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plunger
09-21-2011, 01:13 AM
A mate of mine does jewellry. He cuts stones with a diamond blade that is about a 120mm by 0.35mm thick.The hole in the blade is 16mm. This is where the problemstarts. THe bolt that is on his machine is 1/2 inch so he has problems lining up the blade so it is running true.He has asked me to make a washer of sorts to eliminate this problem but I dont know how to machine such a thin washer Any suggestions? It is called a graves machine but I havent seen it as all he gave me is the nut and blade.

Arthur.Marks
09-21-2011, 01:24 AM
This kind of task is all about workholding. Use either soft "pie" jaws on a lathe chuck to hold the outer diameter (think Taig) or an emergency collet. Cut OD to size from solid. Drill pilot hole much smaller than finished washer ID. Part to thickness required. Turn soft jaws or emergency collet to size. By this, I mean bore a recess to the OD of the washer and at least as deep as the washer's thickness. Then machine a second step roughly at the diameter of your finished washer's ID. Mount work in chuck/collet. Slowly bore out the ID of the washer to the size you want. Use light cuts.

elf
09-21-2011, 01:28 AM
Use super glue to hold the blank, turn it to size, then use acetone (or fingernail polish remover) to release it.

armedandsafe
09-21-2011, 01:50 AM
The first thing I'd do is get two more nuts of the proper size. (Two, so I can screw one up.)

Chuck up the nut and face it true on the side which will meet the blade. Then face it, leaving a 0.35mm +0-.01 ridge, 16 mm in diameter. That means the wall of the ridge will be about 1.65mm thick.

This might not work, but it is the first thing I'd try, before trying to make such a thin piece.

Pops

darryl
09-21-2011, 02:05 AM
So you need a spacer which is .35 m thick, 1/2 inch ID, and 16mm OD. Start with a piece of bar at least 16 mm in diameter. Turn it down to about 3/8 diameter for about 3/4 inch, and face the part from the 3/8 diameter to the full OD. Part it off leaving about .07 or so in thickness of the larger diameter. Then reverse it in the chuck, turn the OD down to 16mm, then face off until you have .35 mm thickness left. Switch to boring and go straight in making a 1/2 inch diameter bore. The washer part will come right off, properly sized all around, and needing only deburring.

Joel
09-21-2011, 02:30 AM
I must be missing something.
Chuck a piece of round, face, drill/bore ID, turn OD, part off a .3 washer (a bit less than the thickness of the diamond blade, or saw it off since it is only a spacer).

philbur
09-21-2011, 02:49 AM
Presumably the blade is mounterd with a flange on either side so: Make/use a thicker washer/flange at say 30 mm diameter with a 16mm upset on it at 0.3mm high.

Alternatively make a second washer/flange for the other side of the blade that fits over a 1mm x 16mm diameter upset on the other washer/flange.

Alteratively look at a sltting saw arbour. 16mm shaft with shoulder, blade between two washers with an end cap to clamp the whole lot together.

Phil:)

Black Forest
09-21-2011, 03:08 AM
You don't need to make a washer. Just take the nut and face one side leaving the spacer you need part of the nut. Just as on an angle grinder nut.

philbur
09-21-2011, 03:32 AM
The blade probably needs to run true to a reasonably high degree of precision/concentricity.

Phil:)


You don't need to make a washer. Just take the nut and face one side leaving the spacer you need part of the nut. Just as on an angle grinder nut.

winchman
09-21-2011, 06:22 AM
Nuts often don't run true to their threads, so I wouldn't count on that approach working.

What would work better is to chuck up a piece of scrap round bar, thread the end leaving a shoulder, mount the nut on the stub thread, and then machine the locating shoulder on the other end of the nut. That way the shoulder is going to run true to the threads regardless of how well the nut is made.

Don't remove the stub thread from the lathe chuck until you're finished modifying the nut(s).

Black Forest
09-21-2011, 06:24 AM
OK, good point. So make a new nut and make all the features without unchucking and then part off.

SGW
09-21-2011, 07:01 AM
I like the idea of making the stepped nut. The other ideas are good too.

Here's another way of doing it, in case none of those ideas appeal to you. Get a piece of 0.30mm shim stock and clamp it down tightly to your milling machine table sandwiched between two very flat pieces of aluminum that are perhaps 6mm thick. Proceed to drill and ream the 1/2" center hole through the sandwich. (This operation could also be done on a lathe faceplate, if need be.)
Remove the sandwich, extract the piece of shim stock with its 1/2" hole, and mount it in the lathe on a true-running stub arbor sandwiched between two flat washers that are a bit more than 16mm in diameter. Proceed to turn the assembly down to 16mm.

torker
09-21-2011, 07:10 AM
I must be missing something.
Chuck a piece of round, face, drill/bore ID, turn OD, part off a .3 washer (a bit less than the thickness of the diamond blade, or saw it off since it is only a spacer).
That's what I thought of also...

loply
09-21-2011, 07:49 AM
That's what I thought of also...

