Measuring toleranced chamfer in the machine

KristianSilva · Mar 25, 2019

Hello,

Im doing a job at the moment that is a 50Kg cast iron part, because of its weight and out of balance nature I want to mill the part complete (on VF3), but the part has toleranced O-ring chamfers (7.8-7.92mm x 45°) at the opening of a bores on both sides of the part, see picture below.

Measuring the chamfer on the second Op is no problem as I can take the part off the machine and measure using Faro arm and then just probe the part back in, but I need a way of measuring the chamfer while it is still on the machine during the first OP so I can bring the chamfer to size and avoid scrap.

I thought about doing a setup piece but this would be tricky as we are a production shop who use fixture plates so I cant easily just throw a vice on, plus this doesnt actually give me a way to measure the chamfer size.

Does anyone know of any measuring equipment that I can use to measure this? Or have any other suggestions on how I can?

At the moment the only idea I have is making a shallow test gauge type measuring gauge where the gauge locates in the bore and on the top face of the bore with the indicator pointing perpendicular to the chamfer face, then creating a known test piece (not on one of our production machines) to compare against.

Hope this makes sense, any questions just ask!

KristianSilva · Mar 25, 2019

How do I take a mold?

lionelt · Mar 25, 2019

Could you get in there with an eye loupe and graticule?

Pepler Optics

KristianSilva · Mar 25, 2019

Unlikley as the bore is only 200mm dia.

Never seen those graticules before, what are they like to use? Do you get good repeatable readings or is the a knack to using them?

lionelt · Mar 25, 2019

KristianSilva said:
Unlikley as the bore is only 200mm dia.

Never seen those graticules before, what are they like to use? Do you get good repeatable readings or is the a knack to using them?

It’s just a scale under the eye loupe, similar to the lines on manual micromer and calipers.

No real knack to use them. The can be used under a microscope to compare size of very small items.

https://www.pyseroptics.com/wp-content/uploads/2017/07/1330_Stage_Micrometers_Brochure.pdf

EDIT..

This is my eye loupe on a 8mm guage block.

Lighting bad as only have phone to photograph.

The scale is 0.1 per division.

Booze Daily · Mar 25, 2019

KristianSilva said:
How do I take a mold?

Repro rubber

KristianSilva · Mar 25, 2019

So I take it the gauge has to be pressed up against the surface you are measuring? If this is right then it wouldnt be so good for a chamfer in a bore?

KristianSilva · Mar 25, 2019

website says 6-8mins start to finish for repro rubber, not sure Id want to wait this long each time I want to measure

AARONT · Mar 25, 2019

I would use the loupe as well.

lionelt · Mar 25, 2019

AARONT said:
I would use the loupe as well.

Use a USB loupe and you can have a photo of the part being measured showing the measurement.

Edit..

But depth of field may be a problem on a chamfer?

litlerob1 · Mar 25, 2019

KristianSilva said:
website says 6-8mins start to finish for repro rubber, not sure Id want to wait this long each time I want to measure

Well now you're just arguing your way out of it. In the time it takes to get a cup of Coffee it sets.

But your print is asking for a Depth, which is what it is (stupid), but you can measure your Chamfer Diameter with a regular Chamfer checker it seems. From that, you can extrapolate your Depth.

You can use tools like these also;
Diangle Taper Angle Gages
Products - Solutions for gauging - Measurement of diameter and length - BMD – Plug Gauge DIATEST - DIATEST Hermann Koltgen GmbH

You can also use a regular DTI.

R

(or gage blocks

)

FredC · Mar 25, 2019

If you are going to be doing these on a regular basis you may want to look at getting or making a "Cameron Ball Gauge". It was mentioned in this thread: Help
The tool would have to be ordered from Cameron I guess, they are an oilfield supplier in east Texas.

michiganbuck · Mar 25, 2019

Perhaps a measuring loop
iGaging 10x Pocket Optical Comparator with #2 Lens - 36-LED10 - Penn Tool Co., Inc

Larry Dickman · Mar 25, 2019

barbter said:
This is the stuff you need Impression Compound For full/partial impressions or copper bands/tracing | Kerr Dental

this is the stuff I like using. But, as discussed in a recent thread, it turns out you need to be a licensed dentist to order it.

Orange Vise · Mar 25, 2019

lionelt said:
But depth of field may be a problem on a chamfer?

Good point. A 4-5X loupe would probably work okay on an average sized chamfer, but the chamfer in OP's print appears to be pretty deep.

KristianSilva · Mar 25, 2019

litlerob1 said:
Well now you're just arguing your way out of it. In the time it takes to get a cup of Coffee it sets.

But your print is asking for a Depth, which is what it is (stupid), but you can measure your Chamfer Diameter with a regular Chamfer checker it seems. From that, you can extrapolate your Depth.

You can use tools like these also;
Diangle Taper Angle Gages
Products - Solutions for gauging - Measurement of diameter and length - BMD – Plug Gauge DIATEST - DIATEST Hermann Koltgen GmbH

You can also use a regular DTI.

R

(or gage blocks )

Its just not practical when running a great number of parts.

How can I measure using a DTI?

litlerob1 · Mar 25, 2019

KristianSilva said:
Its just not practical when running a great number of parts.

How can I measure using a DTI?

What is not practical? Using a Chamfer Gauge?

There are 20 different ways to use an Indicator. Easiest is just run it across the Diameter noting needle drop.

R

specfab · Mar 25, 2019

For initial setup, I would probably do a repro rubber check and loupe check as noted below. For ongoing checking, just a loupe and measuring reticle, once you have things set to required dims. The tolerance shown, at .12mm tolerance envelope, would yield a chamfer face width of about .0066" tolerance envelope. If you can get a good placement of the loupe on the chamfer face, i.e., tilted at 45 degrees, you should be able to easily resolve the chamfer width using a 10X loupe with a reticle graduated in thousandths or 0.1mm increments. This will also help eliminate depth of field issues. This is of course assuming that the cutting angle is a correct 45 degrees, being produced with a correctly ground cutting tool.

Another possibility might be a measuring microscope head on a boom stand placed in the machine for measurement; obviously needs a stand setup capable of making the 45 degree angle.

guest · Mar 25, 2019

You could make a disk that fits the counterbore, and has a chamfer that is smaller than the callout- say a .250" chamfer on the disk. Drop the disk into the hole, and depth mike from the top of the part to the top of the disk. Add the known chamfer size on the disk to your depth mike reading for a total depth.

G00 Proto · Mar 25, 2019

I'll tell you the wrong way to do it

I just drill a hole some place on the part that is going to get machined away. Then I drill or circle mill a chamfer in that hole and measure it with my countersink measuring tool (or a tooling ball). At that point, I know that my chamfer tool Z height and radial compensation is set correctly and then I machine the chamfer in question. I have been doing that for twenty years and I haven't had a part rejected either internally (CMM) or by my customers.

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