UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Cabinet and Chassis Restoration and Refinishing

Notices

Cabinet and Chassis Restoration and Refinishing For help with cabinet or chassis restoration (non-electrical), please leave a message here.

Closed Thread
 
Thread Tools
Old 2nd Mar 2022, 1:50 pm   #1
Nanozeugma
Heptode
 
Nanozeugma's Avatar
 
Join Date: Nov 2017
Location: London, UK. Bury, Lancashire quite regularly :)
Posts: 609
Default Cutting accurate holes in thin plastic sheet.

Hi all,
I'm in the process of attempting to fashion a replacement drum cover, bearing station names, to replace a damaged original for a Murphy A48.
Thanks to the kind efforts of Jerry (cathoderay57) I now have an accurate reproduction (template) of the station names.
I haven't yet decided whether to use clear PETG sheet with clear self adhesive printed film on the back, or just use OHP film.
Now the problem.
Having marked the hole centres, four per side, where the cover is attached to the metal support frame, I'm struggling working out how to punch the holes accurately (in the right place.)
I have a rotary punch which goes up to 4.5mm, and a standalone 5mm steel punch.
The issue is that I cannot see what I'm doing, trying to align the punch over the proposed hole centres, marked on the material with an indelible marker dot.
I wonder if there is a simple answer to punching the hole(s) in the right place that I may have overlooked?
__________________
Thermionic Emission, warms the cockles of your tubes.
Nanozeugma is online now  
Old 2nd Mar 2022, 5:18 pm   #2
Guest
Guest
 
Posts: n/a
Default Re: Cutting accurate holes in thin plastic sheet.

If you have a hollow punch look down it on an illuminated surface.
 
Old 2nd Mar 2022, 7:06 pm   #3
mark_in_manc
Octode
 
Join Date: Nov 2011
Location: Manchester, UK.
Posts: 1,872
Default Re: Cutting accurate holes in thin plastic sheet.

I wonder if you can scribe a cross onto the sheet which centres on your 'dot', with carefully-measured arms of equal length just larger than the radius of your wad punch? Then you can ensure your punch is centred by looking for the stubs of those arms protruding equally just beyond its rim, and you know you'll be bang on.
__________________
"The best dBs, come in 3s" - Woody Brown
mark_in_manc is offline  
Old 2nd Mar 2022, 7:34 pm   #4
wireman
Heptode
 
Join Date: Feb 2021
Location: Edinburgh, Scotland, UK.
Posts: 528
Default Re: Cutting accurate holes in thin plastic sheet.

Note sure I understand 100% but can you stick something on top (paper,tape), and draw concentric circles on it?
wireman is offline  
Old 2nd Mar 2022, 9:36 pm   #5
joebog1
Banned
 
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
Default Re: Cutting accurate holes in thin plastic sheet.

Yes wireman,
I make very very accurate valve base drilling diagrams that way. Basically I draw a circle and gunsight cross hairs where the hole has to be. I normally use paper but I have printed these onto clear film and stuck them down. I use magictape ( the stuff that doesnt photocopy ) to do so.
I use Librecad as the drawing instrument. My printer is a bog standard Brother multi task machine.

Joe
joebog1 is offline  
Old 2nd Mar 2022, 11:09 pm   #6
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default Re: Cutting accurate holes in thin plastic sheet.

You can buy self adhesive strong paper or plastic 'hole strengtheners' which look like a flat / two dimensional polo mint and are sticky on one side. Their actual function is to reinforce the area around punched holes in paper sheets kept in ring binders.

You could place one, or several, stacked, exactly centred over your intended hole centre and the inner hole will act as a guide to keep the punch in exactly the right place, especially if the outer diameter of the punch is exactly the same as the inner diameter of the circular guide.
SiriusHardware is online now  
Old 3rd Mar 2022, 12:17 am   #7
Alistair D
Nonode
 
Alistair D's Avatar
 
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
Default Re: Cutting accurate holes in thin plastic sheet.

After attaching an adhesive label to the material draw horizontal and vertical lines through the centre of the hole you want to punch. When you lay the punch on the surface it is easy to see if it is laying above, below, left or right of the centre.

Al
__________________
I won't tell you how I discovered that.
Alistair D is offline  
Old 3rd Mar 2022, 8:31 am   #8
Electronpusher0
Nonode
 
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,288
Default Re: Cutting accurate holes in thin plastic sheet.

