View Full Version : 45 Cam Bushing Reaming

01-24-2008, 09:00 PM
I need to fit new cam bushings in my 45, and found the special reamer in the manuals. Since I'd use this expensive tool only once, I looked for other solutions.

It seems to me that the reamer was designed for use in locations where a vertical mill wasn't available. I do have a Bridgeport style vertical mill and would like to use it to do the reaming.

I believe Tom Cotten once mentioned several types of reamers, and while I can do the measurements to determine the correct size, I don't know what type/number of flutes to ask for.

Anybody have experience doing it this way?


01-24-2008, 10:01 PM
centerline dimensions are your critical focus. You can hit size by boring. Paps

01-25-2008, 08:37 PM
Good to hear from you, it's been a while.

So...boring, then maybe a ball hone cleanup? No reaming?

01-25-2008, 11:41 PM
Take test pass skin cuts when you bore. Your finish may be better than you expected. Light polishing will suffice if your finish pass is smooth. Boring to finish is a trial an error process, thus the test passes. Honing is fine as long as your boring finish is adaquate and your remaining stock is minimal. Basically, same goes with a polihing finish. To little stock and you end up oversize. To much stock and you hone and polish forever. I like a 16 to a 32 finish for bushings but a 63 will do fine if tolerance is on the low side. In my experience, a bored hole with a reverse dry pass produces the optimum cross hatch. Test passes help determine remaining stock when reversing a feed for a dry pass. Think of a tool bored hole as a screw thread. A screw thread finish will pull on the shaft in the direction of the tool marks. A reverse dry pass creates a reverse tool mark, a cross hatch, if I may say so, a left and a right thread. Pull is drawn both directions thus centering the shaft that runs within the bore. If you retain a small percentage of both of these tool marks, after polishing or honing, you maintain a centering device along with a lube channel. Paps

T. Cotten
01-26-2008, 08:01 PM
Sounds better than any reamer to me!


01-26-2008, 09:15 PM
No reamers sounds good to me too Cotten, thanks for the vote for this method.

Now, about this 16/32/63 finish. What does that refer to? I'm just a recent arrival to the machining world, and need more detail about the tools and procedures.

Should the cutting tool be carbide, hand ground HSS or what? I learned how to grind lathe tools from a set of machining videos I got for Christmas, and it seems like a blunt "spool" type profile provides good smooth results.

Reverse tool cut? does that mean I have to turn the bit around before reversing?

The only honing experience I have is fitting my piston end rod bushings with a ball hone. That produces a nice crosshatch.

I was going to ask about cutting oil grooves in these, but you answered that already.


01-27-2008, 06:44 AM
Search MSC for a finish profile gauge. I have one and it shows finishes in turning and milling work. I would post a pic of mine for you but I am temporarilly using a laptop. My desktop hard drive crashed.

Reverse the feed, not the tool. Spindle spins in same direction both in and out.

If bushing had a groove originally, put it back in. Groove serves as volune and pressure.

Honing creates great cross hatching.

01-27-2008, 06:48 AM
Type of tool bit ? It depends on the capabilities of the machine you use, speeds and feeds, etc., The Machinist Handbook will guide you through that. I'm used to primitive machines so I prefer high speed.

T. Cotten
01-27-2008, 10:10 AM
Let us all not forget the option of hand-scraping for a final fit, no matter how you got to that point.


01-27-2008, 04:45 PM
I assume you are going to bore/ream the cam bushings in the gear cover in-line with the engine case cam bushing. Just curious to know how you're going to set up the assembled cover and case on a mill table with the cover side down. Also, that's going to be a long boring bar and it's going to be impossible to see what it's doing when you get into the gear cover bushings. I just wonder why you would attempt the difficult boring set-up when reaming is the preferred H-D method. Not to mention finding a datum to base the center to center distances on. Maybe I'm missing something.

T. Cotten
01-27-2008, 06:45 PM
Exeric declared: "reaming is the preferred H-D method"


Just because the Service manual prescribes reamers for a 'field repair' is by no means justification to dismiss other techniques.

The Service Manuals also outline the use of lapping tools for the mains.
It is near impossible to imagine that the Factory could have ever achieved the landmark wartime production with hand lapps.
The manuals were written for service under austere conditions.

Indexing a right case (from another case) on a mill table gives marvelous results. So nice in fact, that the cover can then often be fitted to fanatical tolerances by inking-and-scraping.
But the Service Manual writers never expected anyone to have such skills, nor even a mill.

Today, we cannot assume anyone has the patience for even a simple scraper and a felt-tip pen.
But Rex displays the attitude and the will for perfection.

