Mill a ~4mm / 0.160" shim with a slight wedge?

[ClintNZ]

Hi all, help out a milling n00b please. I need to make a steel shim to space out the milling attachment on my new lathe so the spindle centres match closely.

So I'll need a 100x80mm chunk 4mm thick - next job is to measure that ~4mm exactly. I'd also like to put on a slight top to bottom wedge to set the mill column tram front/back, or at least reduce the amount of shimming required. That needs to be 0.15mm / 0.0038"

So please contribute your hot tips on how to fixture & machine this kind of thickness accurately! My 4" milling vice does not open far enough to hold the part. I have a 50mm insert face mill, no fly cutter but i probably should make one sometime. My best idea now is to first face off a thick backing plate, packing one end up with a feeler gauge to get my wedge. Then bolt/screw the shim to that & machine. Maybe with some countersunk cap screws in the middle to keep it flat. The part can be trimmed to size after the thickness is set.



Cheers
Clint

 

[ErichKeane]

I'd consider using a super-glue arbor to glue it down to something (like your thick backing plate), then hold that something in the mill vise. THEN, just use a sine bar (or something similar) to get your angular wedge.

 

[compact8]

I have made the same thing for my bench mill to correct the tram along the Y axis : https://www.hobby-machinist.com/threads/how-to-machine-a-shim-accurately.98278/page-2

super glue was used to hold the ~1.4 mm thick shim onto the backing plate. It worked extremely well. Now I use super glue a lot to hold parts, big or small. Have not failed even once. A couple of recent works :

picture 1 : the small M4 T-nuts being made were glued to the backing plate.

picture 2 & 3 : the lapping plate being made was glued to the mill table which was covered by painters' masking tape first. This is also how the backing plate for the shim was held when being machined.

 

[ClintNZ]

Thanks guys. A follow up for you. As I had excess for clamping around the edges I bolted it down there, also some CS cap screws through where I needed to drill anyway. Fettled the mill tram as well as I could then made some chips.

The plate underneath was shimmed to the correct orientation & checked by traversing it under the dial indicator. Came out pretty good, the targets were 4.05mm & 3.90mm, within .02mm (0.0008") is more than adequate accuracy for this guy.

Next job is to pull the mill column off & cut the plate out to match the mounting surface.

Cheers
Clint