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Hole tolerance help needed.

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Brian Abbott19/03/2019 22:40:11
390 forum posts
66 photos

Hello all, can you offer me some advice.

If i have a diameter 63mm with a h6 tolerance. (Guide bush)

What tolerance should i apply to the bored hole to ensure a good slide fit ?

I have never been any good with tolerances, normally i just machine to fit but on this occasion i am having the holes bored by a contract machining firm in spain and want to make sure i give them the correct tolerance.

Thanks for any help.

Jeff Dayman19/03/2019 22:43:15
1643 forum posts
42 photos

Is it sixty three mm or six point three mm with h6? Just want to be sure before looking it up.

Brian Abbott19/03/2019 22:44:55
390 forum posts
66 photos


yes, 63mm not 6.3mm


Phil P19/03/2019 22:51:39
518 forum posts
137 photos

Depends what you are aiming for but H7 would be a good starting point imho.


Jeff Dayman19/03/2019 23:02:25
1643 forum posts
42 photos

G7 / h6 will give a sliding fit (clearance, but not free running)

According to the chart I use:

G7 for 63 dia hole has tolerance +0.04 / +0.01. Limits 63.040 / 63.01

h6 for 63 dia shaft has tolerance +0.00 / -0.019. Limits 63.000 / 62.981

If you need a close running fit F8 / h7 might be a better choice

Brian Abbott19/03/2019 23:14:07
390 forum posts
66 photos

Thanks Phil, Thanks Jeff.

I have just been through the suppliers info and i think i have wasted your time, sorry.

Bush size is 65mm +0.019 + 0.030,

Hole size should be 65mm +0.00 + 0.019 (H6)

Thanks for your time both.


mechman4820/03/2019 09:59:26
2500 forum posts
371 photos

Hi Brian

Get yourself a 'ZEUS' book; it has the charts for ISO fit BS 4500- 1969 for clearance, transition & interference fits, plus a lot of other useful information.


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