Exactly?

Just take a piece of round stock, drill out the ID, turn down the OD, and part off...

You can part the thing as thin as you want.

If precision is required then part slightly oversized and lap on a surface plate. This will also improve the finish from parting.

I wouldn't bother attempting to hold and turn a 0.3mm thick washer... You could I suppose, but what's the need?

philbur
09-21-2011, 08:03 AM
But what about the precision/concentricity of the thread on the shaft.

Phil:)


OK, good point. So make a new nut and make all the features without unchucking and then part off.

philbur
09-21-2011, 08:05 AM
The washer needs to be 0.3mm not 0.3"

Phil:)


That's what I thought of also...

coalsmok
09-21-2011, 08:16 AM
If I understand correctly you are making a bushing to make the blade run cocentric with the arbor, correct?
If that is the case make a heavy washer with the bushing machined onto it. Just copy what ever features the current flange has but include the bushing in the center.

davidwdyer
09-21-2011, 09:51 AM
"Graves" is the brand of the saw. They also used to (and maybe still do) manufacture faceting machines.

Making a kind of collar/washer with a step in it would be easier than trying to make a thin washer. You just have to be sure that your "step" is slightly thinner than the cutting blade. I think that there is room for a thinnish washer between the blade and the nut. I can check at the office when I get there is necessary.

lynnl
09-21-2011, 11:19 AM
Holy smokes! That sounds like an awfully flimsy blade! 120mm OD by .35mm thick...???

Are there flanges supporting it for much of the diameter?

I can't imagine you'd need all, or most of that 120mm dia for cutting diamonds. ...unless you're working on some real whoppers!

(ooops, reread it) ...well gems of any sort.

davidwdyer
09-21-2011, 11:36 AM
It's thin because with valuable gem material you want to lose as little as possible.

In the case of the quartz family, Amethyst, Citrine, etc. sometimes that isn't large enough. You only get half the blade to cut with and really even less than that with the nut, axle, table and other stuff. It's not uncommon to have to cut from both sides and then break the middle.

With the thin blade, you have to work slowly and carefully.

philbur
09-21-2011, 11:45 AM
I'm confused, I thought punger was the quy with the question and he is in South Africa, you are in Brazil. How do you know the brand name of his saw.????

Phil:)


"Graves" is the brand of the saw.

rowbare
09-21-2011, 11:52 AM
I'm confused, I thought punger was the quy with the question and he is in South Africa, you are in Brazil. How do you know the brand name of his saw.????

Phil:)
I
It was mentioned in the original post:



It is called a graves machine but I havent seen it as all he gave me is the nut and blade.

bob

philbur
09-21-2011, 12:48 PM
Thanks, now I'm not confused.

Phil:)


I
It was mentioned in the original post:
bob

armedandsafe
09-21-2011, 02:28 PM
Holy smokes! That sounds like an awfully flimsy blade! 120mm OD by .35mm thick...???

Are there flanges supporting it for much of the diameter?

I can't imagine you'd need all, or most of that 120mm dia for cutting diamonds. ...unless you're working on some real whoppers!

(ooops, reread it) ...well gems of any sort.

Looking at the pictures of the machine, it appears as if you are using the flat of the "blade" to cut the gem. This is a facetting tool, not a parting/cutting tool.

http://www.gravescompany.com/faceting.htm

Pops

davidwdyer
09-21-2011, 03:27 PM
Looking at the pictures of the machine, it appears as if you are using the flat of the "blade" to cut the gem. This is a facetting tool, not a parting/cutting tool.

http://www.gravescompany.com/faceting.htm

Pops

What you see on this site is their faceting machine, not their saw. And yes, you do use a flat disk to "cut" which is actually a grinding process. "Cutting" gems is really a misnomer.

Some larger diamonds used to be "cleaved" by hitting them in an exact location, along a natural cleavage plane, with a chisel and hammer thus the "cutting" terminology. This is something which only an expert would determine by studying the crystal very carefully. Now that they have better sawing blades and better techniques I'm not sure if they cleave them any more.

Paul Alciatore
09-22-2011, 12:42 AM
Presumably the blade is mounterd with a flange on either side so: Make/use a thicker washer/flange at say 30 mm diameter with a 16mm upset on it at 0.3mm high.

Alternatively make a second washer/flange for the other side of the blade that fits over a 1mm x 16mm diameter upset on the other washer/flange.

....

