Author Topic: grinding things flat  (Read 6237 times)

Offline madjackghengis

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grinding things flat
« on: March 25, 2010, 10:26:38 AM »
Bernd recently suggested a grinding option for a problem I've had with the engine I'm building, and I wanted to relate a grinding method I used a few months ago which may come in handy for someone.  I had a Harley frame from 1937 where the motor mounts were ground by hand and were in no way parallel to anything else in this universe, and the owner was wanting to put an engine in the frame which was built twenty years later, and never should have fit, given it is almost half an inch taller than the engine designed to go in.
    I found a previous owner of the frame had done some modifications that got the frame closer to fitting, but by hand, and totally inaccurate, and insufficient.  After mulling it over for a week or so, and doing some measuring, I found there was room, but I had to get the two motor mounts parallel, and their angle relative to the frame members slightly different, perhaps a degree and a half or so.  With the frame on a steel table which is machined flat, I put a face grinding wheel in a grinding arbor made for my drill press, wedged the frame in proper position with wedges and clamps to hold it in place, brought the head of the drill press down to where its quill travel would handle all the difference needed between the motor mounts, brought the wheel down and touched off, and then sliding the whole drill press like I would a surface gauge, I slid it around on the table, moving the quill down a few thousandths at a time, until the front mount was evenly ground, then, using a block cut to the dimentional difference between motor mount heights, set the wheel up to the height for the back mounts, plus about forty thousandths, and gradually moved it down, sliding the drill press around again, and taking five to ten thousandths off at a time with the drill press tilting up when I moved to fast, and taking care to only add a couple thousandths at a time on the last several cuts, ending up with the two mounts as parallel as I could measure with my table, and with them the proper height distance apart, and having rotated the engine forward a degree and a half or so, and completely clearing the frame in every way.  The key to the whole thing was having a flat table, and being able to slide the light drill press around like a surface gauge.  It had enough mass it was relatively stable, and I could move it until it "sparked out", but was light enough it moved without jumping or sticking.  I've read of doing essentially the same thing with small parts by putting a collar under the table of the drill press, and swinging the table back and forth, with the collar holding it at a specific height relative to the spindle, and using feeler gauges to lower the spindle incrementally.  Mad Jack

Offline Bernd

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Re: grinding things flat
« Reply #1 on: March 25, 2010, 12:20:43 PM »
Nice little write up Mad Jack. I'm liking these little problem solving write ups.

Bernd
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Offline dsquire

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Re: grinding things flat
« Reply #2 on: March 25, 2010, 09:20:02 PM »
Jack

I love these type of solutions. If one thinks about a problem long enough you can usually come up with a plan to repair or replace etc. I know that I have several times said that I would fix or build something and didn't have any idea of how at the time but an idea would come to me out of the blue while I was doing something else.  :D :D
Keep those ideas/fixes coming Jack.  :ddb: :ddb:

Cheers  :beer:

Don


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