Machining Setup's with Few Comments

Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.

Moderators: GlennW, Harold_V

Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Finish grinding the 54.5 degree angle on the part in the SG. I don't know how the required level of fit could be achieved without finish grinding.

I used my "upgraded" small Myford vise for this operation. When not in use, it is carefully stored. It is not to a Hermann Schmidt toolmakers vise standard but it is quite accurate.

This was where I ran into a problem with the grinding operation on the second go around. I tapped the part lightly to bed it on the parallel and apparently this caused it to tilt very slightly which I did not notice until the final checking. This time I used only light finger pressure to bed the part and to "feel" that it was bedded. And then only with very light tightening of the vise jaws just sufficient to resist the grinding forces. Take very light cuts with a freshly dressed wheel.

The angle, this time, was checked with my very best vernier protractor as this is one of my best precision tools in like new condition. Do everything to keep it this way.

Even so, the finish grind was a very tense operation as I kept hitting just slightly above or below the angle mark as we are talking only a tenth or two. In addition, the parallel sides of the diamond have to be the same precision dead accurate slide fit in the cutting blade slot to a tenth or two.

One needs to be in the right frame of mind with no distractions.

to be continued.
Attachments
580 Finish Grinding a Diamond End Side in the Upgraded Small Myford Vise.jpg
581 Checking the Finish Ground Angle with My Best Vernier Protractor.jpg
582 The Finished Part with the Centre Pin Inserted.jpg
Last edited by Carrdo on Tue Aug 30, 2022 10:30 am, edited 1 time in total.
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Some photos of what happens when you do it right and when you do it wrong. As Richard would say of the last two pictures "close, but no cigar".
Attachments
585 The Aligned and Square Cutting Blades.jpg
586 The Aligned and Square Cutting Blades.jpg
587 What Happens When You Get The Angle Wrong.jpg
588 What Happens When You Get the Angle Wrong .jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Moving on to the final machining operation and the final assembly.

This involved grinding the part down to its final thickness so the parts could all be reassembled. As I did not know what thickness to grind to, it was a slow trial and repeat process. One little problem was the SG leaves micro burrs and these have to be completely stoned away to be able to have the part slide in the blade slots. Quite aggravating, as one can hardly hold the part it is so tiny and I do not have any rotary de-burring equipment to take care of this.

First came the assembly of the reamer blades to the internal holder as seen in photo 590 and then the internal holder assembly is set into the reamer body itself and aligned with the rectangular pin as seen on photo 593. This involved more grinding down of the diamond part thickness until the reamer blades were a hard slide fit in the 180 degree slots machined into the reamer body.

Once completely assembled, there is a micrometer collar seen in the last photo which allows one to incrementally increase or decrease the cutting blade stick out.
Attachments
589 Surface Grinding the Internal Diamond Part to Allow Final Assembly.jpg
590 Final Assembly of the Reamer Blades to the Internal Holder Aligning Piece.jpg
591 The Reamer Cutting Head Assembly Set into the Reamer Body.jpg
593 The Floating Reamer Re-assembly.jpg
594 The Re-assembled Floating Reamer.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

More end mill gashing.

This time I have come up with a method for gashing (or centre relieving) the smallest two and four flute HSS end mills I care to do and that is from 1/8" dia to 3/8" dia. Previously, on this thread, I have described how I do end mill gashing on larger HSS end mills greater than 3/8" diameter.

I think the attached photos show the setup used (based on the equipment which I have). Again, with this setup, everything has to be totally secure and rigid especially when down feeding the shaper toolbox so it is done with the added two tool head gib thumb levers set snug as there is backlash in the tool head screw.

The small Dremel cutoff wheel is set over the centre of the end mill with good lighting and an eye loupe. The end mill is turned slightly so the cutoff wheel slot which results does not touch the cutting edge of a tooth.

The last photo shows the transverse slot made in the end of the end mill after gashing.

After gashing, the remaining facets on the end of the end mill will be ground dead sharp on the SG using the Washburn tooth aligning fixture and the commercial end mill sharpening fixture which I have all of which I have described previously in this thread.
Attachments
595 A Not Elegant Plexiglass Shield.jpg
600 Overall View of the Gashing Setup .jpg
596 The Overall Setup for Gashing a Small Diameter End Mill.jpg
598 Gashing a Small Diameter End Mill.jpg
599 Gashing a Small Diameter End Mill.jpg
601 After Gashing.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Dealing with the bane of my existence - blue tempered spring steel. This is truly miserable material to work with. Earlier in this thread I showed what can be done with it in a home shop environment.

Some further experiences.

Blue tempered spring steel can be purchased either as a long coil strip or as (normally) 6" wide sheet which then has to be sheared into the length and width's one requires - see the first photo. If purchased in coil lengths, it will come with rolled edges which leaves the coil on size width wise and with a smooth burr free edge. If the sheet material has to be sheared, the width accuracy will depend upon the setup care of the shear operator (I never have found it to be very accurate) and the sheared edge will be left ragged and not burr free. Also, in commercial shearing, with the large commercial shears which they use, the shear has to have about a 1.5" wide residual material to hold onto when shearing so out of 6" wide material only about 4.5" of it can be sheared into thin strips if that is what is needed.

Further, in Canada, unfortunately, I have not found any local supplier of coil blue tempered spring steel, my supplies of it all come from the USA, it is difficult even there to find it in specific widths and thickness combinations, and when one is fortunate enough to do so, you will have to purchase what is available (usually much more than one will ever use), it is both expensive and due to its weight, the shipping cost is even more so.

