Member postings for Roy M

Here is a blast from the past ! I once worked for a company that had to make batches of cams every few months. This was in the olden days. A cam was made by hand, and clamped with a central bolt on top of the cam blank. This was centralised on a rotary table. A cutter was fitted with a ball race bearing which followed the cam form. The clever bit was that the table cross feed was disabled by unbolting the screw thread bush, thus allowing the table to 'float' freely. The ball race was then pulled onto the cam using a lash up arrangement of strong springs, so that when the table was rotated,the cross slide moved, governed by the cam profile. I can't see any reason why this arrangement could not be adapted for turning profiles. It could be a challenge!

Roy M

My preferred method for a good thread using a split button die is as follows although it requires an extra few mm of material. Leave a couple of thou on the outside dia. Then turn a spigot to about 10 thou above the core dia, (depending on thread size). Adjust the die to cut oversized thread and then run the die along the the bar. The spigot will ensure that the die starts along the bar correctly aligned, and adjusting the die means that you can take a couple of finishing cuts. This results in an accurately sized thread, and a perfect thread with good finish and no tear marks. A similar approach can be used if your thread is less than perfect after screw cutting. Roy K.

Micheal G, there could be logic in your reasoning, but also if there is any initial resistance to cutting (and cutting oil alleviates this to some extent), this may compress the reamer and result in a smaller hole. If you have ever tried to ream aluminium-bronze or really tough stainless, you will know there is a danger of the material gripping the reamer (or drill),and either seizing up, or resulting in an undersized hole. There is a good reason why there is such a wide selection of taps, reamers, drills etc.,in industry. The resourcefulness of the model engineer is to be applauded! Roy M.

Ref; Reaming.  It may be that the coolant mix is not usually used at max strength, or closely monitored,but you have probably noticed that you get a different finish when using cutting oil and it is most likely the same phenomena. I know that the science of cutting fluids is complicated and my observations are only gained from experience and are not at all scientific! I would reiterate that the difference is small, but it is a trick worth knowing. Roy M

Edited By Roy M on 25/04/2015 15:08:52

Info required:- what material are you cutting? What cutting fluid do you have? What type of tap do you have? Is it a blind hole? What type of machine do you have, ( especially how much control do you have?). There will be a difference in speeds between 4 & 12 mm taps, but the machine power may also play a part in your choice of speed. Roy M.

Here is a tip that some of you out there may not know. Given the drilled hole sizes are the same, and all the machine settings are the same, a reamer will cut bigger if you use cutting oil (rocol etc.) as opposed to water based emulsion type coolants. This is a small amount but is sometimes useful. (I'm still toolmaking!) Roy M

I am that old, that I have forgotten how clever I was!

Depending on the grade of stainless,(some is free-cutting),a general rule of thumb would be lower the surface speed, and/or increase the feed rate. You also need to keep the job cool, and the tool keen. Treat the material as tough, and grind your tool accordingly,( take note of approach angle and top rake). Or choose correct insert tip. If the material is really really tough, and you are using tool steel,you may have to keep re grinding your tool. Remember that you have to, somehow, remove the offending hard part of the piece before starting to turn with your re-ground tool.

Roy M

I have a complete manual for the use of a dividing head,including information about change gears(for really abstract divisions),plus info on set ups for helical milling. If there is any interest, I will try and copy it to share.

Roy M.

Do not despair, unless you are going to be seriously out of pocket,you may consider making a series of bespoke inserts to covert the chuck into a sidelock holder, fly-cutter, boring bar, etc., etc. It looks a sturdy bit of kit.

Roy M.

Edited By Roy M on 07/04/2015 21:11:05

Any body out there familiar with a "drill bush bar"? These work on a similar principle to the optical centre punch,(but are easily made). A suitable bar 6" x1" x1/2" has a 1/2" (12mm) hole reamed at one end. This is positioned over the scribed lines using the cylinder lens, but instead of punching and then picking up a centre punch mark with a drill, the bar is clamped in position and the hole drilled using a drill bush or home made bush. Large holes are made using a series of drills or reamers and bushes. By using two of these bars with close fitting pins, exact hole centres can be achieved with the use of inside mic or callipers. These bars are commercially available in the U.S.A. And are used in the aircraft industry for jig making etc., I could post a photo if there is any interest.

Roy  M

Edited By Roy M on 03/12/2014 23:22:14

I designed a knurling tool for use on cnc lathe, the concept is simple and well tried. The company I work for had the need for 3 different diameters of knurled nut/ bolts. I made three bespoke tools and the set ups were simple and the results consistent , with no strain on the machine. If you are interested I can post some details and pictures.

Roy M

Try looking at the 'Ambersil' web-site. Ambersil +40, (I think), is exactly what you are looking for. Cromwell Tools could supply. Roy M.

Off hand ground carbide drill for drilling 62 Rc and hard stainless.(1st and 2nd stages of grinding shown)

Showing hole drilled today, and a simple part off blade holder made some time ago.

Run at 2500 -3000 rpm and push hard, be brave, you can trust me I'm an engineer!

Edited By Roy M on 18/09/2014 23:52:02

I have photos and short video clip showing how to make a drill and drill thro' tool steel.

just trying to figure out how to post them. (guidance appreciated)

Roy M

I have a DRO unit complete that I no longer require

Roy M

I have successfully drilled through tool steel and taps with an easy to make drill made from

either a broken carbide tool or round carbide toolbit . If there is any interest , I will post a sketch.

Roy.

Take care when breathing in mineral oil mists, you can get serious lung problems from a few hours exposure.

I have spent a lifetime on and around milling machines and never found the need for coolant mist.

I have been involved at my current place of work installing and monitoring a 'minimum oil lubrication' system which works very well on aluminium. However, the coolant is quite specialist and vegetable oil based, maybe this is an avenue you could explore.

Hope this is of some interest, Roy.

Just as a point of interest with regard to 'bigger is always better'. I modified a rotary table many years ago,(when gob-stoppers were really large and not considered a health hazard), pre- cnc days. I was making press-tools for clutch housings but the diameter of the table was too small. By fitting a large diameter 25mm plate onto the table, and tapping a series of M10 holes in the plate, I was able to accommodate larger jobs. The second modification involved replacing the handle and vernier scale and replacing it with a hole plate and dividers similar to that which you will find on a dividing head. It was pretty accurate. Roy