Re: Tapered Pins

On 7/23/2024 6:15 AM, Jim Wilkins wrote:

 I didn't suggest following with a second smaller reamer because I couldn't think of a way to ensure it aligned with the first radially and axially, the necessary extended shank could let it wander and there's no easy way to know when to stop.

Milling machine does a fair job with alignment as long as you don't move anything. The reamer will follow the existing hole.
There is a saying, "Drill fast, bore straight, ream to size."  Somebody else must have said it first, but I've never heard anybody else say it exactly that way. For now I am the guy who said that saying until somebody tells me different.
It's a mold so depth is easy to find.  Just open the mold and look.  The pin slot was already 3D machined fairly accurately.  0+ to -.001  or better anywhere along the slot.  The reamer(s) just needs to kiss the hole to make it a smidgen smoother.  Its a lead casting mold so as long as the pin sets at "about" the right position castings will come out fine.  You don't get flashing with upto .004-005 gaps unless the mold and lead are overheated.  I vent .0015 to .003 every day without issues on gravity casting lead molds.  (Resins and injection have their own set of issues and tolerances.)
I have already tested fit without reamer cleanup and it "would work" as is.  I'd just like it to set set a little deeper for ease of dropping in the pin.  I think just kissing off the machine marks from the original 3D op will be just right.
I'd ream to position the large head of

the pin relative to the surface, cut off the small end and bin it for later. For a small pin in a deep hole I'd use a dowel or roll pin instead.
 

A straight pin would work, but the customer wants a taper pin because it will theoretically knock out easier.  It will.  With a straight pin you have to DRAG the pin out of the casting for the entire length.  With a taper pin a light tap with a soft face hammer and it just falls out.
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I'm cutting a mold for somebody that casts a body with a through hole. There are nominal dimensions, but a tapered pin that knocks out easily would be acceptable.
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I may not have done an adequate job of describing the application.  The taper pin is not for "joining" or "aligning."  Its to be used as a removable core.
FYI:  I make similar casting molds all the time with straight pin cores, and they work just fine.  They do require more effort to remove, but they work just fine.  In this case its a custom mold, the customer has no experience with lead casting, and they are a bit OCD.  Its easier to charge them for the work than to argue with them and it needlessly burns less of my time.
Similar mold I make with straight pins larger and longer than the custom mold above. https://www.cncmolds.com/webstore/lead-casting-molds/weights-lead-line-for-nets/ten-count/weight-net-sinker-1/4-pin-4-cavity

Hammerlock chain links have another way to retain a pin. It's turned smaller in the center and passes through a nested pair of large split roll pins with their slots opposed. They expand to let the end pass, then shrink onto the smaller center. Unlike shackles one end is no larger than the bow and fits into chain links. The pin is fairly easy to hammer or squeeze in and punch out.
https://www.riggingwarehouse.com/rw-lifting-rigging-hardware/rw-connection-repair-links/rw-hammerlocks.html
 This is the preferred fitting to splice one chain to another, hammerlocks are wider to accept multiple chains for slings.
https://www.etrailer.com/Accessories-and-Parts/Titan~Chain/TCML13.html?feed=npn&gad_source=1
 I had to go beyond hardware store G30 chain to a logging equipment supplier to upgrade my hoisting gear for the heavy logs.
 The drill press vise would be for the mill, to hold large but light material, mainly sheet metal for electronic control panels etc, plus give more badly needed working space under the spindle for upright jobs like 5C collet blocks.

Did you look a the slide lock vise?  I have actually thought about making a second one to go on the South Bend mill.  In a t-slot table the clamping screw for the split block could also lock it to the table with a t-nut making all adjustment and movement fast and easy from the top of the table.  When I don't need it I can just loosen the knob and slide it out of the way.
I don't know how flimsy of material you plan to drill, but anything heavy enough to not buckle when clamped in a vise works in the step jaw just fine.  I drill aluminum sheet as thin as .080 as needed.  depending on the alloy could go thinner.  Much thinner and I use double stick tape or painters tape and super glue to a backer.  The sacrificial backer would then clamp up in the vise just fine.  They are small. but there is a vertical groove and a horizontal groove milled in the moving jaw of the vise for round stock, and there is no reason I couldn't use a 5C collet block in it either.
For reference.  I once made a fixture for milling paper.  Plane old ordinary .003 thick printer paper.  Talked about it on this group.  I used it to create neatly printed custom button labels for a hybrid phone system back when I was still contracting.

My Clausing 8525 mill is the early version without the column riser block.

Its my understanding that riser blocks for mills were options.  Not included.  You unbolt the head, lift it up, slap in the riser block, and bolt it back together.  I wouldn't mind an additional six inches on my South Bend, but usually I can bolt on a right angle plate, and hang the part off the table if I need to drill something longer than my Z clearance.  I have to swing the head to one side so the long part can clear the knee, but its made to do that.
I had to remove the hard jaws to clamp 6

squares of 5" wide 14 ga steel for a hole saw, and wider steel would have been better for hoist baseplates.  At Unitrode I replaced a worn-out drill press with an RF-31 mill

I had an RF-31 for a while.  I didn't get much use out of it, but I seem to use my South Bend knee mill a lot.  A true 5HP (Running on 7.5hp VFD) spindle makes short work of some roughing and truing jobs even if I do have to turn the handles.
drill and bought an 18 lb 6"

drill press vise for it instead of a 70+ lb milling vise that could crush a foot. Machine work for electronics is mainly on aluminum sheet and light extrusions, and no one wears steel toe boots.

The big advantage of the slide lock is it can't spin, its light weight, and its easily removed or installed.  Of course you can make it any size you need.
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Bob La Londe
CNC Molds N Stuff
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