Jerry Feather

I decided to see if I could make some replacement Auto shift T-Handles using the old fashioned molding process that I am trying to make the Manual Shift ***** with. The T-Handle is much more complex, but I think I have figured out how best it can be done and eliminate the propensity for them to break out at the bottom where the mounting screws are.

I have taken one of the broken ones apart and studied it to see just what is going to be needed. Then I have started the pieces for the mold and have ordered another pound of Devcon Aluminum F-2 to make the body of the mold with. There will be only four pieces of the mold - - the top, the bottom and two inserts to form the recesses for the button openings. The basic handle is utilized for either left or right hand drive cars. The only difference I can see is with the shaft of the button - - one is opposite from the other.

I'm going to design an aluminum core for the handles, or actually two. One will be for the button shaft and the other for the base and the shift shaft. They will both be cast into the hard rubber compound that I'm going to use.

Here are a couple of pictures of the beginning processes. The next step will be to work up the wood for the body of the mold.

Jerry Feather

This is what it will look like when I am ready to take a mold off of it, except that the broken out piece at the bottom will be filled in with Bondo and reshaped to match the original shape. I'll even fill up the screw recesses and the shaft hole so the mold will be smooth in that area.

I have the bottom half of the wooden mold body laid up with epoxy and it will set overnight. Then I'll lay up the top half on it but with waxed paper in between. When that sets and I trim it up to be square and true outside I'll then locate and drill a cross hole for the two aluminum "branches" you see in the handle now. later, as with the 5-speed *****, these pieces will become part of the mold.

Jerry Feather

Later last night I figured the epoxy was hard enough to unclamp the first half of the mold body, so I did so. Then I laid up the other half with epoxy and left it for the night. That will give me more working time on it all today rather than waiting for the epoxy.

Then while measuring some of the pieces to decide on some reamers I'll need to work this up, I discovered that even the shift button is reversible. It comes apart so that it can be configured the other way for RHD cars.

One thing that means, if you don't already know, is that if you have a good shifter out of a 928 with LHD you can reconfigure it for RHD by taking the plug out of one end, taking the button out of the other together with the plastic sleeve around the button recess and then reversing the configuration of the button and it's shaft and putting it back together the other way.

Jerry Feather

To keep the central part of the button body oriented in its bore there is a slot in the bore that is 90 degrees to the shifter shaft bore. However, it is not on the same plane as the long axis of the shifter button, but rather about 15 degrees or so off from it. I still have to figure out just how I am going to measure that angle; and then how I am going to set things up in my mill to cut that angle into some of the pieces. I'll show more about that when I figure it out.

Jerry Feather

I found the mold body pretty well set up so I sanded the mating surface so they match pretty well then screwed them together and trued up the sides. Then I drew a rough outline of the T-handle and carved out the recesses for the handle in each half getting ready for the molding compound to be poured in, when it arrives. Here is what it looks like at this point.

Jerry Feather

My son, the engineer, found that the flats on the ends of the button central shaft piece are oriented to coincide with the difference between the shift shaft and the axis of the button. He measured with my protractor and came up with 8 degrees difference. I measured but with the piece at the very end of the protractor I get 10 degrees, so I think by extrapolating I am going to use 9 degrees. Now all I have to do is figure out how I can put that to use in cutting a couple of slots needed.

Tom in Austin

Great project Jerry, this will be a great help to all the 928 owners with buggered mounting holes!

Jerry Feather

I got the bottom of the handle filled in with bondo and then sanded to shape and milled for the screw recesses. Then I made two mold pieces to fit into the mold to form the recesses in the new handles. Then I drilled the mold to fit the two pieces.

With that I have the original repaired handle ready to take a mold off of. I put it into the top of the mold, since that is the part I'll mold first, then I put a clay dam in so that I could pour half of it first. That way I can keep the top surface flat for the mold compound to flow out to the top edges of the gouged out recess. I'll let it set then see if I can get it apart. If so I'll pour the other half maybe even yet this evening.

The scribbling with a marker on the flat surfaces is for registration. When the mold compound cures and I take it apart I'll then use my belt sander to take the excess compound off down to the original surface and I want that to still be true to the other half of the mold. With the black marks on the original surface it gives me a good guide as to where to sand to.

Jerry Feather

I pulled that apart and it came out perfect. Then I sanded the surface down as planned and put more mold release on the handle and set it up and poured the other half of the mold top. I'll let that set for a couple of hours and see if I am just as lucky. Although I have the feeling that I may have captured a bubble in this pour.

When this works out right it is really fun.

If I don't end up having to patch a bubble, the next thing I'll need to do is mill two pouring holes into the other half of the mold before I can set it up and pour the bottom half of the mold. I also want to mill some registration dimples into the mating surface of the bottom half of the mold to help in continued placement of the mold together rather than relying just on the two faces and the kink there and on the 8 screws that hold them together.

