first time using expandalble reamer on conrod bushings -

[Savedbygrace77]

Hi - so im busy attempting to ream rod pin bushings down about 20 thou. I have a set of expandable USA made reamers and have one dialed in pretty well to leave about 7-8 thou for honing which I do on the drill press and I clamp the rod on the machined surface for a very straight motion of the brush hone (i tested the hone today and it leaves a beautiful final finish)..

Now I have a mini mill too- i have a box of bushings and already ruined one. I ended up clamping the reamer in the bench vise and slowly rotating the conrod around from the top down letting the rod follow the reamer - the finish looks pretty decent and there seems just the right amount left to hone.

Any tips on this backyard method? I can imagine making a fixture for the lathe which would make it alot easier but i dont have the time. im just playing around right now trying to find a method that deliver ok results.. it seems a real slow motion would be ideal?

 

[Phil in Montana]

if you do it free hand it will end badly

 

[AlfaGTA]

How do you get the reamed bore parallel to the big end bore?
This is critical as if it is out of true the piston will be cocked in the cylinder bore. = high wear or failure. Can also lead to high loading on the rod bearing (running out of square on the journal.)

Guarantee that using a flex home will give a bell mouthed bushing
Nothing about your setup sounds like it is capable of giving a reliable fit or geometry on the pin bush.
Cheers Ross

 

[john.k]

In fact ,in pre ww2 engines ,the alignment was corrected by bending the rod............you will find instructions for doing this in Harley Davidson manuals up to the 1970s.........However ,common engines did have jigs available for reaming the bearings with fixed reamers

 

[john.k]

If you have nothing better ,clamp all the rods in a vice so as a plain mandrel aligns all the unreamed pin bushings .......then ,run your adjustable reamer through all the rods together ,and with a bit of care ,the pin bores will be sufficiently aligned with the journals..................I have done this many times with engines such as V4 Wisconsins with complete success.

 

[eKretz]

In fact ,in pre ww2 engines ,the alignment was corrected by bending the rod............you will find instructions for doing this in Harley Davidson manuals up to the 1970s.........However ,common engines did have jigs available for reaming the bearings with fixed reamers

Oh that's nice. Give the guy who already doesn't really know what he's doing another way to cock it up. OP, please do not try to bend the rods. Yes this is possible, but needs to be done carefully by someone who can actually quantify the results. Much better to just get it right the first time. I concur with Ross on the brush hone being a bad idea. This should be rigid honed, and with much less remaining stock after *boring,* not reaming. What are these rods for?

 

[GregSY]

As noted, sounds half-assed. And...do the rod bushings really have .020" they can sacrifice?

 

[MwTech Inc]

As said before, you have no way to correctly do the job....
A drill press is not straight....
If you want this engine to run for anytime take the rods to an automotive shop which has the very specific machine
to do the job and gladly pay the man.

 

[michiganbuck]

Just one or two thousandths out of perfect alignment will be enough to fail the job, possibly destroying the crankshaft and so making it a bigger job.

Having an indicator, one might be able to rotate the spindle with the indicator attached to tram the con rod to be near dead-square to the spindle.
The mini mill may be better than a drill press, but tramming to about .0005 and less would still be needed.

 

[MwTech Inc]

Hey lets get this guy and the guy who wants $10 race jug modeling together....perfect pair........

 

[GregSY]

You guys are dinosaurs. Today's man knows that he just needs to 3D print the proper reamer then use Bluetooth to send it to his shop using the proper app. With the right app and GOOD 3D printer, the impossible becomes I'm Possible.

 

[ernieflash]

find somebody with a CNC lathe take the parts to them they will throw them all in machine and press start and done CNC machined con rods
That's how it works Right ?.No fixtures, no program, just throw them in and press start .

 

[jim rozen]

Suggest you do NOT hone the bushings as the final step. Ballize them. There's a company (balltech) that will sell you graduated steel balls you can press through the bushing to a) upsize it, and b) lock the bushing to the conrod ID very solidly. This works.

 

[PackardV8]

The Sunnen rod shop has been doing this for nearly a hundred years. Most every automotive machine shop has one or two of these and can put the pins perpendicular to the big end and on size to the tenth.

We've also done this with the Tobin-Arp rod boring machine; maybe the most accurate analog machine ever.

jack vines

 

[slowmotion]

Not to mention that if these are solid bronze bushings, not steel backed, they need to be burnished in before any boring/honing is done. This is an easy job for an automotive shop, it's senseless to try this at home when the risk of failure is very high. I always checked rods for straight and twist after re-conning or bushing installs, it's surprising how many rods are out of alignment.

 

[Laverda]

Did I read this correctly, you are trying to ream out .020" from the bushing? That is way too much. Did you make the bushings or were they purchased? I would bore them on the lathe so you only need to hone out a few thou when pressed in to the rod. Measure how much the ID shrinks when pressed in to the rod and that will give you an idea what size to make the bushing ID on the lathe.

Before doing this, make sure the rod small end is round. The are often times not round and will also need honing and then oversize bushings.

As others have stated if it is not perfectly parallel to the rod big end you will have problems from the wrist pin smacking the piston clips on TDC and BDC. After a while the pin will push the clips out and start cutting a groove in the cylinder. I have seen this many times.

 

[CarbideBob]

Lots of no's here.
Right or wrong.
Brush hone?

 

[john.k]

fact is ,when you buy an el cheapo engine rebuild kit ,the small end bushes are often 020 undersize and more ............they certainly are for a V4 Wisconsin ,and as the finished ID is only 3/4 " that a fair bit to ream..............Ive found the secret is to ream a large cut ,and feed thru quickly............any fiddling with fairy cuts will result in chatter setting in,which cannot be cut out. ...........i do know what Im talking about ,having reconditioned hundreds of Wisconsin motors ............I also recall the auction of Donville Precision Auto Engineering ...the Sunnen gear and Tobin Arp pin fitting machines were so worn out ,I doubt you could hold 010 on a cut...........all the Sunnen arbors were worn into hourglass shapes ,with the rods having large curved flats on them........and dont ask about the crankshaft grinder or cylinder boring machines.

 

[gappmast]

Hi - so im busy attempting to ream rod pin bushings down about 20 thou. I have a set of expandable USA made reamers and have one dialed in pretty well to leave about 7-8 thou for honing which I do on the drill press and I clamp the rod on the machined surface for a very straight motion of the brush hone (i tested the hone today and it leaves a beautiful final finish)..

Now I have a mini mill too- i have a box of bushings and already ruined one. I ended up clamping the reamer in the bench vise and slowly rotating the conrod around from the top down letting the rod follow the reamer - the finish looks pretty decent and there seems just the right amount left to hone.

Any tips on this backyard method? I can imagine making a fixture for the lathe which would make it alot easier but i dont have the time. im just playing around right now trying to find a method that deliver ok results.. it seems a real slow motion would be ideal?

If your going to ream wrist pin bushings my advice is just put it together with the old bushings. Old worn out bushings will still be a better fit than a reamed bushing.

 

[tdmidget]

When you say "brush hone" are you talking about the dingleberry hone with the little balls? That will not and cannot produce a cylindrical hole. You are heading for trouble here, I'm afraid.