Drift geometry

[MOblacksmith0530]

I have made some drifts based upone the thread Brian Brazeal had input on and really like the slit punches I have made and used. I have however had a little issue with the geometry of the dirfts going to round and to square on teh doamond. You need the start of the drift to be the same size and shape as the hole finished by the slit punch in order to easily center the drift. Drifting to the square, square with teh bar works almost magically. I really had to work on the grind shape of the round drift to keep from making odd shaped holes with the transition from a say 1/2 inch slot to teh round. if there was any corners to the round I ended up with those in the final hole. I have tried without success at this point to drift on the diamond. Has anyone else messed with this and have any input? Brian if you are out there and want to lend some help I would appreciate it as well.

[Yetti]

I think you are attempting to make a broach?
if the drift is too coarse of angle it may be better to use a broach. it will cut as it pushed through, that way the parts of the metal that would jam the tool are removed as it passes through the piece

[doc]

The idea of drifting a hole is to stretch the metal not REMOVE IT. The slitting punch is designed to remove as little material as possible thus leaving the most material around the hole after drifting (stretching) for strength.

Broaches are used cold where a very accurate and perhaps irregular shaped hole is needed or hot for similar reasons when the area around the opening is quite large and not an issue of requiring strength in its application. A pass through in grill work would be an example of where strength is needed or a hammer head where you're trying to remove as little weight as possible.

[brianbrazealblacksmith]

I have made some drifts based upone the thread Brian Brazeal had input on and really like the slit punches I have made and used. I have however had a little issue with the geometry of the dirfts going to round and to square on teh doamond. You need the start of the drift to be the same size and shape as the hole finished by the slit punch in order to easily center the drift. Drifting to the square, square with teh bar works almost magically. I really had to work on the grind shape of the round drift to keep from making odd shaped holes with the transition from a say 1/2 inch slot to teh round. if there was any corners to the round I ended up with those in the final hole. I have tried without success at this point to drift on the diamond. Has anyone else messed with this and have any input? Brian if you are out there and want to lend some help I would appreciate it as well.

If you go back to to 12th post in "Slitter Geometery", ignore the other holes except the three square holes on that bar. The hole in the middle is on the square, and the other two towards the ends are on the diamond. The tools I used are also pictured. The slot punch is shown along with 2 different square drifts. I do not use a round drift to do square holes. The only difference in the two drifts is the orientation of the taper that fits into the slot that you punch. The drift for the diagonal hole has been tapered where 2 of the diagonals are flattened leading into the corners on the sides. When you drift on the diagonal like I show in the picture, you can see the result with just after drifting in the upper hole, and the result in the bottom hole after hammering on the sides after drifting. I have just recently, thanks to Dan Manders question during a class, discovered an even easier approach to these square holes like I have been using for round holes for awhile. I just haven't documented that yet, but the above method will work, also.

[MOblacksmith0530]

Thanks Brian, I didn't catch that you were hammering the sides back in after the drifting. That should work. I was able to minimize it on the round by putting a radius on teh transition from teh flat to round. I am considering also reducing the cross section after the flat end just slightly until it gets closer to the round section so it starts at teh right size and then maybe is about 10 percent smaller where it was making the marks and see if that helps. I know if I go too small my bar length will change.

[Yetti]

My apology Doc. I guess I didn't understand what he was trying to do

[brianbrazealblacksmith]

I hammer the sides while the drift is in the hole. I am going to try and do some videos on making and using punches and drifts. Drifts are not for stretching holes like most people think. They are for opening up appropriate sized slots with appropriate sized drifts.

[MOblacksmith0530]

Ha, I used to stretch the heck out of holes with my drifts, then I learned better. Yes I assumed you were hammering the sides with the drift in the hole that is the way I would have done it, like I do with hammers. Anyway thanks for the great pics from before I was able to use them and I tested the set I made for the box and they worked well. I made them out of sucker rod and used it as forged without heat treating them. Judging by how tough the metal was to work it will be a good set. probably something like 4340.