How would you check this internal groove diameter?

[Ox]

I don't think that this was mentioned, but maybe it is too easy - as I didn't think of it 'till now.
(or maybe someone DID mention it, and I didn't follow what they were saying?)
The last post made me think of it, but I don't think that's what he was saying?

If you have a probe for your indicator that can reach down in there, then you could mount that to your Height Gauge, zero off the table, and roll the part into place and essentially check the wall thickness between the bore and the table.

This way there is no lash consideration.


--------------------

Think Snow Eh!
Ox

 

[Mud]

Critique this idea. 2 gages like this, slip into place, gage with gage block or feeler gage between them. Could this be accurate enough at this small size?
And how is the customer going to measure this?

 

[Booze Daily]

Brass, so no appreciable tool wear. Maybe finish the front of the bore and groove with the same tool. Monitor the bore, assume the groove tracks the same and pencil whip the inspection report.

 

[boslab]

I did it once with metallurgical casting resin and a shadow graph aka optical projector, but it was a one off for inspection , washer that fits x2 and telescopic guage or re grind the tips of a telescopic guage to fit into the groove, just thoughts .
Mark
Or

M-SURE MS-230-150 Inside Groove Digital Caliper MS-230 Series 8-150mm (0.235-6")

The ground knife edge measuring contacts are raised allowing stepped bores, grooves or seal depths measurement.. Allowing Internal Groove measurements. Constructed from Stainless Steel, Hardened and Ground Frame. UKAS Calibration Available. Data output: Yes

www.allendale-metrology.co.uk

 

[guythatbrews]

Thanks for all the suggestions guys!

After thinking about this for a while I think I'll do this if I get the job. I will use the same groove tool to bore the .312 +- .001 land at the mouth and groove the .330+- .001 groove. Since it is brass I'm not concerned about tool deflection boring vs grooving like if it was say 316ss. These two dias ought to track pretty darn close.

 

[guythatbrews]

Brass, so no appreciable tool wear. Maybe finish the front of the bore and groove with the same tool. Monitor the bore, assume the groove tracks the same and pencil whip the inspection report.

Just saw this. Booze gets the credit, as is often the case!

 

[Ox]

Chopped liver....


------------------

Think Snow Eh!
Ox

 

[EPAIII]

Unless I am mistaken, a piece of spring wire about 0.012" in diameter and bent into a ring will fit in the groove. It could be made with a fair sized gap with the ends bent toward the center and a little beyond. That would make it easy to insert and remove it from the groove with a pair of needle nose pliers with notches in the ends. Care should be taken to be sure the relaxed diameter of the wire ring is only a few thousandths larger then the OD of the groove and that it be very round. This will ensure it rides on the OD of the groove without any gaps.

Then, make a go/no-go gauge to fit inside that wire loop. Cut out one side to allow for the bent ends of the ring. The larger diameter (no-go) of the gauge would check for the maximum diameter (0.331"). If it goes in the groove is too big. The smaller diameter (go) would check for the minimum diameter. If it doesn't go in, the groove is too small.

Put the wire ring in. Check the go and no-go diameters with the gauge and done. Take the ring out. Easy peasy!

You just need to measure the size of your wire and of the go/no-go gauge down to tenths. And to be sure, check them again, after doing all the parts. Throw in a few tenths on both ends of the range to be sure. Example: 0.3293" to 0.3307" instead of 0.3290" to 0.3310".

A couple of test parts without the outer wall of the groove would allow you to check the gauge with easily measured and verified, minimum and maximum ODs.

 

[art.h]

This part is naval brass c46400. The corner radius shown in the bottom of the groove is R.005 +- .005. I will be using a sharp cornered tool so that won't narrow the diameter available to check. I can't think of a readily available measuring tool to check the .330+-.001 internal groove diameter? I'm not interested in cutting a part to check this.

Any ideas? I'm at the quote stage so I can still turn this down.
View attachment 394006

 

[art.h]

This part is naval brass c46400. The corner radius shown in the bottom of the groove is R.005 +- .005. I will be using a sharp cornered tool so that won't narrow the diameter available to check. I can't think of a readily available measuring tool to check the .330+-.001 internal groove diameter? I'm not interested in cutting a part to check this.

Any ideas? I'm at the quote stage so I can still turn this down.
View attachment 394006

I see those now. 0.200 minimum diameter. I'm in the effin jury room with 15 other idiots looking at this crap on my phone and I forgot my glasses.

Best/cheapest option so far. I'll check it out tonight.

I have a Starrett internal caliper 1019-1 as new in box plus a .4000 checking ring gauge which was purchased to do a 100% check on a 400 pcs. one off. It would do your job with a narrowing of tips. $250.00 US plus shipping. Art Harron Peterborough Ontario Canada [email protected] if your interested.

 

[guythatbrews]

I looked at this gauge and $250 is a very fair price. Thanks but I think I will pass. With the dial gauge shown it is not the best to hit +- .001. The. 001 divisions are very close together.

 

[EmGo]

I looked at this gauge and $250 is a very fair price. Thanks but I think I will pass. With the dial gauge shown it is not the best to hit +- .001. The. 001 divisions are very close together.

You know what tho ? I just had a brainstorm. You know those Starret tri-mike things with the bottom anvil you can take off and put a pin in instead ? If you made a t-shaped thing except round and put that in in place of the pin and set your spindle to a known distance, you could measure the wall thickness from the bottom of the groove to the od really easy and fast and pretty cheap. It would be an indirect measurement, have to deduct the thickness from the o.d. but still, as accurate as a mic and handy and inexpensive and what more could you ask for ?

