Fixturing Advice for smooth round parts

Recently ran into a shortage on some parts and had to make (actually still making) about 400 of these stainless steel pins in house. Material 17-4PH 1150.

Pins are about 1.25" diameter and 5.25" long. Pins are cut to length and then turned down on the lathe. The two ends are turned .004 smaller than the center.

The 2nd picture shows the fixture we made that bolts to the table and holds these pins to be clamped end-end with an 8" vise.

First op we load 2 pins in the outer slots with the 'V' detail.
Second op we flip both to the center slots with the flat detail.

Machining for both ops as follows:
1. 1/2" 5 flute Endmill. Removes bulk of material, faces and machines up to shoulder.
2. 3/4" Indexable mill with 1/8" Radius inserts to radius up to shoulder
3. 1/2" Drill. Drill almost all way through(Only 1st side)
4. 1/4" End mill. Mill hole into slot 9/16 wide, 5/8 long
5. 1/4" 90 Deg Chamfer

Total cycle time on the mill is a little over 7 mins per part + handling.
The 1/2" End mill lasts about 80pcs, 1/4" about 160pcs and the others have not been changed.

If i was making the fixture again(which i won't be) i would change plenty of things, i would also probably buy some other tooling but this is what we had at the time and it worked and got us out of a hole.

Where i am going with this(eventually) is:

With things looking slow for next year i am considering moving production of these parts in house. We use about 3,600 per year and have machine time to spare.

The concept i have rolling around in my head at the moment is to invest in a good quality vice/pallet system and to hold the parts in a V-block style fixture (something like the last picture) while also getting some good indexable tooling and getting aggressive with the speeds and feeds. Machine them in a similar style to what we're already doing.

If i can take a chunk out of the cycle and handling time it would really be worth it.

My main concern is getting enough clamping force onto the smooth pin to hold them securely enough to get aggressive with the machining.

Leadwell V80i- BT40 and a big big table.

Thank you for sticking it out until the end... Thoughts?

I wouldn't bother with a pallet system for this. How about:

Heavy steel plate, offset mounted horizontally on a rotary table with outboard support. Plate is bored with four positions for pins, in pairs, with each pair having a split clamp machined in (think two "B's", with the bores being the holes in the B and the pinch clamp bolt going through the "waist" of the B). Plate is as thick as the full diameter length of the pin.

Set parts with axis vertical, mill the two sets of flats in a continual HSM "racetrack" path in climb at max speed and feed (six flute 5/8" or 3/4" carbide endmill). Better still bull nose with 1/8" radius at full DOC, you can set up a rougher and finisher. Flip parts to get both sets of flats cut.

Rotate 90*, drill 14mm hole offset to center of one end of slot, use 3/8" six flute EM to HSM rest of slot length with perimeter finish. Chamfer to suit.

I'd think with optimization such a fixture and process could get four parts done in about ten-twelve minutes or less cut time. A set-up plate with slots to allow rapid setting of pins in the fixture during changeover could speed that aspect.

turned 17-4 with a 63 finish hold in alum pretty well. but if it was me. I would get a few 6" double vises make a tool to cut the dia on the side of each vise jaw like a key seat cutter with the proper rad.( I dont like v-block style for holding)
hold width of vise.
that way you hold the dia of the 2 flat sized in length. drill hole do the one side flat and chamfer.
then other vise use your tool made and blend it with a locating face on the jaws( your tool will cut the face).
from what you say/show in pics the end thickness is about .375 thick and your lengths of each side is 1.75 long. that's a good amount to hold on and supported where your cutting. much better than clamping in a v block.

Milland said:

I wouldn't bother with a pallet system for this. How about:

Heavy steel plate, offset mounted horizontally on a rotary table with outboard support. Plate is bored with four positions for pins, in pairs, with each pair having a split clamp machined in (think two "B's", with the bores being the holes in the B and the pinch clamp bolt going through the "waist" of the B). Plate is as thick as the full diameter length of the pin.

Set parts with axis vertical, mill the two sets of flats in a continual HSM "racetrack" path continually in climb at max speed and feed (six flute 5/8" or 3/4" carbide endmill). Better still bull nose with 1/8" radius at full DOC, you can set up a rougher and finisher. Flip parts to get both sets of flats cut.

Rotate 90*, drill 14mm hole offset to center of one end of slot, use 3/8" six flute EM to HSM rest of slot length with perimeter finish. Chamfer to suit.

I'd think with optimization such a fixture and process could get four parts done in about ten-twelve minutes or less cut time. A fixture plate with slots to allow rapid setting of pins in the fixture during changeover could speed that aspect.

Click to expand...

I like the 4th axis idea

Just an idea,


Lathe with live tooling....

or

fixture or fixtures that would clamp on center section of part. .......mitee bites on a fixture plate.....locate parts using two sides of a pocket. maximize the amount you can run at one go. Clamp in middle and locate off the end or clamp in middle and clamp on the end the bites could push.

I've tried a multiple part V block and missed something when I made it .....I should of made a block with a T slot with small V blocks fitted to it .

best visual a really narrow screw vice.....would of been better...

