JV Puleo

My 1910 Mitchell "parts car" project

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The shaft is 1" in diameter, the same size as the bar with a keyway that is in there. The original center bearing support was a spring loaded plunger of sorts... I'll photograph it when I get to the shop. It's too odd to describe without a picture.

 

I do have an AAMCO line boring rig for the mains and will try to adapt it doing the cam and the magneto/water pump shafts but as yet I don't know how.

Edited by JV Puleo (see edit history)
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This is the top half of the cam bearing. It relies on that spring to put pressure on the cam.

 

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For the torsion plates I made a paper template and glued it to the the steel.

 

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Then drilled the two center oles and put pins in them. This keeps both plates aligned with each other. After that it was just a matter of drilling the remaining six holes. The center holes give me an easy way to bolt the crankcase to the mill table or to the boring fixture I made a long time ago out of a scrap lathe bed.

 

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Then I chased out the threads in the crankcase. There were studs here and the Mitchell method of securing them was to cut a slot on the end and spread them with a chisel...rather than use a lock nut. This made taking them out a real chore and it didn't do the threads any good. I probably should put threaded inserts in the holes but I'll wait on that...

 

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I torqued them up to 25 lbs, not being entirely comfortable with the threads in the low grade aluminum that was used then. I don't think that actual torque spec is too important as long as they are tight and the pressure is uniform.

 

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These should stay in place until all the crankcase machine work is done.

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Joe, it looks like you are getting right down to the "guts" of your engine project.  Redoubtably, your Mitchell will be very much "improved" by your touch yet still being improved with keeping the vintage design in the forefront of your process.  Keep the rally going!

Al

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I want to put brass inserts in as many of the threaded holes in the aluminum as I can. This is the proper way to do it although Mitchell just threaded the aluminum. I have at least 3 places where the steel screw has broken off because it's effectively welded itself in place. But, the brass rod I need won't be in until Friday so I'm working on a device I designed to set the cutter on the boring bar. I have one for my big boring bar but the one time I used it I wasn't completely satisfied with it's precision (though I assume some of that has to do with it being the first time I'd ever used it). In any case, it won't work for the 3/4" diameter bar I need to use to bore the magneto/water pump shaft. I started making it out of steel and decided it was too much work...for something I'll probably use twice, I can make it out of aluminum. The first step was to center a piece of 2" x 2" square stock in the lathe. I do this by putting something round that is 2" in diameter in the chuck and indicating it.

 

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Then loosen the #1 and #2 jaws and replacing it with the 2" square stock.

 

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If the dimensions are close this works pretty well. If I needed extreme precision I'd use a torque wrench to tighten the chuck but this seemed to work just fine for this purpose.

Then it was faced off, drilled & reamed to 3/8".

 

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I faced both ends then set it up in the drill press to drill 1/4" holes in the corners. It's set so that the near side is flush with the side of the vise. That way, I can rotate it 90-degrees and have the next hole in exactly the same spot.

 

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Having finished that, I cut 3/4" off one end.

 

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And faced the sawn side. I wasn't all that happy with the facing on the short piece so I surface ground it. It wasn't out much but it's better now.

 

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The corner holes on the short piece now get drilled and reamed to 7/16 for press-in threaded inserts - again using the setup on the drill press which I hadn't disturbed.

 

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So far, the pieces look good. The threaded inserts came in at the end of the day so Ill be able to continue with this tomorrow.

 

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Edited by JV Puleo (see edit history)
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17 hours ago, JV Puleo said:

I want to put brass inserts in as many of the threaded holes in the aluminum as I can. This is the proper way to do it although Mitchell just threaded the aluminum.

 

I am looking forward to seeing how you do this. I had already been thinking of bushing the existing holes through the Humberette crankcase with brass to help stop the steel corroding. Especially as I had considered using stainless for the nuts and bolts. Although more expensive to make they will not need nickel plating.

Edited by Mike Macartney
a couple of words left out (see edit history)

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I think it will be pretty straightforward. The only fly in the ointment is that the inserts I'd like to use aren't made so I'll have to make them myself. But, you are as well set up as I am for that so if it works it is well worth doing. The critical aspect is that there has to be enough room around the hole for the insert. I can't do it with the bolts that hold the sump on because the little flanges some screw into aren't large enough. I may do it where it's possible. Luckily, none of those bolts are broken off in the holes.

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I made quite a lot of progress today on the device for adjusting the boring bar. The threaded inserts came in...

 

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So I pressed them in with my shop made hydraulic press.

 

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For some reason they didn't seat quite flush.

 

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So I surface ground them. This is not the right wheel for grinding aluminum so the finish isn't perfect but that's a small matter. It is flat.