Jerry Feather

The second pour of the top half went well. The joint between the pours needs a bit of sanding, but that wont be a problem. Here is what the top half of the mold will look like when it is configured for casting, but now it is without the two metal cores that I need to fabricate to cast into the T-handles.

For the cores I still need to find some heavy wall tubing 3/4 inch OD or some 3/4 inch round hollow bar with about a 3/8 inch or 1/2 inch bore. I'll need 6061 T6 in case I decide to tack weld the two cores together before casting.

Jerry Feather

You might notice a couple of minor changes that I have made along the way. One is that I milled out the screw holes and recesses at the bottom of the handle. The other is that I drilled 4 rather than 2 pour holes in the bottom half of the mold. I did that because this compound is stiffer than I remember from the other **** project and it doesn't flow very rapidly. With more holes I can see how far it is flowing from one hole to the next before I move the pour.

The change about the mounting screw holes in the bottom of the T-handle is because I finally decided not to try to have the bottom of the **** CNC milled to the shape of the handle but rather simply use some tubing for the core and pour the handle around it. Thus, I need the provision for the screw recesses. That also gave rise to the two smaller diameter aluminum pieces you see in the pictures since they will also be part of the final mold.

As to the aluminum cores for the two shaft holes in the handle, I had priced a piece of 3/4 inch 6061 tubing that I thought might work for the vertical shaft, and it was $14 per foot. WOW! Then the ID was a bit too big. If I can't find some that is priced better and suitable for finish boring and reaming I'll be stuck with using 3/4 inch round bar and then drilling each piece twice before reaming to size.

The upright shaft hole is not the same size as the cross bore for the shift button. In MM sizes I think they are 15 mm for the vertical one and 14.5mm for the cross one. Then, they are not oriented in a simple T but rather are offset by an amount that I haven't figured out yet how to measure. It looks like about .125 to .150 in, but I'm not yet sure.

When I have both cores made then I'll need to figure out if they need to be spot welded together or maybe glued, versus simply laying then loosely in the mold, held in place only by the aluminum mold pieces.

Then there are several steps in making each of the cores, which I'll probably go into when I get there.

Avar928

You sir are a scholar and a saint. I will certainly purchase one if you sell! Manually shifting the auto while the **** spins in my hand is quite an endeavor.

Jerry Feather

Thanks for the support and the vote of confidence. If this works out I'll be selling these thru my Small Business Membership.

This afternoon I finished some details to the mold bodies and then put them together and poured the compound in to try to form the other half. It is setting up right now.

Since I discovered a very small area in the mold where I might have a sort of "locking" tendency, I think I'll wait until tomorrow to try to pull the mold apart to see the results.

I did some measuring off of the button shaft and have decided that the offset of the two core shafts is right about .115 in. With that I can do some machine work to work up a couple or three sets of the shaft cores. I will also work up a sort of jig that I can place them in to weld them together before casting them in the mold.

Jerry Feather

Some years ago I had bought some used and/or resharpened machine tooling at Boeing Surplus in Kent WA, including a bunch of reamers in odd ball sizes. I rummaged thru some of them a couple of days ago and found three that are 37/64 in. Oddly that is just about the exact size I need for the button shaft bore in the T-handle. Then I calculated and decided that slightly larger, 38/64, or 19/32, is a good size for the main shaft bore. So, I ordered two or three of those off eBay.

Now I am looking for either some hollow bar aluminum or some solid bar. The hollow bar, if it can be found readily available and is not much more expensive than solid bar, will save me one step in the fabrication process of each of the bore liners. Otherwise I'll be drilling a pilot hole in each of the pieces to start with. Even with a half inch bore I'll have to redrill to 9/16 before I can ream to exact size. With solid bar I'll have to drill a pilot hole of about a quarter inch to start with.

I'm going to check the local suppliers today for the prices of either material.

Jerry Feather

Here are the steps I anticipate in fabricating each of the bore liners.

Fabricate the liner for the cross bore button shaft:

1. Cut material to rough length in metal cutting band saw.
2. Chuck workpiece in lathe and finish one end; then drill pilot hole if not hollow bar material.
3. Drill hole to 9/16 inch.
4. Set lathe up and turn workpiece to exact length with finish on the other end.
5. Ream bore to exact size.
6. Turn each end to slight bevel on outer diameter.
7. Turn slight groove inside bore near one end for T-handle plug locking tabs.
8. Clamp workpiece in mill vise and bore hole to match the other shaft.
9. Clamp workpiece in mill vise and cut slot longways thru side of liner for guide tabs on button
shaft.

Steps for aluminum liner for vertical shaft:

1. (Follow steps 1 thru 5 as above with other piece.)
2. Clamp in mill vise and mill flat on one side of workpiece.
3. Re-clamp in vise and drill cross holes for mounting screws.
4. Set up vise and clamp workpiece in vise and machine 3/4 inch offset recess crossways in shaft
liner to mate with other piece.

After both pieces are made they will be put into a jig and tack welded together before placement in the mold for casting.