Technical Door pin reamer question

I am repairing the drivers door hinges on a 32 Plymouth. I have oversize stainless pins I bought from Bob Drake. the pins say .340 diameter but measure .3385 . I drilled a piece of bar stock to 21/64 then tried a 11/32 valve guide reamer I have. Seems a little loose, guess I need a smaller reamer so I thought I would ask what size reamer I should get for these, as someone here has probably used these oversized pins before.


thanks

 

A Q drill is .3320" . Wouldn't be surprised to see the pin fit. Drills tend to drill a very slightly larger hole than their actual size. A R drill is .3390".

 

Yes I could try a Q and R letter drills. I don't mind buying a reamer though. I was thinking predrilling under size then reaming to maybe .340 that would give me .0015 clearance.

 

It's really hard to cleanly enlarge a hole with a twist drill.
I recently ordered a special size Chinese reamer off of the Aliexpress for a specific project. They are usually listed in metric, so to suit your job, an 8.6mm works out to .3386". If the pin is in a bronze bushing, I think that would be okay.

The one I got sure didn't look as good as a Cleveland or Morse brand, but it cut neatly to size in brass.
Of course it comes via the slow boat from China, so holds up the project.

 

It's a little pricey at $33, for a one time use, but McMaster Carr #8803A651 is a .3385 reamer.

 

The first one I looked at from the cheap place is less than $10 with shipping, but won't be as nice as the McMaster Carr piece. But the one I bought works fine. As I am in Canada, it was a choice between about $6 vs. about $75 with shipping, taxes, exchange etc., so I went with Chairman Mao.

 

I picked up some letter drills today. I will drill some bar stock and see what kind of fit I end up with. The hinge is cast steel as near as I can tell . new pins are stainless. I thought about adding a bronze bushing to the door side of the hinge (part that moves) but the holes on the A pillar side( outside edges) of the hinge are egg shaped. The front edge of the door was beginning to chip the paint on the cowl. 90 years of wear. The oversize pin will make things round again but that doesn't leave enough room to add a brass sleeve to the center part of the hinge. 8.6mm reamer would leave about one ten thousandth of clearance for the pin. I called a couple places that sell the oversize pins but nobody knows anything about installing them. I am kind of thinking its like buying pistons or valves where the cylinder or valve guide is a standard size and the clearance machined into the piston or the valve stem. So maybe the .340 number in the spec is the hole size for the pin. I'm trying not to overthink this.

 

I don't mind spending money on quality tools , buying one reamer for this project isn't going to break me. Is a .3385 reamer going to make enough clearance for a steel hinge ?

 

I think it's too tight in steel. Okay for brass or cast iron, which have some inherent lubricating qualities.

 

Next size up from McMaster Carr is .3395.

 

You can actually buy reamers ever half thousands.

 

Unless this operation is being performed in a mill, you will probably never achieve a clean sized hole using a pistol drill. That being said, I would approach it from a different direction. I would select a reamer that is undersized from the .3385 pin size called out. I would test ream some holes to make sure you are not reaming past your .3385 dimension. Then you can commit to reaming the hole in the hinge. After that is done I would remove the extra material the pin is oversize, until it fits the previously reamed hole. It may take some time, but I believe you will be satisfied with the fit. Reaming the hole and hoping the pin will fit using a pistol drill is a crapshoot. 60 Special

 

I have a vertical mill, I am thinking of making a fixture to bolt the hinges to a steel plate or tack weld the hinge halves together and put them in a machinist's vise to drill and ream the hinges. I'm just not sure how much clearance I need for the pin.

 

I sent you a PM

 

My '37 truck hinges were worn very egg shaped and the pin kept walking out of the hole. I finally decided to fix them. I pulled both halves off and brazed all four holes shut plus added lots of reinforcing braze in the thin areas. I had bought brass tube stock to use in the over sized holes but couldn't figure a good way to drill out the hard to hold hinges. The steel seemed to be pretty hard on the one piece I test drilled into, plus I didn't have much metal left to work with. Chevrolet just rolled the steel around the pin, so drilling was going to be a fight since they were no solid round holes.

The brass was easy to file down and shape, I got brave and drilled them one size smaller then the pin diameter. I slowly polished the holes till the pins fit snug. A reamer would have sped up the process, but I was to cheap to buy one for little I was going to use it. So far the brazed holes are holding up good, the door fits much better and no more rattle going down the road.

 

It's not always easy to fixture stuff in a milling machine nice and square and true.
I think king pins are usually reamed by hand, they turn out okay.