[stang5197]

I need to get some suggestions on machining these plates. I normally on machine around 20 to 50 parts so I usually don't make small fixtures.

I need to make 200 of the plates attached (1 time order I know the project so it won't repeat other then 1 or 2 pcs).

I was considering using the carrier method (order the stock thicker then necessary, machine the entire part and flip it over to machine down to thickness).

My on concern there is only 2mm. Worst case is to use the thru holes but that didn't seems time consuming.

Any thoughts?

On Edit: Material is 4140 Steel

[Geof]

4140 hard or annealed?

Getting thicker stock as you mention would be my approach. I would cut it into lengths to fit across a 6" wide vise jaw, probably fit in four parts with about a 4mm space detween the parts; machine everything, drill and counterbore.

Then cut it into separate parts and grip individually to face off the back and deburr the holes; 2mm should be enough to grip in good vise jaws.

[cracker]

first off... there isn't any held tolerance on the over all dimensions

so why wouldn't you just get stock 6mm x 40mm in what ever length you like.
then cut it to your "X" table limit length
fly cut the entire piece at once on both sides to step it. (not the top and bottom)
set up a stop on your table to set a datum
cut 4 holes... run it against the datum... then use a small end mill and cut to length
and cut 4 more holes repeat
you could set this up on a small CNC mill and bang 200 pieces out in less than 40 hrs

[DareBee]

Couple of questions Cracker
How you gonna hold that for the Fly cutting?
All I can think is adhesive sheet (which woul work but a bastard to set up).
4140 is also typically a hot rolled product you wont get 6 x 40 without paying big bucks for the stock.
I would likely use blanks close to right size. Mill the key feature. Drill & C/Sink. Then hold on the key to mill the OD and back. Have to cut light in the back milling.
You could also machine some softjaws so you could cut the ends to size in 1st op. Then rotate 90deg when flipping to back side so that you can hold on the 6mm(+stock) fresh machined ends. May need to remachine soft jaws to get the other 2 ends.

[cracker]

4140 is about 2 bucks a lb. for a 10 foot piece of 6mm x 40 mm
3 pieces w/ pack. and hand. for under 240.00
you need 2 vises and work supports or 3 vises... what ever.
use parallels to clamp on the edge of 3mms. Thats more than enough to hold that part, assuming you will be cutting it in about 2foot lengths, (do the math and stack it up right). Face mill the steps on both sides and do all 15 pieces.
then use a combo drill / counter sink and interpolate the 4 holes, index it cut it off, cut 4more holes index...

or if your good... cut all the holes in each strip then index and cut off.