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Join Date: Apr 2017
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How To Achieve 10h7 Hole Dimension? Hole Is Having Platting After Drill & Ream!

04/03/2017 11:22 PM

Hi,

I am facing lot of issues to achieve 10h7 dimension which is after platting,

Do share if you have any better process to achieve the same.

Thanks !!!!!!

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#1

Re: How to achieve 10h7 hole dimension? hole is having platting after drill & ream !

04/03/2017 11:37 PM

..."Let's say you are ordering a reamer 10H7.

If you are ordering from a standard catalog you will get the correct product. A reamer that will produce a 10mm hole with a H7 tolerance from the first part over the longest time.
The problem comes when ordering a "special" made to your print reamer from a small tool shop.
The tolerance for 10H7 is: 10mm +0.015
However that is not the tolerance for the reamer. That is the tolerance for the hole it makes.
The reamer should be made to: 10mm+0.012/+0.006
If you try to help the producer and give him the tolerance for 10H7 as +0.015 on your print, you may get a reamer that measures +0.002
and will last five minutes before going undersize. You will have to pay the vendor since you specified 10mm+0.015.
He made it to that exact tol.. Happened to us on some very expensive carbide specials.The production tolerance for metric reamers can be found in DIN 1420.
So when ever you order a reamer from a small vendor - make sure he has the right info."...

make plating allowance....

.."In my experience it is usually between .0001 to .0002 build up on small parts. The best thing to do is call your plater and ask them what they can realistically hold for tolerance on the plating because it is up to them how your parts are finished good or not."

..."The standard thickness for Hard Chrome plating in nonsalvage applications is .0002 - .0006” (.00508 - .01524 mm). High wear applications should have .001" or more for the best results. Thickness over 1 mil generally requires the plating to be applied thicker than desired, then ground to size. "...

http://www.practicalmachinist.com/vb/general/metric-inch-reamers-270625/

http://www.practicalmachinist.com/vb/cnc-machining/plating-allowance-225932/

http://www.electrohio.com/Finishing/Chrome/HardChrome.htm

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#2

Re: How To Achieve 10h7 Hole Dimension? Hole Is Having Platting After Drill & Ream!

04/05/2017 11:39 AM

You don't mention the material you are cutting. There are a host of things that contribute to final geometry size depending on the materials. Initially, you should run a dimensional study of the cutting tool, cutting fluid and speeds and feeds to determine what statistical distribution you currently produce so that you can use specific process and tool controls to get the result you need. You can also find out whether the process you have now has any chance of being tuned to hit the range you need.

You also don't mention whether the mating part is a g6 fit. If the mating part is not, then all bets are off as to what your REAL tolerance needs to be.

The tolerance for 10H7 is 10.00 to 10.15. Since you are having issues, I assume the fit with the mating part is tight. If not, let me know.

Are you using any go/no go gaging following the ream? It sounds like you need 10.05 go and 10.16 no go. If the reamers won't hit this tolerance range, check the reamer geometry, lubricants and cutting speed to get into the tolerance. If you can't get the go, add a honing step after the ream to get the 10.05 go. Depending on whether you are on CNC or not, you could substitute a boring operation roll reaming operation to follow the drill.

After plating, use a 10.00 go gage and hone if needed to get the go. You also need to do a dimensional study of the platers results to see if the plater can produce in the size range you need. If not and you can't find a plater who will hit tolerance, then add a hone after plating to the 10.00 go gage.

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