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Old 02-02-2008, 03:06 AM   #1
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Default Needed to counter sink a 4/40 socket head cap screw

Well I finally got some time to get back into the shop this evening. Task at hand was to counter bore the head I am making for the my Webster engine. The 4-40 heads are approximately .215 and the only end mill I have that was large enough is .250. Not wanting to go that large I decided to try to make my own from a M42 drill I had laying around that miked out around .233. I am lucky enough to have a end mill sharpening fixture and a surface grinder. While I have sharpened plenty of end mills I never tried to make one from a drill before. It turned out ok and did the job, however if I am going to use this one again I need to shorten it up. I ended up with some chatter and I am sure it is due to the lack of rigidity from the length. Any where I know how you guys like pics so here are a few.









Hopefully I will have something to post in the progress area soon...


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Old 02-02-2008, 03:18 AM   #2
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Default Re: Needed to counter sink a 4/40 socket head cap screw

I wonder if leaving a pilot on the end might help with the chatter?
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Old 02-02-2008, 06:21 AM   #3
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Default Re: Needed to counter sink a 4/40 socket head cap screw

I also wonder if you might not partially drill out the hole with an unmodified m42 drill bit, then flatten the bottom of the hole with the ground off m42?

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Old 02-02-2008, 02:28 PM   #4
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Default Re: Needed to counter sink a 4/40 socket head cap screw

Or you can make one from drill rod with a pilot on it. The c'bores should be run slow and with a lube on them to get better finish. Harden if used on steel, don't need to harden if used on brass and aluminum.



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Old 02-02-2008, 02:35 PM   #5
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Default Re: Needed to counter sink a 4/40 socket head cap screw

All of you guys have great alternate solutions

Bernd, can you how did you go about making your bit?
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Old 02-02-2008, 03:33 PM   #6
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Default Re: Needed to counter sink a 4/40 socket head cap screw

Being lazy I just use a drill and leave the hole bottom tapered for the really small bolts Then again I am an electrician by trade.
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Old 02-02-2008, 03:54 PM   #7
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Default Re: Needed to counter sink a 4/40 socket head cap screw

With piloted counterbores available for $5.00 or $6.00 each, I can't justify the time to make one. I expect the ones I bought some twenty years ago were about $2.00 each and they have served me well in both aluminum and steel. I bought a machine screw set plus a 1/4". Anything bigger than that, (which is rare) I use a drill bit followed by an end mill.

Unless I am making something that uses a large number of one size screw, I buy socket head cap screws by the box (100) in 1" length and cut to length with a Dremel cutting wheel. For the occasional long screw I buy a few at a bolt supply and have some for the next time.
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Old 02-02-2008, 04:29 PM   #8
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Default Re: Needed to counter sink a 4/40 socket head cap screw

Quote:
Originally Posted by Stan
With piloted counterbores available for $5.00 or $6.00 each, I can't justify the time to make one. I expect the ones I bought some twenty years ago were about $2.00 each and they have served me well in both aluminum and steel. I bought a machine screw set plus a 1/4". Anything bigger than that, (which is rare) I use a drill bit followed by an end mill.

Unless I am making something that uses a large number of one size screw, I buy socket head cap screws by the box (100) in 1" length and cut to length with a Dremel cutting wheel. For the occasional long screw I buy a few at a bolt supply and have some for the next time.
Stan your right, you can buy them but this was more about the challenge of making one, and the things I learned along the way. Plus I wanted to do the counter boring last night

I also buy the most common size cap screws that I use by the 100. I think the last lot I bought was close to $5.00 for the box. The local Ace hardware gets .30 each.
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Old 02-02-2008, 07:57 PM   #9
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Default Re: Needed to counter sink a 4/40 socket head cap screw

deere: As I have said in previous posts, I have spent more time making tooling than making models. The rate of success that I have had hardening and tempering tools, I probably made my rotary table in less time that it would take me to make a set of counterbores.

With imported tools, that are adequate quality for HSM use, there is no need to not have the small basic tools. When I started in this hobby, a cheap indicator was over $100.00. Now, I probably have six that cost less than $10.00 each mounted to various attachments to quickly stick on the lathe or mill.

I don't feel that I have put any American workers out of work by buying import tools. If my only choice was Starrett, I just wouldn't have bought any new tools. I now have a lot of US made tools that were bought used but took years to accumulate
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Old 02-02-2008, 09:00 PM   #10
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Default Re: Needed to counter sink a 4/40 socket head cap screw

deere;
I think the bigger concern to me would be the raised up burr on the periphery of the holes on the face of the part. What could cause that if you had a evenly sharpened and straight bit unless the material was some tough.
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