# How would you hold this for turning?



## rwm (Oct 5, 2017)

I need to turn down the OD of this specialty washer. It seems to be mild steel. I am not sure of an easy way to hold it. I could make an expanding mandrel to fit the hole but that will be  somewhat complex. Is there a simpler idea out there???






The OD of the washer is about 24mm and I need to take it down to 21mm. 
Robert


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## kd4gij (Oct 5, 2017)

You will need to make an arbor.


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## francist (Oct 5, 2017)

If the I.D. across the two rounded sides was close a common size I would probably grind two flats on a bolt and use that as an arbor. The non-flattened sides would still have threads enough to use a nut or pair of nuts to hold the part. 

Might have to use a narrow parting tool to sneak in between the nuts to make the cut, but if you only have to do one part it wouldn't be bad. Multiples might want a better solution, though.

-frank


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## Technical Ted (Oct 5, 2017)

If it were me, I'd probably try to super glue it to a faced off piece of material and take fairly light cuts. Acetone or heat will loosen the super glue when done. You  might have to use a four jaw chuck to line it up unless your glue job is spot on center. 

Worth a try!
Ted


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## Dave Paine (Oct 5, 2017)

1+ with the suggestion from Technical Ted.

I had parted a thin disc from a piece of steel and as "Murphy" would have it the part I wanted had an uneven face on the parted side.

I used CA glue (super glue) to affix this to a piece of aluminium so I could face off the piece.   If I had needed to fix the OD, this would have been easy.

The part can be removed by either a good tap, or applying heat.   A hair dryer on High setting may be sufficient.  

Whatever is used to mount the work needs to be sacrificial.


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## rwm (Oct 5, 2017)

Thanks all! I have not had good luck using CA glue to hold parts. It may be my glue. Who makes the best CA glue? 
The center hole is 14mm. I think a mandrel is the best option so far. 
Robert


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## Technical Ted (Oct 5, 2017)

Another idea is to find a bolt that will fit through the hole and then clamp the washer between two nuts. Chuck up on the bolt and go to work. You could even us a 3 jaw chuck and then tap the washer to line it up before clamping it tight for final turning.

Edit: Or if the bolt is threaded all the way, just use one nut and the head of the bolt to hold it. Whichever works out better for you...

Ted


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## darkzero (Oct 5, 2017)

I agree with Ted. I do this quite often for small & thin parts except I use 5 min epoxy. Epoxy releases easy with heat & in my case I need parts to be free of any glue residue. Since heat will loosen epoxy, careful not to get it too hot.

I never tried CA so I'm not sure which holds better. My guess is the CA may hold better but CA won't always come off clean on many materials.

In this case since it has a through hole I'd probably go with the mandrel route. You don't necessarily even have to make something with the 2 flats. You can just use a bolt that will fit inside the 2 flats. Drill & thread a hole in a piece of stock for the bolt. Then slightly snug it, if you have one of those ball bearing pusher tools you can use that to get it centered up well enough, then tighten down the bolt. Or use a 4 jaw.


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## mikey (Oct 5, 2017)

I would use a rod with an OD smaller than your 21mm and turn a short section the size of the rounded part of the ID of the washer. The length of the short section would be just shy of the thickness of the washer. If you have them, use collet blocks to cut the flats. Then drill and tap for a bolt or screw to go in the center, slip a washer on the bolt and lock it all down. If you have many washers to do, this would be the fastest, simplest way to securely hold them.


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## randyjaco (Oct 5, 2017)

If you can deal with this cost, Cerrobend or one of its cousins are made to solve such problems.
Randy


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## rwm (Oct 5, 2017)

Technical Ted said:


> Another idea is to find a bolt that will fit through the hole and then clamp the washer between two nuts. Chuck up on the bolt and go to work. You could even us a 3 jaw chuck and then tap the washer to line it up before clamping it tight for final turning.
> 
> Edit: Or if the bolt is threaded all the way, just use one nut and the head of the bolt to hold it. Whichever works out better for you...
> 
> Ted



Ted- this is a great idea. I will try it! That's why I post here!
Randy- I have some cerrobend on hand! How would I best use it in this application?

