Taper Mandrels

[ChrisHParticipant @chrish]

[ChrisHParticipant @chrish]

I would be pleased if some light could be shed on taper mandrels please.

As I understand it, a taper mandrel has a fine taper which holds a small item requiring work to be done to it.

What I am unsure about is what is the norm for the included angle of the taper – 1 degree?, more?, less? – and what is the mandrel small end diameter relative to the work being held, that is, is the small end the same diameter as the bore of the work item or slightly smaller, if so, by how much? My thoughts are that the taper must be very fine and the small end diameter a tad smaller than the work bore, but I have no idea how to quantify this.

In use, say using MS for the mandrel and something soft like brass or bronze for the work, would one bore the work to exact diameter before mounting on the mandrel, or after, thus allowing any marking or distortion caused by the mandrel to be cleaned up? The latter seems more obvious if the work could be held to final bore it but concentricity might be a problem, but I have never used a mandrel before and thus have no experience with them.

Many thanks for any information on using mandrels,

Chris

[JasonBModerator @jasonb]

1deg should be plenty. You want as little play in the parallel part of the mandrel as possible as that is what registers in the bore and the taper is just to hold the item. You generally bore to finished size and then use the mandrel to get at the bits you were holding it by to bore.

J

[ChrisHParticipant @chrish]

Ah, Jason, are you saying the mandrel has a predominately parallel part and just a wee taper on the end. If so, I didn't know that – but it makes more sense to me.

Chris

[JasonBModerator @jasonb]

Yes most is parallel and then it just tapers out at the chuck end.

[ChrisHParticipant @chrish]

Thanks Jason, your answers seem to have cleared using taper mandrels up for me, much appreciated,

Chris

[Nigel McBurney 1Participant @nigelmcburney1]

Commercially made taper mandrels are tapered for their full length,hardened and ground,the work piece is usually reamed to size then pressed onto the mandrel, the taper is about 1.5 to 2 thou over length,and usually marked plus at the large end,the centres are recessed so that pressing or hitting the end of the mandrel does not damage the centre, they are generally used for between centres turning or used between centres of a dividing head on the mill,for light gear cutting etc , they can produce very accurate work but if buying second hand make sure that they are not bent. The mandrels usually have a machined flat at each end for the clamp screw of a lathe carrier.

[John Stevenson 1Participant @johnstevenson1]

I agree with Nigel's post, never seen any parallel ones and then a taper unless home made ?

Most of the use I have used them for in the past is on grinding machines. Problem with them is you need hundreds of the damn things to cover only a short scale of sizes.

[JasonBModerator @jasonb]

Yes I. Was talking about home made ones, Harold hall describes the same thing here and I think Sparey and Mason have also

 

Edited By JasonB on 06/03/2014 22:42:15

[John Stevenson 1Participant @johnstevenson1]

OK Jason, we were talking about different animals then.

Just threw a handful of rusty pitted ones away a few weeks ago and one orphan the other day, saved them as bar stock but too hard to do anything with.

[LambtonParticipant @lambton]

I have a few Jones & Shipman taper mandrels, inherited from my Dad, exactly as described by Nigel. Does anyone know if this type are still made and where can I buy some more ?

I know that Arc sell a variety of useful looking expanding mandrels but I find the tapered type very useful for precision work between centres.

Eric

[mickParticipant @mick65121]

A taper mandrel has a 0.003'' taper over its entire length. 0.001'' under at one end and 0.001'' over at the other. you probably won't even need to set the compound slide off the zero mark to achieve it.

[JasonBModerator @jasonb]

Mick, -0.001 to + 0.001 is only 2 deg over the length?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 07/03/2014 09:16:11:

Mick, -0.001 to + 0.001 is only 2 deg over the length?

.

Jason,

Don't you mean thou ?

MichaelG.

[ChrisHParticipant @chrish]

Jason, thanks for your link to Harold Hall's website explanation, all you ever wanted to know about taper mandrels simply explained!

Chris

[JasonBModerator @jasonb]

Yes Michael I meant thou but its still two and not three

[John McNamaraParticipant @johnmcnamara74883]

I have a set that in some ways work like ER collets in reverse, The taper is the bore the outside is parallel. There is also a set of centred and ground tapered mandrels that fit inside the Taper bored collets.

The set covers from about 12mm to 40mm.

This set is similar: **LINK**

Regards
John

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi ChrisH ,

Mandrels are used almost exclusively for second operation work . That is when the bore is finished to size and some or all other surfaces have to be machined true relative to the bore .

A simple example would be a pulley or gear blank . A common model engineering example would be a cylinder block having end faces skimmed .

Between centres taper mandrels are examples of friction hold mandrels . Work is run along the taper until it locks by friction and after machining pressed off again .

There are many other types of holding device for second operation work – here are just a few :

Parallel between centres mandrel with one step and nut or two nuts .
Fresh turned single ended mandrel with or without nut .
Expanding mandrels and collets as mentioned .

Any type of mandrel with a specific shape turned on it – for instance a Morse taper so that a sleeve can be held by the taper for grinding the outside . Sometimes need nuts to push the work off again .

Machined in place soft jaws .

Note that the simple bore holding mandrels do not require any accurate side faces to exist on work – accuracy of mounting is detemined by bore only .

Where mandrel has register steps and nuts at least one face and ideally two on workpiece have to be machined accurately relative to bore before mounting on mandrel otherwise they may not run true . An example is a loco wheel casting – back and bore premachined before mounting on mandrel to turn the treads .

Regards ,

Michael Williams .

PS: A quite skilled turner in work years ago had some fun when using a between centres mandrel to turn some blanks out of a high Nickel alloy .

As he turned the end faces the initially tight blanks kept migrating along the mandrel . Combination of high expansion alloy and some heat build up was the simple cause – though no amount of coolant would stop the problem entirely .

Edited By MICHAEL WILLIAMS on 07/03/2014 12:44:04

Edited By MICHAEL WILLIAMS on 07/03/2014 12:48:42

[jonathan heppelParticipant @jonathanheppel43280]

Why are taper mandrels used with an arbor press? English as she is spoke I guess.

[mickParticipant @mick65121]

Hi Jason.

How can you work out the angle without knowing the length?

[ChrisHParticipant @chrish]

Hi Michael, many thanks for your explanations, much appreciated,

Chris

[Nigel McBurney 1Participant @nigelmcburney1]

The mandrel that gets the most use is a one inch dia on which I mount various milling cutters for cutter grinding, I bought this second hand,my smaller ones I bought new forty odd years ago I think they were Jones and Shipman another fine company gone for good when governments let our engineering industry go to the wall, I have not seen any new ones for sale,probably no use in modern production engineering now that wonderful things can be cnc machined with little second op work.

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