Dovetail messed up

[Jonathan Coates]

I couldn't get the measurement over the pins to go down. Cut after cut there was always a little still to come off. Now I know why, I messed it up due to incompetence and old eyes.

 

[timo_gross]

I couldn't get the measurement over the pins to go down. Cut after cut there was always a little still to come off. Now I know why, I messed it up due to incompetence and old eyes.

Haha, poor you! Did you already cut the other part?
30% of my mistakes are incompetence, 80% impatience, 10% poor or wrong equipment and at least 20% someone elses fault. The remaining 70% is casued by my poor math performance and insufficient thinking ahead.
In this case it is obviously a faulty dove tail cutter! (so someone elses fault) (it always is)
I would probably scrap the part, or cut the entire top off and bolt a new piece on top that you can machine separately or bolted on.

 

[Jasonb]

The rods were a bit too large to start with even if the cut had been along the full length of the D/T

 

[Jonathan Coates]

Well disaster was very narrowly avoided. After I put a bigger cutter in and trimmed off the offending parts, the dovetail was 0.5mm too small. But it works anyway. If I can devise a way to attach a steel wear strip I'll ruin the dovetail even more and fix it with a steel shim so that the locking screw doesn't dig in so much. There's enough travel on the slide lock that it grabs it firmly for now, so I can have a test.
Timo, the other part was there all along. This part is a kind of prototype thing for grinding lathe tools on the Deckel as I'm fairly sure I'm going to have to cut a twin start Acme thread in the near future and insert tips are only available in expensive and very expensive flavours.


This aluminium one is a test and I don't expect that it'll last years (though I expect that it'll see very little use, so maybe?) but it seems to allow angles to be ground accurately which will do nicely. I need to work out how nose radii are going to be set up.
I saw something similar on an e-bay listing but the required part doesn't seem to be sold on it's own so I had to make one.

 

[kf2qd]

Your rod that you were using for measurements was to big in diameter. you were not measuring the dovetail, you were measuring the corner. And depending on chamfer or how sharp the corner is it will give you different results.

 

[clockworkcheval]

If you want Aluminium special tooling to resist wear you can get it hard-anodized. I love chunks of precise rectangular Aluminium blocks to make all sorts of special tooling. Easy to work and often seldom used. A simple holder for a grinder will stay as is. For use on my antique toolgrinder I made a very precise Sine Block - plus minus 0,01 mm overall, which will suffer from any little wear. At a local Special Shop I got it hard-anodized. They will etch off a layer of 0,02 mm and add the same amount by hard-anodizing. I checked and indeed all dimensions were still within tolerance. This shop charges private persons a flat fee of € 50,- (= about $ 50,-) for work that can be done in one charge. The brass segments on the Sine Block allow a quick setting with the lower precision of 1/10 of a degree.

 

[Circlip]

Mechanical Horse has got it right Jonathan. Don't waste money using Steel for infrequently used tooling. Check back in the files of this forum for the D-3 adaptor made by Deere guy. We saved him scrapping the Alumin(i)um unit he made by Hard anodising it.

Regards Ian.

 

[Jasonb]

Isn't steel cheaper than aluminium even without the cost of the hard anodising on top?

 

[Circlip]

Isn't steel cheaper than aluminium even without the cost of the hard anodising on top?

Possibly but Alloy is kinder to milling cutters.

Regards Ian.

 

[clockworkcheval]

Isn't steel cheaper than aluminium even without the cost of the hard anodising on top?

Well....... Steel in the raw may be half the price of Alumium in the raw, but by the time you have machined during long hours your chunk of steel back to useful and precise dimensions and by the time you have ground and reground your cutting tools the initial joy of lower material cost is long forgotten.

 

[Jasonb]

You can also buy several new cutters for the 50 euro anodizing fee plus getting the part to them and having it sent back.

 

[TSutrina]

Have used hard coat aluminum for aerospace where steel is too heavy. Hard coat surface will not be as flat as the machined aluminum and gets worse with thickness. Rule of thumb is the aluminum is changed by a chemical reaction to make the ceramic, hard coat. and it goes about as deep into the surface as above it, the volume of the ceramic compared to one of its component Aluminum must by double. It is brittle so when we ground it the ceramic cracked like what you see with old paint on antiques. Retained hardness but failed a high pot test for insulation value.

 

[clockworkcheval]

My country The Netherlands is small and I live in the South in a High Tech area. Therefore I can easily visit suppliers and discuss what must be done - part of the fun! The anodizing firm I mentioned subcontracts among others to ASML, the leading builder of chip machines. They comply with the ASML process control requirements. The obvious benefit for me is very high quality work - no variety in dimensions or chipping and cracking of the hard anodized layer with this outfit! For material I go to a supplier that sells leftover lots of material from the wide variety of machine shops in the area. That means that I get my material, be it aluminium, brass or steel in near-net-shape at a bit above scrap price, in small quantities.