Gallery, Projects and General > Project Logs

Putting right my tailstock DRO.

(1/7) > >>

bogstandard:
This is another of my round tuit backlog jobs that has been on the cards for a couple of months.

This all started about a year ago, when I installed my then new lathe, and decided to fit a couple of extra DRO's, one on the compound and another on the tailstock, to compliment the two it came with. Once you get used to the accuracy of using something like this, you soon realise that drilling to 'accurate depth' under normal situations is not very accurate at all. More like a disaster waiting to happen.

On the tailstock, I had machined a rail carrier for the glass slide out of ali, and had it running on four ball races. Unfortunately over the last year, swarf had found it's way into the top channel, and the rollers had then forced and embebbed it into the aluminium. When you operated the tailstock by the handle, you didn't feel anything, but once the rail was disconnected from the tailstock ram and slid along by hand, it felt rough as old boots. This will only get worse, so I have decided to relocate the assembly to on top of the tailstock and make the rail out of a more durable material. Then I should be able to protect it a little better than I had done before.

This is a picture taken before I set to work.




Ten minutes had the tailstock almost back to original.




This is the old ali rail, and a lump of Ralph's 'garage special' to make the new one out of.




As usual with this sort of unamed material, it isn't very happy at being reshaped. So I had to persuade it a bit with a tungsten tipped shifter. Nothing too critical at this time, just cut down to split the line.




I had to stop at this point, but this job has now to be finished before anything else. So if time and luck is on my side, I can get back onto it soon.


Bogs

bogstandard:
A little bit more of boring metal munching.

After hacking all the rough outer off in the last episode, the first thing I did was mount it up onto the surface grinder and gave it a lick all over.




Isn't it marvelous what is inside such a crappy looking lump of iron.
It gives you a feeling that you want to do more to it now, rather than struggling with the old outer casing.




Even though it looks like a nice piece of material, it is still the same old lump of tough stuff, and I have got to cut some very accurate 4mm slots in it.
It all starts by getting the cutter into the right position and taking a shallow cut (0.75mm) down the rail. This is a 3.5mm cutter, and the stripe down the rail is high pressure cutting oil (tapping fluid) to help with the cutting.




This is getting ready for the return run. The depth has been set to 1.4mm, oil down the groove and the return run was carried out. Once that was done, the operation was repeated on the other side.




So now that I had my two channels, a 4mm cutter was fitted and set to a total depth of 1.5mm. This will skim the two side faces and the bottom of the groove. Same again, oil was used and a fast cutter speed with very slow feed.
In fact each of the slotting cuts took 15 minutes each. Thank goodness I have power feed, an hour and a half of slow cutting would have almost killed me if I had to do it manually.
Also, by taking it easy, both cutters lived to cut another day.




The four end corners were nibbled off with one of my little hogger cutters.




All that long steady machining had really paid off. The bearings were a perfect fit in the slots, with the merest hint of side play.




A little relief was made in the side to allow for a modified fitting regime. By doing this, I can squeeze the complete read head width up by as much as 15mm compared to the previous fitting. Also a couple of mounting holes were drilled and tapped to 4mm.

This picture actually proves that you can make a silk purse out of a pigs ear.

The original rail is in the middle, the new silk purse at the bottom and what bolts onto it at the top.




That is the boring stuff finished.
 
Next is getting the tailstock onto the mill and drilling accurate holes all over the top of it.


Bogs

Darren:
John if I understood correctly, with little cutters like 3.5mm you up the spindle speed and slow the table right down?

Interesting, thanks  :thumbup:

Nice looking rail, like the bearings, now puzzled how it works but I'm sure we are about to find out .....  :ddb:

bogstandard:
Darren,

Very similar to when using a drill, the smaller the size, the faster it should go. The centrifugal force helps to keep the cutter more rigid and so prevent breakage. The slow feed is to allow the small cutter to clear away the swarf generated, also to allow a finer finish and again it helps to prevent breakage.


John

Stilldrillin:
Nicely done John!  :thumbup:

David D

Navigation

[0] Message Index

[#] Next page