dec 17, 2014

RC99 said:
This feels like the Spanish Inquisition at times..

haha, where are are those red hot pokers when you need them

MCritchley · Dec 17, 2014

JST said:
I just put a tiny amount of detergent in water and go with it. Been doing that for years, and it works fine. No magic. The water has to "wet" the wheel, which the detergent makes happen.

Windex or any glass cleaner works too. It also cleans up Cannode spoting ink.

Accu-finish sharpener

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Titanium

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Attachments

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Stainless

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