Mandrel shaft

[Doug]

Quite a while ago whilst perusing at a show I happened upon & bought a new madrel shaft in readiness of one day changing my old one, this I did a few months back whilst tidying up the workshop & coming across it again in the safe place I'd stored it (fallen behind my tool chest)

At the time I didn't try the mandrel but very conveniently disposed of the old shaft when I did get to turn a pen I quickly realised the shaft appeared undersized, so much so that I need to shim the shaft with a piece of writing paper.



The shaft measures 6.15mm the internal dimension of my bearing is 6.27mm. As I no longer have the old shaft to measure I wondered if anyone could measure & tell me the size of their shaft (oh-err, no, stop it, titter ye not) I'm presuming that it's 1/4" bar I want, but thought I'd check, many thanks

 

[Phil Dart]

Mine (Rotur) is 6.6mm Doug

 

[Jim]

Doug, i know we have issues with Bushing sizes and i have an over sized rod, have you tried other bushing on the rod?

 

[Doug]

Mine (Rotur) is 6.6mm Doug

That's interesting Phil, I need to check more of my bushings internal dimensions as from the sounds of things they wouldn't fit yours

 

[Doug]

Doug, i know we have issues with Bushing sizes and i have an over sized rod, have you tried other bushing on the rod?

Only tried the slimline & Jr gent bushing if I'm honest Jim, both of which needed shimming

 

[bellringer]

My one measures 6.24 mm they should be centreless ground to I have thought about getting some made but they would be only for people using a mandrel saver is this something people would be interested in?

 

[Walter]

Axminster 6.29; Turner's retreat 6.28; PSI 6.26; Rotur 6.26.

 

[Penpal]

So many variations in this theme making it difficult to be the perfect fit for so many people to fit what you use. Macine bolts of length suitable using the various brasses as go no go guages work perfectly in any collection of any rods from anywhere you will find variations even if you custom order them so I wish you well guys.Also your measuring instrument will vary from mine how tight you bring them together etc, quite a can of worms really.

Peter

 

[Walter]

So many variations in this theme making it difficult to be the perfect fit for so many people to fit what you use. Macine bolts of length suitable using the various brasses as go no go guages work perfectly in any collection of any rods from anywhere you will find variations even if you custom order them so I wish you well guys.Also your measuring instrument will vary from mine how tight you bring them together etc, quite a can of worms really.

Peter

I agree completely Peter, especially as regards the pressure on the digital vernier or whatever instrument is used.

Here is a link to a guide on using calipers:

http://www.google.co.uk/url?sa=t&rc...=DjYOGoAQjUCGwoBGQFDAyg&bvm=bv.96339352,d.ZGU

 

[Phil Dart]

That's interesting Phil, I need to check more of my bushings internal dimensions as from the sounds of things they wouldn't fit yours

Spot the typo Doug - sorry, a naughty little "2" slipped away. Not 6.6 but 6.26. When I make bushings or have them made, the bushing ID is 6.3. Should have gone to specsavers.

 

[wm460]

I will read that link later Walter,
But one thing springs to mind.
I used two digital verniers to make one pen, one pair of verniers at each end of the shed being too lazy to walk less than 26' I used the nearest one.
when I assembeled the pen I found the was 0.02mm differences.

 

[EStreet]

Friends don't let friends use mandrels!

Measure the hole in the bushings and see what you find. ....

 

[Gizmo3k]

I had problems with a new mandrel shaft once - I was using the Rotur mandrel and mandrel saver, bought a different brand of replacement shaft and it was slightly too big to fit. I ended up sanding it down to size!

 

[Normancb]

As said, there are variations between mandrels and in instruments. My four mandrels measured with a decent micrometer are 6.24, 6.18. 6.22. and 6.22mm. I suspect they are designed for a 1/4" bore (6.35mm). I make bushes using a 6.3mm drill which gives a nice sliding fit.

You can get precision-ground mild steel and silver steel rod in 300mm lengths from many engineering suppliers in both metric and imperial sizes

 

[Penpal]

As said, there are variations between mandrels and in instruments. My four mandrels measured with a decent micrometer are 6.24, 6.18. 6.22. and 6.22mm. I suspect they are designed for a 1/4" bore (6.35mm). I make bushes using a 6.3mm drill which gives a nice sliding fit.

You can get precision-ground mild steel and silver steel rod in 300mm lengths from many engineering suppliers in both metric and imperial sizes

I would love a link it would enable me to use the correct terminology when ordering every trade uses their own terms otherwise its like talking Martian I have found.

Ordering from Fuller in America cost me dearly for a ground step drill the owner of this state of the art business failed on three occasions even with brass tubes as go no go guages one of Europes finest the same probs. For smooth fit bushes or mandrel saving I drill undersize and kicking a small end mill at a slight angle in the metal lathe bore in superfine cuts to get exceptional round and clean holes using the edge of one cutter with the endmill. I also gave up buying reamers for the same reason.

Peter.

 

[Grump]

Seems to me another good reason for not using a mandrel?

After reading this I dragged my 4 mandrels out of the drawer and measured with 2 cheap digital vernier gauges and a micrometer.
The mic I trust to be the most accurate although the Verniers did agree which surprised me as they are different makes, years etc.

All 4 mandrels once again from different suppliers in different years vary in size size from 6.19mm to 6.25mm.

I gave away all my bushes because I found them a sloppy fit and bought new ones which also were a sloppy fit.
There is much to be said for turning between centers, a method I still prefer.

 

[Doug]

I've spoken to an engineer friend about this so I'm going to see him on Sunday & get it sorted.
Luckily I have at least one set of all the bushings I use which have the same internal size, then again there should be as I bought the majority from the same supplier, though over the last 10years I have also been given quite a lot of pen turning stuff.

Hopefully I'll be able to report back with progress on Sunday

 

[Normancb]

I would love a link it would enable me to use the correct terminology when ordering every trade uses their own terms otherwise its like talking Martian I have found.

Ordering from Fuller in America cost me dearly for a ground step drill the owner of this state of the art business failed on three occasions even with brass tubes as go no go guages one of Europes finest the same probs. For smooth fit bushes or mandrel saving I drill undersize and kicking a small end mill at a slight angle in the metal lathe bore in superfine cuts to get exceptional round and clean holes using the edge of one cutter with the endmill. I also gave up buying reamers for the same reason.

Peter.

Should have responded earlier - sorry

Silver steel (drill rod in the US) is a water-hardening high carbon tool steel. Pretty much any engineering supplier carries it - do a Google search for "silver steel rod", or try people like MSC, Cromwell Tools or ebay (lots of suppliers). It comes in both metric and imperial sizes in 13" lengths and is precision ground to close tolerances. It's quite tough to machine, but can be turned, sawn, milled and filed. It can be hardened and tempered pretty easily so it's often used to make small tools. Incidentally, there's no silver in silver steel - it gets its name from the bright, ground finish.

The equivalent flat (or square) material is sold as "ground flat stock" or sometimes "gauge plate" - an ebay search for "ground flat stock" will produce lots of suppliers. It's precision ground to close tolerance. Main difference is it's usually intended for oil hardening, not water.

Precision ground mild steel is less common. It's low carbon steel, ground to precise dimensions. It's much easier to machine than silver steel, but not hardenable by heat treatment. If you do a Google search for "precision ground mild steel ", you'll find several suppliers, again both metric and imperial. The range tends to be more limited but its generally cheaper than silver steel.

Whichever takes your fancy, it's worth shopping around as prices can vary a great deal.

Hope this helps