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Thread: Fixed Column Riser Block Build
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20th Dec 2019, 04:54 PM #1Member
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Fixed Column Riser Block Build
Hi people
I'm building a riser block for my mill and after some thoughts an opinions
It is made up of 6 pieces of 12 mm thick plate (it's for a square column Hercus Mill)
The 4 sides have been milled to within 0.01 mm of each other (that was a mission)
The next stage will be joining the top and bottom and facing them off parallel
I'm considering either bolting everything together or welding it
Welding will obviously warp everything, but I think would be more rigid than bolting
I've also recently acquired a surface grinder (not running yet), so should I just weld it and surface grind it?
Capture.JPG
The dovetail on the front will be cast iron, and will be bolted and keyed on
And scraped into alignment
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20th Dec 2019, 09:59 PM #2Most Valued Member
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Provided that you watch your heat input and your welding sequence you should be OK.
I'd clamp the pieces in place onto a FLAT surface, making sure that everything is square, spray cooking oil or similar to prevent the weld spatter sticking, then weld it.
Without knowing if you want the weld inside or out, I can't really give a sequence as such, as the pull will be different whether inside or out.
HTH,
KrynTo grow old is mandatory, growing up is optional.
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20th Dec 2019, 10:31 PM #3
Hi Guys,
I agree with Kryn ! Weld it then true the faces. Make sure that you clamp it firmly to reduce any distortion. A few internal tacks might not go amiss.Best Regards:
Baron J.
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21st Dec 2019, 12:19 PM #4Senior Member
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Bolt it with good quality bolts correctly torqued. Add epoxy to the join if you want.
Welding will induce unnecessary stress in the part.
No point having got to 0.01mm to then weld. You could have got to closest 1mm, welded and then machined.
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21st Dec 2019, 02:28 PM #5.
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Just one Bob's worth.
The base of a two tee slot tabled No.O mill is approximately 240mm wide x 255mm deep. You could make your riser from mitred and welded PFC with the face or web of the channel facing outwards to facilitate the mounting of the dovetail extension. Flycutting the surfaces would probably suffice. I don't imagine Hercus would have gone to any more effort mounting the column to the base casting.
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21st Dec 2019, 07:06 PM #6Member
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21st Dec 2019, 10:08 PM #7Senior Member
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Just wondering how high you were considering making the riser block. Also with needing a longer Z axis screw were you considering extending the existing one or machining a new one. Another thought that crossed my mind is,, I am wondering if the existing z screw is a shortened version of the small hercus lathe lead screw. Perhaps a hercus guru could chime in on this thought.
I too have a hercus O mill and agree that the Z axis movement is way too small for some of my jobs. I have often thought about a riser of some sort.
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22nd Dec 2019, 06:54 PM #8Member
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I checked by removing the vertical head of mine and raising the table right up, the table can reach a fair bit higher than the centre of the spindle from memory (I did this about 6 months ago)
I worked out that there should be at least 100 mm of travel remaining in the screw
If not, I had a look at the female thread at the base and I'm pretty sure there is clearance to space this guy up somewhat
All up I'm adding 120mm of height, which doesn't seem like a lot but should solve a lot of my problems (indicators, drilling, swapping tools etc)
My vertical leadscrew is much chunkier than my lathe leadscrew (I have a 9" Hercus), also the pitch is different at 2mm where I think the lathe is 8tpi
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22nd Dec 2019, 08:40 PM #9.
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TG,
I just had a look at my O with the table wound down to the bottom of its travel. There is only about 8mm of clearance above the nut on top of the riser. If you jack the main casting up by 120mm with the aim of increasing the Z by the same amount, the nut and riser would need to remain as is because you would still be lowering the table to its original position above the base casting. Increasing the riser's height will prevent the table from being lowered to its original position. A new screw or a screw extension may be the answer.
BT
PS. My comments may be irrelevant. My O is a 2 slotter, yours is a 3.Last edited by Anorak Bob; 22nd Dec 2019 at 08:46 PM. Reason: Just looked at TG's power feed video.
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22nd Dec 2019, 09:10 PM #10Senior Member
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Thanks TommyG & Anorak Bob for your comments. I will need to have a close look at my mill, its a 2 slotter. One of my issues is when the vertical head is fitted, which is the majority of the time, and I have the milling vice on the table there is not a lot of Z axis travel, maybe 100 - 125mm. When the endmill is factored in also there is only around 50 - 60 mill or less depending on the endmill size.
I'll do the research and see what I can up with, with minimal work and modification.
Good luck with build TommyG, keep us posted with pics if you can of the alterations involved to make the project work. Also keen to hear about obtaining a slab of cast iron for the dovetail extension Cheers Ian
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27th Dec 2019, 07:17 PM #11Member
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I've already sourced the grey CI for the dovetail
I arranged it with a foundry in SA
It's 10 mm oversized for machining allowance
20191127_214916.jpg
I'll keep you up to date as this progresses
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27th Dec 2019, 07:21 PM #12Member
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You had me worried until I read the last bit!
You are right my knee has angled plates that bottom out first (clear of the leadscrew nut)
Although I now have a niggling doubt. I think I'll get out the engine hoist tomorrow and double check! Now is the time to get it right
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