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Is there such a thing as an 'external reamer'?

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Robin Graham26/08/2021 00:20:28
1089 forum posts
345 photos

Apologies for not getting back to this and replying to further contributions sooner - I've been bad in health recently and unable to face going down to the dungeon (aka workshop), so I've been enjoying a pampered superterranean existence.

I have digital scales on my lathe, so in principle I could use the cross slide scale to achieve the reproducible accuracy I'm aiming for. The reason that I was wondering about tailstock tooling is that I need either to (a) change tooling to part off each item, or (b) remove the stock from the lathe to saw Obviously (b) would lose reference, and I worried that (a) would do too. I normally use a Chinese QC toolpost:

qctoolpost.jpg

but I don't know how accurately it relocates the tool after a change. Perhaps I should measure, or maybe someone can tell me.

I'm intrigued by the idea of a cross-slide stop, but at the moment I'm not sure how I could implement one on this machine. I have made a longitudinal stop, and, despite having scales, it's paid make the time of making many times over when doing repetitive work

In the light of Dave S's post, I'll try a home-made tailstock cutter just to see.

Robin

Howard Lewis26/08/2021 09:02:32
7227 forum posts
21 photos

If the stock is large diameter, parting off in the lathe will save your muscles, although wastes more material.

If it needs to be said, ensure that the Tailstock is properly aligned before using a cutter in the Tailstock, to minimise the risk of cutting oversize on OD, and undersize on ID..

Howard

noel shelley26/08/2021 09:43:22
2308 forum posts
33 photos

I did check new relavent rotabroaches and I found 9.6mm or 10.4 ID so no help ? Noel.

Michael Gilligan26/08/2021 10:41:37
avatar
23121 forum posts
1360 photos

Just a thought …

For Robin’s application, the body of a ‘surplus’ drill-chuck could be modified to accept three cutters.

[ no, I’m not suggesting using the jaws ]

MichaelG.

ega26/08/2021 11:08:03
2805 forum posts
219 photos

Robin Graham:

Cross slide stops: I have an album with a couple of photos which might help.

Dave S26/08/2021 12:28:12
433 forum posts
95 photos

Just remembered seeing this:

A rolling blog of everyday life on and around the workbench (shwoodwind.co.uk)

where Stephen uses an ER collet as a cutter.

Dave

Tony Pratt 126/08/2021 17:14:39
2319 forum posts
13 photos

Cross slide stops, you don't need them you have a DRO on your by the looks of it decent lathe? The QC tool post you have has been tested on YouTube many times & will typically repeat within .0005", I may be proved wrong but your 'external reamer' will be a waste of time.

Tony

Robin Graham28/08/2021 03:07:36
1089 forum posts
345 photos

Thanks for further replies. I realise that this is getting into 'by the time I'd written/read all these posts I could have made a hundred' territory, but for me the point of making stuff is not only the finished part, but also learning about tooling and techniques. When I started out I didn't even understand how metal could cut metal, but now I know about HSS and Carbide and Rockwell scales and all that stuff.

Pause to polish fingernails on lapel.

Howard - I once cut a 2" round steel bar with my muscles and a hacksaw. Never again. It looked like it had been chewed through by a mad beaver. I bought a bandsaw.

Noel - I looked at rotabroaches, but I think they are designed with the OD in mind, and anyway I I think the shank diameter is too big to mount in a tailstock chuck. Thank you for checking though.

Michael - food for thought perhaps. Though from your somewhat gnomic reply I'm not sure what exactly you have in mind.

ega - I had a look at your album. Nice work, but I'm not sure that in my case the effort of taking off the saddle to drill for the stop would be worth it as I have a digital scale.

Dave S - I've bookmarked that, An interesting 'DIY' approach.

Tony - half a thou repeatability for the QCTP would be fine - I'm astonished actually, I'd been thinking more like 5 thou, I'll have to measure.

Robin.