 

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Then I set the piece up in the mill to make the hole for the boring bar.

 

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My 47/64 drill is too long to use in the mill so I drilled and reamed the hole on the drill press.

 

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To get this...

 

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I then milled a slot in the larger piece for the micrometer spindle.

 

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This will give you an idea of how it works. The micrometer head will be adjusted so it's on zero when touching the boring bar. I'll add .375 (half the diameter of the bar) to the measurement so a micrometer setting of .125 should make a 1" hole.

 

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I also drilled two holes so I can reach the set screws that will hold the boring bit and started milling flutes in the sides. It will be a lot easier to adjust if I can see the pieces. I suspect this will be a bit clumsy to use but if it gives me the precision I'm looking for it will be worth the effort.

 

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Nice work Joe, You are crafty for sure.  If you need it, build it...what a good attitude.

Al

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This morning I came up with a way to hold the boring bar tool so I could turn the end where the micrometer head goes.

 

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I had planned to go further but got worried that I was coming too close to the slot... if I make another one for the big boring bar I'll change the design a little.

 

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This is as far as I can go until one of the two micrometer head's I've ordered comes in. I decided not to use this one because it will measure 10th of a thousandth and I'd rather save it for the tool I'll probably make for the big boring bar.

 

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Then, because the brass rod came in, I started on the threaded inserts.

I'm threading the outside with this lathe threading tool - it's from India. The workmanship is quite good but I've decided its really best for fairly small, fine threads.

 

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All threaded...

 

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Then I drilled with a #7 drill - the size of 1/4-20 threads.

 

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And cut it off at 1/2"

 

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I also checked the thread with this nut from my lifters since it was threaded with the same tap I'll be using here.

 

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I made 4 of them. I'm not thrilled with the first two so tomorrow I'll probably make a couple more. It takes a few to get a system going.

 

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I finished the threaded inserts... trimming them to size...

 

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Then tapping the center.

 

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I ended up making 7 of them (I need 4) and now I can't tell which ones I wasn't happy with so I guess they are all good.

 

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I also made the larger ones but forgot to take a picture. Once I had a system this went quite fast.

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Questions Joe,

 

When making or putting in the inserts, do you:-

  1. Drill out the original thread in the aluminium casting and tap a new thread for the brass insert at a larger size?
  2. Do you not drill all the way through the aluminium so that the threaded bush does not unscrew through the other side while you tighten the bolt?
  3. Do you lock the brass threaded insert in place with thread lock, or something else?

With the boring bar tool you are making:-

Apart from 'blowing me away' with the design and build.

  • Is it for adjusting the amount of cut of the boring bar while the boring bar is still mounted in the part that you are line boring?  If so, designing that must have taken a lot of thought.

 

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With the inserts, I will drill through the appropriate piece of aluminum, thread and screw in the brass insert with a little Locktite on the threads. I have a trick for that too to make the insert bottom exactly flush with the top of the case. I may get to this today but before I do it I want to get a new 7/16-20 tap as the old one I have has a long taper and I'm not certain I have enough room to use it.

 

As to the boring bar tool, yes, it is intended to make it possible to adjust the diameter of the bore on the bar while it is mounted on the part. Once set up, you do not want to disturb it.

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3 minutes ago, JV Puleo said:

As to the boring bar tool, yes, it is intended to make it possible to adjust the diameter of the bore on the bar while it is mounted on the part. Once set up, you do not want to disturb it.

 

So am I correct in assuming that with this sort of boring bar you only take one cut? Or, am I missing something from my understanding of this process?

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No... the tool should allow me to adjust the cutting tool so I'd take a cut, put the tool back on and readjust, take it off and make the cut. The idea is to be able to make really fine adjustments. It will be tedious to use but if it works accurately it will be worth the effort. I have run into a snag though. There is no way the crankcase will fit on the mill table so that I can get the holes that have to be drilled under the spindle. The arms that stick out to mount it make it impossible to move it in far enough. I've thought of a possible solution but, of course, it will require making more fixtures. I want to put the holes in with an end mill because the original holes look as if they were drilled freehand through the crankcase and the top of the clamp. Since I'm making the top half of the clamps I have to get the two holes perfectly centered and I have to be able to clamp the top half to the crankcase to do that. This is an occasion where a Bridgeport mill would be really useful since the head is mounted on an arm that can be pulled out but I don't have one and I'm not about to buy a different milling machine for one job.

 

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I think I'll make some arms that extend out from the table to the front and mount the crankcase so it faces in perpendicular to the table rather than parallel. I had anticipated that this might be a problem so it isn't a complete surprise but the problem is more difficult than I'd thought. Fortunately, the holes don't have to be super precise as long as the cap screws that hold the two pieces together line up.

