Author Topic: Drill holes in a bolt circle  (Read 11504 times)

Offline Bernd

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Drill holes in a bolt circle
« on: January 30, 2009, 02:40:03 PM »
Why am I asking this? Check out this THREAD first.

As I said I was going to ask this question here and see how many can come up with an answer. The criteria is that you can't use an indexing head or DRO. Since I don't have an indexing head I can't use that. But my Bridgeport does have a DRO, but I'm not going to use it.

The piece that will need the holes is the side of the bull gear (minus it's teeth) in this pic.


This will be a bit of a tip for the newbies. I'm sure some of you old pharts know how to do this. So let the answers begin.

Bernd
Route of the Black Diamonds

Offline Darren

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Re: Drill holes in a bolt circle
« Reply #1 on: January 30, 2009, 02:50:53 PM »
If you hadn't machined the teeth off the gear? Use another gear?

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Offline sbwhart

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Re: Drill holes in a bolt circle
« Reply #2 on: January 30, 2009, 03:20:36 PM »
Hi

I'd use another gear.

This is a cheap and chearfull devider I made when I first started up, spent a load of cash on other bits, neaded to divide a part up, got hold of a gear with 12 teath this gave me 2, 3, 4, 6, divisions, I still use it from time to time quick and easy to set up just grip it in the vice. Job Sorted  :thumbup:



Cheers
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Stew
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Location:- Crewe Cheshire

Offline Darren

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Re: Drill holes in a bolt circle
« Reply #3 on: January 30, 2009, 03:24:43 PM »
Stew, you forgot one  :scratch:
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Offline Bernd

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Re: Drill holes in a bolt circle
« Reply #4 on: January 30, 2009, 03:31:11 PM »
Nope, can't use a gear.

We are going to create this from scratch.  :smart:

By the way the number of teeth on the bull gear "was" 76. Not a very divisable number once you get past 4 positions.

Bernd
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Offline Darren

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Re: Drill holes in a bolt circle
« Reply #5 on: January 30, 2009, 03:33:41 PM »
Print that autoscetch and fold the paper, nah, can't be that....can only get about 4 or 5 folds..... :lol: :lol:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

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Re: Drill holes in a bolt circle
« Reply #6 on: January 30, 2009, 04:20:54 PM »
There is a bolt circle calculator in the little workshop proggy that I put in the downloads section, but it only goes up to 12.

Maybe you could download this one and try it out.

http://iwr.ru.ac.za/~iwdf/lathe/pcd.html


Bogs

Offline sbwhart

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Re: Drill holes in a bolt circle
« Reply #7 on: January 30, 2009, 04:28:36 PM »
If you're mills got a DRO that'l do it with co-ordinates, if not you can work the co-ordinates out, or consult a text book that with tables to work out co-ordinates.   

I feal a banna dance comming on

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Stew



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Location:- Crewe Cheshire

Offline SPiN Racing

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Re: Drill holes in a bolt circle
« Reply #8 on: January 30, 2009, 09:56:08 PM »
IIRC for the times I have had to draw up a bolt circle...    hoo.. been a while.. and my geometry is one of those things that sits in a closet of my brain.. And I can apply it to a specific project..


If it were me.. I would take a sheet of paper. I would then draw a circle with a compasssss. (this is pre-CoC for those who are not familiar.. this charcoal in wood device.)
Im assuming drawing it in Auto cad is out as well.

SO I would then find the center of the circle. Then I would Bisect the circle and mark the diameter of the bolt circle.

Scribe a circle at the new dimension.

THen figure on paper how many degrees of seperation angle between each bolt.  Say its 4 Bolts.. then its 90 per bolt.

Simple Bisect it, then with the compass, mark your 90 degree angle and scribe the line.

Mark the hole at each intersection of the bolt circle diameter.

If you have more intersections, you will need to figure how many degrees of seperation you have and start to bisect the angles... aka the 90 divides to 45s. THen those to 22.5. Etc.
Then select the combination of angles to mark off your number of bolt holes.

