Forming a D shaped hole

[Spark plug]

Ok so I have a job to do that involves makeing a pair of bushes with D shaped holes in them.

Has Anyone done this before?

I'm thinking making a punch and punching it hot?

 

[CRB]

?Material, sizes?

 

[Spark plug]

In steel, nominal bore 1" and 1 " thick

 

[AndersK]

Drill full dia and weld back a half circle?

 

[Rocketman]

If you can't split the bush at the flat and it needs to be accurate EDM or wire EDM. If you have someone local it shouldn't cost too much.

Edit - alternatively you could insert the flat, but it's hard to say with no sizes.

See the size now 1inch by inch, probably a bit tricky for inserting for the sake of quick EDM job.

 

[Pete.]

EDM would make a good job of it or you could try making a wobble broach.

 

[Rocketman]

Here is what I was talking about when I said insert it. Could use some GFS for the insert. Looks possible.

 

[scott0031]

You could also make a 'D' section piece of the same rad as the larger hole, machine the flat back as necessary. A very small Prep and Tig it in, clean up by hand on the inside if required, This would be pretty accurate if done correctly the problem is you do not really give enough detail, accuracy required usage and material. If the D has to drive anything it may also be possible to drill and ream through the main body and use some soft dowels made from silver steel or such like to give some more resistance to any shearing action. Maybe a possibility to also 2 x drill and tap into the back of the D piece if there is enough depth there. If any accuracy is required would be confident to get that within 2 thou without any major struggles. Also as mentioned making it split is very feasible and using the right methods could be tigged together maintaining very good accuracy.

Your idea of using a static broach will work but will require some forethought. Doing it hot will be tricky as it will try to splay the OD out as its in a plastic state. That can be resolved by making a nice heavy duty bush ( preferably out of something nice and tough) to slip over the outside, this will then contain any splaying and distortion that will occur to the OD, this will also maintain the accuracy of the internal D shape with little tapering. Static broaching will also work but would ideally need a well made form and may need grinding as there is a lot of surface area in contact. Stuff like this just milled can bind up a lot as the surface finish is not that good with milling.

Kind regards,


Scott

 

[PSweeney]

have it laser cut.

 

[Spark plug]

EDM would make a good job of it or you could try making a wobble broach.

I think a broach of some sort I going to be the way to go, never seen a wobble broach before TBH

Here is what I was talking about when I said insert it. Could use some GFS for the insert. Looks possible.View attachment 62781

I think that would be a very good solution if the part was bigger, but I'm limited on wall

You could also make a 'D' section piece of the same rad as the larger hole, machine the flat back as necessary. A very small Prep and Tig it in, clean up by hand on the inside if required, This would be pretty accurate if done correctly the problem is you do not really give enough detail, accuracy required usage and material. If the D has to drive anything it may also be possible to drill and ream through the main body and use some soft dowels made from silver steel or such like to give some more resistance to any shearing action. Maybe a possibility to also 2 x drill and tap into the back of the D piece if there is enough depth there. If any accuracy is required would be confident to get that within 2 thou without any major struggles. Also as mentioned making it split is very feasible and using the right methods could be tigged together maintaining very good accuracy.

Your idea of using a static broach will work but will require some forethought. Doing it hot will be tricky as it will try to splay the OD out as its in a plastic state. That can be resolved by making a nice heavy duty bush ( preferably out of something nice and tough) to slip over the outside, this will then contain any splaying and distortion that will occur to the OD, this will also maintain the accuracy of the internal D shape with little tapering. Static broaching will also work but would ideally need a well made form and may need grinding as there is a lot of surface area in contact. Stuff like this just milled can bind up a lot as the surface finish is not that good with milling.

Kind regards,


Scott

Lots of ideas there Scott, hear is a pic I have to machine the part from:

The part is used to keep a wheel on an axle the large diameter side goes against the wheel and the small diameter has a nut keeping everything in place.

 

[piman]

Hello Sparkplug,

if it is basically a spacer, why have the flat, just bore it round?

Alec

 

[Spark plug]

Hello Sparkplug,

if it is basically a spacer, why have the flat, just bore it round?

Alec

The spacer needs to remain static to prevent the lock nut from unscrewing.

 

[Pete.]

Just a spacer? Turn it round, cut across the hole on the line of the flat with a mini-grinder, weld a piece across and turn it back round on the OD.

 

[Master-of-none]

To stop a simple spacer rotating, use a round hole, cross drill/tap and fix with a grub screw

 

[rtbcomp]

^^ Or even use a roll pin

 

[mike os]

Rocket man's approach looks straightforward

 

[Spark plug]

Grub screw won't work with the clearance I have:

The spacer goes beyond the second thread.

 

[Shox Dr]

Locking wire?

 

[shedfull]

Drill it and file it

 

[Wendelspanswick]

Bore it out small and then rotary table and shaper!