No one-size reamer guarantees perfection.
The journals vary.


01-27-2008, 07:21 PM
I'm still curious as to how you are going to set the case and cover up on a mill table and feel confident that the thrust surface is perpendicular, and the bore is parallel to the main bearing? What surface do you pick up and how do you clamp it to the table? I hope you can come up with a good method because I have the same situation with an early pan case and gear cover and I only have one bushing set to worry about. Besides all of that, a reamer is just a boring bar that you don't have to dial in and they give you a fantastic finish when run slow in a milling machine.

01-27-2008, 07:55 PM
I salute you Cotten.

The trick to line boring case halves and gear cover, is the setup. Flywheel mains are your zero point. You need a fixture to do the complete job correctly. A horizonal mill is easier to setup but a vertical can suffice,. with adaquate travel range.Give me a week or two to get my pc tools in satifactory operational condition. I'll post a pic of the correct mill setup. Pic will be of a horizonal setup with fixture. Paps

T. Cotten
01-27-2008, 08:16 PM
Meanwhile, everyone needs a supply of these:
triangular scraper (http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1747081&PMT4NO=36670770)

Low tech rules.

These are mystical wonders!
With enough concentration, I can levitate one out of my hand to stay suspended in mid-air,... slowly drop its point to touch my finger,.. and then rise to resume its mid air hover, with absolutely no visible means of support.

This ain't no barroom trick!

02-02-2008, 07:50 PM
Paps, Cotten, Exeric-

Thanks for all the insight concerning the possibilities and potential difficulties in this operation. Access to your combined experience is the only reason I contnue to tilt at such windmills.

You can do all that with the $2.37 scraper shown in that link!?

Actually I do have a scraper similar to that but didn't know what was until now. Been using it to clean out mower decks and grease encrusted old farm machinery. Can you please describe the inking/scraping process? Sounds interesting, since I've got some projects coming up that may involve babbit.

What do you mean by "aligning a case from another case"?

Looking forward to the pics of your setup, and thanks for telling me about the finish gauge. That will help.

I haven't located a source for the specific purpose built reamer shown in the manuals, but I'd rather spend the money on a new boring head and bars that I can use on other projects too. If you know a source let me know.

I'm also curious to see how I'll get this thing set up right but as Cotten said, I've got the desire to learn, time, and help to see it through. My brother has a machinist's degree and I've got a building full of steel, brass, and aluminum cutoffs to make jigs and fixtures for odd shaped pieces. That along with MSC, J&L, etc. tooling and materials aren't a problem.

At this point I'm just looking at opitions.


T. Cotten
02-02-2008, 08:38 PM

The scraper comes into play when the fresh bushing has been produced slightly undersized.
Commercially available bushings often come out of the package a perfect fit to a fresh journal. But when the bushing is pressed into a hole that has ~.0015" interference, the bore of the bushing collapses slightly as well, usually about a half a thou, depending upon the thickness of the bushing wall.

The journal will stick in the bore of course. Forcing it in and out will make marks (or you can use a felt tip pen and look for the exposed metal).
Merely scraping the highspots in a cross-hatch fashion will allow the journal to be inserted slightly further.

As the operation is repeated, the area of contact will widen.
The amount of material removed is in the order of tenths of a thou, so it is a long process.
But if the other end of the journal is properly located within its bushing, it will actually show any misalignment in the new bushing as you gently force the cover on and off of the dowels.

You will only be removing metal from where it is needed. It also must be noted that often the interference signature can often be opposite of the true highspot, so some careful observation and a little intuition go a long way: Such as if you realize the signature is opposite a bulge from where the bushing has been pinned.

Even a piloted reamer or hone will 'walk' slightly to the side of a pinning bulge, so a scraper is the only way to accurately remove only the bulge.

I also spin an abrasive nylon brush within the hole to smooth any burr, and further illuminate the highspots with the next trial assembly.

It is harder to describe the process than it is to perform, but it does take much more patience than most modern metal butchers can muster.

I'm certain a better tutorial can be found at http://www.lindsaybks.com/

PS: I mentioned "supply" of scrapers in my previous post. You want them very sharp on their hollow-ground edges.

02-03-2008, 03:37 PM
That's a good point Rex. I need a boring head for the mill in my backyard shop. My cage rattling was from the perspective of a machinist who has to do a job in a reasonable amount of time with a minimum of specialized fixturing. I want to be optimistic and hope that Paps comes up with some good ideas because I have other motors to do. Unfortunately I have a vertical mill but maybe his fixture can be transposed to work vertically.

