Need recommendation as to parts, please. See photos and video.

scotchleaf

scotchleaf

Joined
Oct 23, 2006
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I'm trying to increase the power (and allow variable speed) of my Craftsman 2x42 sander for grinding knife blades. I sent an email like this to the salesperson at McMaster Carr earlier today, but they responded (after about 10 minutes) with "We looked into it and we can't make a recommendation for your custom solution."

When I asked "Do you have a name for the type of adapter which might work, or the name of a supplier who might be able to help?" They said "We are unable to suggest the adapter type or a supplier that can support your application."

I'm disappointed so far with McMaster Carr, and with Sears for using what is apparently a unique shaft size (though I can't understand why 1 cm is uncommon)
I would appreciate your looking this over and providing recommendations.

I need a (micro v groove?) pulley with a 10mm inside diameter (or an adapter to fit the ID and hub of a pulley) and a 2-4 ft belt for it.

The idea came from this video:

[video=youtube;2qfYT_m2Tw0]http://www.youtube.com/watch?v=2qfYT_m2Tw0[/video]


One problem I've had so far is finding an appropriate wheel for the left side of the craftsman.

Here is what I came up with myself - of course I plan to bolt down the grinder and the rear motor (and come up with some kind of dust shield) and to allow for changing belts via springs or a wedge.

BTVt75z.jpg




It won't work because the rubber doesn't grip the belt well (and its the wrong kind of belt for the rear shaft), and, more importantly, the rubber is out of balance so the machine will be ruined if run at high speed.


As you can see, I'm hoping to use an old treadmill motor which came with this kind of pulley wheel on the rear:



CmNrE3Y.jpg



Here is the shaft on the left side of the Craftsman unit

1zjqlMt.jpg


The measurements for that shaft are 10.07 mm, or 51/128 inches, as you can see below

u2R2gF8.jpg




If possible, I'd like to be able to use this pulley wheel from the treadmill, which I already have:

sfsHo8Q.jpg




the wheel's measurements (inside diameter) are 41.11 mm, and the inch measurements are 1 and 79/128 inches.



Any ideas?
 
Do you have access to a lathe/ friend who has a lathe/ local machine shop? If you're stuck with the 10mm shaft you may need to turn an adapter. Or look for a different pulley set which has the right bore.
 
I think where you ran into trouble with McMaster, is they often cater to engineering companies, manufacturers, etc., and so usually will be supplied with specific specs for a part or set of parts.

For iinstance, if you said I need a pulley set for these shaft sizes, with approx so/so ratio and x horsepower rating, specify keyway, collar, or set screw retention, then you would get a lot further with them.

Some pulleys can be easily bored out, so you can order the next size down and buy a reamer (which would require proper setup on a rigid drill press at minimum, or throw it on a lathe (superior option).

If you search for metric pulleys you may find one with a 10mm bore, but I can't predict how likely it will be to find one with that same grooved belt type. If I was doing this, I would probably end up making a pulley or modifying a stock pulley.
 
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Just like McMaster, I'm not going to tell you what you want to hear - After you go to all the trouble and cost to do this it isn't going to last long. The treadmill motor won't last long as a grinder motor, and the grinder isn't made to take side loads on a very small shaft.


The cheapest method of getting all that cobbled together would be to have a machinist take the old sanding disc hub that fit on the shaft and either turn it down to fit inside the treadmill drive wheel, or screw&glue a piece of material ( nylon, wood, aluminum) to the sanding disc face and turn that down to fit. With a reasonable fit and some epoxy, it will make a receiver pulley for the treadmill belt. Normally that would be a poor idea, but in this case it is probably the best. Don't expect much and you won't be disappointed.
 
I don't know, maybe this is inappropriate but, I feel like a 43 year old lawyer should be able to afford to do this in a manner less "Junkyard Wars" style. This feels more like a Gary Pogue project. Why not buy a real variable speed grinder like a KMG and focus on the craft?

