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Metric or Imperial

This topic has 35 replies, 10 voices, and was last updated 18 November 2013 at 10:20 by Oompa Lumpa.

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16 November 2013 at 19:37 #17214
Oompa Lumpa
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@oompalumpa34302
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16 November 2013 at 19:37 #135732
Oompa Lumpa
Participant
@oompalumpa34302
First off – this is not a criticism, more a bemused observation.

I have recently bought a Century Mill in "as new" condition. It has the X and Y handwheels, as you would expect, in fractions (which is a bit confusing to be honest 1000ths would have been better) but now I have noticed that both the Z axis and the Quill fine feed are in Millimetres?

Is this normal or am I missing something?

A scale in Millimetres or even 1000ths of an inch would be good – are such things available? A "stick-on-Scale"?

graham.
16 November 2013 at 19:41 #135734
Oompa Lumpa
Participant
@oompalumpa34302
Sorry, the Mill is in the "Imperial" configuration hence I say "as you would expect" Just for clarification.
16 November 2013 at 20:05 #135736
Sub Mandrel
Participant
@submandrel
! I didn't think any modern machines had fraction dials!

How many graduations on the dial and what pitch leadscrews. If 64 graduations and 1/16", then close enough to a thou over short distances (e.g. for applying a cut) but over 2% error so no good for precision work over more than about 1/4 – 1/2". My lathe has a 1/16" pitch leadscrew and I have this annoying issue.

The other leadscrews on my lathe are 1mm/40 division and 0.025mm is close enough to 0.001" for most things.

A 1.5mm pitch leadscrew with a 60-division (0.025mm) handwheel gives the same 0.3% error, so is usable over a couple of inches for most purposes. My mill has the 1.5mm pitch leadscrews, but the handwheels have 75 0.02mm divisions making imperial work a mind-bender. I must fit 60 division handwheels…

Neil
16 November 2013 at 20:31 #135737
JasonB
Moderator
@jasonb
My old imperial Emco lathe had a handwheel on the end of the leadscrew with 125 divisions of 0.0005"each eg 16tpi. Can you post a picture as unless its a very coarse leadscrew you won't get many divisions even if its 128ths of an inch.

For a stick on scale why not stick on a DRO

Edited By JasonB on 16/11/2013 20:32:53
16 November 2013 at 20:45 #135738
JasonB
Moderator
@jasonb
Just had a look on the Chester forum and some of there other mills have 0.0625 div handwheels on 16tpi leadscrews which is indeed a PITA so quite likely teh century is the same in which case a DRO is the only real way to sort it apart from changine to metric leadscrews, nuts and handwheels which are likely to be 2mm pitch, may explain why it was for sale.

J

Edited By JasonB on 16/11/2013 20:47:20
16 November 2013 at 21:30 #135741
mickypee
Participant
@mickypee
Why not fit the machine with a DRO which will have an option to switch between metric and imperial. Probably cost around £400 which you might spend converting the machine any way. Very accurate and takes care of any wear that it might have. I have DRO's on my mill and both lathes, couldn't imagine life without them.

Mike
17 November 2013 at 08:44 #135758
Michael Gilligan
Participant
@michaelgilligan61133
Just an aside …

It was quite common, until at least the mid-1960s, for American draughtsmen to work in 1/128ths of an inch.

I had hours of fun trying to understand all the strange dimensions on the drawings for a Polaroid 5×4 film holder … until I realised that it had been designed in 1/128ths and then later "modernised" to decimals. Once I had reverse-engineered the "rounding", the design made sense.

MichaelG.
17 November 2013 at 08:49 #135759
Oompa Lumpa
Participant
@oompalumpa34302
Thank you for all your replies, I am pleased to see it wasn't just me. A DRO is of course on the cards but so is a great deal of other tooling and you can only buy so much at a time.

I am really quite pleased with the machine, it has opened up a great many new avenues to me. It doesn't matter which one you buy, from the smallest to the biggest, they will all have their shortcomings, I am happy with what I have so I will work with that.

Bloody annoying though
17 November 2013 at 09:33 #135762
Sub Mandrel
Participant
@submandrel
Oompa – you could print out temporary 0.001" graduated scales, get them laminated and fix them to your dials, until you get a DRO, cheap or expensive.

Neil
17 November 2013 at 09:43 #135763
Oompa Lumpa
Participant
@oompalumpa34302
Posted by Stub Mandrel on 17/11/2013 09:33:27:

Oompa – you could print out temporary 0.001" graduated scales, get them laminated and fix them to your dials, until you get a DRO, cheap or expensive.

Neil

Yes, I think I would like to do that Neil, is there some sort of formula? I am not yet that dim witted that I could work it out myself but if there is a "quick and dirty" solution I would go with that.

