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Thread: Sizing Roll Pin Holes
10-24-2009, 03:59 PM #1
Sizing Roll Pin Holes
Is there any standard in machinists handbooks for determining the correct drill size in relation to roll pin diameter when drilling the holes? Thanks in advance for any help given.
10-24-2009, 04:14 PM #2
I'm not sure of any rule, but making the hole .020" under per inch diameter has always worked for me. Usually I work with roll pins up to .250" dia.
Just checked MH, and it gives no info on roll pins (at least my 1940s ed.)
10-24-2009, 04:31 PM #3
Roll pins are sized by the diameter of the required hole, i.e. a 1/8" roll pin will fit tightly in a 1/8" hole.
No calculation required.
Limy Sami liked this post
10-24-2009, 04:34 PM #4
Hmmm - my understanding was that the pins were made to fit holes at the standard nominal size, ie the pins are oversize in the relaxed state.
I checked my Unbrako Sel-Loc literature, and it confirms this.
The recommended hole size for a 1/4" pin is 0.250 - 0.256"
for 1/8" pin it's 0.125 - 0.129"
(PS: while I was writing and checking this, Leigh typed the same thing more succinctly)
10-24-2009, 05:34 PM #5
10-24-2009, 05:41 PM #6
"Brevity is the soul of wit"
Lord Polonius, Hamlet, Wm. Shakespeare
Glad everyone agrees this time.
This business is well ended.
My liege, and madam, to expostulate
What majesty should be, what duty is,
Why day is day, night night, and time is time,
Were nothing but to waste night, day and time.
Therefore, since brevity is the soul of wit,
And tediousness the limbs and outward flourishes,
I will be brief: your noble son is mad:
Mad call I it; for, to define true madness,
What is't but to be nothing else but mad?
But let that go.
10-24-2009, 05:48 PM #7
10-24-2009, 06:40 PM #8
Leigh has it right, I remember this one clearly from early in my career.
Pardon the digression;
I was a ME at a well known co designing a supercomputer. My boss had an outside consultant design the door extrusions. The doors were designed to pivot on roll pins. I had no part in the design and my boss took a vaction when the parts were supposed to come in and had me check on them. Well the consultant undersized the holes - never bothered to look up the design data for roll pins. I figured out the problem and obviously all the prototypes had to be reworked to fit. Somehow the design error became my fault
Left there within 6 months - they never succeeded in the supercomputer business.
110octane liked this post
10-24-2009, 08:47 PM #9
11-02-2009, 02:25 AM #10
Thanks for your reply. I just spent $40.00 on a 5/8 shaft for my DoAll and needed this info before drilling.
07-22-2016, 12:15 PM #11
Roll Pin Data
We can make it official. As stated by the real Leigh,the nominal size is the drill size. If the site will allow links, here is a published table:
Spring Pins, Roll Pins, Split Pins Size Table ANSI/ASME B18.8.2 | Engineers Edge
extropic liked this post
07-22-2016, 12:25 PM #12
take roll pin and use a drill bit gage plate the ones with holes drilled in a plate to quickly find drill bit size
usually .250 roll pin needs .265 hole to go in by hand. not sure exact size but the definitely are bigger than stated size and they compress smaller to go in a hole
drill bit gage plate - Google Search
07-22-2016, 12:33 PM #13
07-22-2016, 12:42 PM #14
But the whole idea of a roll pin, a spring pin is that it is deliberately a bit oversized and it will shrink to size as it is inserted in the nominal size hole. Thus some force is needed to insert one. The ends of the roll pins are tapered for a short distance to facilitate the insertion. This ensures a tight fit but it can be easily removed and reinserted many times.
It also allows the holes to be slightly different in diameter and the pins will still function as intended. Thus, you can just use common drills. Reamers are not needed.
07-22-2016, 12:43 PM #15
Yeah, I got caught by this too. About a week before Christmas, the boss says he wants to help out a neighbor... a glass shelf in the cabinet that housed her ceramic figurine collection had collapsed, jamming the doors, and it took hours for her daughter, the only one with arms small enough to fish the figurines out through the small amount they could open the door, to clear the wreckage. A postmortem determined that while the glass shelves could handle the load without deflection, the crappy shelf clips had failed. I suggested he replace them with stainless dowel pins, and to keep from wrecking the wood veneer with pins that would stick in the holes, I suggested we order 6mm dowels (.236" dia.) At the last minute, someone noticed that stainless roll pins were considerably cheaper than dowels, and substituted them on the order. Well, damned, can you believe a 6mm roll pin is larger than 1/4"? About .257" dia or so. This is now the DAY BEFORE CHRISTMAS EVE, and I still need to source four dozen 6mm dowels. Luckily McMaster had them in stock, but I am NEVER going to forget that roll pins are larger than their nominal size.
07-22-2016, 12:57 PM #16
usually roll pin is about .010 to .015 bigger. i suspect you got 1/4" instead of 6mm roll pins. happens quite often person filling order puts wrong stuff in the bag. i have even seem stuff in box from China and the mistake happened in China even though shipped from a USA industrial supply company. big industrial suppliers rarely check stuff. they just ship out stuff taking what is printed on label as correct
07-22-2016, 01:16 PM #17