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Thread: Drilling jig help
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13th June 2009, 12:36 AM #1Intermediate Member
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Drilling jig help
I am trying to make a quantity of small model engine piston conrod forks and have tried to find plans or ideas for a jig, so I can do a small production run. As I am not one to reinvent the wheel, I googled and did not find what I was after. Has anyone built or know of a design that could be set up to mill a slot on the end of some rod and drill a hole 90 degrees to the slot position? My small mill has not digital read out or CNC and is totally manual and back lash is quite bad.
Here is a rough picture of what the part looks like (showing pin installed)
Kind regards
Steve
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13th June 2009, 08:25 AM #2
It strikes me that with operations in two different planes you would be better off keeping the operations separate rather than making up a complicated jig to do them together. There are better minds than mine out there though, it will be interesting to see what they come up with.
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13th June 2009, 01:46 PM #3
Hi Steve
How's it all going over there? Haven't heard from you for a long while. If you can give me a detailed drawing of the part, ie. dia, length, hole size etc. I can draw a jig for you. How many do you want to machine at each setup?
Kody
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13th June 2009, 03:31 PM #4SENIOR MEMBER
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Hi Steve,
Use a side & face milling cutter. The cutter width should be the same width as that required in the job. Always go to the full depth required in one go. So set the speed & feed correctly, remembering to use a copious supply of coolant to the task in hand.
Whether you do it using a vertical or horizontal milling machine REMEMBERr to feed the metal into the cutter, against its rotation - this is called up-milling. Do you have a rotary table to use? I don't thing a jig needs to be made for the basic operation(s) you have to do - a bit of overkill I would say. Just a vice (with a V in one of the clamping faces - datum point) would be ideal.
Regards
MH
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13th June 2009, 04:44 PM #5Intermediate Member
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Hi Joe,
I have been flat out with other stuff and needed some time out, but have build three engines that I have always wanted to build, two Stirling engines and one small wobble air/steam engine, and now addicted to Stirling's of many different designs.
As most engines I want to build can use the same piston fork for most designs and piston size, and as it is not easy for me to drill and slot exactly 90 degrees from each other, I thought a jig would be the way to go, as this type of milling is common with a lot of different designs.
My inexperienced thoughts of how I could do this was to use some square block, drilled to somehow clamp the rod into and then drill my hole and turn the block over 90 Degs and mill the slot. I was also trying to find a simple setup that could use a small indexing ring, that could turn 90 Degs in a set position,
Joe, I have sent you a sketch and also some other plans to look at, this will then explain my problem a lot better than words, and you may see even a better way to make a piston fork,
Thanks all for your help and feed back,
Kind regards
Steve
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13th June 2009, 04:56 PM #6Intermediate Member
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13th June 2009, 07:05 PM #7Fit to Machine
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Maybe cut the slot first in all the components.
Then make a jig from a bit of flat plat. Make the flat plate the same size as the slot and sit the part over the plate. Could maybe weld sometabs on each side to hold the part in the right spot. Or maybe machine a bit of square down to a H-shape where the part fits into the centre of the H.
Just a few ideas.
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13th June 2009, 09:12 PM #8
Hi Steve
I have figured out the answer to the problem. You will have to make them two at a time and use a jig similar to how you described it. I will post the drawings when done and send you a copy.
Kody
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13th June 2009, 10:49 PM #9Intermediate Member
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14th June 2009, 03:09 PM #10
Hi all
The attachments show the method I would suggest for holding and maching
the slots in the rod ends. Start by machining the two steel blocks.
They are made from 14mm steel bar. The critical dimension is the
height. Fit the two M6-1 cap screws after machining the two blocks to
thickness, clamp together and then finish the machining all over the
other faces.
Dont forget to mark a witness in the blocks so they will go together
exactly as made. Drill the 23/64" hole using the lathe and the four jaw chuck.
This hole must be as truley centered on the split line as possible. This can be
easily done if the two blocks are exactly the same thickess or as close as you can get them. The hole location is then positioned for center in the four jaw chuck using a dial indicator. After drilling, ream to size or finish to size with a boring bar. This is all easy to do. (Hmmm, ok, it's easy for me).
When the hole is finished, remove from four jaw chuck and undo the screws. Take a cut of about 0.15 from one face of the two blocks. This is to ensure the rod ends will be correctly clamped when placed in the mill vice.
Machine the rod blanks to size as shown. Position one between the
blocks and clamp in the mill vice. Align the cutter in the middle of the rod end and cut the slot.
The best cutter to use is a Slot Drill. It MUST be sharp, preferably a
brand new unused one. Use a cutter that has negative rake angles. I have some that are made from TC and they cut perfectly in brass. I would not use a side and face cutter or a slotting saw for this job. Run each cut with the slotting drill at a depth of no more than 1.5mm.
When the slot is finished to size, remove from the vice, de-burr and
then machine the other end. A new jig is then made to drill the holes. When I have finished the drawings I will then post them for you.
This will be a fun job for you.
kind regards
Joe
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14th June 2009, 03:43 PM #11Intermediate Member
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Hi Joe,
Wow that was quick,
I have just printed the plans off and will make a cup of coffee and digest your instructions. The plans look fantastic and at a quick glance, would say this will be a nice test for me and am sure will do the job.