 

 

Edited By Robin Graham on 28/08/2021 03:08:50

Edited By Robin Graham on 28/08/2021 03:15:39

Edited By Robin Graham on 28/08/2021 03:17:22

Michael Gilligan28/08/2021 06:56:42
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23121 forum posts
1360 photos
Posted by Robin Graham on 28/08/2021 03:07:36:

Thanks for further replies. […]

Michael - food for thought perhaps. Though from your somewhat gnomic reply I'm not sure what exactly you have in mind.

.

I didn’t have anything exactly in mind, Robin

… it was just a fleeting thought perhaps [or perhaps not] worth sharing.

The empty shell of a 1/2” Jacobs tailstock Chuck [locked-up tight] could be adapted to accept a cutter or three … possibly saving a lot of tool-building time.

MichaelG.

.

33526553-0f4b-4214-b93c-d3cb4e95bc1c.jpeg

Credit: https://toolsmach.com/en/content/14-drill-chucks

Edited By Michael Gilligan on 28/08/2021 07:05:09

DiogenesII29/08/2021 11:29:13
859 forum posts
268 photos

Forgive the truly appalling 'fag-packet' sketch.. ..I hope there's enough information for a man of your experience to see what I'm driving at, and how it might be made to work - something I've been pondering for my own ends..

The bracket / block should just clear the cross-slide body, I think it will be okay as something to bring the slide to a stop against. rather than crash into with abandon..

..I'm rather assuming that your lathe has a pair of bolt holes in the lower front of the saddle?

img_1800.jpg

Tony Pratt 129/08/2021 12:29:24
2319 forum posts
13 photos

Trouble with driving a screw driven slide against a stop is that you can easily ‘overcome’ the stop so losing repeatability

Tony

Andrew Johnston01/09/2021 09:37:33
avatar
7061 forum posts
719 photos

A UK supplier, although still not cheap:

Hollow End Mill

Andrew

Tony Pratt 130/09/2021 12:01:46
2319 forum posts
13 photos

So Robin Graham, was this ever sorted?

Tony

John Reese02/10/2021 01:38:45
avatar
1071 forum posts

I am not sure if anything was sorted out.

An approach that was not mentioned is adapting a dial indicator to the cross slide. Many machinists use a magnetic back dial indicator to make saddle or cross slide travel repeatable.

JasonB02/10/2021 06:56:53
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25215 forum posts
3105 photos
1 articles

But why use a dial indicator when the lathe already has a DRO?

Michael Gilligan02/10/2021 08:13:36
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23121 forum posts
1360 photos
Posted by Andrew Johnston on 01/09/2021 09:37:33:

A UK supplier, although still not cheap:

Hollow End Mill

Andrew

.

Those look useful, Andrew …

“For machining outside diameters such as lugs and recesses in castings. Size range available in imperial and metric from 3/32" to 1" and 3.00 to 21.00 mm”
[these being the bore sizes, I note]

… but I have two questions [one simple, and one perhaps pedantic]

  1. Are they intended to simply be held in a collet by the outside diameter ?
  2. Being end-cutting … Do they really qualify as ‘external reamers’ ?

MichaelG.

Edited By Michael Gilligan on 02/10/2021 08:16:16

Andrew Johnston02/10/2021 09:26:49
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7061 forum posts
719 photos

Posted by Michael Gilligan on 02/10/2021 08:13:36:

  1. Are they intended to simply be held in a collet by the outside diameter ?
  2. Being end-cutting … Do they really qualify as ‘external reamers’ ?

1. No idea

2. A machine reamer cuts on the leading chamfer, not the flutes, so essentially end cutting

Andrew

Michael Gilligan02/10/2021 10:32:46
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23121 forum posts
1360 photos

yes

Robin Graham03/10/2021 00:20:59
1089 forum posts
345 photos
Posted by Tony Pratt 1 on 30/09/2021 12:01:46:

So Robin Graham, was this ever sorted?

Tony

Apologies for failing to report back on this. What happened was that I found that the repeatability of the QCTP was indeed much better that I had supposed as you suggested - perhaps not half a thou, but good enough. So I ended up turning in the normal way, with the aid of the DRO and a bed-mounted carriage stop.

This topic has had over 50 replies and I can't acknowledge every contribution individually, but I have read and been informed by every one - my thanks to all who have replied.

Robin.

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