Need suggestions on a simple milling project using a LMS 3990

J

jrdarrah

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I finally got the mill trammed and I'm ready to try and make some metal chips unfortunately my first project is a little challenging since I can't find a 5/32" mill with at least a 1" cutting depth. The moving parts of the project are attached. The critical pieces of information are that the steel blocks are 1" high and the hole when closed has a 5/32" diameter and extends the whole height of the blank. In the drawings, the blue and red slide from the open position to allow for the insertion of a copper blank and stop when the opening is round. So far I can't find a end mill 5/32" that has enough cutting depth to take the metal off the side of the two pieces of stock. I guess I could cut as far as I can from the top and then flip it to cut the lower side. My problem with that is I'm new to milling so the odds of me getting it back in the vice properly aligned are low. I thought of milling it with a larger bit that will cut the 1" depth then clamping the two sides together and drilling the hole. I'm thinking the large radius from the bit will remove too much metal so I won't get a hole when I drill with a 5/32" drill.

Given I'm new some of my assumptions are probably faulty. I have some tooling, but my motto is "every new project requires at least one new tool". If I need to buy something else all options on the table. How would you machine these two part to accomplish my end goal?
 

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OK, i think you're looking at this problem the wrong way :) Milling a 5/32 slot 1" deep would terrify an experienced machinist! Luckily there's another way here, and it's brilliantly simple. I'd approach like so:

Mill the faces of all sides that don't form the step. As it's critical that the step heights are equal, finish the step feature last with both parts clamped in the vise side by side. The depth of the step needs to be to the centreline of the hole when closed exactly. We'll worry about the radius in a moment. Aim for clean, sharp edges with a nice fresh end mill. Deburr nicely on removal.

Clamp the pieces in the "closed" position in the vise, indicate or edge find to get the spindle right over the centre of where the steps meet, spot accurately and drill slightly under size. Ream to 5/32. Drilling through the join line works perfectly well assuming your fit is good between the two pieces.

Job done, no scary deep slot milling with a tiny mill!

Tools I'd want for this project are an edge finder and a stop for the vise or a table mounted stop. No need for anything fancy, you can do this all with hand wheels and a nice sharp 1/2" end mill or whatever you have to hand will do :)

Let us know how you get on!
 
Thanks I knew that there was a better way. I was stuck looking at the problem from the perspective of the drawing. On my own I wouldn't have thought to mill both pieces at the same time. I have an edge finder and a 1.25" end mill. I'm curious on what a stop for the vice or table mounted stop would look like. I have a set of reamers but none go down to 5/32". I have a set of letter size drill bits so for my purposes I can sneak up too the final dimension.
 
Thanks. I did some video viewing and did some googling. I found a simple plan for x-axis stop that will work with my lms 3990. Only a couple of parts and mounts in some tapped holes in the side of the bed. It looks simple enough for my first project.
 
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