Chuck Keysor
10-25-2014, 02:21 AM
Hello Shopbotters,,,,,,,,,, With the fall elections upon us, I finally volunteered to make some campaign signs for a good friend who is running for the Illinois House of Representatives. As the signs won't even need to last two weeks, I picked up OSB, 1/2" thick, and pocketed the text (3" tall letters), to a depth of 1/8th" using a 1/4" end mill.
The first few letters cut fine, at what later measured out at .135" depth. But after maybe 5 letters, the depth of cut decreased to .068". This was easy to see by eye that the depth of cut was shallow. And I went, oh no, my bit must be loose! However I let it keep running, since the job was more of rush, throw away sign. But as I watched, the depth changed back to .135", and then it got deeper, with some letters later measuring at .18" deep. On maybe 5 or 6 letters, the depth changes within individual letters! The cut gets deeper, towards the middle of the pocketed letter, almost like there is a ramping cut going on! But the cuts seemed to wander in depth.
The board is laying really flat on my table top, so warping, and moving of the stock up and down is not the problem.
When the sign was done (1 hour and 30 minutes), I moved the bit back to where I had zero'd it initially, and the bit was above the board by about .04"! And I tried to snug up the collet. I was able to tighten it a little, but it was really pretty tight. And with the bit ending up about .04" above the board, why would some of my pocket depths be .055" too deep???? I have never had such a problem! My cuts have always been the correct and consistent depth. I have never seen anything like this. I am confused!
I can post some pictures, tomorrow, as it is too late now. But all you will see is some letters that are shallow, some that are deep, and some that change depth within a single letter! Yikes!
Any ideas, beyond running the next piece with the collet even tighter?
Thanks, Chuck
The first few letters cut fine, at what later measured out at .135" depth. But after maybe 5 letters, the depth of cut decreased to .068". This was easy to see by eye that the depth of cut was shallow. And I went, oh no, my bit must be loose! However I let it keep running, since the job was more of rush, throw away sign. But as I watched, the depth changed back to .135", and then it got deeper, with some letters later measuring at .18" deep. On maybe 5 or 6 letters, the depth changes within individual letters! The cut gets deeper, towards the middle of the pocketed letter, almost like there is a ramping cut going on! But the cuts seemed to wander in depth.
The board is laying really flat on my table top, so warping, and moving of the stock up and down is not the problem.
When the sign was done (1 hour and 30 minutes), I moved the bit back to where I had zero'd it initially, and the bit was above the board by about .04"! And I tried to snug up the collet. I was able to tighten it a little, but it was really pretty tight. And with the bit ending up about .04" above the board, why would some of my pocket depths be .055" too deep???? I have never had such a problem! My cuts have always been the correct and consistent depth. I have never seen anything like this. I am confused!
I can post some pictures, tomorrow, as it is too late now. But all you will see is some letters that are shallow, some that are deep, and some that change depth within a single letter! Yikes!
Any ideas, beyond running the next piece with the collet even tighter?
Thanks, Chuck