Machine a rectangle from a bar

I have a piece of round aluminium turned just under 2 inches diam & 2.5 inches long

I am making a 4 facet drill sharpener ( Gadget builder) & want to get this to a rectanglular section 1.2 inches wide * as much as practical. Dims not critical & 2 corners when it is laid flat could actually be slightly rounded. However, all side must be parallel & square to each other, as I intend to bore the piece for a 1 inch parallel Er 32 collet holder (on order from RDG, comp with collet set & MT collet holder, as new year prezzie to self) with the hole at a pre determined height which has to be true in all respects for drill sharpening.

It will not fit in that lathe as 47mm diam will not fit across the teeth ( teeth not deep enough) so I have to mill the faces held in the vice.

So far I have milled one face 1.2 inches wide & it seems to have parallel sides so my mill is tramming Ok. I used a 50mm shell mill obtained from bangood about which there are several you tube vids & mention on this forum.( I just wish I could recall what better teeth to buy)- Link please!!!!

I now have to cut 3 more faces & my question is this:-

Do I now treat the first face, as the face & put it to the back of the vice & cut a face edge at 90 degrees (as a carpenter would) or do I turn it 180 degrees & cut the opposite face then cut the 2 opposing faces last?

Is there a preferred order to do this?

I would like to know because once I have done this I will go on to make a 4 sided collet block & that will need a high degree of accuracy

After that I have just purloined a piece of hexagonal brass 50mm across * 75mm long, which might make temporary 6 sided block & the machining of that should just be a process of skimming (& boring) provided I can get it right. Good machining practice at least

If you clamp it with the just-machined face in the bottom of the vice, the clamping forces will be in the plane of the face so nothing to force the face down to help ensure the next face is parallel to the first. Best therefore to clamp with the machined face against the back of the vice (if you're confident it is vertical) and machine the next face at right angles.

This is based on a standard milling vice, the horizontal bar should be shorter than the face it is on to avoid marring machined corners. If you clamp the machined face to the fixed face of the vice ( as John suggested) you can then put a horizontal round bar or even a ball bearing between the moving jaw and the workpiece (not in a vee if the jaws have them, it needs to be able to roll) to ensure it is as flat as possible against the fixed jaw. this will get two of the faces at 90° to each other. Check this is giving a good result before continuing. Then repeat, keeping the first face against the fixed jaw and use a square or 123 block on the base of the vice against the second machined face. This should give 3 faces that are perpendicular to each other. Once you have done that you can use either the base of the vice or a parallel in the vice to machine two more faces. The last face do not use the round bar or ball bearing on the already machined faces as it will mark them but at this stage you should be able to hold the part supported on two parallels or the base of the vice and tap it down with a machinists hammer/mallet/suitable heavy lump before machining. Providing your mill and vice is set up well this should give a good rectangular block to work with.

Martin C

I agree with both John and Martin on the method.

Also you are lucky that you don't need the measurements to be precise. So you can cut the first and second face, then check for square with the best square you have available, then cut the second face again ( just a skim) if there is any error, using small pieces of shim or paper etc between the vice jaw and the first face to corrrect the squareness of the second and so on for each subsequent face. This is standard practice when accurate work has to be done with kit which may not be the very best. Any errors may be due to the machine vice itself or not thumping the workpiece down hard as you tighten the vice.

Rod

Thankyou to you all for those explanations

Much appreciated

Sam Longley

Edited By Sam Longley 1 on 03/01/2022 11:45:09

I'm no expert, having received no formal training, but here's a couple of quite informative videos

And a shorter one, where the idea id to prepare a block oversized for subsequent grinding, so a perfect finish on each edge isn't quite so important.



The trouble was at my end, that the last ones I did were on the shaper, as my milling vice isn't big enough for the blocks in hand.

Bill

I bought some Korloy ones for mine intended for aluminium and the finish was very good as were the YG-1 Inserts for steel and a lot better than two lots of BG ones. At the time ARC did not do these inserts but now that they do I would go with those as they are about half the price of the Korloy and I can't tell the difference in finish. Both want a dash of paraffin when used on aluminium

As for your job I would keep turning it 90deg with the just machined surface going against the fixed jaw of the vice.

Just done it as suggested in posts 1 & 2 & have cut 3 faces. I realised that I do not need the 4Th face as this sits on top & does not reference anything. Being round it will sit in the hand better when removed for adjusting or checking the drill tip.I do not have it perfectly parallel on the 2 sides, but close enough for it all to work OK.

A bit more practice & I will have it nailed I am sure. It did not take long & I have 3 metres of the bar stock to play with before I go to steel.

It is now small enough to fit in the lathe chuck jaws & I am wondering if that would true the 2 sides up better ( more parallel)  with just a smidgeon taken off one of the opposing faces.

Edited By Sam Longley 1 on 03/01/2022 13:49:24

I got good results for this operation by using the 4 jaw in the lathe

Looking forward to hearing about your build, Sam. I'm interested in making Gadgetbuilder's drill sharpener as well.

I have almost finished. I hate trying to work to a set of instructions, rather than a proper sheet of drawings so made a couple of silly errors. However, today i reached a stage where I was able to sharpen my first drill bit. An old 8mm one. I have to say that I was somewhat impressed with the result.

However, I would recommend not doing what I did & buying ER 32 collets in lieu of smaller size recommended on the design. The set up is not designed around it & the nut etc gets in the way. I bought a set of ER 32 collets with a morse taper chuck along with a 25mm * 150mm parallel shaft chuck ( for this project) because I wanted a set for my mill & lathe as well.

I bought the grinding disc from RDG along with the collets & fitted it to a small grinder that I have had for years. I had to make some adaptions as the nut in the centre of the grinder fouls the trunion pivot arms. I also feel that the distance between the trunion pivots is small. One pivot comes in the centre of the grinder disc & I would prefer it to be much wider such that the complete disc sat between the 2 pivot supports .

The other problem is that it is a faff changing collets for each drill bit size. Systems whereby the drill sits in a channel would possibly be much quicker to use. However, it produces such a good accurate grind on the end of the bit it may be possible to grind once then touch up a couple of times on my belt sander.

This was an interesting project & i am now proposing to start on a more detailed sharpener. I have built a Tinker but find it lacking due to the fact I did not have the full set of drawings. There is a model with a dipping head shown on this forum & ( Forgotten where the link is!). I will try that for fun. It all improves my skills before I finally venture to a quorn

It certainly feels nice to drill a hole in steel & get 2 even spirals of swarf rise from the hole.

Edited By Sam Longley 1 on 20/01/2022 17:13:03

Thanks for the update, Sam. If only I could get one made as quickly as you.

The collets maintain the drill centre in a constant location. Using a simple V may mean adjustment to bring the centre back to the correct position is required. It all depends on exactly how the kit is designed to work but it may be a case that the speed of a simple V is offset by needing adjustments for each drill size to get the best results.

Martin C

If the collets are a faff to change you could go the whole hog and fit a self centreing 6 jaw chuck - that will speed things up no end. Or copy the clarkson drill grinding attachment ? Noel.

The benefit of this tool is that it is nice & compact, taking up little room. nice & light & easy to slide under the bench. The collet chuck is multi functional.  I suspect that something using a six jaw chuck might be in a different ball game

Edited By Sam Longley 1 on 21/01/2022 11:51:07