Thanks.

[Red Robin]

Like I said a month of Sundays.

Haha Yeah it'll definitely take some time but it should work with high quality carbide end-mills, that is, once he get's a solid mounting option... The main concern is how to get the jig clamped/bolted onto the Sherline, it seems this mill uses proprietary vices OR it can only be retrofitted.

[Red Robin]

The 2.25" throat dimension is going to be the limiting factor.
There would not be room for a vise and a lower fixture to be clamped in the vise.
Just take the lower receiver fixture and drill holes in it so it can be bolted down directly to the table.
That is the only way you will be able to reach the middle of the receiver to mill the fire control pocket.

I'm by no means a machinist, please bear with me. I have no clue what the "throat dimension" is (even after a Google search). By lower receiver fixture, do you mean the jig? The jig he has is about half an inch short on the bottom, which means the lower sticks out .5" and the jig doesn't contact the table... are you positive the 2" vice won't work?

Definitely this. If I recall the specs properly, the table uses 10-32 threading for the T-nuts.

http://www.sherline.com/3056pg.htm you're right!

[Whiterabbit]

but it should work with high quality carbide end-mills.....

I'm by no means a machinist, please bear with me.

I'm pretty sure HSS is the material to use here for the endmill.

Milling vise will lift too. it's usually not enough to matter but on tighter tolerance stuff it makes a huge difference. There are tricks to holding a part in a vise to insure it is in there square.

cool, good stuff to know. Do you have any specifics on those tricks, or general ideas on how those tricks are accomplished? Would these same tricks work with a drill press vise compared to a milling vise? AR-15's aside, I am about -->||<-- this close to saying forget vises for any work I have to do (not much) and just use clamps, it seems like I spend twice as much time fixture fighting when I could just clamp the work to the table on some 1-2-3's and have at it.

[kcstott]

The issue I see is trying to hang an endmill out there 1.25" + to do the FCG pocket then 1.340" to do the trigger slot. it uses a mores #1 with a very small through hole. that with a .08hp motor??? I don't see you being able to take more then .030" depth of cut per pass. these machines were designed for prototyping small plastic and wood parts.

The spindle is not rigid enough to take a .050" depth of cut, the motor can't drive an endmill bigger then 3/16" effectively.
This machine would be perfect for finishing an AR 80% for a 12" GI JOE but not a full size AR. I'd only use this if i had nothing else to use and even then I'd try to figure something else out.


Whiterabbit
it's easier just to take a picture


Get a good piece of hardened and ground rod. 3/4" diameter is good but on lager parts 1" work well. and on smaller stuff 1/2" is fine.
what this does is remove any influence the movable jaw has on your part. and we'll say that my 123 block is the part you are trying to square up.
Drop it in the vise, place the rod against it, clamp down firm, hit it with a rubber mallet to drive it down. Take your cut across the top. remove the part, debur the edge, clean the vise and the part. Now place your freshly cut surface against the fixed jaw, use the rod again, Clamp firmly, hit it with a mallet to drive it down, take your cut across the top.

You now have two sides that are as square as your vise is. Now for most parts you can for go using the rod once you have two square sides but the tool maker in me won't let me do that. So I use the rod on every surface until i've cut the last side. this insures no influence from the movable jaw. it's over kill but i can trust my parts are square.
The other big issue with squaring up parts is keeping everything clean. I'm constantly wiping down the clamping surfaces of the vise with a clean rag and clean hands to pick up any minuscule debris. One tiny chip with ruin a job

[ar15barrels]

I'm by no means a machinist, please bear with me. I have no clue what the "throat dimension" is (even after a Google search). By lower receiver fixture, do you mean the jig? The jig he has is about half an inch short on the bottom, which means the lower sticks out .5" and the jig doesn't contact the table... are you positive the 2" vice won't work?

http://www.sherline.com/3056pg.htm you're right!

Jig/fixture are used interchangeably in our context.

The throat is the dimension from the column to the center of the quill.
With a 2.5" throat, you can only drill a hole or mill a slot 2.5" from the edge of your fixturing as your fixture will crash the column if you try to go beyond that.

The solution for the lower hanging out of the fixture is to simply make spacers tall enough to get the receiver clear of the table.
Then, put the spacers under the fixture when you bolt it to the table.

The vise will possibly add so much thickness to the setup that you would not be able to mill the far side of the fire control pocket in the same setup as you use for the near side of the pocket.

[krwada]

Milling vise will lift too. it's usually not enough to matter but on tighter tolerance stuff it makes a huge difference. There are tricks to holding a part in a vise to insure it is in there square.

OK ... What are the tricks?

I have a precision milling vise, and it lifts by around 0.001 to 0.002". How do you get it to hold square?

I already took the thing apart, and honed the parts that hold the part down square. It improved a lot ... however, it still lifts the part a very tiny bit.

Thanks!

[krwada]

The issue I see is trying to hang an endmill out there 1.25" + to do the FCG pocket then 1.340" to do the trigger slot. it uses a mores #1 with a very small through hole. that with a .08hp motor??? I don't see you being able to take more then .030" depth of cut per pass. these machines were designed for prototyping small plastic and wood parts.