Of course, I build a lot of my own stuff including my grinders. If I were doing this project and I were determined to make the treadmill motor work, I would machine a hub for the large pulley to adapt to the grinder shaft. McMaster sells the belts you need in various lengths. They are called Ultra-Flex J-Section V-belts. You need a 10-rib. They also sell the pulleys in various diameters but the bore is too large and would again, require a adapter hub. Their pulleys might still be the best way to go because they have holes in them on the side so they can be affixed to a flanged hub whereas, your pulley does not appear to have any alternate mounting options. The other issue I see is that there is not a lot of shaft to work with on the grinder and you need to keep the belt as close to the housing as possible. The adapter would probably need to be setup so it can be mounted and tightened first and then the pulley attached.

Good luck,

Bob

Edited to add - Switch your caliper to get rid of the fractions. All machine work is measured in decimals whether imperial or metric.
 
RangerBobTX said:
I don't know, maybe this is inappropriate but, I feel like a 43 year old lawyer should be able to afford to do this in a manner less "Junkyard Wars" style. This feels more like a Gary Pogue project. Why not buy a real variable speed grinder like a KMG and focus on the craft?

Of course, I build a lot of my own stuff including my grinders. If I were doing this project and I were determined to make the treadmill motor work, I would machine a hub for the large pulley to adapt to the grinder shaft. McMaster sells the belts you need in various lengths. They are called Ultra-Flex J-Section V-belts. You need a 10-rib. They also sell the pulleys in various diameters but the bore is too large and would again, require a adapter hub. Their pulleys might still be the best way to go because they have holes in them on the side so they can be affixed to a flanged hub whereas, your pulley does not appear to have any alternate mounting options. The other issue I see is that there is not a lot of shaft to work with on the grinder and you need to keep the belt as close to the housing as possible. The adapter would probably need to be setup so it can be mounted and tightened first and then the pulley attached.

Good luck,

Bob

Edited to add - Switch your caliper to get rid of the fractions. All machine work is measured in decimals whether imperial or metric.
Click to expand...


I agree with that, start with a grinder in the box kit, or at least a NWG and use standard components, buy a used or NOS motor on ebay to save some bucks, but make sure it's the right one.



Edited to add - Switch your caliper to get rid of the fractions. All machine work is measured in decimals whether imperial or metric.
I noticed that too,

51/128 Who can understand that ? the people that came up with that need a kick in the arse.
 
It feels like a mission now: I've challenged myself to do this as cheaply as possible. Also, with two kids and one income, $ is tight.
 
Keep in mind that the price of a grinder in a box kit is a couple days labor, even for someone who makes so-so money.

If it is purely hobby and something you plan doing in your free time as relaxation, then staying within budget can be ok, but remember it's better to buy better once.
 
Cheap, low cost, and economical aren't necessaril synonymous.

You can spend a couple hundred bucks for a cobbled together grinder that will never work like you want it to (and probably end up failing in short order), or you can save yourself a whole lot of time, effort, heartache, and ultimately more money, by building a tried and proven grinder like a NWGS or a GIB.

Just my $.02. YMMV.
 
Put the disc back on. It works really well for flattening handle material. Buy a pyroceam platen liner from USAknifemaker and a short piece of 2"x3" angle and upgrade the platen. Buy a Bruce Bump file guide at the least and if you can swing it buy a Bubble Jig from Fred Rowe. The Bump file guide is carbide faced amd awesome. Use steel that is stable during heat treat so you dont have to grind much after ht, or learn to dunk a lot. Make about 80-100 knives and see if you want to upgrade.

Thats what I'd do (and exactly what I've done/am doing.)

If you pay shipping, I've got a piece of 2x3 3/8 angle of send you, and I could probably even be coerced into drilling and slitting it for you, since I'm going to be doing mine at the same time. Upgrade the platen past the stupid ceramic tile trick is making a huge difference. Huge. My email is in my profile, let me know.
 
scotchleaf said:
It feels like a mission now: I've challenged myself to do this as cheaply as possible. Also, with two kids and one income, $ is tight.
Click to expand...
As cheaply as possible would be using the Craftsman as is and getting some grinder time. That's what I'm doing while I save up for a a KMG or other variable speed grinder. While I agree, it would be nice to slow down the Craftsman and I've thought about it. I've come to the conclusion that I can make a decent blade even with the hyperactive Craftsman and I'll be way ahead of the game once I get a 2x72 variable speed later.