Phil:)

I like these two ideas. 0.3mm = 0.0118" so I highly doubt you can "part off" that thickness with any confidence. Besides, if the shaft/arbor is threaded, that thickness will not allow centering unless the thread is 0.15mm pitch or less.

darryl
09-22-2011, 01:05 AM
This whole thing about diamonds reminds me of a show I watched some decades ago. A guy was sitting there sweating, had this huge diamond set up and he was going to cleave it. If he did it right, a beautiful multi-faceted diamond emerges- if he screws up, millions of dollars go down the drain with one hammer blow and somebody blows his brains out. Old black and white film- don't remember what happened.

Anyway- yeah, I don't think you can machine that washer as a separate part unless as someone suggested you glue it to a faceplate for the final thinning. I like the idea of incorporating it on the nut, though it's not always easy to mount the nut concentric enough. Often enough, once you remove the nut and put it back on again, it will have some runout. Best way to deal with that might be to single-point the threads in the custom-turned nut. For me anyway, that always seems to work out better.

winchman
09-22-2011, 01:45 AM
Is there a way to dress the wheel after it's been mounted?

malbenbut
09-22-2011, 02:57 AM
Most thin washers are punched out off sheet material, its no big deal to make a punch for round washers you dont even need a press for that thickness just a hammer to hit the punch. Mount material on wood board and hit punch with hammer. Job done.
MBB

Joel
09-22-2011, 03:15 AM
I highly doubt you can "part off" that thickness with any confidence.
http://img.photobucket.com/albums/v186/JoelinTX/Spacer363.jpg

First attempt took just under 15 minutes from finding stock, to cutting off the flange left from parting (perhaps the trickiest part). I only rate maybe a 30 on the Stevenson proficiency scale, but this was just too easy not to go and verify. In my haste, I was aiming for .32 like a fool, and I undercut. Should have shot for .35 and sanded it down a hair if needed.

Keep in mind that, even if the thin blade was a correct fit for this machine's shaft, it would similarly have added runout from the threads.
I don't think there is much doubt that the highest accuracy would be obtained by boring a pair of relatively thick flange washers to a snug fit on the threaded shaft and turning one side with a raised center to a tight fit for the blade. Relieving the opposite side eliminates the depth tolerance and will add durability, so that seems likely a good idea. Not sure super accuracy is really necessary here, but at least the user wouldn't have to worry about losing the spacer.

One thing is for sure, anything will be a whole lot easier and more accurate than what the OP's friend has been living with by simply eyeballing it.

davidwdyer
09-22-2011, 05:24 AM
Here is the site for the saws.

http://www.gravescompany.com/trimsaws1.htm

I agree with Joel. At least one washer with a raised center. The center dia. will need to be undersized so that the nut will still put pressure on the blade.

I don't think the shaft is threaded all the way. If I remember, there is a smooth part where the blade rides.

philbur
09-22-2011, 05:40 AM
You will need to make sure the inside corner of the step has a zero radius. The alternative yto avoid this is to reccess the existing flanges by say 1.5mm deep and x 16.5mm diameter each and then make a 3mm long sleeve. This gets around the corner radius issue.

Phil:)

Black Forest
09-22-2011, 05:56 AM
Philbur that is a good idea to recess the flanges and make a sleeve.

Why didn't I suggest that? I know, I wasn't smart enought to think of it!

Circlip
09-22-2011, 06:56 AM
In most cases it's never neccesary to make an adaptor "Washer" to mount cutting discs whether abrasive or milling types.

Piece of 1" (or 25mm) Dia bar, turn end to precision Dia (16mm) to fit bore of blade x 5 or whatever long, bore to suit machine mounting shaft and part off. We now have a sleeve that is concentric on diameters and square faced to bore.

Now make a clamping "Washer" 16mm bore x 5mm (Or whatever to suit previously made spiggot) deep, bore to suit machine shaft and part off.

You now have a "Carrier" for the blade which should go onto the spindle without trying to fanny about with "Shims"

egards Ian.

philbur
09-22-2011, 01:47 PM
It looks like it's a table saw so extending the spindle will put the blade in the wrong place.

