Gallery, Projects and General > Gallery
Tool post grinder build Clough42 inspired
PekkaNF:
--- Quote from: Sea.dog on October 20, 2019, 04:58:41 AM ---Nice work, Pekka, but you seem to a problem with the PCD function. The rear two holes definitely look off centre from the scribed circle.
--- End quote ---
There were few contributing factors on this discrepancy:
1) Scribing and DRO were using a little offset zeros.....I realized that only when I was aligning it into milli vise.
* Scribing was centered on welded plate - that in turn was only eyeballed to slit collar assembly, hence a little uncertainty. I was concentrating only to get the plate face plane square to collar OD.
* DRO zero was centered to collar ID (normal centering in X/Y). and PCD had local (INC) zeroed to this computational centre - not into scribed centre. I felt I trusted more to math than my eyes.
2) Sloppy scribing.....using only ruler and while PCD scribe was fairly round 45 degree scribe lines did not come out exact (hot rolled edge, welds, not using surface plate, sines etc.)
3) Picture was taken in oblique angle, even holes don't look round but eye is master in seeing discrepancies. I am really sloppy with photocraphy and while I try to explain my logic (instead of very detailed punch by punch instructions) I often fail to verbalize my logic. I try to be more inspirational than instructional, because this has very little orginality and only few things are critical (like bearing aragenment and bearing fits).
I appreciate your comments. Thank you.
* Typos
Sea.dog:
Fine. I wasn't being picky, just wondering why, that's all. :thumbup:
PekkaNF:
No problem. Give a comment if you see something odd or going pear shape.
I started drawing the mount to lathe M16 tool post stud. Plenty of room there. I even found good chunks of mysterysteel. BUT problem is that I really don't have good way of making about 60 mm long 38 mm diameter hole.
Alternative method would be to make holes to two 12 mm thick hot rolled steel plate. This is bit easier in hole making, but to make them true and in one line after mounting would need another method. Also 12 mm thick plate does not leave huge amount of material for tighteneing apparatus.
I have 36 mm hole saw but that is pretty poor in long holes. Would need holes on circumference or slits, or something to let swarf to fall.
I have ordered boring head (old is pretty crappy) but it hasn't arrived yet.
Line booring in lathe would be completely unchared territory for me, but probably I need to go there.
Both methods are pretty labor intesive if I need to start from 25 mm hole.
Multiple choices, but none is obiviously superior.
PekkaNF:
Had a minor hickup. I had about 60x60 mm section of mystery steel. Cut cube out of it with band saw and it turned out to be very tough material. It was really hard to mill and I started thinkking that carving it o swiss chese might be hardder than necessary.
Then I found about 100 mm OD, lenght 75 mm offcut of spherical cast iron. Sawed it to bit over 50x60x70 mm block and started squaring it close to final dimenssions with the same milling cutter. Could get it close, but it refused to square up better than 0,1 mm and surface finish looked good, but was out of level. Even when spindle tram was checked straight and vise was square to 0,01 mm/100mm in both axis.
Put the block into TCG and immediatelly saw the problem. BAP face mill is way too brutal for this 300 kg mill-drill spindle.
Changed another face mill of 45 degree anfle and different insert and got closer with it. Then I choose two sides that were closest to straight line and chuck it back to bagnetic chuck and ground it parallel and clean. Way oversize but size is not issue, parallelism is and squares is high on list. urned out beter than 0,01 mm parallel (as grinding machine will do) but not quite perfectly square, mabe 0,03 mm / side. This level of paralleism and squares was not needed, but when I want to make my own tools it is nice to know that it can be done.
PekkaNF:
That sorted out was time to make hole for the spindle. Plan was to reserve enough space in depth to allow 38 mm spindle and 16 mm toolpost screw to fit AND flexure to tighten whole thing up. Therefore attitide of the block is 50 mm height and 60 mm width (to drill/bore).
I didn't have a 38 mm rotabroach and the ones that allow 60 mm depth are not that cheap. I went huntig for core saws and afer testing three I concluded that nominally 37 mm hole saw would do the trick if used on both sides!
Centered the block with edge finder/DRO and checked that it looked ok.
Hole saws pretty much suck on deep cuts, made 10 mm groove to give some space for swarf to fall off.
Mounted the vise stop to allow making hole from the both ends. Double checked center position and sighted how it would fit. I was very concentrated to make the hole meet in the middle. everything had to be straight and repeatable.
Noticed that I used the last mm of depth capacity of the hole saw, that got me a little woried but the hole came out fine.
Pekka
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version