Making Your Own Transfer Screws

[BobWarfield]

As I'm bumbling along making a backplate for my collet chuck (which I want to use on the Team Build), I playing with several things that are new to me. I thought I would share one here, which is making your own transfer screws.

Transferring hole locations is one of those finicky operations that a budding machinist has to learn. Most of us start out clumsily measuring things with digital calipers and then wondering why they're off by quite a lot. It's hard to measure holes precisely!

Pretty soon we discover transfer punches, which are really cool. Eventually, we have a blind hole and can't use a transfer punch. The answer there is a transfer screw. It has threads on one end and a point on the other. Screw it into the blind hole and voila: you can transfer! I was so pleased when I discovered these that I promptly ordered all the small imperial sizes I like to use. These things are not cheap, but I find I use them pretty often.

Unfortunately, my chuck backplate project requires M10 bolts. Not wanting to spend the money or worse wait for another set of transfer screws to be shipped, I set about making a set. It's quick and easy for anyone to try. Here are a few photos to show what I'm up to:

I started with an M10 bolt and a couple of nuts to protect the threads.

I chucked that assembly in my 6-jaw (a 3-jaw will do), set the compound over for a 60 degree point, and started shaving the head of the bolt. I'm using a 1/2" shank CCMT indexable carbide turning tool for the task.

Eventually, you get the nice 60 degree point and you are done.

You can see them a little better here. For some unknown obsessive compulsive reason I felt compelled to set all the points to exactly the same height. I must have that obsessive compulsive disease!

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[BobWarfield]

Next, I set up a rig that made it easy to crudely center the backplate blank atop my transfer screw equipped existing backplate:

It's not elegant, but it was quick and pretty close. It doesn't have to be terribly close as I'll be turning that blank on the lathe once I can mount it to get it just right.

Having centered the blocks, I flip the blank so the marking dye side is down and give the works a hammer tap. This gets me some barely discernable pips. I then when over those with my Starrett automatic marking punch.

Once I've got a clear set of pips that I verify are in the right spot, I give it a mighty whack with Mr Slammy and the Big Punch. I don't want my bit to have cause to wander!

And now I have to get back down to shop to make more progress on the backplate!

Meanwhile, I have a new set of M10 transfer screws to add to my collection of store bought transfer screws. Cool!

Cheers,

BW

 

[Brass_Machine]

Transfer screws are neat. I discovered them when trying to machine up a new clutch cover for a motorcycle engine. A real life saver they are.

Good job Bob!

Eric

 

[Powder keg]

We make those for guys at work sometimes. Remember though, they are for marking the hole only. Use a regular center punch to make your pimp bigger for drilling. A big hammer will just mushroom the end of your screw.

Wes

 

[BobWarfield]

Good point Wes!

In fact, the points are noticeably soft and would be easily damaged. Hence, I use the word "tap" with the transfer screws, I progress first to the Starret Automatic Punch, and only then, and after measuring to make sure things are copacetic, do I bring out Mr Slammy and the big punch!

BTW, if you have a mill with DRO on the X and Y axes, you can as easily use that. Place the master component on your mill, and locate all the features you want to transfer in the usual way (edge finder or spud if you prefer). Note down the coordinates. Make sure, BTW, you have some locating datum for making sure your second piece goes down in exactly the same place as the first. You're using your DRO as a poor man's CMM to reverse engineer the part you need to duplicate or mate up to.

Now place your second workpiece down, the one you need to machine, and use your list of coordinates from the DRO to go back to the exact same places. This will likely be faster and more accurate than making a set of transfer screws!

If you don't have a DRO (I only have X and Z axes on my mill, never got round to my Y, DOH!), you can also use a surface plate and height gage along with appropriate fixtures to take precise measurements of the locations of various features and then transfer those coordinates to your new part. I am also doing some of this for my chuck backplate work. I will post that when I get done. It's tedious work, but kind of interesting if you like geometry and metrology.

Cheers,

BW