Best Tool for Opening Hole from 15.80mm to 15.88mm (5/8 inch) - Drill Bit or Reamer?

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4Cruisers

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I'm replacing the upper distributor shaft bushing on an early F engine distributor. The new Toyota bushing is 15.88mm OD, but the old bushing is 15.80mm OD. So I'm thinking the easiest way to go is to open up the hole in the distributor housing. It turns out that a 5/8 inch hole is exactly 15.875mm, or essentially 15.88mm. Seeing as how that's not very much metal at all to remove, I was thinking a new 5/8 inch drill bit will open the hole up nicely, and stay centered. But I've also read that a reamer can be used to slightly enlarge a drilled hole. What would be best? Any input would be appreciated.
 
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The new bushing is larger so it is a press fit into the distributor housing. Just press it into the hole as is.

Nick
 
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The new bushing is larger so it is a press fit into the distributor housing. Just press it into the hole as is.

Nick
I might try that. Would it help to put the bushing in the freezer beforehand? And maybe heat the housing?
 
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I think the new bushing has just enough of a larger OD that it won't press in, so I reduced the OD a bit.

I pulled my 31/64 inch drill bit from the toolbox and wrapped it with a few layers of Scotch tape until the bushing was a pretty tight fit. I spun the drill using a some light passes with a course file, then a fine file, and followed that with some 220 grit sandpaper. I then made a final pass with a 320 grit sanding block to smooth out the surface. It's getting really close to the desired OD. As a test, I stuck it in the freezer while I finish my second cup of coffee. I'll pull it out in a while and measure it cold. If all looks good, I'll apply a small amount of Lucas Oil assembly lube and press it in using my HF 20-ton shop press. I'm keeping my fingers crossed, but it may work.
 
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It only had a .003" press fit to start with according to your measurements. Much less than that and you run the risk of spinning the bushing in the housing. The 20T press would have pushed it in easily as it was. Now I would be inclined to use a bearing mounting compound instead of assembly lube to make sure the bushing doesn't spin. Or knurl the bushing to help it bite the housing a little better.

Nick
 
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It only had a .003" press fit to start with according to your measurements. Much less than that and you run the risk of spinning the bushing in the housing. The 20T press would have pushed it in easily as it was. Now I would be inclined to use a bearing mounting compound instead of assembly lube to make sure the bushing doesn't spin. Or knurl the bushing to help it bite the housing a little better.

Nick

Thanks for the info. I have at least 25 or 30 more identical new bushings to work with, I'll give it a shot.
 
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I do believe in the old adage that it is best to modify permanently the cheaper and/or more easily replaceable part...
 
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Do you have a lot of these to do? Just buy a mini lathe. It will pay off quickly
Probably five more at least. Plus I have been modifying '78 through '80 and '81 through '87 distributor housings to accommodate different NipponDenso vacuum advancers.
 
ntsqd

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.003" press is a LOT of press at this diameter. More typical at this diameter would be .0005" to .001" depending on other design constraints. Are you sure that the likely cast aluminum housing can handle stress that high? I wouldn't be.

Another thing to consider is if the bushing in question is a sintered bronze type bushing then a press fit that high will force the ID to be smaller. Likely smaller than desired or that will provide the operational clearance to the shaft that is required.

To answer the OP's question I would buy a reamer of the correct press fit size. Machinery's Handbook has tables in it for setting how much press fit to use.
 
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UPDATE, similar question but for a slightly different application.

I received a 0.204" straight flute reamer from McMaster-Carr in the mail yesterday. I plan on using it to enlarge the holes in Land Cruiser distributor drive gears and distributor shafts. I decided to go that route because new gear pins were only sold with new gears, both of which are NLA. I bought a length of 0.204" (#6 wire gauge) drill bit stock from McMaster-Carr a few months ago, and have been filing the OD down slightly with a file, while spinning it in a drill (I don't own a lathe), to fabricate new gear pins. I figured it would be easier to use a reamer on the holes, which are 0.201" ID. In order to ensure alignment and a clean cut through the gear and shaft I was thinking of pressing a short section of hardwood dowel through the gear and shaft from the back side - it should hold the alignment as I ream the holes and the reamer will push the dowel out as I finish the hole. Does that make sense?

I was also thinking of machining a flat bottomed dimple in a small piece of hardened steel plate that is slightly larger than the OD of the gear pin. After driving in a new gear pin I would place the shaft and gear over the dimple in the plate and hit the top of the pin with a hammer to mushroom both ends of the pin. But is there an easy way to mushroom one end of a pin before I install it?
 
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ntsqd

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Why not make the pins a press-fit? Make them .2042"-.2043" OD by getting them close with the file and then using some crocus cloth, backed by the file, to get them to the finish diameter.

OR while these would be easier McMaster-Carr - https://www.mcmaster.com/roll-pins/coiled-spring-pins-6/system-of-measurement~metric/diameter~5mm/material~steel/ you're slightly beyond their upper end hole size. So what I would do is use one of these: McMaster-Carr - https://www.mcmaster.com/roll-pins/slotted-spring-pins-6/system-of-measurement~metric/diameter~5mm/for-hole-diameter~5-5-2mm/material~steel/ followed by one of these: McMaster-Carr - https://www.mcmaster.com/roll-pins/slotted-spring-pins-6/system-of-measurement~metric/material~steel/diameter~3mm/
In such an application as yours the clocking of the slots is important. The first pin should have it's slot either at 12:00 or 6:00 and the second pin should be installed with it's slot in the opposite position of the first pin's slot.
 

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