Robert


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## umahunter (Oct 6, 2017)

Could you epoxy  it to something else and go from there


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## JimDawson (Oct 6, 2017)

I would turn a stub arbor the OD of the washer, this will allow easy centering.  Drill & tap the end of the stub arbor, maybe 3/8-16, and secure the part with a heavy washer and capscrew. Then turn the the securing washer, the part, and the stub arbor to size.  The whole process wouldn't take much more time than it took me to type this. (but I type slow at this time of night )


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## RJSakowski (Oct 6, 2017)

An interesting illustration of the order of operations.  I would guess that the washer was purchased to simplify the fabrication of a custom part which is a great way to go.

Having a lathe and mill, I would be inclined make a piece like this. 
Turn a suitable piece of bar stock to 20mm or so, turn boss with a diameter equal to the I.D. of the keyed washer and slightly less height than the thickness of the washer.  bore a suitable through hole and part.  Move to the mill and cut the flats.  Not having a mill, a little file work will suffice.  The flats need not be perfect, they only serve to allow the washer to fit on the fixture.  Assemble with a suitable bolt, washer, and nut.  The fixture could be made from aluminum to make fabrication easier in the event that hand work was required. 

This is definitely the way I would go if I had multiple pieces to modify




Another option would be to solder the keyed washer to a suitable piece of round stock with acid core solder.  Pre-tin both surfaces to ensure a good bond.  Mount the keyed washer in the lathe chuck and turn to true the fixture to the washer.  Flip it around, mounting the fixture in the chuck and turn the washer to dimension.  Heat with a torch to separate and wipe the washer with a rag while the solder is molten to remove the solder.


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## jim18655 (Oct 6, 2017)

Might be heresy but how critical is the look and finish of final part? Stick a bolt through it and spin with a drill against a running bench grinder.


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## RJSakowski (Oct 6, 2017)

jim18655 said:


> Might be heresy but how critical is the look and finish of final part? Stick a bolt through it and spin with a drill against a running bench grinder.


My assumption was that diameter was somewhat critical.  This would imply the concentricity is also an issue.  Just using a bolt small enough to fit the flats as a mandrel will not ensure concentricity.


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## jim18655 (Oct 6, 2017)

RJSakowski said:


> My assumption was that diameter was somewhat critical.  This would imply the concentricity is also an issue.  Just using a bolt small enough to fit the flats as a mandrel will not ensure concentricity.


That's why I asked. Maybe overlooking the obvious and making it harder than it needs to be.


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## higgite (Oct 6, 2017)

Is the hole in the washer shaped and sized for a close fit on a stud or whatever? Or is it elongated to allow side to side adjustment on a round protrusion? If the latter, concentricity may not be critical and Jim's solution might have some merit. It always helps to know the application to keep folks like me from cluttering up a thread with speculation. 

Tom


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## RJSakowski (Oct 6, 2017)

Tom, you could be right but I would expect the hole to be a slot with the rounded ends the same diameter as the width of the slot.  It always helps to know what the intended use of a part is when deciding what the acceptable .tolerances are.  The desired end diameter will end up with a wall thickness of about 2.5mm parallel to the flats.   Any non-concentricity will reduce that thickness on one side.


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## Jimsehr (Oct 6, 2017)

I would take a piece of stock and face and tap it so a bolt would fit thru center of piece to be turned down . Then I would hold piece to be turned by pinching it to face of the tapped arbor with a washer and a bolt leaving it loose enough that you can use a roller bearing against the OD to true it up . Then tighten it up and turn it.
Jimsehr


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## Frank Ford (Oct 6, 2017)

If the O.D. doesn't need to be precise or exactly round, I'd walk over to the other side of the shop and introduce it to Mr. Beltgrinder, and be done in about a minute. . .