02-03-2008, 07:23 PM
Eric, If you have enough vertical travel on your mill, this horizonal fixture will do the job. I just got back up online. I'll dig the fixture photos out in a few days. Email me direct so I can get them to you. Mention the fixture in your email subject line. Paps

Email addy.... vtwinrebuild@yahoo.com

Cotten....excellent explaination on scraping !

02-11-2008, 07:32 PM
Did you receive the mill fixture pics I sent to you ? Paps

02-13-2008, 10:40 AM

Yes, saw them Monday. That's one heavy duty fixture! I was considering a similar sandwiched plate for my vertical mill using 1/2" plate with end plates down to the table, but that's as far as I got.

I can't see how the cam cover and case are attached so the case can be removed without disturbing the cover. Can you describe this?

Again, thanks for taking the time to do this. Couldn't do it without you guys.


02-13-2008, 10:45 AM
Originally posted by exeric
My cage rattling was from the perspective of a machinist.....

I don't mind a little cage rattling when needed. My cage has been rattled here before with good reason and probably will be again. I see it as a valuable part of the learning process.

Don't hold back!


02-13-2008, 10:51 AM
Originally posted by T. Cotten

The scraper comes into play when the fresh bushing has been produced slightly undersized....


Thanks for the direction to the Lindsay Library. I've gotten several books from him about casting, copperwork, etc.

When doing test fits with ink, since the journal will always touch somewhere leaving a mark, how do you know when you're done?


T. Cotten
02-13-2008, 07:16 PM

When there is no trace of bind, it is as sweet of a fit as cam be hoped for.

Beware that fully torquing the covers screws may produce yet another bind.

Patience is a virtue.


PS: I'm a little diaspointed that no one called me down on my claim that I can levitate a scraper to hang in mid air.

02-13-2008, 08:26 PM
Originally posted by Rex
You can do all that with the $2.37 scraper shown in that link!?


That was questioning the levitation claim..

About the cover screws. Is this in reference to the end play/shim fitting, or can unequal torque on the cover screws cause the cover to be not square with the case?


02-13-2008, 08:53 PM
The particuliar fixture I presented to you utilizes the dowel pins. Bear in mind, this fixture is for line boring unmatched number cases but matched cases can be done using it as well. Feel free to post the photos. I'm sure many will comment on them. Wish I could take credit for the design and build of this fixture but it was turned on to me by another enthusiate who wanted to help me out. It helped me considerably. This fixture design turned out to be the best mill tooling I was ever introduced to. The plate used for the fixture is a little overkill but no way will it move without a crash. Paps

T. Cotten
02-14-2008, 10:07 AM

Fastener torque has a way of moving metal, no matter how straight everything appears.

It metal didn't 'move', it would be too brittle to use.

If any poor soul walks into my shop today, I'll get him to snap a photo of my levitation act.

Late edit:

It is a small wonder that no one came in today, as I have had a large sign in the front door for months that says "Go Away".

Nonetheless, I managed a few pics inspite of the loss of concentration due to focusing a slow digicam: Kind of like firing a flintlock.

When I bought these scrapers, they were still only $.89

Uh, where did the attachment button go? Please see next post.

T. Cotten
02-14-2008, 07:39 PM
Disbelievers may post me direct at liberty@npoint.net (liberty@npoint.net) for enlarged versions of the individual shots.

'Dis ain't no barroom trick!


02-14-2008, 09:20 PM
Now for all 3 at once!
I'll even drive over there to shoot the picture.

I hope OSHA dosn't see this, looks like a potential safety issue.

02-15-2008, 08:26 AM
I am "priority overnight shipping" you a carb. to be repaired !
You obviously are in dire need of something to do. Worried about you bro ! ( Neat trick and you know i'm kidding )

J Wall
02-16-2008, 12:51 AM
I sure would like to see the picture of that fixture, love to learn

T. Cotten
02-21-2008, 09:03 PM

Uh, Oh,... No carb has arrived.

I hope it didn't go the way of the photos.....

Uh,... Where did the attachment button go?

02-22-2008, 09:48 AM
Email me direct and I will send them to you. Paps

02-29-2008, 08:46 PM
did the pics upload ?

guess not

T. Cotten
03-01-2008, 07:32 PM
Behold the mystical machinist's scraper as it hovers suspended by nothing more than my sheer concentration.


03-01-2008, 08:03 PM
How do you do that Cotten ? Ya know..........I've had the pleasure of re machining machine ways and the scrapers did the final fitting. It is something to watch them work a flat surface, even flatter. Their patience is unequaled. Paps