Home Model Engine Machinist > Building Them > Questions and Answers > Counterbore Concentric issues
Reply
 
Thread Tools Display Modes
Old 01-30-2013, 10:05 PM   #1
Nhat
 
Join Date: Jan 2013
Posts: 7
Liked 3 Times on 3 Posts

Default Counterbore Concentric issues

I was wondering if anyone knew of a method to drill concentric counterbores on both sides of a rectangular block of acrylic with a through hole? I've tried one method of drilling a counterbore one side and then drilling a hole through the center. Then flipping the piece and placing its hole through the drill bit to center it and clamp it down before doing another counterbore. This method works okay, but I was wondering if anyone knew of a more efficient method that gives better results?



__________________
Nhat is offline  
larry1 Likes This 
Reply With Quote Quick reply to this message
Old 01-30-2013, 10:11 PM   #2
Alchymist
 
Alchymist's Avatar
 
Join Date: Dec 2010
Posts: 62
Liked 18 Times on 14 Posts
Likes Given: 31

Default

IF your block is perfectly square, set up two stops for adjacent sides, drill , counterbore, then flip so the same two adjacent sides are against the stops. Counterbore. If every thing is square, the counterbores will align.



__________________
Alchymist is offline  
 
Reply With Quote Quick reply to this message
Old 01-30-2013, 10:16 PM   #3
Nhat
 
Join Date: Jan 2013
Posts: 7
Liked 3 Times on 3 Posts

Default

Alchymist, thank you for the tip. I'm actually trying to drill counterbores for a rectangular piece; however, I have access to a milling machine.

__________________
Nhat is offline  
 
Reply With Quote Quick reply to this message
Old 01-30-2013, 10:22 PM   #4
goldstar31
 
Join Date: Feb 2010
Posts: 404
Liked 107 Times on 84 Posts
Likes Given: 71

Default

The most accurate method of boring is NOT to start from both sides, or have a boring head or whatever. The accurate way is to drill a hole and then put an inline boring bar through.
It comes out perfectly parallel.

This is the way that Chaddock did his Quorn tool and cutter grinder

__________________
goldstar31 is offline  
 
Reply With Quote Quick reply to this message
Old 01-30-2013, 10:26 PM   #5
johnmcc69
 
Join Date: Dec 2011
Posts: 127
Liked 16 Times on 15 Posts
Likes Given: 20

Default

Are you using a "standard" screw ct'b that has a pilot on
it or are you doing something different?

John

__________________
johnmcc69 is offline  
larry1 Likes This 
Reply With Quote Quick reply to this message
Old 01-31-2013, 05:55 AM   #6
Nhat
 
Join Date: Jan 2013
Posts: 7
Liked 3 Times on 3 Posts

Default

Goldstar31 - I like your method. I will try to do that. Thank you!

Johnmcc69 - I was actually using this wooden counterbore because that's all I had at the time: http://www.lulusoso.com/upload/20120...D_WOOD_BIT.jpg

I'm gonna try to find an adjustable counterbore and that will work a lot better. Thank you!

__________________
Nhat is offline  
 
Reply With Quote Quick reply to this message
Old 01-31-2013, 07:33 AM   #7
goldstar31
 
Join Date: Feb 2010
Posts: 404
Liked 107 Times on 84 Posts
Likes Given: 71

Default

Quote:
Originally Posted by Nhat View Post
Goldstar31 - I like your method. I will try to do that. Thank you!
It appears in G H Thomas Model Engineers Workshop Manual along with many detailed improvements. True, they may have to re-scaled or drawn for lathes other than the Myford but they really do work.

You will that after you have spent hours making a part that a Thomas tool will not let you down.

So success

Norman
__________________
goldstar31 is offline  
 
Reply With Quote Quick reply to this message
Old 01-31-2013, 09:20 AM   #8
Jasonb
Project of the Month Winner!!!
 
Jasonb's Avatar
 
Join Date: Mar 2008
Location: Surrey, UK
Posts: 1,878
Liked 306 Times on 181 Posts
Likes Given: 11

Default

How big is the block of acrylic?

I would hold it in the 4 jaw drill then bore the trough hole, bore the counterbore then turn it the other way round and clock it true with a DTI then bore the other counterbore, should be able to get within 0.001"

J

__________________
Jasonb is offline  
larry1 Likes This 
Reply With Quote Quick reply to this message
Old 02-01-2013, 03:53 AM   #9
smithtools2007
 
Join Date: Feb 2013
Posts: 1
Default Counter Bore

Quote:
Originally Posted by Nhat View Post
I was wondering if anyone knew of a method to drill concentric counterbores on both sides of a rectangular block of acrylic with a through hole? I've tried one method of drilling a counterbore one side and then drilling a hole through the center. Then flipping the piece and placing its hole through the drill bit to center it and clamp it down before doing another counterbore. This method works okay, but I was wondering if anyone knew of a more efficient method that gives better results?
We are a leading manufacturer of counter bores as per picture attached. If you have any enquiry, you may send us smithtools2007@rediffmail.com
Attached Thumbnails
counter-bore-125x125-125x125.jpg  
__________________
smithtools2007 is offline  
 
Reply With Quote Quick reply to this message
Old 02-02-2013, 10:19 PM   #10
Krutch
 
Krutch's Avatar
 
Join Date: Dec 2012
Location: The taxed gulag of Illinois
Posts: 39
Liked 8 Times on 8 Posts
Likes Given: 3

Default

If I read the post right, the OP wants counterbores to be aligned at both ends of a hole on a rectangular block.
Make the first bore then using a locator of the bore size to locate the first bore on the table under the spindle. This will put the opposing surface up and the first bore under the spindle putting the second face under spindle for the alignment. Make the second bore. If both faces are parallel the bore will be aligned.
If the opposing faces are not square with each other, make the locator for the bore and long enough to locate the through hole and hold on an angle plate using a surface parallel with the hole.

My .02 cents worth.



__________________

Krutch

If I'd a known I'd live this long, I'd a had more fun getting here!

Krutch is offline  
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Drilling Concentric Holes dusty Questions and Answers 14 08-18-2013 10:07 PM
Bollaero 18 issues.... Eartaker Questions and Answers 1 07-13-2011 10:16 AM
Eclipse Piloted Counterbore Set. wla421 Tools 0 05-13-2010 06:10 AM
drilling concentric holes oregonsteam Questions and Answers 2 08-31-2009 03:50 AM
Making your own counterbore Bernd Tools 0 02-04-2008 08:53 PM




- Top - Member List