press or interference fit

I have a question for you more experienced machinist types. I have a bicycle hub fitted with sealed cartridge ball bearings - R8-2rs - so 1.125 nominal OD. This is mounted to a 20 inch rim.

I need to remove one bearing and press in a hub/flange for a disc brake - and possibly in future a drive pulley. The removed bearing will be installed in the added hub. I am using CRS for the new part. What kind of interference fit do I need? How much bigger does my shaft have to be than the hole? Am I best to do a dry fit or dhould I be using a permanent shaft locker like a green LocTite?

The stub of the hub/flange going into the hole in the hub is 8 mm (5/16 inches) - the sise of the R8 outer bearing race - and the wheel will be run on a threaded axle with a spacer between the bearings, with the wheel hub and the flange/hubconstrained by the axle.

For anyone interested this is to add bicycle disc brakes to my reproduction 1919 Briggs and Stratton Flyer. The possible drive pulley application would be a 1925 Auto Red Bug.

I am machining the parts on my Myford Super 7 lathe and will be putting together a rotary table using my myford chuck on my benchtop drill press to drill the flange for the 6 on 44 mm bolt pattern for the disc rotor I have just completed my front steering axles and am working on the "facsimile" motorwheel using a 6:1 reduction 2.5hp (8 cubic inch) Briggs engine. Looking for a 9 cubic inch to take it's place and also considering making an adjustable timing gear camshaft to advance the valve timing for more bottom end torque (since I do NOT need the full

3600RPM!!) This would involve machining the gear off one camshaft, and machining the camshaft out of another gear then fitting the machined recess in the back of the gear over the machined flange on the camshaft and securing with 2 bolts through elongated holes. to enable splitting the difference between 2 teeth - 44 teath on the cam gear is just over 8 camshaft degrees or 16.4 crankshaft degrees per tooth and I require 3 to 7 crankshaft degrees of advance (I estimate) - so roughly 1/4 to 1/2 a tooth - - -
Reply to
Clare Snyder
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I'd shoot for about a .001 interference fit on the flange to hub fit . Depending on the thickness of the original bearing bore wall I might make it as much as .0015 ... and dry fit . If I was using a sleeve retaining loctite I'd probably go for about .0015+ clearance . That stuff needs a little film thickness to work right .

Set a compass to 22 mm to draw the circle , then step around the circle with that setting . The chord of a 44 mm diameter circle with six flats is ... 44 mm (well , pretty close) .

If that cam gear is a straight spur gear of either 16 or 20 dp I may be able to make you a gear so you don't have to burn a second camshaft ...

Reply to
Snag

I have a question for you more experienced machinist types. I have a bicycle hub fitted with sealed cartridge ball bearings - R8-2rs - so 1.125 nominal OD. This is mounted to a 20 inch rim.

I need to remove one bearing and press in a hub/flange for a disc brake - and possibly in future a drive pulley. The removed bearing will be installed in the added hub. I am using CRS for the new part. What kind of interference fit do I need? How much bigger does my shaft have to be than the hole? Am I best to do a dry fit or dhould I be using a permanent shaft locker like a green LocTite?

The stub of the hub/flange going into the hole in the hub is 8 mm (5/16 inches) - the sise of the R8 outer bearing race - and the wheel will be run on a threaded axle with a spacer between the bearings, with the wheel hub and the flange/hubconstrained by the axle.

For anyone interested this is to add bicycle disc brakes to my reproduction 1919 Briggs and Stratton Flyer. The possible drive pulley application would be a 1925 Auto Red Bug.

I am machining the parts on my Myford Super 7 lathe and will be putting together a rotary table using my myford chuck on my benchtop drill press to drill the flange for the 6 on 44 mm bolt pattern for the disc rotor ...

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If the brake rotor is bolted to the hub you have little to gain and much to lose from an additional tight press fit. I'd make the fit light enough to disassemble it without damage, like car alternator bearings, perhaps by running cap screws into two opposing tapped holes in the rotor.

Almost everything I've built has had to come apart several times during construction. That 6 jaw lathe chuck was constantly being taken apart and scraped or stoned to reduce the excessively tight fit of the top jaws. I disassembled prototypes of the second generation Segway so many times I could do it in the dark, like field-stripping an army weapon.

How do you like the Myford?