I have sucessfully drilled valve base holes in thin(ish) aluminium by clamping it between sheets of plywood.
I printed a drawing of the hole layout at full size I centre popped and drilled the corner mounting holes as accurately as I could.
I drilled the same holes in the plywood sheets and bolted the sandwich together.
I stuck the drilling drawing to the top and drilled pilot holes and finally the large holes using the pillar drill.

Using the ply sandwich prevented distortions of the metal. Should work for thin plastic.

Peter
Electronpusher0 is offline  
Old 3rd Mar 2022, 8:47 am   #9
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 8,809
Default Re: Cutting accurate holes in thin plastic sheet.

I'm not fully understanding the application, so my suggestion may not be suitable. I use brad point drills to obtain a fine edge when drilling through thin materials.
Attached Thumbnails
Click image for larger version

Name:	Screen Shot 2022-03-03 at 07.48.10.png
Views:	49
Size:	39.3 KB
ID:	252860  
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is online now  
Old 3rd Mar 2022, 11:18 am   #10
60 oldjohn
Dekatron
 
Join Date: Dec 2004
Location: East Yorkshire, UK.
Posts: 3,958
Default Re: Cutting accurate holes in thin plastic sheet.

Quote:
Originally Posted by SiriusHardware View Post
You can buy self adhesive strong paper or plastic 'hole strengtheners' which look like a flat / two dimensional polo mint and are sticky on one side. Their actual function is to reinforce the area around punched holes in paper sheets kept in ring binders.

You could place one, or several, stacked, exactly centred over your intended hole centre and the inner hole will act as a guide to keep the punch in exactly the right place, especially if the outer diameter of the punch is exactly the same as the inner diameter of the circular guide.
I think this is the way to go, maybe give them a quick rub on a piece of cloth to reduce the stickiness making them easy to remove once the hole has been punched. https://www.ebay.co.uk/itm/132091200...8AAOSwax5YnFwI

The BVWS and other calendars use them on the first page. Not that you could use these, for information only.
John.
__________________
My favourite text message "I'll be there in five minutes, if not read again"

Last edited by 60 oldjohn; 3rd Mar 2022 at 11:26 am.
60 oldjohn is online now  
Old 3rd Mar 2022, 10:59 pm   #11
Nanozeugma
Heptode
 
Nanozeugma's Avatar
 
Join Date: Nov 2017
Location: London, UK. Bury, Lancashire quite regularly :)
Posts: 609
Default Re: Cutting accurate holes in thin plastic sheet.

Thanks for all the ideas, I'm inclined to think the hole reinforcements idea is the way forward.
I do have some, but they're clear so kinda defeats the object.
Some white vinyl ones on order.
I might just have a dabble with brad point drills on some gash material, if unsuitable, they'll always come in handy for wood
__________________
Thermionic Emission, warms the cockles of your tubes.
Nanozeugma is online now  
Old 6th Mar 2022, 12:45 am   #12
Silicon
Nonode
 
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,152
Default Re: Cutting accurate holes in thin plastic sheet.

Would it help if you heated a sewing needle and made (melted) a small hole in the plastic at the centre of the final hole position?
Silicon is offline  
Old 6th Mar 2022, 12:34 pm   #13
Nanozeugma
Heptode
 
Nanozeugma's Avatar
 
Join Date: Nov 2017
Location: London, UK. Bury, Lancashire quite regularly :)
Posts: 609
Default Re: Cutting accurate holes in thin plastic sheet.

Quote:
Originally Posted by Silicon View Post
Would it help if you heated a sewing needle and made (melted) a small hole in the plastic at the centre of the final hole position?
I'd actually contemplated something similar, to whit using a pointy bit on a temperature controlled iron on low heat to make the hole (instead of a punch.) ..... At least, trying the idea out on some off cuts of the material...
__________________
Thermionic Emission, warms the cockles of your tubes.
Nanozeugma is online now  
Old 6th Mar 2022, 3:11 pm   #14
Guest
Guest
 
Posts: n/a
Default Re: Cutting accurate holes in thin plastic sheet.

I have often made holes in plastic with a soldering iron, it leaves a ring behind, once cold this is easily removable with a quick slice with a blade.
 
Old 16th Apr 2022, 5:41 am   #15
majoconz
Heptode
 
majoconz's Avatar
 
Join Date: Jan 2008
Location: Ashhurst, Manawatu, New Zealand
Posts: 570
Default Re: Cutting accurate holes in thin plastic sheet.

Getting the transparent reinforcing rings in the right place is made easier if you pick up the ring with the tip of a small knife. You can see the whole ring and position it very closely, especially if you have drawn crosshairs through the desired centre.
__________________
Cheers - Martin ZL2MC
majoconz is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 10:29 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.