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So, while I scrounge for material to use setting up the crankcase I started on the boring bar guides. This is two pieces of 1" x 2" aluminum. I put them on the surface plate and clamped them together.

 

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Then drilled a #7 hole for a 1/4-20 screw and set a stop on the drill press so I could drill the upped piece out to 1/4".

 

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Then tapped the lower piece with this long pulley tap.

 

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The two pieces screwed together. The idea is to machine them as one piece so that the guides for the boring bar will be is perfect alignment with each other.

 

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Oh... and about 4 or 5 years ago I visited Dunster Castle with a friend of mine. When I made these doors for the shop he insisted I was overly influenced by the castle's enormous oak doors.

 

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Edited by JV Puleo (see edit history)
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I continued with the boring bar guides today. First putting two center holes in exactly 5-11/16 apart - that is the center to center measurement for the gears.

 

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Then drilled and reamed both holes to 1".

 

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As near as I can measure they appear to be right on but they are probably a few thousandths out. I don't think that is critical as helical gears are a little forgiving.

 

Then I sawed about 1" off one end and milled the ends square.

 

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And broached a 1/4" keyway in the short end. This end will attach to the keyed shaft in the camshaft bearings.

 

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The two pieces should be mechanically identical as long as I keep them in the same alignment.

 

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I also drilled and tapped the keyway end, opposite the keyway, for 3/6 set screws.

 

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And was able to take them apart. I still have to deburr the threaded hole and press in a couple of bushings but these pieces are nearly done.

 

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One aspect of this that I was worried about was keeping the boring bar rigid. That is essential for boring a smooth hole and last night a way of tightening the guides on the keys shaft occurred to me. I drilled and threaded the ends for a cap screw. I put fender washers under the screws and was able to tighten the guides up against the crankcase.

 

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This is what I'm striving for. It will need a center support which will be made from a flanged pillow block but the really critical issue, did the two ends line up and leave the bar movable seems to have worked out.

 

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In order to position the bar perfectly the center of the bar must be 45mm above the magneto bracket. This is because virtually all mags have an armature center line of 45mm. It made them interchangeable between cars. There are a few that are 50mm but they were rarely used in automotive work. In order to do this, I ground this piece to 1.397" - 45mm less .375, half the diameter of the bar.

 

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Here it is. So far, it's gone well. The bar moves easily. The bushings in the guides were lapped to  a sliding fit in he bar so I was quite relieved when I was able to put it together and it moves freely. Also (although you can't see it here) it looks as if it aligns perfectly with the saddles. Tomorrow I'll make the center mount. Then I have to figure out how the device that advances the bar while turning actually works. I've had it for years but so far I've yet to understand it.

 

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What is the next piece of this nice bar assembly?

Al

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The bar is turned with an electric drill. I'm going to use the feed mechanism from my AMMCO boring bar. I've had it for about 5 years but until today I didn't know how it worked. Necessity being the mother of invention, I finally figured it out. It's pretty hammered from the original owner so I'll have to fix a few things first but I think the additional pieces I will need to use it with this 3/4" bar are going to be fairly simple and won't effect the original tool. I'm relieved to have figured it out. It's one of those little things that's been nagging at the back of my mind for a long time.

 

More photos tonight...

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These two pieces of aluminum are going to be the center mount for the boring bar.

 

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Cutting slots for the bar and the bolts to pass through.

 

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Then clamped together to be drilled and tapped.

 

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The finished piece...

 

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Mounted on the engine. I pressed the bar against the ground gauge I made to make certain the center of the shaft was at the correct height.

 

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The bar will be driven with an electric drill but to control the feed I have this from my Ammco Boring Bar. Until today I didn't know how it worked and it appears that the adaptors I'll have to make are very simple. As you can see, it had a hard life so I'm going to replace the center shaft first.

 

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This is the sort of thing you often have to deal with when working with old, 2nd hand machine tools. Not everyone was careful with them.

 

 

Edited by JV Puleo (see edit history)

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Is the aluminium stiff enough to hold the boring bar, to achieve the accuracy you are after?

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I think so... the bar is held on both ends and I will only be boring aluminum. The length of the bar between the bearings is only about 9 inches so I don't think it will deflect. The actual size of the holes isn't critical in this case but I want to test everything before I do the cam shaft... Actually, the camshaft is probably a bigger problem because the bearings will have to be about 24" apart. I may well have to take very small cuts but, in that case I will be making a seat that a bronze split bearing will be pressed against.

Edited by JV Puleo (see edit history)
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I would sure like to see a short video clip of your boring bar fit and running.  You have given me "food for thought" on this project!

Al

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I have no idea how to make a video and I'm certain I don't have whatever it takes but I'll ask around. Someone I know must know how.

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