Reply to
Jim Wilkins
3600RPM!!) This would involve machining the gear off one camshaft, and machining the camshaft out of another gear then fitting the machined recess in the back of the gear over the machined flange on the camshaft and securing with 2 bolts through elongated holes. to enable splitting the difference between 2 teeth - 44 teath on the cam gear is just over 8 camshaft degrees or 16.4 crankshaft degrees per tooth and I require 3 to 7 crankshaft degrees of advance (I estimate) - so roughly 1/4 to 1/2 a tooth - - -

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You can buy or make offset keys to shift the crank gear instead.

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Reply to
Jim Wilkins

You mean 22mm? - 6 equalateral triangles

Shipping the gear would likely cost as much as a second used camshaft

-- up here to Canada. - same camshaft as small old vertical shaft briggs lawn mower engines - - back before every lawn mower had a 6 1/2 hp engine - - - - - - They are getting a lot more scarce on the kerb these days - seeing more Honda and Kawasaki engines showing up - OHV stuff. Used to be I could get 5 or 6 free briggs lawn mower engines in a month - - - - and a couple snow blower or tiller engines - for nothing or a few bucks. Those days appear to be gone - - - and a local small engine shop wants $30 each for used camshafts.

Reply to
Clare Snyder

You're right , I don't know why I thought it was a half-circle sweep per .

Reply to
Snag

You're right , I don't know why I thought it was a half-circle sweep per . Snag

--------------- Despite being mathematically sophisticated in other ways, the ancient Babylonians took Pi as 3 times the diameter, or 6 times the radius as in stepping out the hexagon of equilateral triangles around a circle with a compass.

The Egyptians were closer with Pi = 256/81, or (4/3)^4, but it's less accurate than 22/7. That kills the notion that advanced space aliens helped them.

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Perhaps the ancients weren't skilled (or interested) enough to accurately lay out the scale on a ruler. Greek geometry specifically prohibits markings on the straightedge. Surviving artifacts show that they were highly skilled at making other things.
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Reply to
Jim Wilkins

I cheat anymore and use an arc chord calculator app on my cell phone these days. 22mm radius & 60 degree angle. The chord length is 22mm out to 6 decimal places anyway. Seems the rule of thumb used is pretty darn good. I'll try to remember that one.

If you are interested:

ArcCalc V1.4 No permissions requested No mobile data used No ads

App data does not show an author.

I also use a triangle calculator, but it has in app ads. They are small enough they never interfere though.

Reply to
Bob La Londe

I cheat anymore and use an arc chord calculator app on my cell phone these days. 22mm radius & 60 degree angle. The chord length is 22mm out to 6 decimal places anyway. Seems the rule of thumb used is pretty darn good. I'll try to remember that one.

If you are interested:

ArcCalc V1.4 No permissions requested No mobile data used No ads

App data does not show an author.

I also use a triangle calculator, but it has in app ads. They are small enough they never interfere though.

Bob La Londe

------------ My personal preference is for apps that use the larger screen on my laptop or its 19" external monitor, and if I can't find what I want I write one for practice as a program or spreadsheet. For example I've automated the IRS tax forms, though I file the result from my sister's H&R Block software. For the last several years my numbers have matched hers. I'm not mobile enough to benefit from iPhone apps, the (old, free) phone is merely tethered to the (old, $15) laptop for my cellular Internet.

I wrote a spreadsheet to turn half round ball joints for a hoist base from a dumbbell. The spreadsheet gave the infeed dial setting for each step along the length, starting at 0 with the tool touching the OD and end of the blank. The radius and step sizes were constants that I changed between the coarse roughing and finer finishing passes. When the steps were small enough I filed it smooth.

I have a rotary table and a BS-0 indexer to mill smaller gears and splines to acceptable angular accuracy. Since my 1950's Clausing mill lacks a DRO or good safe places to install the scales I lay out larger mounting hole patterns and bolt circles with dividers or a vernier height gauge, then center punch and match-drill the hole locations. The holes align well enough as long as I mark one as an index and don't rotate the parts relative to each other, because drill bits may not center exactly on pilot holes, and unhardened custom drill bushings wear quickly. Usually manual layout gets me within 0.005". Rolled threads on commercial bolts aren't parallel or concentric enough to the shank to benefit from closer tolerance anyway. When I was building custom industrial machinery the components had to be located and aligned on the welded frame by manual methods. As I learned the hard way, jigging the pre-drilled parts in position doesn't overcome weld shrinkage. For some reason my father, an accountant, had a copy of the Audel Millwrights and Mechanics Guide which helped a lot.