Blue tempered spring steel likes to fracture! See the second photo. This material is so hard and brittle even when tempered, that any slight mis-punching or handling will result in what is seen. Hence the need for precision punching dies and methods when working with this material.

The third photo shows a successful punching operation but the setup has been modified about three times to get to this point. To be noted, a normal bench arbor press is not the best equipment to use in this situation - others have used 4-8 ton commercial punch presses which are much better as this material should be sheared this way. But not having such equipment...

I do have a surface grinder and the setup used needs to have one or access to one. This is because the punch itself is made from hardened tool steel which means the punch shape can only be ground. As well, all of the inner die blocks forming the rectangle opening are made from HSS and need to be ground truly square and on size and length. In addition, experience has shown that the total gap between the punch and die, in order to have a clean sheared edge can be no more than 0.0015"-0.002" total clearance anywhere. This means that the punch has to extremely closely aligned to the die opening at all times.

For the punch itself, the end rectangular shape has to be of the shallow inverted "V" form as seen in the photo and it is best if all sides of the punch taper back about 0.5 degree from the cutting edge. The punch itself is a close shake less push fit in its holder which has a flat machined on it to locate and lock it into the ram of the arbor press. This particular arbor press was purchased used and came with a precision central hole machined into the end of the ram and a locking set screw (a very useful feature) into which the punch assembly again is a shake less push fit. Once the punch assembly is set into the ram, the punch and the rectangular cutting edge of the punch has to be aligned dead square to the front face of the ram.

The inner pieces of the die are all made from HSS to form the inner rectangle and are ground all square with a sharp edge. The entire die is bolted through to the base of the arbor press but the mounting bolt holes are made slightly oversize so the die can be shifted and turned slightly so that it is truly square with the front face of the arbor press ram which it needs to be. In the latest version, the inner HSS rectangle pieces are all ground 0.005" lower than the top of the (all ground top surface) outer hot rolled machined frame and there is a central cross aligning slot, machined the width of the spring steel strip (3/8" wide), from the front to the back of the frame into which the spring steel blank half sits into as the spring steel thickness is 0.010". It is hard to see in the photo but it is there.

Once everything is aligned, the die (without the top cover or the spring steel strip installed) is manipulated so the punch just slides down through the rectangular opening in the die. The clearance is that close one will feel a slight resistance. Then fully secure the die mounting cap bolts which bolt the die to the base of the arbor press.

One can now partially install the spring steel blank and the die top cover as shown in the third photo and lightly clamp the top cover to the bottom part of the die. The top cover has a central hole with inserted bronze bushing that is exactly coincident with the rectangular opening in the bottom part of the die. This is achieved by making the top cover bolt holes oversized so the top cover can be moved around slightly to achieve the above. The internal bore of the top cover bushing is again a shake less slide fit in the round lower portion of the punch tool.

All of the above is necessary to guide the punch tool exactly over the rectangular opening in the lower part of the die as the ram of the arbor press is not a precision fit in the head of the ram and as a result the arbor press ram can move from side to side quite a bit. It is imperative that the punch tool not hit any of the HSS edges in the die rectangular opening or they will chip the cutting edges of the punch/die rendering them useless. With the top cover bushing set in place and lightly tightened check again that the punch is dead aligned with the rectangular opening in the bottom of the die. The end of the leaf spring blue tempered steel blank can the be gently tapped in position over the rectangular opening in the bottom portion of the die. How this position of the leaf spring is determined lengthwise I have shown elsewhere in this thread.

Other points. The punch tool has to strike the leaf spring blank ideally when the ram lever is in the horizontal position for a maximum punch. Undersize spacer pieces can be employed in the central hole in the bottom of the arbor press ram to achieve this. One should hit the ram lever with a hard sharp blow to simulate a punch press.

There are shims shown in the last photo. These can be used to adjust the size of the rectangular opening slightly if needed or to adjust the punch die clearance. Of course, everything has to be tested again for alignment after any of these adjustments are made.
Attachments
604 Strip and Coil Blue Tempered Spring Steel.jpg
604 Strip and Coil Blue Tempered Spring Steel.jpg (1.6 MiB) Viewed 937 times
605 Spring Steel Likes to Fracture.jpg
605 Spring Steel Likes to Fracture.jpg (662.87 KiB) Viewed 937 times
606 The Overall Setup for Punching Blue Tempered Spring Steel in a Non Precision Bench Arbor Press.jpg
606 The Overall Setup for Punching Blue Tempered Spring Steel in a Non Precision Bench Arbor Press.jpg (853.25 KiB) Viewed 937 times
607 The Hardened Spring Steel Punch.jpg
607 The Hardened Spring Steel Punch.jpg (1.04 MiB) Viewed 937 times
608 Details of the Punching Die.jpg
608 Details of the Punching Die.jpg (799.43 KiB) Viewed 937 times
609 Details of the Punching Die with Shim Pieces.jpg
609 Details of the Punching Die with Shim Pieces.jpg (861.22 KiB) Viewed 937 times
User avatar
liveaboard
Posts: 1971
Joined: Sun Dec 08, 2013 1:40 pm
Location: southern Portugal
Contact:

Re: Machining Setup's with Few Comments

Post by liveaboard »

That's a whole lot of work to make the part you want.
Thanks for sharing.
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Hi liveaboard,

Yes but when there are few, if any options. Phosphor bronze has been used as an alternative material and is easier to work with but is "unobtainium" here.

Also, I didn't mention that 0.012" thick blue tempered spring steel is just about the thickest material one can use with a simple bench mounted arbor press as shown.
Post Reply