Building a bed turret

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pete
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Re: Building a bed turret

Post by pete »

I use a couple sets of 1,2,3 blocks under each strap clamp position for parts fixed down to the table as spacers. Even the cheap Chinese sets are made close enough to dimension they should be more than good enough for this type of work. Ideally it's important the work isn't being forced into a pre stressed condition before you start the machining. There's no way those plates won't have highs and lows on them so I use shims as well until the part doesn't rock at all when sitting on the blocks and only then will I add the strap clamps.
John Hasler
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Re: Building a bed turret

Post by John Hasler »

pete wrote: Wed Nov 25, 2020 5:05 pm Yep a ball bearing will work great, but I'd add you really need a proper flat face surface ground on the bearing and use that flat face against the movable jaws face. Not having that flat that increases the surface area can create a dent in even hardened vise jaws if you tighten the vise to where most of us would. Personally I prefer using a length of heavy gauge copper with with the insulation stripped off. Use it horizontally between the moving jaw and the parts edge. The copper is soft enough to deform on any high spots and mostly level out on the parts edge to increase grip.
I like the copper idea.
John Hasler
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Re: Building a bed turret

Post by John Hasler »

RSG wrote: Wed Nov 25, 2020 5:11 pm
John Hasler wrote: Wed Nov 25, 2020 2:29 pm If it were me I'd dispense with the vise and do the job on the table. Better finish, no overhang, no bowing. Use work stops for repeatable position control.
So do I elevate the slugs with something so I can mill the sides as well or do you flip it up and mill it from the top, sort of like option "A" only with an angle block instead?

I'd use an angle block if I had a big enough one.
RSG
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Re: Building a bed turret

Post by RSG »

Harold_V wrote: Wed Nov 25, 2020 3:50 pm While your objective most likely isn't critical, when you want edges to be at a right angle, don't hold long or wide pieces in a vise. Clamp them to an angle plate
That's great but how do you clamp it to an angle plate with a piece 12" long? I assume you'd use a "C" clamp but it would have to have a deep throat section to get around the block, that or buy another angle plate for one at each end?

Like this?

Image


I apologise if it seems I'm going around in circles but I just want to be perfectly clear before I start cutting into these blocks after spending what they cost to cast.
Vision is not seeing things as they are, but as they will be.
John Hasler
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Re: Building a bed turret

Post by John Hasler »

I wouldn't try to use that small an angle plate with that large a part. I'd clamp to the table with spacers and side mill the ends, relying on spring passes to minimize deflection. Flipping the part over before the finish pass could also help with that.

Was it less expensive to have those blocks cast than to purchase bar stock?
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GlennW
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Re: Building a bed turret

Post by GlennW »

Note the lower image in Post #4 made by me in this thread.

1-2-3 or 2-4-6 blocks have holes in them to enable bolting them to the table (or to each other, or whatever) to clamp stuff to them.

That's an 18 or 20 inch cast iron bar I'm squaring.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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Harold_V
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Re: Building a bed turret

Post by Harold_V »

John Hasler wrote: Thu Nov 26, 2020 11:15 am Flipping the part over before the finish pass could also help with that.
Flipping a part isn't very effective unless you understand why you're flipping, and how often it must be done. The whole idea of this slick process is to limit the amount of material removed from each side for each operation, so one keeps the stresses relatively balanced. Note, also, that the flipping process tends to be one by which the degree of error is reduced with each iteration. The idea is to mount the work piece without altering its natural state. Shimming is very much a part of the process, and one must understand that shimming is not to influence the part, but to prevent the clamps from doing so.

The comment about spring passes to limit deflection. Yep, I agree, but it should also be understood that a perfectly square cut may or may not be required, that if there's a thou or two of taper, that it makes no difference, as the edge may be nothing more than an air fit. Decisions on how an edge should be machined should be made on an individual basis---it may or may not be critical.

Yeah, I realize these comments are obvious---but they may not be to the unwashed. We're trying to help folks with little or no experience when we post on this board.

H
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liveaboard
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Re: Building a bed turret

Post by liveaboard »

Harold_V wrote: Thu Nov 26, 2020 5:21 pm We're trying to help folks with little or no experience when we post on this board.
H
Yeah, and we unwashed types appreciate it.
John Hasler
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Re: Building a bed turret

Post by John Hasler »

Actually I had in mind flipping before finishing the edges. The idea is that if the previous pass left a slight taper due to deflection flipping should result in a subsequent spring pass tending to remove it rather than tracking it since the greatest depth of cut will then be closest to the spindle.

Note that this is somewhat dependent on the properties of cast iron. Don't try to do spring passes on stainless.
RSG
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Re: Building a bed turret

Post by RSG »

Thanks for the insight guys! I think I have decided to use Glenns method with 1-2-3 blocks or two - 4.5" angle plates I have handy. This of course is only for the squaring of the blocks, I will still do the intricate work in the vise for all the holes, pockets and so on.

I appreciate all your input so far.
Vision is not seeing things as they are, but as they will be.
pete
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Re: Building a bed turret

Post by pete »

If your table is like mine RSG and I think it is there should be a proper tee slot on the front face of the table. If so you could use a step block, strap clamp and tee bolt on either side of the plates as well as a couple of your angle plates and C clamps on the table top to fully clamp and support the work. Depending on where you run your ram position you may need to extend it to reach the part edge your machining with it against that front table face. Just be aware any BP type mill isn't as rigid as we'd like to think. Extending the ram will very likely change your head tram to the table by a bit. The toughest part of getting these plates to size is just going to be the set up and juggling all the parts to get it clamped into position.
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Harold_V
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Re: Building a bed turret

Post by Harold_V »

liveaboard wrote: Thu Nov 26, 2020 5:58 pm
Harold_V wrote: Thu Nov 26, 2020 5:21 pm We're trying to help folks with little or no experience when we post on this board.
H
Yeah, and we unwashed types appreciate it.
Thanks. I hope I do more good than bad, though. I'm a bit anal about how I like to go about machining.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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