Someone will probably think of why, but for now, seems like the best way to do this, to me.

this isn't the one I am thinking of, the one I'd want has the bottom comes off and you can make or use your own pins, but the idea is the same

 

[EmGo]

Hang on, hang on, these'd work too if you butchered them, maybe even better. I was never really confident in the feel of these but for +/- one, should be good ?

but the baby jesus wept, what in the hell is with prices these days ? $350 for a set of stupid 1" mics ? Are these people crazy ? And you guys pay that ?

 

[CarbideBob]

Duh, forehead dope slap.
I think EG has nailed it here in post #52.
Mitutoyo uni mike.
.250 dowel pin turned or ground to a tee shape.
Maybe a carbide pin if you have a diamond wheel and spinner. (same way you neck down carbide endmills or make under-cutters for toolholder pockets)
$200 new, $75 used. Now you can measure both in the machine and out.
We use these to measure hole concentricity in inserts. Much better than our first method which was calipers.

 

[guythatbrews]

You know what tho ? I just had a brainstorm. You know those Starret tri-mike things with the bottom anvil you can take off and put a pin in instead ? If you made a t-shaped thing except round and put that in in place of the pin and set your spindle to a known distance, you could measure the wall thickness from the bottom of the groove to the od really easy and fast and pretty cheap. It would be an indirect measurement, have to deduct the thickness from the o.d. but still, as accurate as a mic and handy and inexpensive and what more could you ask for ?

Someone will probably think of why, but for now, seems like the best way to do this, to me.

this isn't the one I am thinking of, the one I'd want has the bottom comes off and you can make or use your own pins, but the idea is the same

I have done thus a lot, but for bigger tolerances. Mitutoyo calls these multi-anvil mikes and they are handy. I have an assortment of little anvils.

I really thought the other caliper anvil type mike you show in your next post was available with suitable anvils for this groove, but couldn't find anything. I could probably modify as you suggest but and it would work great, but then i woulda had to buy a mike to ruin plus grinding wheels to break.

 

[guythatbrews]

Duh, forehead slap.
I think EG has nailed it here in post #52.
Mitutoyo uni mike.
.250 dowel pin turned or ground to a tee shape.
$200 new, $75 used. Now you can measure both in the machine and out.
We use these to measure hole concentricity in inserts.

The great thing about this is you can check very tiny grooves this way.

I got my anvil mike NIB pretty cheap on ebay.

 

[Hodge]

Unless I am mistaken, a piece of spring wire about 0.012" in diameter and bent into a ring will fit in the groove. It could be made with a fair sized gap with the ends bent toward the center and a little beyond. That would make it easy to insert and remove it from the groove with a pair of needle nose pliers with notches in the ends. Care should be taken to be sure the relaxed diameter of the wire ring is only a few thousandths larger then the OD of the groove and that it be very round. This will ensure it rides on the OD of the groove without any gaps.

Then, make a go/no-go gauge to fit inside that wire loop. Cut out one side to allow for the bent ends of the ring. The larger diameter (no-go) of the gauge would check for the maximum diameter (0.331"). If it goes in the groove is too big. The smaller diameter (go) would check for the minimum diameter. If it doesn't go in, the groove is too small.

Put the wire ring in. Check the go and no-go diameters with the gauge and done. Take the ring out. Easy peasy!

You just need to measure the size of your wire and of the go/no-go gauge down to tenths. And to be sure, check them again, after doing all the parts. Throw in a few tenths on both ends of the range to be sure. Example: 0.3293" to 0.3307" instead of 0.3290" to 0.3310".

A couple of test parts without the outer wall of the groove would allow you to check the gauge with easily measured and verified, minimum and maximum ODs.

I was thinking similarly but using a modified internal circlip

 

[guythatbrews]

IF i get this job I will use the same tool to cut the first bore and the groove. The two should run together very closely. Then make an anvil for my multi-anvil mike to confirm the wall thickness to the od. If the two checks match I'll be happy.

Thanks again for all the ideas!

 

[michiganbuck]

HACK RUBE GOLBERG
With a probe of .010 or .012 thick made of steel it would be difficult to get accuracy because so thin that it would tend to flex/bend so a carbide probe might be better.:

Have a 4 1/4 to 6 1/4" long 1/4"dia steel rod with a hole through to pivot off at 6" (or4") at one end (the out end).
At the other end have a round carbide insert perhaps flat ground thin to .012 or what
that is held flat on the rod's other end (the going-in gauge end) held with a 10-32 or 8-32 screw and washer.
Set the insert (gauge probe) in/on the .297 bore to zero a tenths dial indicator and then travel to in the groove under an indicator to see the .0075 drop to gauge size to a few tenths. Yes, would need to undercut the rod behind the insert. perhaps grind a flat on the rod topside where the indicator would touch very close to the part..
Yes, a 1/4" insert would be OK.
.

6mm Round Hollow Ground Carbide Insert Cutter for Wood Turning | eBay

Can be used with a variety of mounting screws including a 4-40 standard thread or M2.5. 2.8mm center hole (.113) countersunk. 2.3mm thick (.094).

www.ebay.com

 

[p-moon]

When I had the shop, we made gobs of fixtures for many QC departments. Never liked using a mic or anything that was operator dependent. I used to have a gage block with the size ground off and could hand it to 3 different people to mic and get 3 different answers.

To measure this groove, I would first gage pin the .297 hole. Then grind up a round probe maybe .250 dia, grind away the od for a ways and add radii to the projection at the end, so it can reach the bottom of the groove. Mount to a.0001 dial indicator or digital indicator. Measure the internal step, do some math and you’ll have your measurement, no human influence required. Let me know if you would like a sketch.