Knee mill riser - most useful height?

[frankcal]

I know that this is a subjective question depending on work being done/personal preference but overall:
- who here has added a riser to the column of their knee mill?
- what height (inches) did you select?
- did you find the height you selected as being overall useful...or wishing you had gone higher/lower?

Riser heights typically seen are 4, 6, 7 and 8"....and seen feedback about "pain to install..sometimes wishing it wasn't on" and then occasionally the riser is once again posted on eBay from whence it came...

 

[TOBARApprentice]

My mill is a 6x30 and I decided on 8 inches having emailed John (Twastard Engineering on Youtube). His is 5 1/2” as I recall. I put my boring bar into the quill, and measured as though I was boring a 6 inch block in my vice...... and I’m hoping I don’t run out of capacity again.


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[ducdon]

I have a 9X35 with 5 1/2 inches of quill travel. I don't see much advantage to a riser block taller than the quill travell? The more height added the more rigidity lost!

 

[Janger]

I decided on 6”. It’s still in progress and has been in progress for quite some time now. I need to finish the holes, tap, weld it together and face it off flat. Paint.

I hope the height is correct...

 

[PeterT]

Its a function of the work you do but its surprising how certain setups can gobble headroom in a hurry. 15" from quill bottom to end of spindle sounds like a lot but.... a typical mill vise can use 4" from the table top, more if it sits on a swivel casting. Or a typical rotary table (5-6") plus maybe a mounted fixture/chuck (4"). Then subtract top side tooling like drill chuck + drill or an end mill arbor + EM (3-6" depending on size). Sometimes there isn't a lot of room remaining for the part. If you use a dividing head or flip the RT perpendicular to table, that can use up 6" or more. Tapping heads are also longish ~6"

My smaller RF45 mill actually had a teeny bit more vertical than baby Bridgeport. I can see where riser blocks are desirable for some. Bigger mills typically have more usable gap. The downside is the draw bar nut is up in the clouds. So unless you are 6'5" or have a power changer the step stool must always be close. Another consideration is shop ceiling height particularly if you are in proximity of things like garage door tracks. Riser block opens the useable range but does nothing for table height, so you may still find you want the mill elevated.

 

[frankcal]

re: RF45; is there any sort of riser on that unit?

 

[PeterT]

Nope it’s a rear dovetail column that power head travels on. Table height remains constant. Referred to as bench top mill

 

[TOBARApprentice]

I don’t know that by going the 8 inches vs 6 sacrifices much rigidity as I used a block 8 inches round and a wall thickness of 3 inches. My thinking was that 5.5 inches would do.... but I have never heard any person complain about having too much capacity or too much mill.......


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[frankcal]

my biggest concerns:
1) adding a riser that is so tall that it negates shallow work; you dont want to 'fix' one problem and generate another...and adding/removing a riser would be a lot of effort
2) paying up for a riser (say, 4") and then wishing it was a 8"...considering the amount of risers I see for sale and comments I see on other boards, there appears to be much in the way of 'riser-buyer remorse'....

 

[Tom Kitta]

One has to think in these cases why original design, years old, doesn't have riser block in it. Cost of extra casting cannot be that high. Maybe most users simply don't need it? What are draw backs? There has to be some negatives to every solution. Would the machine be as stable and as rigid as before?

 

[frankcal]

do you have/have you used a riser?

 

[Tom Kitta]

I have never used a riser and I don't seem to have the need for it. Maybe my mill is larger then what other people have? The distance from lowest knee position table top to the tip of the quill is very large I am guessing like 20" or something like that. If I need more for say engine boring I have either horizontal mill or radial arm drill - I guess these would be too small for say large catepilar engine or a tank engine but I don't anticipate that work.

