Building a milling machine

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philf:

--- Quote from: NormanV on June 20, 2014, 04:17:00 PM ---Phil, how did you get the angle correct?

--- End quote ---

Hi,

I had access to a huge profile projector where I could project a magnified image of the tool onto a screen to which I clipped a 20:1 or 50:1 (can't remember exactly) template drawn on to translucent drawing film. I ground and stoned the 40 degree profile and root radius to the template.

Now I'd use my Quorn T&C grinder to do the 40 degree form but would probably still stone a radius on the end.

For hobby use I don't think the angles and radii are super-critical but I would imagine that 55 degree grooves are a bit too far out and would lead to vastly accelerated wear and slippage.

Phil.

NormanV:
I saw JS's comment that 55degrees would do. That happens to be the size of the only carbide tip that I have. I could use it but I have quite a lot of work invested in one of my pulleys and have no desire to mess it up. So, what depth should I cut each groove?
Phil, I fear that you are correct concerning the wear.
45 years ago I worked as a draughtsman at an engineering company and one task I had was to produce drawings at 10 times size to an accuracy of 100th inch to place on a "Shadowgraph" machine to check the profile of parts to 1000th inch. I had good eyesight in those days!

vtsteam:
If you have access to an ordinary computer scanner, put the tool you are grinding on it and scan it. You can then just blow it up in any paint program to measure angles and check profiles.

Distortion is minimal compared to a camera, and even a cheap scanner these days will scan at 2400 DPI or better, which can be blown up tremendously. Photos on this forum are probably displaying on your monitor at 96 DPI, to give you some idea of the degree of enlargement possible.

NormanV:
Good idea Steve, I hadn't thought of that. It's a bit slower than the shadowgraph machine but will do the job.
Thanks.

vtsteam:
Norman, I've often used my scanner as a microscope for small objects. I once wanted to identify seeds that mice were storing -- it's amazing the detail you can get.

Also if you lay a rule alongside the object, you can scale from it.

You can also work out a calibration from a scanned standard for future use. Screw threads can be looked at, etc. Gets a little more use out of an old scanner than it usually gets otherwise.

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