smallbrother
Elder Statesman
Errors aplenty, progress slow, but progress nonetheless!
Posts: 2,268
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Post by smallbrother on Jun 7, 2020 11:32:14 GMT
Not sure if I have the correct term - rebate, recess? Anyway I need to create a rebate in the coupling rods of Juliet for the shoulders of the bushes to sit in. The rebate is 7/16 while the hole right through the rod is 5/16.
I ground a 7/16 drill bit at a very flat angle and started it off and this seems like it will do the job.
Just thought I would check to see if this is a bad idea before I go too far!
Pete.
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Post by ettingtonliam on Jun 7, 2020 12:03:33 GMT
If you can drill deep enough with a standard 7/16" drill until the full diameter is formed, then yes, a 7/16" drill ground flat will do the rest to form the bottom. 'Counterbore' is the posh Sunday name for what you are doing. The problem with flat or flattish drills is that they will tend to wander unless there is something to restrain them, so you need to start off with the normal drill. A 7/16" endmill will also do the job. Over the years I've a number of home made counterbores (silver steel) with inserted pilots just for jobs like yours. Also used for spotfacing castings to form seats for nuts or bolt heads.
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smallbrother
Elder Statesman
Errors aplenty, progress slow, but progress nonetheless!
Posts: 2,268
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Post by smallbrother on Jun 7, 2020 12:23:41 GMT
"Counterbore"! Thank you for clarifying that and for the advice.
Yes I did start the wider hole off with a standard bit so will do the rest using the same method.
Pete.
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Post by Roger on Jun 7, 2020 12:34:24 GMT
I agree that a 7/16" end mill or slot drill is probably a better option because they are so much more rigid than a drill. A drill is likely to go oversize, at least at the start of the cut before it finally centres. You can always sacrifice a drill by chopping it in half to make it more rigid.
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uuu
Elder Statesman
your message here...
Posts: 2,800
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Post by uuu on Jun 7, 2020 12:42:47 GMT
The use the shortened drill to cut a hole in a stub of metal, glue the top part of the drill into the stub, and it's still useable!
Wilf
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