I am confident that others would find your jig very handy for other applications, get back to you soon,
Thank again Joe,
Kind regards
Steve
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14th June 2009, 07:57 PM #12Intermediate Member
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Oh dear,
I had to change my nick name as the system did not like the word sm#$t in smu%$ley, so the admins asked if I would change it, so they did not have to authorises my posts every time I made a new thread or posted a reply, wow sensitive software............. lol
Anyway I am now STEAM (should have put blowing off steam, but software may not like blowing off)
Regards
Steve (steam)
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15th June 2009, 01:01 AM #13GOLD MEMBER
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Is there any reason why you couldnt get away with using only the one fixture and doing your Slotting and Drilling without removing the Conrod untill you have machined both ends.
Could you just change the Dimensions of the Jig and make it Square.
Do you slots in the Vertical Plane on both then rotate 90 degrees and put slot Horizontal and Drill your holes.
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15th June 2009, 01:06 PM #14Intermediate Member
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I thought this would be the way to go at first to, but I think kode has done it this way because there is not a lot a meat to clamp on to, as the parts are quite small, so if I am going to drill and slot, there will be some force on the part.
Lets see what kode comes up with for the drilling side of things
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15th June 2009, 02:56 PM #15
Hi
That's easy enough
Use two pieces of angle iron at least 6mm wall thickness, fastening one angle iron inside the other as shown in the VERY ROUGH sketch.
Depending on just how accurate and repeatable you need these con rod ends to be you may want to machine the "base" of the jig so that it is flat AND square to the holes drilled for clamping the con rod ends.
I do recommend the use of a side and face cutter as this will ease the production and process of manufacture. When in actual use, after initial positioning, ALL motion of the jig will be in the X axis only. The quill will be used to drill the holes in the Z axis. (I am assuming your mill has a quill for drilling purposes)
STEPS TO MAKE JIG
Cut two pieces of angle iron (at least 6mm wall thickness. One piece (the bottom or lower piece) to be 100mm longer than the top piece.
The length of these angle irons is arbitrary, depending on the capacity of your mill and how many con rod ends you want to or can mill in a single session.
Cut two pieces of "packing" material. (I suggest 4mm - 6mm rod or square bar). These are to raise the inside angle iron away from the internal radius (web) of the lower angle iron. Alternatively you could mill one or both angle irons to allow them to fit together, however I see this as extra (and not really necessary) work.
At this point, if desired machine the bottom face of the base angle iron flat.
Place the two pieces of angle iron together, with the packing material between the two faces that will become the bottom of the jig.
Clamp these angle irons together so that the top angle iron fits flush internally behind the face to be drilled with the clamping holes. the other two faces will be separated by the thickness of the packing pieces.
Drill holes in the "base" side for camping bolts. The number of "clamping" holes may vary depending on how long you make the jig, but of course you will need at least two holes (one at each end).
Take these two clamped pieces of angle iron and mount them in a vice or on an angle plate so that the base part is precisely vertical with the milling table Z axis and the BASE part is exactly parallel with the milling table X axis.
Starting near one end, drill or mill holes through BOTH pieces of angle iron. These holes are to be accurately sized to fit the smaller diameter of the con rod end - a good sliding fit.
The position of these holes (vertically) from what will be the top edge of the jig needs to take into account the size of the mill or drill used to drill the holes for the con rod pins. Allow sufficient clearance for the collet or drill chuck to drill the FULL depth of the larger diameter of the con rod end.
The position of these holes on what will become the horizontal plane (during the use of the jig) is again arbitrary. I suggest something like XX turns of the table travel in the x axis. This will make it MUCH easier to use the jig than measuring for example "27mm" on the dial.
While mounted in this position, drill two or more holes for bolts that will keep the two vertical faces together during operation of the jig. These holes will need to be approx 1mm larger in diameter that the bolts that go through them. This is to allow the clamping action to work whilst maintaining a close fit of the two surfaces of the angle iron faces.
USING THE JIG
In use the jig will be positioned such that the clamping holes are parallel to the milling table Y axis and therefore the drilling action is perpendicular to the clamping holes.
Clamp the jig to the milling table ensuring it is parallel with the x axis. Place ONE packing piece at the outer edge of the jig. The clamping holes should be lined up
Place a con rod end in each of the clamping holes.
Tighten the clamping bolts these will attempt to cause the clamping holes to become (vertically) offset to each other thus clamping each of the con rod ends.
Starting at one end of the jig, (the same end at which you started when drilling the clamping holes) carefully position the drill/mill to create the hole in the first con rod end.
Now advancing the x axis BY THE SAME NUMBER OF TURNS used when making the jig, you should be in the correct position to drill the next con rod end.
Repeat this x axis advance for each con rod end.
When all holes are drilled, reposition the milling table so that you can use a side and face cutter to mill the slot across ALL con rod ends in one smooth x axis movement.
Loosen the clamping bolts and remove completed con rod ends.
I expect you could do at least ten con rod ends in one "setting"
I recommend you drill he holes first then mill the slots. The holes will help ease the burden on the milling cutter and help (in a small way) to clear the milling swarf.
See my very quick and VERY ROUGH sketch attached...
This jig will not require any rotational movement of your parts and will not be adversely affected by back lash providing (during machining) all movement of the jig is made in the ONE X axis direction.
I hope this helps...
I am Perth so if I have missed something in my description or you want to ask a question then please give me a call. I'll send my mobile number to you in a pm.Kind Regards
Peter
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