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More machinists questions.......

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Robertvina1717

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So I was squaring up edges on a piece of 3/8" x 11.5" x 4.5' hot rolled flat stock on the mill. Cleaned up the rough edges on a belt grinder, milled off maybe 30-40 thou on the long sides with no issues. After I checked the dims and it was like .035" off from one end to the other over 11". I don't know why though. I went and checked my setup again, the head is square front to rear and left to right, the vise is leveled and squared up. When I trammed the table I'm well within a thou over 4.5".

If anybody can tell me WTH I'm doing wrong or maybe what I should check or maybe it's just a sh!tty mill and that's the best I can expect?

Any input is appreciated!
 
Could be as simple as a wayward chip under your stock. What condition is the mill in? Have you checked for play in the ways?
 
Im assuming you clamped your workpiece in your vice with the 4" dimension vertical and you milled the first edge and then flipped the part and milled the opposite edge ? Is your vice indicating dead flat ? Possibly a chip was setting your piece out of parallelism ?
 
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Curious to see the set up.
Will be playing with my mill soon and learning on the way
Did you support any over hang out of the vise.
Any slop on the ways/gibs
I can easily see a mill table acting like a seesaw
 
11" part set in a 4" vice is not likely to stay put.
Mount flat to the table on a spoiler with clamps on the short edges and one in the middle - align one long edge to the axis (center clamp on opposite long edge) and take a cleanup cut
Move the center clamp to the side you just cut and cut other long edge to dimension.
Move one end clamp to long edge close to the end to expose the short edge and take cleanup cut
Move the other end clamp and cut to length.

Since the part is never moved it will be as good as your machines ways are.
 
What mill are you using?
What end mill did you use to true the long edges?
How did you clamp the piece into the vise (vise width?)?
IME, having something hang even 1" beyond the vise jaws usually needs support of some type. Even if you have the item on it's long edge (so 4.5" tall, 3/8" wide) you'll need support. With it sticking up from the vise base, you'll probably want more side support too. I've clamped up items in my 6" vise that were tall using more stock to sandwich it. Making it more rigid in the vise. Feeds and speeds could also play a part in the item being off.

For clamping longer/larger items, I have a Saunders Machine Works fixture plate and three of their Mod2 vise setups. It allows me to easily clamp larger/longer items for machining. I have a piece of steel that I'll be machining that's 6"x12"x1/2", soon. I'll use two of the Mod2 vises to hold it (one on either end). Mostly because there's really not room to hold it with three of the vises. I could, but the stock wouldn't be fully clamped on either end at that point. I've used this setup with another piece that was thinner and it worked out very well.

For most things I get cold rolled/finished steel these days (when using steel). Especially after the issues with hot rolled when you want to machine it. Unless it's short enough to clamp via the cut ends that is. Cold finished just makes setup easier since you have square edges (not rounded like hot rolled) to clamp to. Even if they're not to high precision, it's easier to machine with those. Clamping against them is also easier (or having them rest in a vise).
 
I trimmed all four sides but not the faces. I didn't measure the length end to end just side to side. All manual hand wheel work. I do have a cheapo DRO on the Z. I touched off on the high and low spot and then started milling at the high end and milled the complete length (and well beyond) in several passes at about .007 per pass until it was cleaned up. So there was no backlash issues. I was using a 5/8" end mill.

I just went through the mill and cleaned and inspected everything a few months back and it's actually pretty tight. There was a thread about it. There is backlash but not bad and it's manageable.
 
I use a dial indicator in the quill to level the vice and then a test indicator in the quill to bring it into square. I use one of these things to tram the head to the table which hasn't changed since I went through the mill a few months back though I do recheck it fairly often. The vise does have a rotating base plate that I don't typically use so it's not attached as it adds too much height for normal ops, other than that the vise is a single unit.
 
Try measuring from the table to the bottom of the plate on both sides. You can use you calipers as you don't need an accurate measurement, just a comparison from side to side.
 
I would’ve cut it jigged right up on the table itself, sitting on a set of parallel bars. Clamp at each end of the smaller width edges, then cut the long edges parallel. Then swith to trim the overall length.

Maybe I missed it, but did you conventional (up) mill or climb (down) mill?

www.harveyperformance.com

Climb Milling vs. Conventional Milling - In The Loupe

There are two distinct ways to cut materials when milling: Conventional Milling (Up) and Climb Milling (Down).
www.harveyperformance.com www.harveyperformance.com
 
jct61765 said:
Depending on what your trying to do, that part is sitting way to high. That vice is to small, unless your just trying to drill holes. How did you square up the top of the lower sitting against the back of the vice?
Click to expand...
I was just checking to see if the vice would hold the lower enough to drill the trigger pins and safety. I have a milling side plate under the lower to keep it leveled

To do any actual work I'll clamp directly to the table or a right angle block. 20230218_175636.jpg
 

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pastera said:
I was just checking to see if the vice would hold the lower enough to drill the trigger pins and safety. I have a milling side plate under the lower to keep it leveled

To do any actual work I'll clamp directly to the table or a right angle block.View attachment 722637
Click to expand...
What are you using as your zero? I've never worked on an 80% lower. Are the holes already partly drilled? I made thousands of lowers, uppers, gas blocks etc at sig sauer when I worked there.
 

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