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jbonfoey

Junior Member
On the attached picture does the line referencing the countersink mean to make the top (largest part) of the countersink hole .225 in diameter? I made it .225 deep using an 82-degree countersink and it’s huge for a 4-40 FH screw. Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole?

Using an iPad and can’t find some of the characters on the print. Thanks for help with dumb question.

Math challenged.
Jack

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Barnbikes

Well-Known Member
It is telling you to drill a .116" hole. Then take your 82 degree countersink and make the top of the hole .225 diameter.

Way I teach guys at work is take hole size subtracted from countersink size. Divide that number by 2. Take your caliper and mark that distance on both sides of the hole and countersink to that mark.
.225" - .116" = 109
.109"/2 = .0545"

jbonfoey

Junior Member
Thanks Barnbikes, that seems quite straight forward.

SmithDoor

Well-Known Member
I fit the counter sink to fit the screw.
The only time I worry about want the drawing say if I doing work for some else.

Dave

On the attached picture does the line referencing the countersink mean to make the top (largest part) of the countersink hole .225 in diameter? I made it .225 deep using an 82-degree countersink and it’s huge for a 4-40 FH screw. Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole?

Using an iPad and can’t find some of the characters on the print. Thanks for help with dumb question.

Math challenged.
Jack

jbonfoey

Junior Member
Thanks SmithDoor, makes sense. I guess maybe in the back of my mind I was hoping I hadn’t ruined the piece I was countersinking....but to no avail.

SmithDoor

Well-Known Member
A complete drawing will even have the finish for each operation.
Some times it give statement unless otherwise the finish is to be ######.
I do not outside the drafting class I seen a complete drawing for machining.

My self most life all my work was in shop.
The only time I had worry about drawing details is sending out work.
I did work for few years work shops and drawing that came in the door was a real mess.
Statement like fit ball bearing with no other details.

Dave

Thanks SmithDoor, makes sense. I guess maybe in the back of my mind I was hoping I hadn’t ruined the piece I was countersinking....but to no avail.

jbonfoey

Junior Member
Well, thank you again SmithDoor. I’m learning as I go, and I’ve learned about the countersinking process today. Seems I often learn by mistakes anymore, but since this is my hobby mostly it’s time I waste.
Take care,
Jack

Richard Hed

Well-Known Member
Well, thank you again SmithDoor. I’m learning as I go, and I’ve learned about the countersinking process today. Seems I often learn by mistakes anymore, but since this is my hobby mostly it’s time I waste.
Take care,
Jack
You might also remember thant counter-sinkings purpose is USUALLY to have the screw below the surface and that is all that is needed__usually. Occasssionally there is some other purpose but on models, this is probably the purpose to just get the screw below the surface.

jbonfoey

Junior Member
Yes, good reminder Richard, thanks. These happen to be quite obvious, so I’ve remade the part.

Rugbyears

Member
Well, thank you again SmithDoor. I’m learning as I go, and I’ve learned about the countersinking process today. Seems I often learn by mistakes anymore, but since this is my hobby mostly it’s time I waste.
Take care,
Jack
I appreciate it can be quite frustrating, but remain positive as mistakes are a useful way of learning. If you make a mistake, you seldom make the same one. If it is a hobby, enjoy yourself, life is to short to fret over a silly mistake. Remind yourself the next time you’ve made a mistake that you’ve just learn something new. I am a complete newbie, and am prone to making mistakes, but what a wonderful opportunity to be able to learn and engage with all you knowledgeable and skilled people

easymike29

Member
Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole?

BillC

Well-Known Member
Trigonometry - all (most all) hand held calculators have trig functions. Tangent of 41 degrees = .869286. From there basic math. Then touch off the countersink on a suitable shim and plunge the hole for the countersink size needed. Handy for multiple holes for consistency.
Your drawing shows the depth as .0627" which will not result in a .225" dia. countersink.
Rough sketch:

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BillC

Well-Known Member
Your drawing shows the depth as .0627" which will not result in a .225" dia. countersink.

kinggt4

Member
HMEM Supporter
Easymike29 and Billc are both correct. Easymike is not showing the full depth of the tountersink travel as Bill is.

easymike29

Member
Trigonometry - all (most all) hand held calculators have trig functions. Tangent of 41 degrees = .869286. From there basic math. Then touch off the countersink on a suitable shim and plunge the hole for the countersink size needed. Handy for multiple holes for consistency.
Your drawing shows the depth as .0627" which will not result in a .225" dia. countersink.
Rough sketch:
I believe you need to rethink your logic on the total travel. I could be wrong.
Eugene

BillC

Well-Known Member
I wasn't really giving precise data but the means of acquiring it. My math is probably all wrong just as the wish to help out on this forum. I need counseling too... I've made out OK for 72 years without smart ass comments from here so my help of any sort will be curtailed completely. I'm away from this forum - no reply needed any longer.

Bentwings

Well-Known Member
I wasn't really giving precise data but the means of acquiring it. My math is probably all wrong just as the wish to help out on this forum. I need counseling too... I've made out OK for 72 years without smart ass comments from here so my help of any sort will be curtailed completely. I'm away from this forum - no reply needed any longer.
I wasn't really giving precise data but the means of acquiring it. My math is probably all wrong just as the wish to help out on this forum. I need counseling too... I've made out OK for 72 years without smart ass comments from here so my help of any sort will be curtailed completely. I'm away from this forum - no reply needed any longer.
I don’t want to enter an argument. I haves black book that has another every calculation needed for machine work it compliments machinery’s manual. I simply look up what is needed. Some times posing the question to look in the index is harder than doing the work, it’s been in my machine toolbox for 20 years or more once I got to cad it was more of constructing the simple model then adding what ever dim. I needed my current cad can go to 14 decimal places if necessary. But I don’t do that except to impress the nay sayersLOL

jbonfoey

Junior Member
Thanks you all for your input everyone, I’ve printed out the diagrams and hopefully learn something.

SmithDoor

Well-Known Member
Drill dia is 0.116
Counter sink dia 0.225 @ 82°

Dave

On the attached picture does the line referencing the countersink mean to make the top (largest part) of the countersink hole .225 in diameter? I made it .225 deep using an 82-degree countersink and it’s huge for a 4-40 FH screw. Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole?

Using an iPad and can’t find some of the characters on the print. Thanks for help with dumb question.

Math challenged.
Jack

easymike29

Member
Thanks you all for your input everyone, I’ve printed out the diagrams and hopefully learn something.
If you copied BillC's sketch you should know that the use of (a = b x Tan B) is not correct in this instance.
Eugene