Surface Finishing

[julianthegypsy]

Just rechecked. Ideally it should be 0.025 across 40mm, or 0.0015 per inch. If the surface is ok then I reckon the copper leaf will take care of it. I've milled castings before with a fly bar and had results that worked without any further finishing work, so with a thick glass plate andvery fine sand paper I reckon it should work fine.

 

[AndyStobbs]

I'm keen to hear what you're making, is it going into space?

 

[julianthegypsy]

I'm keen to hear what you're making, is it going into space?

Haha. Hardly, though it is going into A space lol. There will be photos etc when the first one is finished.

 

[MrFluffy]

Just rechecked. Ideally it should be 0.025 across 40mm, or 0.0015 per inch. If the surface is ok then I reckon the copper leaf will take care of it. I've milled castings before with a fly bar and had results that worked without any further finishing work, so with a thick glass plate andvery fine sand paper I reckon it should work fine.

If you've got away with flycutting the surface in the past its probably still a tighter spec to be working to than it needs. If your mill is only a tiny bit out of tram in either x or y axis a flycutter will generate a dished surface and the larger the flycutter the more pronounced the dishing. And that is assuming all tables and gibs etc are completely wear free and not half shagged from a hard life in industry like my mill is. Be interesting to blue up one of the blocks you have that work and see what the contact area is like on a surface plate for sure.
Anyway, look forward to seeing what it is you are making, now your out of space shuttle telescope mirror territory tolerances measured using a optical flat into surface grinder in reasonable condition territory

 

[julianthegypsy]

If you've got away with flycutting the surface in the past its probably still a tighter spec to be working to than it needs. If your mill is only a tiny bit out of tram in either x or y axis a flycutter will generate a dished surface and the larger the flycutter the more pronounced the dishing. And that is assuming all tables and gibs etc are completely wear free and not half shagged from a hard life in industry like my mill is. Be interesting to blue up one of the blocks you have that work and see what the contact area is like on a surface plate for sure.
Anyway, look forward to seeing what it is you are making, now your out of space shuttle telescope mirror territory tolerances measured using a optical flat into surface grinder in reasonable condition territory

Haha. Indeed. The flybar was pretty well set up on a biggish mill, but yes, it worked ok. It was done by the company that gave me such grief first time around. This time I want to do it just that bit better, and in the privacy of my own workshop, just in case they get funny ideas. I won't get the finish from the mill that I got before, but it will be flatter and with a finer finish and better heat transfer, which should give me significantly better results, though definitely not space station levels, but that's not needed. I have a pile of work to do this week then I will make a start, the copper leaf arrived today, and by coincidence, my furniture restoring friend and workshop neighbour was doing some gilding so I got a quick lesson! :-)

 

[AndyStobbs]

You could try giving these guys a call Elite Grinding services 0151 355 5588, they are local to me, and I know a guy who works there, I mentioned your thread to him and he thinks the finish you're after is easily achievable, worth the phone call.

Andy

 

[julianthegypsy]

You could try giving these guys a call Elite Grinding services 0151 355 5588, they are local to me, and I know a guy who works there, I mentioned your thread to him and he thinks the finish you're after is easily achievable, worth the phone call.

Andy

Thanks Andy, I might well do that. I've been busy as hell making a wood fired range this week and haven't managed to spend any time on it, but I'm still accumulating all the assorted bits and bobs that aren't actually interesting or vital but you can't actually do without. By the time I get going I will have assorted envelopes all over the workshop and no idea where to find them, as normal :-)

 

[Lawnmowerboy]

I can grind anything if needs be. Got several manual surface and cylindrical grinders and a cnc flatbed.

 

[Pete.]

If you've got away with flycutting the surface in the past its probably still a tighter spec to be working to than it needs. If your mill is only a tiny bit out of tram in either x or y axis a flycutter will generate a dished surface and the larger the flycutter the more pronounced the dishing.

I always figured the larger the flycutter the flatter an out-of-tram cut would be.

 

[Lawnmowerboy]

It's the turred that will determine how flat and square your job will end up. Clocking the turret up is an important thing to do.

 

[Shox Dr]

It's the turred that will determine how flat and square your job will end up. Clocking the turret up is an important thing to do.

Sure is, I use a co-axial indicator, very fast

 

[Lawnmowerboy]

If you think about it when your fly cutting or using a carbide face mill if the cutter is Leant forward or back especially on the y axis you are using some of the arc/radius it rotates by and creates a low spot in the middle. A quick way to check is see if you're getting any backcut when skimming a face.

 

[julianthegypsy]

I shall probably use a smallish end mill rather than a face or fly cutter, that way I might have ridges to get rid of but I won't have to worry about bowing if the head is half a degree off. My mill has a rotatable head but it doesn't have any reference marks on it. It's a Centec 2a mill but the head is unidentified, it's not made by centec and that's all I know about it.

 

[Lawnmowerboy]

Needs to be spot on upright either way! I doubt you'll get the finish with an end mill to be honest. Just clock the head up and fly cut or use a carbide face cutter. An end mill on a head that is slightly out will leave sort of steps where it's cutting heavier one side than the other.

 

[brightspark]

if your so worried about accuracy on your mill buy one of these to set it up . i think rdg do themhttp://www.dailymotion.com/video/xet45b_milling-machine-set-up-using-the-pr_tech

 

[Shox Dr]

if your so worried about accuracy on your mill buy one of these to set it up . i think rdg do themhttp://www.dailymotion.com/video/xet45b_milling-machine-set-up-using-the-pr_tech

That thing only has one use, buy a Co-axial Dial indicator, they are around 55quid and can be used for finding the centre etc etc

 

[julianthegypsy]

if your so worried about accuracy on your mill buy one of these to set it up . i think rdg do themhttp://www.dailymotion.com/video/xet45b_milling-machine-set-up-using-the-pr_tech

The link doesn't seem to be working, the video plays music but has a blank screen?

 

[scott0031]

if your so worried about accuracy on your mill buy one of these to set it up . i think rdg do themhttp://www.dailymotion.com/video/xet45b_milling-machine-set-up-using-the-pr_tech

Personally I would not recommend those things to anyone. 1) totally no need to spend money when a standard lever type dti on a arm will do the job better, plus a standard level type dti can be used on everything. 2) They do not clock over a big enough distance to get a head totally square, you should be clocking over the biggest distance possible or at least a good distance which those things can not do. 3) They are more a gimmick for the unwitting rather than a tool that is actually required call it a fashion accessory.




Just my view as a toolmaker.


Kind regards,



Scott

 

[julianthegypsy]

That thing only has one use, buy a Co-axial Dial indicator, they are around 55quid and can be used for finding the centre etc etc

Just bookmarked one. Annoyingly there are two on ebay for just under £60 from allendale, but they have a 10mm shank. I habe a 1/4, 3/8 and 1/2" collets and I know already that I can't get 10mm in my collet, so I have to try and find a 10mm collet on a MT2 with a 3/8 whitworth thread. Oh joy...

 

[Shox Dr]

Really easy to clock a rotary table, takes me less than a minute I'd say