# Using a collet block with a mini-mill



## ARC-170 (Jul 25, 2020)

I'm making a cylindrical part that will require the use of a collet block because I have to mill a slot on the end, then drill and tap a hole perpendicular to the slot. My vise jaws are 1" high. This seems like it will not adequately support the work standing on end. So, I'm thinking I'll need to clamp the collet block to a right-angle fixture (properly aligned) for the slot, mill the slot, then rotate the block, re-clamp it to the right-angle fixture, and drill the hole.

Anyone ever done an operation like this on a smaller mill? Is my thinking sound/safe? I have an LMS 3990 mill.


----------



## mickri (Jul 26, 2020)

What is the diameter of the part and how long is it.  What type of collet block are you using? 4 sided, 6 side or ????  A 4 sided block would probably work best for what you are trying to do.

You could have the work horizontal instead of vertical.  Mill the slot then rotate the work 90 degrees and drill and tap the hole.  If the bottom of the slot needs to be flat you could then use a file to make the bottom flat.


----------



## ErichKeane (Jul 26, 2020)

What does your part look like?  Have you considered using a slitting saw to cut the slot?  That way you could make the slot with it laying down, AND cut/tap the hole in the same operation.


----------



## C-Bag (Jul 26, 2020)

Wouldn’t a v block do what you want to hold it vertical and horizontal?


----------



## ErichKeane (Jul 26, 2020)

C-Bag said:


> Wouldn’t a v block do what you want to hold it vertical and horizontal?


i think his reasoning for the collet block was that he needs to do 2 operations at 90 degrees to each other.  If you swap with a V-block from vertical to horizontal, you end up having to re-align the result of the 1st operation to be 90 degrees to the 2nd.  A collet block allows the setup to be consistent and correct.

That said, doing this in 1 setup seems best ot me


----------



## JimDawson (Jul 26, 2020)

ARC-170 said:


> I'll need to clamp the collet block to a right-angle fixture (properly aligned) for the slot, mill the slot,



I see no problem with what you propose.  Clamping to an angle plate is a good way to hang on to the collet block for the milling operation.  Then lay it down in the vice, or just clamp it to the table for drilling the cross hole.


----------



## higgite (Jul 26, 2020)

I won’t speculate on why you need to mount the cylinder vertically to mill the slot, but will offer an alternative to a right angle fixture. If you mount the cylinder in a collet block or V-block, can you mount it vertically in your vise and mill the slot on the Y-axis? That will give much more support to a vertical work piece than slotting on the X-axis will. Then just lay it over horizontally in the vise and drill the hole.

Tom


----------



## C-Bag (Jul 26, 2020)

I’ve done such operations when I made a tool holder and it’s why I decided against the usual Kurt vise and went with a CNC style vise which is just a bigger tool makers vise. You can lay it on it’s side which you can’t do with a regular I’ll vise. I’ve also got a 2” and 1” toolmakers vise. Also small v blocks. So far they have done what I’m not sure a collet block could have done in my circumstances. But YMMV.


----------



## ARC-170 (Jul 26, 2020)

Here is what I'm making. It's a project in the Beginning Machining class I'm taking.






The slots need a flat bottom. There are also flats to machine. The instructions call for standing the part up vertically to machine the slots, then lay the part down and mill the flats and drill the holes. All straightforward if you have the proper tooling. The instructions call for a C5 collet to be put in a collet block. I don't have one, but could probably borrow one. I thought of making a collet block for the R8 collets I have, since no one seems to sell them. The machines at the adult school or full-size Bridgeports with full-size vises, too. I have a small LMS 3990 mill and a small vise.

To give you a better idea of what I thought I would do, here is a picture. I have placed the R8 collet in the proper position for milling the slot. You'll have to imagine it being held by a collet block and being properly clamped. The angle bracket is about 2-1/2" high, so should provide enough support. I would just rotate the collet block 90 degrees to make the holes and flats. You can see that my vise is not very big.


----------



## mickri (Jul 26, 2020)

This is how I would do it.  I would scribe lines on the end of the work that are perpendicular to each other.  To do this I would mount the work in the vice and then find the center of the work.  I would put a scribe in the mill and use it to make the lines.  I would then mill the slot.  Reposition the work to being horizontal in the vice so that the line that is perpendicular to the slot is now vertical.  Then dill and tap your holes.


----------



## ARC-170 (Jul 26, 2020)

mickri said:


> This is how I would do it.  I would scribe lines on the end of the work that are perpendicular to each other.  To do this I would mount the work in the vice and then find the center of the work.  I would put a scribe in the mill and use it to make the lines.  I would then mill the slot.  Reposition the work to being horizontal in the vice so that the line that is perpendicular to the slot is now vertical.  Then dill and tap your holes.



So I would be "drawing" a cross on the end of the cylinder, correct?
Then, mill the slot. Then, rotate the part 90 degrees (from upright/vertical) to horizontal and then drill the holes, right?
But, how would I not move the part out of alignment/perpendicular when going from vertical to horizontal unless it was in a collet holder? How would I re-align it without using a collet block? I could "eyeball" the lines with a right angle square, but that cannot be accurate enough.


----------



## ARC-170 (Jul 26, 2020)

higgite said:


> I won’t speculate on why you need to mount the cylinder vertically to mill the slot, but will offer an alternative to a right angle fixture. If you mount the cylinder in a collet block or V-block, can you mount it vertically in your vise and mill the slot on the Y-axis? That will give much more support to a vertical work piece than slotting on the X-axis will. Then just lay it over horizontally in the vise and drill the hole.
> 
> Tom



This seems to be the best option using what I have. I'm not sure the v-blocks will hold the part securely enough based on using them once and having the part move just a bit. Maybe it wasn't locked down enough. I'm willing to try again, though.  Milling along the y-axis will give me a little more support, so thanks for the suggestion!


----------



## JimDawson (Jul 26, 2020)

Let's break down the problem a bit.  This is what separates machinists from the rest of the world, problem solving and the ability to make anything starting with nothing. 

The goal: Slot and Drill & Tap a piece of round stock per print.
In all projects there is an order of operation. In this case, there are two ways to do this:

Drill & tap, then slot
or
Slot, then drill & tap

Either can be accomplished mostly with the tools I see in the picture, but you may have to make a fixture.  Making soft jaws for the vise is not out of the question here if you have some aluminum or steel stock on hand.

In any case, once you have drilled the hole or milled the slot you have a surface to indicate on.  A drill bit stuck in the hole would give you something to indicate on to align the slot, or the slot would give you a surface to indicate on.  Either way, works.

That non-machined surface in the back corner of your angle plate might be useful for holding the piece vertical, might require a little shimming to get the work squared up.


----------



## brino (Jul 26, 2020)

I guess you can see that there's many ways to do it.

I would recommend the collet block as they are quite useful.

You could mill the majority of the slot while the part is horizontal (taking depth of cut to suit the machine and material), and then turn it to vertical to square the slot bottom corners. This would depend on the how much vertical adjustment you have on your mill.

If there is still any concern with vise grip either mill in the y-axis, or rotate the vise 90 degrees and mill in the x-axis.

5/16 = 0.3125, so I guess your using a 1/4" end-mill.

-brino


----------

