Proper way to make this part?

[MikeKParticipant @mikek40713]

Hi all.  I’d like advice on making a part.  Moderator, if this is too beginner-ish, feel free to move the thread.

The part is 1″ diameter and 1/2″ long.  It has a through-bore of 0.625″ and a 0.666″ bore that is 0.375″ deep from one end.  I can do all of the work with one lathe setup, but I need the opposite face (the small bore end) to be square to the bore.

I’ve tried a turned spigot and super glued the part, but the bore didn’t clock true after the glue dried.  I then tried another spigot and heat shrinked the part to it, and that resulted in the bore even more out of true.  Is there a preferred method to do this?  Or am I just not doing it properly?

Mike

[Alan CharlestonParticipant @alancharleston78882]

Hi Mike,

There are two ways that I would approach this. Both assume the exposed end has been turned square to the bore.

The first is that if you are confident you can part the work off, then do so leaving a mm or so clearance beyond the finished length. The end will be square to the bore but may not be flat. Insert the piece into a 3 jaw chuck (loosely) and bring the tailstock without anything mounted in it nearly up to the work and lock it in place. Place your finger behind the work and push it firmly up against the tailstock quill. Tighten the chuck while doing this. Then face off the piece to the required length. You can test if this gives parallel faces by trying it out on a piece of scrap before doing it on something you have invested some time in.

The second method is to get a piece of square tool steel which will fit between the chuck jaws set for 1 inch and sits up against the face of the chuck. The work is then snugged up in the chuck with the turned end facing the chuck and hit with a soft hammer as the chuck is fully tightened. If done properly the square behind the work will probably need to be driven out. Then the exposed face is turned to the correct length and should be parallel with the other face.

I’m not sure if these are the best ways of achieving what you want, but I’ve used both methods in the past successfully.

Regards,

Alan C.

[JasonBModerator @jasonb]

Similar to Alan you can use something parallel against the 3-jaw face to push the previously turned face against as you tighten the jaws. Don’t forget to remove it before starting the lathe.

If you have soft jaws for your 3-jaw chuck then they can be machined with a step that acts as a “back stop” for the good fac eto be pushed back against. I use this method a lot.

I’m not sure why your spigot/arbor method is not working, unless you are removing it from the chuck part way through

[JasonB]

On JasonB Said:

…you can use something parallel against the 3-jaw face…

Maybe if he has never done so in the length of time he has owned the lathe, it would be worth removing the jaws from the chuck and verifying with a gauge that the face of the chuck is true.

Another method is to skim the outside when boring the inside (so ID and OD are concentric). Then, when it is flipped over, it can be dialled in in a four jaw chuck.

A method I have seen described for washers might also work: face both ends while still attached to the parent stock, make the larger diameter counterbore and do the 0.625″ bore last, which also parts off the part.

The stock between left side of part and chuck jaws will need reducing in diameter to a little less than 0.625″ diameter so you can face the chuck side of the part. It is quite wasteful of material.

The blacksmith way of doing this would be to take 5/8″ round stock and upset the end of it until it exceeds 1″ diameter or to take 1″ diameter stock and draw out a 5/8″ tail on it so it could be gripped in the chuck.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, another way is to make a split bush as shown below.

Just face off a suitable size piece bar and drill a large hole that is smaller than the piece you are working on, then cut a slice off, and hold it in your external chuck jaws with the side you faced off, flat against the jaws, and then cut the recess to fit the diameter of the piece you need to finish, making sure you undercut the inside corner slightly, so your piece sits flat into the back of the recess. Then cut the slots with a hacksaw, holding it in a vice with protective jaws, so you don’t damage the machined faces. You then mount the bush in your external jaw chuck, with the slots in-between the jaws, and holding the piece you wish to face off, and making sure it’s pushed back flat with your tailstock, while tightening the jaws.

Regards Nick.

[Chris GunnParticipant @chrisgunn36534]

I would proceed as you have so far, and part off, and just hold the part in the 3 jaw and face it off to length, even if the bore does not run true, the end faced off will be square to the OD, and thus the bore. Unless of course the chuck is extraordinarily bad. No need to faff about really for all practical purposes it should be fine.

Chris Gunn

[Martin ConnellyParticipant @martinconnelly55370]

As shown in the split ring photo if you are going to mount a ring on a spigot there must be clearance in the corner of the spigot or a chamfer on the ring. Otherwise your part does not sit true. I suggest remaking the shoulder on the spigot and undercutting the spigot slightly at the internal corner to ensure the (probably) sharp corner of the ring is not sitting up on a radius. This is also important when using soft jaws.

My preference is to use a mandrel between centres and machine both faces at one setup when parallelism and/or thickness is important.

Martin C

[HOWARDTParticipant @howardt]

Why not turn the part completely from with the shared face out wards from the chuck.  The 0.666 bore can be opened out before parting off from the other end.  Where features are critical to one another they should always where possible be machined in the same holding process, even dedicated tooling will impart some degree of error into a second work holding.

[MikeKParticipant @mikek40713]

These are all very helpful responses.  Thanks gents.

The lathe is the ubiquitous 7x Chinese mini-lathe, although I have one of the better prepared brands with the long bed and better finish.  The 3-jaw chuck face may be good enough?…I just now measured 0.0005″ TIR at the edge of the face, with the center of the face (where the part will sit) barely registers any runout.

I’m going to make up a few more blanks to try the suggested methods.  The bush is for the spindle of my 8″ bench grinder.  I’m following Harold Hall’s “Tool and Cutter Sharpening”.  Unfortunately, my grinder is too large to fit my lathe.  My quick measurements show that the rotor alone would just miss fitting, but I’d have to disassemble the grinder to know for sure.  I just might be able to get it to fit if I set the rotor between centers and push the tailstock to hang off the bed a tad but that’ll be my last resort.