Once you have the exact number of bolt holes, I would erase the other crapola leaving the exact pattern.
Cut a opening in the paper to fit it around the part.. then overlay it, and with a punch center punch each bolt hole.

The alternative is to dykem the face of the part, and repeat the above procedures.


Thats about how I would pull it off LOL.

Right?  Not sure. But it would likely work.
SPiN Racing

Offline Bernd

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Re: Drill holes in a bolt circle
« Reply #9 on: January 31, 2009, 08:20:10 PM »
As I stated in my thread on the index head, this might not work for this particular project.

I'll have details in the next few days because I think it's something of interest if you have no other means of dividing a round part for indexed hole drilling. (Does that even make sense?) :scratch:

Bernd
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Offline Bernd

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Re: Drill holes in a bolt circle
« Reply #10 on: February 01, 2009, 11:31:28 AM »
Here's a quick and dirty write up of what I was going to do. The reason I say was is because the circumference  of the worktable on the drill press was a bit larger than I had anticipated for doing this. Hopefully by showing the method of approach you'll understand why.

I first got a piece of paper about the width of the rim of the table. Wrapped it around so the paper folded over itself.


Then using a square I made sure I cut a square corner on the paper.


Now the careful layout begins. I'm only going to use a portion of the paper to demonstrate the process. Draw two lines perpendicular to the strip of paper, both are end lines. Using a metric ruler I divide the horizontal line (paper) into 8 divisions. I used 320 at the left end and 0 at the right end. If you divide 8 into 320 you get 40. So every 40 centimeters I made a mark for a vertical line.


This is what you'll wind up with.


Next fasten the paper to your table.


Then make up a pointer such as shown to line up the  lines on your paper. Now you can drill your holes.


I have not gone into great detail on this method as it would take a large amount of time to explain. Hopefully those with some insight can figure out what is being done.

The reason this wouldn't work for me is the fact that my drill table is over 42" in circumference. Trying to divide a piece of paper that long called for one long angle to come up with a number divisible by 24.

So it looks like I will be using the DRO on the Bridgeport after all.

Perhaps someday I will give this method a try on a smaller part,

For those who would like to read further on this method you will need either the old copies of "The Home Shop Machinist" Nov/Dec 1988 where he wrote the series on a Model Makers Dividing Head or his Shop Wisdom of Philip Duclos. He gives a full description of how it's done.

If there are any questions I'll try to answer them as best I can.

One other method of originating an index plate is written up in Guy Lautard's Second Bedside Reader. You will need a lathe for that project.

Bernd
Route of the Black Diamonds

Kludge

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Re: Drill holes in a bolt circle
« Reply #11 on: February 02, 2009, 07:11:20 PM »
The reason this wouldn't work for me is the fact that my drill table is over 42" in circumference. Trying to divide a piece of paper that long called for one long angle to come up with a number divisible by 24.

Actually you could do it with some finesse and low peasant cunning.  Center a smaller circular piece on the table and use it for the markings, then fabricate an extension to your pointer that reaches the smaller piece.  This should allow you to use the drill press's table to do your majique rather than resorting to the DRO.

BEst regards,

Kludge

Offline Bernd

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Re: Drill holes in a bolt circle
« Reply #12 on: February 02, 2009, 07:26:29 PM »
Actually you could do it with some finesse and low peasant cunning.  Center a smaller circular piece on the table and use it for the markings, then fabricate an extension to your pointer that reaches the smaller piece.  This should allow you to use the drill press's table to do your majique rather than resorting to the DRO.

BEst regards,

Kludge

To late Kludge, I've already used the DRO.

I was going to go with a smaller circular table but didn't want to take the time. Just lazy I guess. :coffee:

Bernd
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Kludge

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Re: Drill holes in a bolt circle
« Reply #13 on: February 02, 2009, 08:00:23 PM »
To late Kludge, I've already used the DRO.

I was going to go with a smaller circular table but didn't want to take the time. Just lazy I guess. :coffee:
No worries.  I'm actually surprised I came up with a useable solution on my current med load.  :)

Best regards,

Kludge