[cordvision]

I'm going to make a couple hundred units of the part pictured (a little less than 4 inches long). I start with stock that is just a tiny amount oversized so I can mill it quicker as I don't have to mill the contour out of a whole sheet. The two holes will be threaded for M4. I'm looking for suggestions on work holding this part to cut the contour. The obvious solution would be to just screw it down with M3 screws. However, since M3 screws are pretty flimsy I was hoping to avoid that. Also, I don't think that holding it down with a vacuum table would work since the surface area is quite small. Any other suggestions how I could avoid having to use M3 screws?

[dobey]

If you only had to chamfer the one side I would drill/countersink/tap the holes in the oversize blank and then screw them to a fixture plate for the profile and chamfer op. If you have to chamfer both sides I think dowel pins and vacuum fixture would be faster and worth making.

[cordvision]

I only have to chamfer on one side. However, I wanted to avoid having to screw them down as mentioned in my first post because I would have to use M3 screws and they are just a little bit to flimsy for my taste.

[IMT]

How thick is the part? How big is the chamfer?

[cordvision]

3mm thick (0.12"). Chamfer goes 2mm deep.

[cobrakai]

I've used tiny #4-40 screws to hold down a part like this many times of the same thickness. No issues whatsoever, just make sure you do a finish pass, it will turn out beautiful.

[cordvision]

I'm not worried about the M3 screws holding. It's more for practicality. I was hopping to avoid them because I'm not looking forward to hand tapping 40 plus M3 holes and also think a lot of "fiddling around" will be involved with screwing down all the blanks for every run.

[Mooser]

What's the part material?
M

[IMT]

Hmm.. That thin I would use the 3mm screws and double sided tape. Carpet tape works well if you clean the surfaces properly and apply enough pressure to activate the adhesive. It takes quite alot of pressure to activate the adhesive. I've used a press to seat the sheet stock to a fixture plate before.

[cordvision]

Part material is 6082 Aluminum (similar to 6061). Using adhesive would work but is not practical for "mass production" as it takes a lot of time to remove the parts.

[Mooser]

Aluminum changes everything (I think)
I make some little parts out of .093" stainless and hold them down through two holes (#6-32) that are tapped into a steel plate. The plate has two bosses (.156 dia) that fit nicely into the holes in the parts and the tapped hole is in the center of the boss.
[IMG][/IMG]

I run these in batches of 100 as well but it's a repeat job

For the span you have there I think I'd make a little steel bar that went from one hole to the other and maybe slightly bent in the center to help hold pressure on the center.

I use a small cordless screwdriver with clutch and an allen key to put the screws in/out

HIH
M


I use a small

[Uman]

How about the tab technique? Use bar stock in vise or fastened/clamped to fixture plate, drill holes, chamfer then profile cut with tabs and manually break and clean tab points. If it is real delicate and you want a clean separation, use an adhesive substrate with the tab technique and cut it clean on the machine.
-uman

[Steve Seebold]

I would make the part with an extra 1/8 to 3/16 of material thickness, finish the shape of the part then flip it over and remove the excess material.

[CadRhino]

Why would you have to hand tap them? You could hold them down with locating pins and bar to fixture plate while they are being tapped by the torn Machine. Then screw them in.

I'm not worried about the M3 screws holding. It's more for practicality. I was hopping to avoid them because I'm not looking forward to hand tapping 40 plus M3 holes and also think a lot of "fiddling around" will be involved with screwing down all the blanks for every run.

[cordvision]

It looks like I'll just have to use M3 screws. I'm hand tapping because I don't have a tapping head at the moment. Thanks for all your replies!

[C*H*U*D]

It looks like I'll just have to use M3 screws. I'm hand tapping because I don't have a tapping head at the moment. Thanks for all your replies!

For what it's worth, I make a lot of parts similar to yours. I use M3 screws to hold them down all the time with no problems. I use M3 because that is what the final product uses:

Attachment 341074

Attachment 341076

Attachment 341078

For these parts, I clamp 2 sheets of 1/8" Delrin to the fixture and let it go...never had an issue.

Attachment 341080

[adchrome]

Tap with a cordless drill, works great and fast

Sent from my SM-G900T using Tapatalk

[TurboStep]

I'm going to make a couple hundred units of the part pictured (a little less than 4 inches long). I start with stock that is just a tiny amount oversized so I can mill it quicker as I don't have to mill the contour out of a whole sheet. The two holes will be threaded for M4. I'm looking for suggestions on work holding this part to cut the contour. The obvious solution would be to just screw it down with M3 screws. However, since M3 screws are pretty flimsy I was hoping to avoid that. Also, I don't think that holding it down with a vacuum table would work since the surface area is quite small. Any other suggestions how I could avoid having to use M3 screws?

If you've already prepared your stock this may not be an option but I'd try the vacuum table starting with a plate for 10 to 20 pieces. Make a carrier for the required batch size with o-ring seals around the holes and neoprene seals around each contour. This is a fair amount of preparation but only needs to be done once.
To machine the parts first drill the through holes, then rough out the contour but not to the full depth - leave something around 0.5mm. Countersink the holes and chamfer the contour with a drill mill. Make the threads, preferably with a thread mill to reduce the risk of pulling the part upwards. Finish the contour with a smaller end mill than for the roughing pass. This last pass will only take off any remaining stock from the sides and cut through the remaining 0.5mm leaving the part free. The vacuum should be able to pull each part down with at least 10kg (1kg cm^2), which should be enough for this last op.
The advantage is that no fiddling with screws is necessary and only one setup would be required.
Disadvantage: if you've already prepared the stock this method won't work.
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