Need help making a hole for Dowel Pins

[ibuildstuff4u]

Hey guys, I'm working on a project that needs a 3/16" (.1857) dowel pin installed, but for some reason I can't get a hole cut to create a perfect fit so the pin can be pounded in to place.  I'm making the part on the lathe and start off by center drilling the hole and then I drill it out with a .157 drill bit (.030 under sized) and then I'm finishing it off with an under sized chucking reamer (.184)

The hole ends up too large and the pin is a slip fit.  I tried drilling the hole out with a smaller bit and then re drilling the hole with a larger bit instead of the chucking reamer and sometimes it works, and sometimes it doesn't.  I can use the same combo of drill bits and one time it's too big and the next time I bend the pin when trying to install it.  

I have had really good luck installing a 1/4" dowel pin by simply using a "Letter D" drill bit which is slightly under sized, but I can't get the 3/16" dowel pin to work correctly.

Thanks for the help!

Dale P.


Here is the project that I'm working on.  The handle uses two 1/4" dowel pins and I drill the hole out on my milling machine.  The center pin is the 3/16" dowel pin and I'm drilling it out on my lathe.  I drill and ream the hole 1/2" to 3/4" deep, but the pin is only driven in 3/8" deep.

*Please note the picture shows common drill rod being used, but I am using precision ground doweling pins. 

[sbwhart]

Hi Dale

I take it your drilling the 3/16 hole from your tail stop with the drill held in a chuck, if so your problem is almost certainly due to misalignment of your drill with the centre line of your work, this is due to a build up of errors, from tail stop, chuck, and the chucking of the drill, this is why some times its ok sometimes not as the errors can build up on each other or cancel each other out, each time you assemble the tools together. You've done the right thing in using a roughing drill followed by your finisher, but you need to have the finisher floating to find the correct centre line, the trick the old guys used was to not lock the tail stop and push the drill through with it.

But looking at what your trying to do I would think that fixing the Dowel in the tool with some high strength loctite would result in good functional tool  .

Another way to fix a sloppy fit would be to put a straight knurl on the dowel pin then drive it into the hole. 

Hope this helps
Have fun

Stew



 

[ibuildstuff4u]

Thanks Stew,  I bet your right.  Ill take a look at the tail stock and see how things line up.  I have been using locktight for them but make these all the time to sell and was hoping to fix the problem so I don't have to keep gluing them in place.

Thanks again for the help!

Dale P.

[Stilldrillin]

I find I get far more accurate "reamed" holes, (using a drill!), by winding my tailstock ram well out, and hanging the drill well out of the drill chuck.

This extra long assembly allows the "reamer" to centralise. 

David D

[stovebolt]

I use a lot of 3/16 x 1/2 dowel pins,  when I first started using them I had the same problem as you.  I now use a .180" drill and drill well past the depth I need, then use a .185" drill to the required depth,  I found that if I had to drill even a small amount of depth with the .185" drill the hole would open up to larger than .1875".    Hope this helps.

Jim