Now, if I was dead set on finishing what you have started. I'd just bolt the treadmill pulley to the center of the existing disk plate on the Craftsman and go to town. Good luck!

P.S. I also did platen mod that medicevans described above, this makes a big difference!
 
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HallHandmade said:
Keep in mind that the price of a grinder in a box kit is a couple days labor, even for someone who makes so-so money.

If it is purely hobby and something you plan doing in your free time as relaxation, then staying within budget can be ok, but remember it's better to buy better once.
Click to expand...

The time would be relaxation, but the issues are: the cost of the NWG, my not knowing how to weld/tap/die, the fact that I'm just trying to make a few knives for myself, and I don't like burning up blades with the super-fast Craftsman's speed.
 
No reason not to do what you plan .... just know that it will be a temporary grinder.

I didn't give any build instructions because I really would prefer you didn't make this conversion, but the basic way to do what you want is this:

First, DON'T even think of trying to turn down the hub while running on the grinder. That will end very badly.

OK, now, get a block of really tight grain hardwood, or a block of nylon/UHMW/hard plastic/aluminum/etc.. The block should be a bit thicker than the multi-groove hub you have from the treadmill, and a little bigger than the hole in the hub.
Sand the block smooth with 100 grit paper on one side, and also sand the sanding disc from the grinder at 100 grit. Glue the block to the disc as close to centered as you can eyeball. Let it cure well.

If the multi-grove hub has any splines sticking out inside it, trim them flush so the inside is a circle.

Set the hub on the block and draw a circle to mark the inside center hole. Again, eyeball it as close as you can. This will roughly be the size you turn the block down to and mount the hub on. Drill the block through the disc so you can run three 3/16" bolts through to hold the block tight to the disc. These should be well within the circle for the hub. Bolt the block to the disc and trim off any excess bolt length. Locktite on the threads is a good idea.

Have someone with a lathe turn the block down using the shaft hub on the disc as the mounting point. Carefully and slowly turn down the block into a circle until it is a snug fit for the multi-groove hub. Don't turn down the disc, as it will be the surface the pulley sits against. When the hub can be pushed on snug, but isn't too tight, stop turning. Epoxy up the mating surfaces and glue the hub on the disc, clamping it tight to the disc surface. Once cured, the new assembly can be mounted on the grinder, and the multi-groove belt installed from treadmill motor to grinder.

All this can be done for nothing to just a few dollars, depending on what you have laying around the shop, your shop skills, and who you know with a lathe.
 
Curious, how many knives have you made on your craftsman and how many blades have you burnt up?

While it's fast it's also underpowered. With enough pressure I can bog down mine quite a bit if I wanted to. For me LIGHT multiple passes are the key to using it. As a hobbyist I'm fine with it for now, while I would love a KMG one day but it's just not in the cards for me for a number of reasons.
 
I'm not trying to be critical but I have a hard time believing the stock grinder is too fast. Top speed on my grinder is 7000 sfpm and it's easily useable when doing a blade, I slow it way down for wood . How fast is the craftsman? Do you keep the blade moving and dip in water to keep it cool? I don't claim to be an expert but a simple technique change might be all you need.
 
bladsmth said:
No reason not to do what you plan .... just know that it will be a temporary grinder.

I didn't give any build instructions because I really would prefer you didn't make this conversion...
Click to expand...

Thanks very much for the idea. Why do you prefer that I don't make the conversion?
 
Wil D. said:
I'm not trying to be critical but I have a hard time believing the stock grinder is too fast. Top speed on my grinder is 7000 sfpm and it's easily useable when doing a blade, I slow it way down for wood . How fast is the craftsman? Do you keep the blade moving and dip in water to keep it cool? I don't claim to be an expert but a simple technique change might be all you need.
Click to expand...

I may well be pushing too hard. The grinder has 4400 rpm Belt Speed, 3500 rpm Disc Speed and I have to dip the blade every few seconds.
 
How fast are you sweeping the blade across the belt? You should be able to push somewhat hard you just need to sweep faster. From plunge to tip on a 4"ish blade is maybe 2 seconds for me. If you're going slower or dwelling in one spot, speeding up the side to side motion should help with not heating the metal too much.
 
What is a Bruce Bump file guide? where do you get one? I looked at his site, but dont see a clear explanation.
 
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