Sometimes I find that the device I'm mounting wasn't drilled accurately in the factory fixture. I had to re-machine a hydraulic pump end plate with holes that didn't all align with the ones on the other end. I didn't identify the problem until I had taken it apart and fussed with it too much to return it, and it was a tempting precision machining challenge. After the repair it's given me 20+ years of service on the log splitter. That job taught me the limitations of my old milling machine, such as the quill free play increasing as it extends. I used the knee feed to bore straight and parallel.

-jsw

Reply to
Jim Wilkins
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I've been using Glen's spreadsheet to check my work. A second opinion is helpful. It's the most involved spreadsheet I've ever loaded... Use that data to fill in the Fed's pdf forms...

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Reply to
Leon Fisk
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I've been using Glen's spreadsheet to check my work. A second opinion is helpful. It's the most involved spreadsheet I've ever loaded... Use that data to fill in the Fed's pdf forms...

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Leon Fisk

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The valuable aspect of my spreadsheet is that it incorporates and preserves my understanding of the rules, which I read through every year to update the spreadsheet, and then use to help plan my deductible purchases and investment choices and improve my record-keeping. Its extra Paid and Received sheets are also useful check lists of all the paperwork I need to take to my sister's house, since she demands to see and highlight the originals, and anything that may be missing or questionable like the recently optional IRA minimum required deductions. Understanding the forms and performing the calculations have become separate operations which are individually less demanding and confusing.

The H&R Block program that actually computes my taxes gives no useful feedback and doesn't relate to the IRS forms, especially the Social Security and Qualified Dividends worksheets. I created them first and then realized I was more than half way to doing the other, simpler forms. Most of the math is addition, subtraction, copying to another sheet, and selecting the Min or Max of two values, extensive rather than intensive complexity.

-jsw

Reply to
Jim Wilkins

I use applications on the PC all the time of course. Monthly bills and "cash" on hand go in a spreadsheet for quick checking to see what I can pay, payoff, and pay down. One I built up is for converting volume to weight for a variety of common casting and injection materials. Some of the first larger G-code files I wrote was using macros for iterative work in Lotus 123. In college I wrote programs to help me understand algebraic and economic equations.

In high school I wrote a program to generate random test problems for am algebra 1 class. The instructor asked me to write something that would generate random test questions because he had rampant cheating in the class. After the test was administered he asked for the answer keys. "Answers keys?" I responded innocently. "You didn't ask for answer keys." He picked the entire stack of tests off his desk and dropped them in the trash.

As to cell phones. I really wanted to remain a Luddite in that regard just like you. Basic communication, and to respond to customer calls. Unfortunately being in the communication contracting business and one of the first (if not the first) contractors in my area to setup remote access video over Internet I was forced kicking and screaming against my will to embrace smart phones. In the long run it was a good thing. The computing power in my pocket dwarfs the computing power of some of the computers I used in high school and college like a highly intelligent human dwarfs the intelligence of an amoeba.

At my desk top the CAD software does most of the heavy lifting for me, and I can always use the lookup tables in the Machinery's Handbook, but in the back shop I use my cell phone at the machine like some people used to use their slide rule.

Reply to
Bob La Londe
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You want to really piss away some time... install Termux on your Android smart phone. Don't use the crippled version from the playstore either:

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You'll have a Linux style terminal now. So you can then install wcalc:

pkg install wcalc

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They have a graphical display available too but having a Linux terminal that supports a lot of software I'm already familiar with is good enough ;-)

Reply to
Leon Fisk

On 2/26/2023 8:07 AM, Jim Wilkins wrote: ......

--------------------- At my desk top the CAD software does most of the heavy lifting for me, and I can always use the lookup tables in the Machinery's Handbook, but in the back shop I use my cell phone at the machine like some people used to use their slide rule.

Bob La Londe

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That's the difference. You are everywhere, expertly managing your enterprise, while I'm an old retireded geezer puttering away at home. Even at work I was stashed out of sight in the lab, like Dan Aykroyd at his boiler room desk in Spies Like Us. At least I was beside the boiler room instead of in it, and I had a large window to watch the black helicopters parked outside.

Just kidding about the helicopters. They were unmarked white cargo vans equipped to monitor radio signals.

Reply to
Jim Wilkins

It's not just pretty darn good, it's trigonometrically perfect. sine(30 degrees) = 0.5, exactly.

Clifford Heath.

Reply to
Clifford Heath

Expertly? Thank you. That is something I aspire to. LOL.

while I'm an old retireded geezer puttering away at home.

Reply to
Bob La Londe

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