Output shaft preload

[WarrenSen]

Hi Guys, bit confused, I put the new bearings on the output shaft and commenced reassembly. But solder on the edges, 1.6mm didn't crush or I couldn't tell, so I made two little coils and used them, they crush to 1.45mm/1.5mm this is about as accurate as I can get,

Standard value for pre-load is 0.055 - 0.115mm so this would suggest I need a spacer for behind the outer race of say 1.44mm, theory being .06 would be the mid point so 1.45-0.06 = 1.39 or 1.5-0.06=1.44.

Looking at the rebuild pages MD718521 is equal to 1.4mm so seems like the right one, can any confirm I'm doing this right.

I think I've got it wrong - Preload of 0.06 to 0.115 would be negative wouldn't it? So if I have a 1.45 gap then I need 1.45 + 0.875 to give me midway preload which would be 1.5375 and the nearest to that is 1.55 part number MD718526

Oooh bugger

So that's put tin hat on it, I decided to repeat the exercise and try get a more consistent measurement and one of the output shaft retainer bolts has sheared, no stud at all to get an extractor on and its at the bottom of a 4" shaft approx 10" deep. I'm so pissed off right at the moment, spend a small fortune and no closer to rebuilding this motherf.. I've really no idea where to go with this now, I don't even know of an engineering company in the UK that could tackle this

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Cheers

 

[twicks69]

You have solder that is measuring 0.057" and 0.059", take the average, so 0.058" and add 0.007" preload. That puts you at 0.065" for a 0.007" preload, which is MD718530. Any shim in the MD718528, MD718529 or MD718530 (0.063"-0.065") will work fine.

As for the bolt snapping, well shoot, that sucks alot. Are you using a cordless impact or doing this by hand and torqueing to spec by hand? Were you cross-threading it or something that it snapped??

The flange bolt you broke is MD727938, shallow head #7 M10x37mm.

Here's a drill bit you can use to fit all the way down to drill it. -- https://www.mcmaster.com/#2955a24/=1dd9jcs

Then, use an Irwin / Hanson male extractor with a 13mm/14mm socket on a 12" extension and remove the broken stud portion installed, then use a Metric M10x1.25 thread tap or chaser (Irwin 8339 - M10x1.25 tap) with a metric spline drive socket and 3/8" extension on a ratchet.

It might be easier to drill it all the way out 25/64th bit and then try a left-turn bit and catch the threads out. Either way it will be a time consuming one.

 

[WarrenSen]

You have solder that is measuring 0.057" and 0.059", take the average, so 0.058" and add 0.007" preload. That puts you at 0.065" for a 0.007" preload, which is MD718530. Any shim in the MD718528, MD718529 or MD718530 (0.063"-0.065") will work fine.

As for the bolt snapping, well shoot, that sucks alot. Are you using a cordless impact or doing this by hand and torqueing to spec by hand? Were you cross-threading it or something that it snapped??

The flange bolt you broke is MD727938, shallow head #7 M10x37mm.

Here's a drill bit you can use to fit all the way down to drill it. -- https://www.mcmaster.com/#2955a24/=1dd9jcs

Then, use an Irwin / Hanson male extractor with a 13mm/14mm socket on a 12" extension and remove the broken stud portion installed, then use a Metric M10x1.25 thread tap or chaser (Irwin 8339 - M10x1.25 tap) with a metric spline drive socket and 3/8" extension on a ratchet.

It might be easier to drill it all the way out 25/64th bit and then try a left-turn bit and catch the threads out. Either way it will be a time consuming one.

I'm weepin in my beer at the moment, the 3/8" drilll you mention would leave me with a 10mm hole, that's a lot bigger than it looks. At a guess I need a 4mm drill down the centre of the stud then a male extractor but given the depth of the shaft I think the drills will snap and then so will the extractor....I've been looking at this all afternoon, I've managed to dremel a dent dead centre that I can now drill, but I don't have drills long enough or a chuck narrow enough to get down there. 'Well shoot' don't cover it pal, I'm seriously pissed off!

 

[twicks69]

Well, they should be a 14mm head bolt which is a m10x1.25 fastener, and a 3/8" bit is 9.525mm.

 

[Mello]

The nominal minor thread diameter for a 10M x 1.25 is 8.778mm (.3456"). A 3/8 drill is too large & will reduce the thread engagement to only 29% making for a easy to strip threaded hole. 8.8mm (.3456") drill yields 73% engagement but you'd have to make sure you're drill perfect down the center or you cut into the threads. I would consider a smaller diameter drill to leave some room for location error, possibly a Ø5/16 (.3125") drill if not even smaller. Drill size is inversely proportional to "room for error".

 

[twicks69]

Thanks for the catch, I am so used to having to helicoil stuff .

I'd go with the 5/16" then, SAE XXL drill bits are typically quite a bit cheaper than Metric.