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Author Topic: How would you clamp this?  (Read 6999 times)

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How would you clamp this?
« on: February 07, 2014, 12:15:41 PM »
I want to make this part on my milling machine, (photo attached) when I have machined the first side and cut it from the plate I will need to turn it over to mill the recess on the other side, and also the radius. How would you hold a job like this while machining the second op?
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« Reply #1 on: February 07, 2014, 01:00:32 PM »
You could leave holding tabs when milling the first side, then cut (almost) right through when doing the second.

Alternatively, only do the radius and recess on the first side and do the whole cut out from the second.
Re: How would you clamp this?
« Reply #2 on: February 07, 2014, 10:00:15 PM »
Predrill the two end outside holes and bolt it to a fixture subplate using close fitting bolts for location. Machine one side, flip the part over and bolt it down with the same holes and do the other side. Two separate programs but uses the same datums. Closer the fit the better.

Offline Sam

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Re: How would you clamp this?
« Reply #3 on: February 17, 2014, 06:28:01 PM »
Agreed...sub plate is the way to go on that. If its critical, I would drill, and likely ream to fit shoulder bolts OR two dowels and use other two holes to bolt down with. Then go back after all is finished and drill out to size.
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."
Re: How would you clamp this?
« Reply #4 on: February 17, 2014, 08:25:04 PM »
You know, the first question I'd ask is how many are you making?  The answer for 1 is very different than for 100! For instance you could simply clamp it down from the top on one side and cut the other side and maybe the holes.  Then put clamps on the other side and finish it.  Flip it locating along the straight edge with a dial indicator and indicate the center of one hole. I have done a lot of one offs this way, and I don't have a pile of fixtures plates I'll never use again.

A very good machinist once made me a very expensive fixture that added nearly 5 dollars a part to 100 pieces. Another machinist had made a very simple fixture for $20 and did the same number of parts for about $300 less.

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Re: How would you clamp this?
« Reply #5 on: February 17, 2014, 08:52:10 PM »
Very true Gary. Just figured it was a larger quantity. One can always "make do" for just one or a small quantity. So, Jimster...what is the part? It's got one of those "Ive seen that somewhere" looks to it.
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."
Re: How would you clamp this?
« Reply #6 on: February 18, 2014, 09:59:40 PM »
It is very easy to design a very expensive part, and quite difficult to design cheap parts.  At my last job another engineer designed a part. I looked at it and said it would be very expensive to make because it would have to be fixtured 6 times. He said "No it won't, they do it with a CNC machine".  I asked him who was going to do the part and when he told me I said "You know they have Fadal 4020 machining center, and I happened to actually have run one for 3 months and then continued doing the programming for another 6 months!"  He still didn't believe me, until he got the price.

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Re: How would you clamp this?
« Reply #7 on: February 18, 2014, 10:55:41 PM »
Yeah, you can always tell when an engineer has little or no manufacturing experience. There can be countless phone calls and emails back and forth, telling them they need change something. It either cant be machined, or the cost to make it by their design would be astronomical. More times than not, you loose money just from the time invested with collaboration. After a while, you can just look at a print, or model and tell where it came from, and instantly factor in "X" amount of hours to add in to the quote for ignorance.
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."
Re: How would you clamp this?
« Reply #8 on: February 27, 2014, 06:11:15 AM »
The part is a shock bracket for autograss racing car.