Milland said:

I wouldn't bother with a pallet system for this. How about:

Heavy steel plate, offset mounted horizontally on a rotary table with outboard support. Plate is bored with four positions for pins, in pairs, with each pair having a split clamp machined in (think two "B's", with the bores being the holes in the B and the pinch clamp bolt going through the "waist" of the B). Plate is as thick as the full diameter length of the pin.

Set parts with axis vertical, mill the two sets of flats in a continual HSM "racetrack" path in climb at max speed and feed (six flute 5/8" or 3/4" carbide endmill). Better still bull nose with 1/8" radius at full DOC, you can set up a rougher and finisher. Flip parts to get both sets of flats cut.

Rotate 90*, drill 14mm hole offset to center of one end of slot, use 3/8" six flute EM to HSM rest of slot length with perimeter finish. Chamfer to suit.

I'd think with optimization such a fixture and process could get four parts done in about ten-twelve minutes or less cut time. A set-up plate with slots to allow rapid setting of pins in the fixture during changeover could speed that aspect.

Click to expand...

Alas.. No 4th. The clamping method could be adopted to work with a palletised version. Or no pallet at all. There is probably enough room on the table to set up the 4 stages as above and just eat the load time.

tonymor said:

Alas.. No 4th. The clamping method could be adopted to work with a palletised version. Or no pallet at all. There is probably enough room on the table to set up the 4 stages as above and just eat the load time.

Click to expand...

Sounds like a good excuse to get one. In fact, you can find rotary fixturing that works off simple M codes or even mechanical actuation, no need for a full 4th-axis. It just has to be a stiff setup so good S/F can be maintained.

Delw said:

turned 17-4 with a 63 finish hold in alum pretty well. but if it was me. I would get a few 6" double vises make a tool to cut the dia on the side of each vise jaw like a key seat cutter with the proper rad.( I dont like v-block style for holding)
hold width of vise.
that way you hold the dia of the 2 flat sized in length. drill hole do the one side flat and chamfer.
then other vise use your tool made and blend it with a locating face on the jaws( your tool will cut the face).
from what you say/show in pics the end thickness is about .375 thick and your lengths of each side is 1.75 long. that's a good amount to hold on and supported where your cutting. much better than clamping in a v block.

Click to expand...

I'm one of those folk from the new generation that landed straight on a CNC and never had to make no tool for myself. If I'm understanding your method you would end up with four ops per part? 4 pieces in each double vice, two sticking out either side milling one flat at a time?

JS said:

Just an idea,

Lathe with live tooling....

or

fixture or fixtures that would clamp on center section of part. .......mitee bites on a fixture plate.....locate parts using two sides of a pocket. maximize the amount you can run at one go. Clamp in middle and locate off the end or clamp in middle and clamp on the end the bites could push.

I've tried a multiple part V block and missed something when I made it .....I should of made a block with a T slot with small V blocks fitted to it .

best visual a really narrow screw vice.....would of been better...

Click to expand...

I have the y axis lathe. But I have doubts as to the oomph in the driven tool to really get after it. Can't remember if it's a 5.5 or 7kw motor but by the time it makes its way through a gearbox or two there's only a fraction of that left. I have also thought clamping in the middle and end might get it to where it needs to be.

Milland said:

Sounds like a good excuse to get one. In fact, you can find rotary fixturing that works off simple M codes or even mechanical actuation, no need for a full 4th-axis. It just has to be a stiff setup so good S/F can be maintained.

Click to expand...

Yeah... I won't run that by the boss man just yet. Rigging something like that up would definitely be pushing my skills and knowledge to the limit, but hey that's what we're here for.

I see larger batches as being key to cutting the cycle time per part. I also suggest top/bottom clamping on both one end and part of the center while working on just the free end of the pins. This will give you more clamping force and allow heavier/faster cuts.

I see two pallets, each holding 10 or more pins, depending on the length of the table. And a table mounted clamp fixture with two fast change faces, one to match the original round tops and the other to match the flat tops after the first operation.

The first pallet has round slots to provide maximum friction for good holding. It is loaded with 10 or more pins and placed under the clamp mechanism with the clamping face with the half round openings. Mill one end with a single cutter with inserts with your 1/8" radius. One or two passes if you have the power for it. Change tools and chamfer the edges.

Unclamp and change the clamp face to the one for the flat ends. Reverse the first pallet and mill and chamfer the other end of the pins.

The second pallet has slots with flat bottoms. And it is made to fit upside down on top of the first pallet with it's full load of half machined pins.

Unclamp and place the second pallet with flat slots on top of the first one. Flip it over and remove the first pallet. Ten pins are quickly moved from one pallet to the other.

The table mounted clamping fixture still has the face for the flat pin ends in it so no change in needed there. Clamp the second pallet with the half machined pins and machine the first ends flat. Change tools and drill the holes. Change tools and mill them into slots. Change tools and chamfer the edges.

Unclamp the pallet and turn it around. Mill, drill, and chamfer the second ends of the pins.

That should give you 10 or more parts with the same tool changes needed for one or two. And you only need to manually load them in a pallet ONCE. And because they are just round pins at that time, that initial, manual loading can be done with no need for proper orientation: just drop them in.

You will probably want to make those pallets from aluminum to keep the weight down.