Phil:)

aboard_epsilon
09-22-2011, 03:10 PM
ive made spacers for big stuff ..

like wood circular saw blade ..and i put aluminium wire in the holes ..

the aluminium will deform when you tighten it ..
and sort out all the problems .

all the best.markj

rivett608
09-22-2011, 08:40 PM
I have done this a bunch of times..... chuck a bigger than 16mm brass in the lathe..... turn outside dia., drill out under size, bore w/ boring bar or just a lathe bit with enough clearance. ...... grind a thin cut off bit... maybe .015" or use a "ThinnBit".... I grind mine from 1/8" cobalt stock, I stack two together to get me to a 1/4" high.... cut it off. I have done this on a Taig dozens of times... even cut off parts as thin as .005" thick....... make sure it free machining brass.

darryl
09-22-2011, 08:57 PM
Speaking of adapters for the table saw blades- I made one to replace the separate pieces they were using (and losing )- it's basically a step on a blade stabilizer disc to adapt a 1 inch hole blade to a 5/8 arbor. But the funny part of this is that the new guy at work mounted a blade the other day without the adapter- I never saw anybody move so fast to shut off the saw- by the time I heard the vibration and looked over, the motor was coasting to a stop and the blade was moving up and down by about 3/8 of an inch :o

KEJR
09-22-2011, 09:00 PM
I apologize if I haven't read through the other threads properly, but if you are trying to align a 16mm (0.629") disc hole to a 0.5" shaft why not make a adapter to go over the 0.5" shaft that has a 16mm boss on it? I haven't drawn it, but I think this wold work? when you tighten the bolt it would lock the blade to the adapter to the shaft.

KEJR

Silverback
09-24-2011, 09:56 PM
The problem with a lot of the answers is that anything thin and washer like is not going to want to center well on a threaded shaft, and I suspect that you don't have room really put something thick in there.

I like the idea of cutting a centering step on the nut, but like someone else noted, threads in nuts are rarely centered in the nut, so the solution is to get a bolt with the same thread, put it in the lathe chuck with the head behind the chuck jaws, tighten the jaws down on the bolt and thread the nut onto the threads sticking out of the jaws, that way the bolt threads are pretty close to centered in the jaws, square and then the nut threads are centered on it about as close to what you'd get with the nut threaded and tightened against the hub. Then just face and cut the shoulder.

You might get some variation depending on how well the threads are rolled on the bolt vs the saw's arbor, but it will be about as close as you're going to get unless you want to take the saw's arbor apart and chuck that up in the lathe to use to hold the nut that you're cutting, and it should be much better than any reasonable thickness stepped washer.

DATo
09-25-2011, 06:47 AM
I've had to do this many times in my career and in my opinion if ABSOLUTE concentricity is required then SGW's method is the way to go.

The only thing I'd do differently would be to turn the stub arbor to a shoulder, the depth of cut on the X axis of which would be a few thousandths of an inch less than the thickness of the workpiece, then sandwich the workpiece with a keeper plate which has a center-drilled hole supported by a live center to turn the OD.

SGW suggested using shim stock of the exact size, and that's a good idea, but if this is unavailable you could also just flycut a piece of stock as a baseplate, then clamp your oversized (thickness) material to it using screws or small C or toolmaker clamps, and flycut to the exact thickness by lowering your mill the required amount from the reading of the baseplate cut. This will insure a parallel thickness over the surface of the part. Then drill (or better yet REAM or BORE) the hole to the exact size, cut out (saw or otherwise remove excess material) with the OD oversized and then go to the lathe to turn the OD over the stub of the arbor which will have the lathe's inherent concentricity built into it provided you do not disturb it after turning the arbor diameter.

I liked what Joel accomplished as well. You could just drill and bore the ID extra deep to the exact size and attempt making the cut-off feeding VERY slowly with the parting tool exactly squared to the workpiece. This would be far faster than the method outlined above but it might take several parts before you nail the thickness exactly. I'd use this approach first but I don't feel it is as "guaranteed" to produce the same level of perfection as the one described by SGW. It all depends on what level of accuracy you are willing to accept. I think with aluminum Joel's way is fine but with steel I'd go the other route.

IanPendle
09-25-2011, 09:41 AM
Talking of cleaving diamonds, I remember reading an account of a famous incident of this. It concerned one of the largest diamonds ever found – I forget it’s name now. The diamond was huge but was acknowledged to have some flaws in it. It was purchased by a syndicate at auction and sent to Amsterdam to THE expert diamond cutting company. Their panel of experts studied it intensively for days and then decided the best strategy for cleaving it into the most valuable combination of pieces. Come the day, it was set up and the expert amongst experts deputed to do the cleaving. He took up his hammer and favourite chisel, and gave it a whack. There was a horrible ‘crack’ sound and the guy doing the cleaving fainted. When he was revived, it turned out that his chisel had broken! The diamond was undamaged. Eventually, perhaps after a stiff brandy, and he was persuaded to have another go. This time it worked according to plan and the resulting flawless pieces netted the investors a handsome profit.

Ian

DATo
09-25-2011, 06:24 PM
Ian,

I can relate. I've come close to fainting a few times in my career too on projects not nearly as important. *L*

IanPendle
09-26-2011, 02:30 AM
DATo,

Yes, I can relate to it too. I read about it many years ago and it always stuck in my mind. The state of his underwear was not mentioned!

Ian.