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## Ulma Doctor (Oct 6, 2017)

Hi RWM,
as a suggestion, get a sacrificial carriage bolt and center the washer on the bolt and lock it down with a nut and washer.
you could indicate concentricity as desired before locking it down.
you could center drill the carriage bolt head and use a 4 jaw chuck and tailstock center if accuracy is a necessity.


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## benmychree (Oct 6, 2017)

RJSakowski said:


> An interesting illustration of the order of operations.  I would guess that the washer was purchased to simplify the fabrication of a custom part which is a great way to go.
> 
> Having a lathe and mill, I would be inclined make a piece like this.
> Turn a suitable piece of bar stock to 20mm or so, turn boss with a diameter equal to the I.D. of the keyed washer and slightly less height than the thickness of the washer.  bore a suitable through hole and part.  Move to the mill and cut the flats.  Not having a mill, a little file work will suffice.  The flats need not be perfect, they only serve to allow the washer to fit on the fixture.  Assemble with a suitable bolt, washer, and nut.  The fixture could be made from aluminum to make fabrication easier in the event that hand work was required.
> ...


I would make a nut mandrel with a body diameter to chuck, a turned and milled part like the above writer suggests, then a smaller diameter threaded to fit a nut and washer to retain the workpiece in place for turning; trying to chuck on a nut or bolt head invites inaccuracy, as nuts and bolts are not so concentric hex to threads.  Of course on need consider how many washers need to be machined; simpler, one could make the mandrel chucked with the machined flat detail and make a centered slug of steel to push the part up on the holding part of the mandrel with the tailstock, and so avoid the threaded part for the nut and washer to retain the part for machining.


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## Wreck™Wreck (Oct 6, 2017)

You have not supplied the most important piece of information which will have a profound effect on the choice of work holding,
How many parts, 1, 10, 100, 1000?


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## RJSakowski (Oct 6, 2017)

Intended use and how many parts are often omitted when someone asks a "how do I" question.  It wouldn't hurt for the OP to include the equipment at their disposal and required accuracy as well.  

Perhaps a sticky post in the beginners forum showing how to effectively ask a "how do I" question would help newcomers to the HM forum?


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## Doodle (Oct 6, 2017)

Pair of pliers and a grind wheel.


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## Silverbullet (Oct 6, 2017)

Well I'd turn the hole dia a bout 30 thousandth under width. Then I'd mill the flats , then drill and tap for 3/8" bolt with a sacrificial washer I'd bolt them in the lathe turn to dia , file both edges and remove and repeat. Till orders done.


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## rwm (Oct 6, 2017)

Wow, thanks for all the replies! Concentricity is important but the tolerance is about 0.010. I will need 4 of these. They are axle washers for my electric bike. It has a 14 mm flatted shaft.

Here is what I did: I sandwitched the part between two washers on a 10 mm bolt. Similar to what RJ showed but without the special mandrel. I then mounted it in the lathe and used my ball bearing bump center device to get the OD centered before fully tightening the nut. See Jimsehr's comment. I then took light cuts of .005 to reduce the diameter. Came out great. One is off about .006 and the other about 0.010. Two more to go later.
Robert


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## bfd (Oct 6, 2017)

I have a small 4 jaw chuck ( sherline ) that the part will just fit on that's how I would do it


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## Tozguy (Oct 7, 2017)

Could the last two be ganged on the 10mm bolt and done together?


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## rwm (Oct 7, 2017)

bfd said:


> I have a small 4 jaw chuck ( sherline ) that the part will just fit on that's how I would do it


I have one. Sherline chuck jaws are 8mm thick. Won't fit even with just 2 jaws in the hole.
Robert


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## rwm (Oct 7, 2017)

I spent a sleepless night thinking about making a part with a 0.010" error....

















I feel much better now.

Robert


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## mikey (Oct 7, 2017)

Looks good!


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## rwm (Oct 7, 2017)

While we are considering these washers, is there a coating other than paint that would be useful to retard rust? 
Robert


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