Right now I would like to reserve whatever grey matter is left for important stuff, like should I have one bacon sandwich or two this morning?
17 November 2013 at 09:47 #135764
NJH
Participant
@njh
Oompa

Free up you brain's resources – don't even think about it – go for two!

N
17 November 2013 at 09:51 #135765
Michael Gilligan
Participant
@michaelgilligan61133
Try here … this is much better than "quick and dirty"

MichaelG.
17 November 2013 at 10:30 #135772
IanT
Participant
@iant
You do seem to find some interesting places out there in Webland Michael.

Thank you for this one – I'm sure it will come in handy one day (added to favourites!)

Regards,

IanT
17 November 2013 at 11:25 #135777
Bazyle
Participant
@bazyle
Rather than expensive full DRO you may be able to set up a cheap tyre gauge to gvie you the digital readout for fine control Just go to the nearest whole number '0' with the existing dial, lock the gauge holder somehow, zero it, and you have a DRO for the last bit that is difficult.
17 November 2013 at 11:58 #135779
John Stevenson 1
Participant
@johnstevenson1
Posted by Michael Gilligan on 17/11/2013 09:51:39:

Try here … this is much better than "quick and dirty"

MichaelG.

Can't see a way to do a linear strip with say 100 division on a set radius ?
17 November 2013 at 12:11 #135781
Michael Gilligan
Participant
@michaelgilligan61133
Posted by John Stevenson on 17/11/2013 11:58:12:

Posted by Michael Gilligan on 17/11/2013 09:51:39:

Try here … this is much better than "quick and dirty"

MichaelG.

Can't see a way to do a linear strip with say 100 division on a set radius ?

.

Really ?
17 November 2013 at 12:23 #135782
Oompa Lumpa
Participant
@oompalumpa34302
Posted by NJH on 17/11/2013 09:47:54:

Oompa

Free up you brain's resources – don't even think about it – go for two!

N

I went for the Double Decker, bacon and egg in the end
17 November 2013 at 12:26 #135783
Oompa Lumpa
Participant
@oompalumpa34302
Posted by John Stevenson on 17/11/2013 11:58:12:

Posted by Michael Gilligan on 17/11/2013 09:51:39:

Try here … this is much better than "quick and dirty"

MichaelG.

Can't see a way to do a linear strip with say 100 division on a set radius ?

Oh it's there allright.

Great link by the way, thank you for that. Off to measure the radius of the wheels right now………
17 November 2013 at 12:27 #135784
John Stevenson 1
Participant
@johnstevenson1
Posted by Michael Gilligan on 17/11/2013 12:11:22:

Posted by John Stevenson on 17/11/2013 11:58:12:

Posted by Michael Gilligan on 17/11/2013 09:51:39:

Try here … this is much better than "quick and dirty"

MichaelG.

Can't see a way to do a linear strip with say 100 division on a set radius ?

.

Really ?

OK having a thick day,

can set to do 50mm radius but where do you set 100 units ?
17 November 2013 at 12:37 #135787
Oompa Lumpa
Participant
@oompalumpa34302
Nope – tried all that, wants $15 annually to print out a linear scale.

I will resort to that old standby, math.

graham.

(PS – I am not a cheapskate by any means but I have better uses for a tenner other than this.)
17 November 2013 at 13:24 #135789
Bazyle
Participant
@bazyle
IN around 2001 I had a free version of Turbocad that would step and repeat round a circle to make dials, not just the ticks but numbers too. Do any of the current free CAD programs do that?
17 November 2013 at 14:08 #135798
Michael Gilligan
Participant
@michaelgilligan61133
Graham

Sorry I spoke

… it's easy enough to do manually.

MichaelG.

Edited By Michael Gilligan on 17/11/2013 14:09:16
17 November 2013 at 14:10 #135799
John Stevenson 1
Participant
@johnstevenson1
No idea not heard of this but the program I use, Fastcad, has a macro called DIV where you select a line, type in how many division you need and it puts a small line at each division.

Simple job from there to trim to the lengths needed, Numbers will be have to be added manually.

Have half an idea that the CNC Utilities program has a sub routing to get G code for this, not got it on this laptop so can't check.
17 November 2013 at 14:34 #135801
Oompa Lumpa
Participant
@oompalumpa34302
Hey Michael, please don't take offence. You link was great, just the guy was being a little OTT in my opinion with regard to the tenner for a dial sticker.

Obviously he wants to get paid for his efforts and good luck to him. Just not for me right now. He has obviously put some great effort into this and I can see people would take advantage if this is a business model.

Thank you for taking the trouble to point it out though.

graham.
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