 

[ducdon]

I have a baby bridgeport style mill. 16.5 inches quill to table. And yes I've faced some situations were space gets tight. I've been able to work around those situations by: Ditching the vice and mounting work directly to table. Ditching the Jacobs chuck and mounting the tooling in a Collet. Shortened tooling such as Reamers as they are generally longer than what I need. Zero dials on work location, move to side for tool changes and then move back to work location. I find its usually drilling or boring operations were space gets tight. I've never done it but I've heard of a big work item being located on the floor behind the mill and the head reversed to do the work there.

 

[ttlrfrank]

ducdon: sounds very similar to experiences I've had. Have even offset the vise to one side of the table so that I have the dual-height option on small pieces (table vs vise). with the re-jigging options you mentioned, I can usually get close to the work height I need...but often enough there is still that last few inches that would have saved a tool/holddown reconfiguration.
Started heading in the 4" riser direction but then started reading more articles with 'swapped a 4" for a 6/ 8' stories and considering any riser is pricey (for what they are) and 4 upsize to 6" is only another $50USD, I 'd have no problem paying the difference...but I DEFINITELY do not want to buy a 6" and then find situations that I want to remove it....install/stay is what my end goal is.

Any insights on where a person could find risers that are <$300CAD to leave some money should a different size be needed (used risers seem to be same/more$ on eBay than new ones...)

 

[PeterT]

TomK> The distance from lowest knee position table top to the tip of the quill is very large I am guessing like 20" or something like that.

In the Taiwan Bridgeport clone series, the Z height increases with larger overall machine sizes, but not by leaps & bounds. Using PM mills as example, you only get 2" extra going to the biggest mill of this series. If you have sufficient power, table size, weight with a smaller mill the only cost effective option is to add Z with a spacer. Like you say the job type & frequency kind of dictates the machine.

935 (baby bridgeport) 24x12 Z = 15"
https://www.precisionmatthews.com/shop/pm-935ts-tv/
949 34x13 Z = 16"
https://www.precisionmatthews.com/shop/pm-949ts-tv/
1054 36x15 z= 17"
https://www.precisionmatthews.com/shop/1054t-precision-knee-milling-machines/

 

[PeterT]

Any insights on where a person could find risers that are <$300CAD to leave some money should a different size be needed (used risers seem to be same/more$ on eBay than new ones...)

I know Modern & the typical machine tool importers have access to riser blocks. The NAm vendors tend to feed from the same offshore factories. I don't know price though. I'm guessing the block itself is one number, but shipping add might be the killer. Hard to speculate but you might benefit by it arriving in conjunction with their crates of other machines, so FOB the city is located in rather than dinger fees to your door FOB Ebay origin or whatever. Some sellers have the shipping/customs game figured out & shipping to Canada is no problem. Others just aren't interested. So its up to you to figure out whats best. There are some YouTube videos/other info sources that discuss the actual installation. If its a generic blank not really suited to your machine without mods, that would obviously factor too.

 

[ducdon]

I've been watching some Keith Fenner vids on You Tube. He has a horizontal mill with a vertical head. For really long work pieces he flips the head to horizontal and does his drilling and boring horizontally. Hmmm, Dear, I need to buy another mill. Maybe we could park the car outside?

 

[Janger]

Need a cheaper riser? Start fabricating one. If you need more amps to weld with then come to my place or another buddy.

On my mill the table goes too high. Can anyone explain why they would build it this way? Look at the photos. Is this typical a on other mills? The table actually goes 1/2” higher than the bottom of the spindle. I wish they had built it 4 inches offset the other way. Once I get this riser installed what am I going to think? The table goes so high I “think” it’s going to be ok.

Here is the riser beside the vise.

 

[Janger]

What about going the other way and lowering the table? Here is the guts underneath my mill. The column holding the acme screw could have been shorter and the screw made shorter too. You can see the casting could have been modified to include dovetail all the way down where I marked it. Like Tom said why is it done this way?

 

[Janger]

One problem I know I’m going to have is Y axis travel. The vise and table are going to hit the horizontal spindle on this mill. I’m going to lose 2 inches.