The spindle is not rigid enough to take a .050" depth of cut, the motor can't drive an endmill bigger then 3/16" effectively.
This machine would be perfect for finishing an AR 80% for a 12" GI JOE but not a full size AR. I'd only use this if i had nothing else to use and even then I'd try to figure something else out.


Whiterabbit
it's easier just to take a picture


Get a good piece of hardened and ground rod. 3/4" diameter is good but on lager parts 1" work well. and on smaller stuff 1/2" is fine.
what this does is remove any influence the movable jaw has on your part. and we'll say that my 123 block is the part you are trying to square up.
Drop it in the vise, place the rod against it, clamp down firm, hit it with a rubber mallet to drive it down. Take your cut across the top. remove the part, debur the edge, clean the vise and the part. Now place your freshly cut surface against the fixed jaw, use the rod again, Clamp firmly, hit it with a mallet to drive it down, take your cut across the top.

You now have two sides that are as square as your vise is. Now for most parts you can for go using the rod once you have two square sides but the tool maker in me won't let me do that. So I use the rod on every surface until i've cut the last side. this insures no influence from the movable jaw. it's over kill but i can trust my parts are square.
The other big issue with squaring up parts is keeping everything clean. I'm constantly wiping down the clamping surfaces of the vise with a clean rag and clean hands to pick up any minuscule debris. One tiny chip with ruin a job

OK ... now, I see how you do it.

Next question ... How do you square the thing up if you need to elevate the part?

Or should I square it using the drilling rod 1st?

Thanks again!

[yari]

Parallel bars. Paper tabs and a dead blow mallet.

Those mini mills are used a lot by jewelers for cutting wax. I'm waiting for an end result to say I told you so. Thing is way to small.

[kcstott]

OK ... now, I see how you do it.

Next question ... How do you square the thing up if you need to elevate the part?

Or should I square it using the drilling rod 1st?

Thanks again!

If it's not to small of a part elevate it with a parallel bar. same technique
if the parts are very small, that's when you brake out the tool makers vise and indicate it in.

[Excitable Boy]

OK ... What are the tricks?

I have a precision milling vise, and it lifts by around 0.001 to 0.002". How do you get it to hold square?

I already took the thing apart, and honed the parts that hold the part down square. It improved a lot ... however, it still lifts the part a very tiny bit.

Thanks!

Two words: Kurt vice

Stoning a vice is pretty imprecise. As far as I know, the only way to square a worn one up is with a surface grinder and some good grinding skills.

OK ... now, I see how you do it.

Next question ... How do you square the thing up if you need to elevate the part?

Or should I square it using the drilling rod 1st?

Thanks again!

Square it up first. Good old machinist tricks here.

Parallel bars. Paper tabs and a dead blow mallet.

Those mini mills are used a lot by jewelers for cutting wax. I'm waiting for an end result to say I told you so. Thing is way to small.

Yup. That machine just isn't up to the task at hand.

Don't forget good old fashioned stainless shim stock as another tool in the arsenal.

[kcstott]

OK ... What are the tricks?

I have a precision milling vise, and it lifts by around 0.001 to 0.002". How do you get it to hold square?

I already took the thing apart, and honed the parts that hold the part down square. It improved a lot ... however, it still lifts the part a very tiny bit.

Thanks!

Thing is honing will not help if the the vise is not square to begin with. Never trust the specs unless it says Suburban. When I was in the tool room we would grind all our stuff in, brand new out of the box didn't matter. We will at a very minimum indicate it to see how far out it is. My milling vise is about due for a regrind but I ground it in flat, parallel, and square, to .0005" over six inches. Thats over kill but you can then trust it and never have to guess how the vise is effecting your parts.

[kcstott]

Two words: Kurt vice

Stoning a vice is pretty imprecise. As far as I know, the only way to square a worn one up is with a surface grinder and some good grinding skills.



Square it up first. Good old machinist tricks here.



Yup. That machine just isn't up to the task at hand.

Don't forget good old fashioned stainless shim stock as another tool in the arsenal.

I'm talking about a Kurt vise. they lift too. Brand new out of the box. you can clamp a standard in it an indicate it. and you can watch it lift.
use the dowel pin and zero lift.

[Excitable Boy]

I'm talking about a Kurt vise. they lift too. Brand new out of the box. you can clamp a standard in it an indicate it. and you can watch it lift.
use the dowel pin and zero lift.

Yeah, my comment about good old machinist tricks here was directed at your post about the dowel pins. I wasn't clear in my post. That works.

Looking at the machine in the OP, I'm pretty sure a 6" Kurt outweighs the mill he was originally asking about!

[kcstott]

Yeah, my comment about good old machinist tricks here was directed at your post about the dowel pins. I wasn't clear in my post. That works.

Looking at the machine in the OP, I'm pretty sure a 6" Kurt outweighs the mill he was originally asking about!

Yeah I don't think they understand just how small that machine is.

You could set that thing up on a child's desk and still have room for the kid to do their home work

[Red Robin]

Thanks for all the helpful comments guys, I'll let you know if it works for him.