Frankenmill: Bridgeport J head onto Victoria U2

[Pete O]

Got a few hours on the frankenmill yesterday and today. I ground both faces of the front plate on the surface grinder, had to take the back fence off the mag chuck and push the limits of how wide a piece the grinder can accommodate. The back edge of the plate contacted the column of the surface grinder with the front edge just behind the front face of the wheel. I do like a ground finish though.
   
   

I cleaned up the overarm ways and gib and used a wire wheel to get the layers of paint of the big adjusting screws, installed the overarm to the top of the mill and discovered that the bottom inside edge of one of the cheek plates fouled on the top of the machine so i couldn't slide the ram in.
Had to disassemble and trim the edge of the cheek plate with a file.

While the cheek plate was off, I took the opportunity to drill and tap the holes for the DRO display bracket. The two angle fixtures I made earlier in the build were at least useful for this.
   
   

Reassembled everything to the overarm and this time it slides in & out without any problems.

I used an edge finder to establish the centre line of the horizontal spindle, clamped a parallel upright in the vice and spent a bit of time making the parallel stand up dead straight. Found the edge, moved it in half the thickness of the edge finder then raised the knee to transfer the spindle center up to the to plate. This will result in the J-head spindle being in line with the horizontal spindle, not sure if that will ever matter bit it seems like a good idea.

   
   

The DRO can be seen in the above photos, I think the location will work out well.

I cut a disc of coreflute to represent the size of the nose piece, to figure out the height I can place it to clear the existing bolts on the front plate. That enabled me to mark the centre of the nose piece, which will be spigoted onto the front plate and secured with a circle of bolts.
   


I'm having second thoughts about casting the nose piece, not sure that it would be wise for my first-ever iron casting to be such a critical component. I'll see how much of my hard-earned the steel merchants will sting me for a 75mm slug of 180mm diameter 4140.

[TomG]

Great progress, Pete! Thanks for posting all the pics.

Tom

[Dr Stan]

For your steel plug you may want to check EBay.  I've purchased drops and plasma cutouts at very reasonable prices compared to what a metal supplier would charge.

[Pete O]

No luck finding cheap offcuts anywhere and I didn't want to risk the scrap yard and end up with something unknown that I couldn't get a finish on, so I paid retail price for this lump from a steel supplier near work yesterday. 4140, 200mm diameter, 75mm long (or thick I guess). I've never milled a T-slot so starting with a circular one has me nervous. I'm thinking of using a trepanning tool in the lathe to cut the opening of the slot, as I'll be facing it and cutting the other features in the lathe- anyone got any thoughts or advice on that?
   

[TomG]

You are most likely to get in trouble with the trepanning tool if you try to go too deep in one cut. Limit the depth of cut to the width of the tool or so and then step over and take another cut. Same goes when you are cutting the tee.

Tom

[Pete O]

(02-27-2019, 08:14 AM)TomG Wrote: You are most likely to get in trouble with the trepanning tool if you try to go too deep in one cut. Limit the depth of cut to the width of the tool or so and then step over and take another cut. Same goes when you are cutting the tee.

Tom

Thanks for that Tom, I will take that on board. The second part of your statement has me puzzled though- the T-slot cutter I have ordered is of a size that will cut the width and depth of the cross part of the 'T' in one pass- is that not how it should be done?

[TomG]

I thought you said you were doing the entire tee slot on the lathe. If you are milling it, I would do everything on the mill and skip the risky trepanning step.

Tom

[Pete O]

Ok thanks again for the advice. I had considered cutting the entire T-slot on the lathe but I figured it would risk leaving an offset between the two sides of the T, so the head of the bolts would only bear on one side. I'll take your advice and do it all on the rotary table.

[TomG]

Mill your slot to finished width and slightly deeper than the tee. That will take some stress off the cutter by giving the chips somewhere to go.

Tom

[Dr Stan]

(02-27-2019, 06:04 PM)TomG Wrote: Mill your slot to finished width and slightly deeper than the tee. That will take some stress off the cutter by giving the chips somewhere to go.

Tom

Plus plenty of coolant to flush the chips away from the cutter.