I think first up is pushing the part against some parallels against the chuck face.

Mike

 

 

[MikeK]

On MikeK Said:

…………………………

I think first up is pushing the part against some parallels against the chuck face.

Mike

 

As well as using flat parallels to space a part forwards in my 3/4 jaws, I also keep a stock of old bearings.
It doesn’t matter is they are roller or ball, but the inners and outers will be ground very close to parallel
Separate the parts, and keep a pile of inners and outers to act as round parallels.
The likelihood is that you won’t be able to remove them after tightening the jaws on the  workpiece, and obviously you don’t want them rattling around.
A long thin strip of some sort of foam around the outside of the bearing, will keep it roughly central and prevent rattling.

Bill

[old martParticipant @oldmart]

To get a flat face on a disc square when reversing it in the chuck, I often use the nose of the tailstock drill chuck with the jaws withdrawn and the tailstock locked to the bed. The quill can be used to position disc accurately.

[JasonBModerator @jasonb]

How does that work as you will be pushing against a possibly sawn surface

[old martParticipant @oldmart]

I would get the faces skimmed before boring the hole.

[JasonBModerator @jasonb]

But still leaves the problem the OP is asking about and that is how to get the second face true to the first.

[MikeKParticipant @mikek40713]

I going to take another stab at this today.  I recently disassembled the grinder to see about setting it up in the lathe, although the spindle has no center drilled ends.  I also cleaned and repacked the spindle bearings.

[old martParticipant @oldmart]

Sorry for getting confused, I got muddled up. The OP’s first post says the part is 1/2″ long, not a disc as shown in later pictures.

I have drawn a rough sketch of the piece and now think I have a different method. Bore the small diameter and face the end in the same chucking first. That makes the bore true to the hole. Those are the only tight requirements mentioned. Turn the work round and bore the larger diameter.

I would use a four jaw independent for precision work, although all the chucks at the museum are 0.002″ tir at any diameter, and yesterday I chucked up a piece of 25mm aluminium and turned it round in the three jaw scroll that happened to be fitted at the time, (a 15 year old Chinese K11 125mm) and got better than 0.0005″ tir. The overlapping diameters looked like it was turned in one pass.

[vintage engineerParticipant @vintageengineer]

It’s quite simple. Machine everything from one end and then use a back facing tool to face the back face to length.

[vintage engineer]

On vintage engineer Said:

It’s quite simple. Machine everything from one end and then use a back facing tool to face the back face to length.

… with the work-piece held how exactly ?

MichaelG.

[Howard LewisParticipant @howardlewis46836]

FWIW, my advice would be to do as much machining as possible, before disturbing the workpiece.

In this way diameters will be concentric and faces square to the lathe axis.

Hopefully, as long as you don’t force things, the parted off face should be reasonably flat.

You are going to clean it up by facing, anyway.

In any case the work can be pressed against the step in the chuck jaws, or against a spacer (An old bearing race is a very good idea), for the final operation(s).

The workpiece will be located using a face that has been machined square to the lathe axis, so the final op should result in a face that is parallel to the other end of the work.

Howard

 

[Ian PParticipant @ianp]

This might be a silly question coming so late into the thread, but the OP has stated that the part he wants to make is a cylindrical part with closely specified details and particular reference to both ends being parallel.

OP says ‘The bush is for the spindle of my 8″ bench grinder’.

Obviously I dont know all details but if the bush is for centering an abrasive wheel on a grinder then the ends of the bush do not need to be square and could even be hacksawed at an angle.

Maybe the bush the OP wants is for some other purpose than ensuring wheel concentricity.

Ian P

 

 

[Ian P]

On Ian P Said:

if the bush is for centering an abrasive wheel on a grinder then the ends of the bush do not need to be square and could even be hacksawed at an angle.

Maybe the bush the OP wants is for some other purpose than ensuring wheel concentricity.

Ian P

My apologies if I’ve been less than clear.

The bush sits on the grinder spindle to provide a larger surface for the flange that presses against the wheel.  The factory “lip” on my grinder spindle is unbelievably small, only 20 thou in height.

Attached is a picture of the first bush that I made, not fully installed.  I will heat shrink it into position to avoid galling and I don’t want to use adhesive.  It will sit almost entirely on the larger diameter to the right of the bearing, with about 1/16″ sitting on the smaller diameter.  The wheel flange then presses against this larger face.  Then the wheel, outer flange, and nut are fitted.  I’m literally following Harold Hall’s book, except for dimensions and I won’t be using adhesive.

It’s the outer face that needs to be square to the bores.  The inner face doesn’t matter, except if necessary for chucking to machine the outer face.  The entire spindle is quite long and doesn’t fit on my mini-lathe, although I’ll have a try with the fixed steady rest.  The spindle ends are not center drilled for mounting between lathe centers.

Mike

[Dave HalfordParticipant @davehalford22513]

In which case don’t forget the wheels mount with cardboard either side, you don’t need anything like the spec you are striving for.

[vintage engineerParticipant @vintageengineer]

By holding the work piece in the chuck with a gap between the work piece and chuck face!

 

[vintage engineer]

On vintage engineer Said:

By holding the work piece in the chuck with a gap between the work piece and chuck face!

 

I assumed that was what you were proposing … but I failed to see how you would avoid the risk of either damaging the chuck, or tool, or leaving a residual lip on the workpiece.

Not saying it’s impossible … just that it may not be “quite simple”

MichaelG.

[bernard towersParticipant @bernardtowers37738]

ON the dia that holds the bearing should there not be a close fitting spacer that protrudes through the bearing fixing plate and that is where the backing washer for the grinding wheel sits. The spacer should be just long enough to extend beyond the 20 thou step. Possibly?

[Author]

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